{"gene":"SLC16A2","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":1994,"finding":"SLC16A2 (then called XPCT) encodes a predicted 67 kDa protein containing twelve hydrophobic transmembrane domains characteristic of transporter proteins, with an N-terminal PEST domain, and is subject to X chromosome inactivation despite proximity to XIST.","method":"Positional cloning, expression studies, structural prediction","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 — original positional cloning with structural characterization; single study","pmids":["7981683"],"is_preprint":false},{"year":2005,"finding":"MCT8 (SLC16A2) functions as a specific transporter of triiodothyronine (T3) into neurons; inactivating mutations cause elevated free T3 and lowered free T4 in blood, indicating loss of T3 transport function.","method":"Mutation analysis in six families with Allan-Herndon-Dudley syndrome, biochemical thyroid hormone measurements","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — replicated across six independent families with consistent biochemical phenotype","pmids":["15889350"],"is_preprint":false},{"year":2005,"finding":"The MCT8 A150V missense mutation in transmembrane domain 2 abolishes T3 uptake and causes intracellular retention of the protein rather than plasma membrane expression; wild-type MCT8 forms multimers.","method":"125I-T3 uptake assay, immunofluorescence, dimerization studies in transfected cells","journal":"European journal of endocrinology","confidence":"High","confidence_rationale":"Tier 1 — in vitro transport assay plus subcellular localization and dimerization studies in single rigorous paper","pmids":["16131597"],"is_preprint":false},{"year":2005,"finding":"A frameshift MCT8 mutation (c.1834delC) decreases cellular T3 uptake and intracellular T3 metabolism, demonstrating that MCT8 is required for both substrate entry and subsequent metabolism by deiodinases.","method":"In vitro T3 uptake assay and T3 metabolism assay in transfected cells","journal":"Journal of medical genetics","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro transport and metabolism assays with defined mutation","pmids":["15980113"],"is_preprint":false},{"year":2008,"finding":"MCT8 mutations cause loss of thyroid hormone transport function through three distinct mechanisms: reduced protein expression, impaired trafficking to the plasma membrane, or reduced substrate affinity; mutants with residual transport activity (L434W, L568P, S194F, ~20–37% of WT) correlate with milder psychomotor phenotype.","method":"T3/T4 uptake assay, T3 metabolism assay, Western blotting, affinity labeling with N-bromoacetyl-T3, immunocytochemistry, quantitative RT-PCR in transfected JEG3 and COS1 cells","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal methods (transport, affinity labeling, localization) in a single rigorous study","pmids":["18187543"],"is_preprint":false},{"year":2008,"finding":"MCT8 mRNA and protein are expressed in cerebral microvessels (blood-brain barrier) in human, mouse, and rat in addition to neurons; in rat, Mct8 localizes to both luminal and abluminal microvessel membranes; in choroid plexus MCT8 is concentrated on the apical surface.","method":"mRNA expression analysis, protein immunolocalization in cerebral microvessels and choroid plexus of human, mouse, and rat","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 — direct protein localization across three species with membrane-domain specificity","pmids":["18687783"],"is_preprint":false},{"year":2009,"finding":"The majority of T3 uptake in primary cortical neurons is mediated by Mct8; pharmacological inhibition and mRNA profiling show that L-type amino acid transporters (LATs, including Lat2) are co-expressed in mouse neurons and provide functional complementation in Mct8-deficient mice but not in developing human neurons where LAT2 is expressed in microglia rather than neurons.","method":"Primary cortical neuron T3 uptake assay, pharmacological inhibition, mRNA profiling, immunolocalization in murine and human brain","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — direct neuronal uptake assays with pharmacological dissection plus human/mouse comparative localization","pmids":["19641107"],"is_preprint":false},{"year":2009,"finding":"MCT8 mutations can impair both T3 uptake and T3 efflux in patient fibroblasts; the F501del mutation causes a milder phenotype because it reduces T3 uptake only modestly while strongly reducing T3 efflux, potentially retaining T3 in cells.","method":"T3 uptake and efflux assays in patient-derived fibroblasts, type 3 deiodinase activity measurements, T3-responsive gene expression analysis","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 1–2 — bidirectional transport characterization in primary patient cells with multiple functional readouts","pmids":["18636565"],"is_preprint":false},{"year":2009,"finding":"Functional activity and plasma membrane surface translocation of MCT8 missense mutants (e.g., ins235V, L568P, R271H) are cell-type dependent, suggesting tissue-specific interacting proteins influence MCT8 trafficking and function.","method":"Stable cell lines in JEG1 and MDCK1 cells: T3 transport assay, surface biotinylation, kinetic analysis, immunocytochemistry","journal":"Journal of molecular endocrinology","confidence":"High","confidence_rationale":"Tier 1 — reconstituted transport with surface biotinylation across two cell systems","pmids":["19648159"],"is_preprint":false},{"year":2011,"finding":"Tyrosine kinase inhibitors (sunitinib, imatinib, dasatinib, bosutinib) dose-dependently inhibit MCT8-mediated T3 and T4 uptake in a noncompetitive manner, with IC50 values of 13–38 µM.","method":"125I-T3 uptake and efflux assay in MDCK1 cells stably expressing human MCT8; kinetic analysis of inhibition mode","journal":"The Journal of clinical endocrinology and metabolism","confidence":"High","confidence_rationale":"Tier 1 — in vitro transport assay with defined kinetics and mode-of-inhibition characterization","pmids":["22031512"],"is_preprint":false},{"year":2011,"finding":"Zebrafish Slc16a2 (Mct8) transports T3 in a saturable, Na+-independent, temperature-dependent manner (Km ~0.8 µM at 26°C); at 26°C it does not transport T4, but does so at 37°C; it is highly expressed in brain, gills, pancreas, liver, pituitary, and heart, and expressed from mid-blastula stage.","method":"Cloning, heterologous expression, 125I-T3 uptake kinetics in transfected cells; tissue expression by qPCR","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 1 — reconstituted transport with Michaelis-Menten kinetics and substrate specificity characterization","pmids":["21952246"],"is_preprint":false},{"year":2012,"finding":"PTTG-binding factor (PBF/PTTG1IP) physically binds MCT8 in vitro (co-immunoprecipitation/pulldown), shifts MCT8 subcellular localization away from the plasma membrane, and reduces MCT8 surface expression; PBF overexpression in mouse thyroid in vivo causes enhanced thyroidal TH accumulation and reduced TH secretion, phenocopying Mct8 knockout.","method":"Co-IP/pulldown, cell surface biotinylation assay, immunolocalization in PBF-transgenic mice, thyroid TH accumulation assay","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal interaction validated in vitro and confirmed by in vivo phenocopy in transgenic mice","pmids":["22535767"],"is_preprint":false},{"year":2013,"finding":"Arg445 (TM8) and Asp498 (TM10) of MCT8 are critical for thyroid hormone transport; mutations altering the charge at either position nearly abolish TH uptake without affecting protein expression, stability, or localization; charge-exchange double mutant (R445D+D498R) partially restores T4 uptake, indicating a functionally important charge pair between these residues.","method":"Site-directed mutagenesis, T3/T4 uptake assay, Western blotting, confocal microscopy in transfected cells","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis with charge-swap rescue experiment","pmids":["24265446"],"is_preprint":false},{"year":2013,"finding":"His192, located at the border of TM1 and ECL1, is critical for TH uptake: DEPC modification of His residues inhibits T3/T4 uptake (but not efflux), and this inhibition is blocked by pre-incubation with substrate; H192A mutation reduces TH uptake and abolishes DEPC sensitivity, placing His192 near the substrate recognition site.","method":"Chemical modification with DEPC, site-directed mutagenesis (H192A, H260A, H450A), T3/T4 uptake assay in transfected cells","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 1 — chemical modification plus mutagenesis with substrate-protection control","pmids":["23610131"],"is_preprint":false},{"year":2013,"finding":"His192 and His415, together with Arg301, form a substrate recognition motif within the MCT8 transport channel; mutations at His192, His415, and Arg301 significantly alter substrate transport kinetics; molecular modeling places T3 between His415 and Arg301 analogous to the His-Arg clamp in the T3 receptor.","method":"Site-directed mutagenesis, T3 transport kinetics in MDCK-1 cells and Xenopus oocytes, molecular modeling","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis in two independent expression systems plus structural modeling","pmids":["23592749"],"is_preprint":false},{"year":2013,"finding":"MCT8 mutations can be classified into two mechanistic groups: those causing partial or complete loss of transport activity while retaining plasma membrane localization (G221R, P321L, D453V, P537L), and those that mainly disrupt protein expression and trafficking causing ER retention (insV236, G282C, G558D).","method":"Live-cell imaging of MCT8-CFP fusion constructs in Flp-in 293 cells, T3/T4 uptake assay in multiple cell types, FRAP analysis","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 2 — live-cell imaging combined with functional transport assays in multiple cell models","pmids":["23550058"],"is_preprint":false},{"year":2013,"finding":"Mct10 (Slc16a10) facilitates thyroid hormone efflux from liver and kidney, contributing to the elevated serum T4 phenotype of Mct8-deficient mice; Mct10/Mct8 double knockout partially restores serum T4 levels compared with Mct8 single KO, demonstrating that Mct10 contributes to TH efflux from peripheral tissues in vivo.","method":"Mct10 KO and Mct8/Mct10 double KO mouse generation; serum TH measurements, tissue TH content analysis","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in vivo using double KO mice with direct TH measurements","pmids":["24248460"],"is_preprint":false},{"year":2014,"finding":"Combined deficiency of MCT8 and OATP1C1 in mice strongly reduces brain uptake of both T3 and T4, causing cerebral hypothyroidism, delayed cerebellar development, reduced myelination, and compromised differentiation of GABAergic interneurons; single Mct8 KO mice do not show these neurological phenotypes because residual T4 entry via OATP1C1 compensates.","method":"Mct8/Oatp1c1 double KO mouse generation; brain TH content, deiodinase activity, TH target gene expression, histological and behavioral analysis","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with double KO plus multiple mechanistic readouts; landmark study","pmids":["24691440"],"is_preprint":false},{"year":2014,"finding":"Triiodothyroacetic acid (TRIAC/TA3) is not significantly transported by MCT8; it bypasses MCT8 in neuronal and oligodendrocyte cell lines and in patient fibroblasts, and can replace T3 to promote neural differentiation in cerebellum and cerebral cortex of MCT8-deficient mice.","method":"Radiolabeled substrate uptake in SH-SY5Y and MO3.13 cells and patient fibroblasts; TRIAC transport assay in MCT8-transfected cells; in vivo treatment of Pax8-KO and Mct8/Oatp1c1-DKO mice with assessment of TH-dependent gene expression and cerebellar/cortical development","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 1 — in vitro transport assays in multiple cell types plus in vivo rescue experiment","pmids":["25389909"],"is_preprint":false},{"year":2010,"finding":"Retinoic acid (RA), acting through retinoic acid receptor (RAR) binding to a consensus RA-response element 6.6 kb upstream of the Mct8 coding region, transcriptionally induces Mct8 expression >300-fold in F9 cells, increasing T3 and T4 uptake; this was abolished by a selective MCT8 inhibitor.","method":"Promoter-reporter assay, chromatin immunoprecipitation (RAR/RXR binding), T3/T4 uptake assay, pharmacological inhibition in F9 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — ChIP plus functional promoter assay plus direct transport measurement","pmids":["20573951"],"is_preprint":false},{"year":2016,"finding":"Silychristin (a flavonolignan from milk thistle) inhibits MCT8-mediated T3 uptake with an IC50 of ~100 nM, at least 1 order of magnitude below other known MCT8 inhibitors, and shows specificity for MCT8 over MCT10 in overexpressing cells and endogenous Mct8 in primary murine astrocytes.","method":"Non-radioactive T3 uptake assay in MCT8-overexpressing MDCK1 cells and primary murine astrocytes; IC50 determination; MCT10-specificity control","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 1 — quantitative in vitro inhibitor characterization with specificity controls in primary cells","pmids":["26910310"],"is_preprint":false},{"year":2016,"finding":"AAV9-mediated delivery of human MCT8 to brain barriers via intravenous (but not intracerebroventricular) injection in Mct8 KO mice increases brain T3 content and expression of T3-responsive genes (Hairless), demonstrating that MCT8 at brain barriers (including choroid plexus) is the critical site for T3 entry into the brain.","method":"IV and ICV AAV9 injection in Mct8 KO mice; brain T3 content measurement, Hairless gene expression, MCT8 protein localization by immunohistochemistry","journal":"Thyroid","confidence":"High","confidence_rationale":"Tier 2 — in vivo gene delivery with functional readouts demonstrating route-specific mechanism","pmids":["27432638"],"is_preprint":false},{"year":2016,"finding":"Chemical chaperone sodium phenylbutyrate (NaPB) rescues protein expression and transport function of several destabilized MCT8 mutants (S194F, S290F, L434W, R445C, L492P, L568P, delF501) in a dose-dependent manner; kinetic analysis shows these mutants have near-normal substrate affinity (Km for T3), indicating destabilization rather than active-site disruption as the primary defect.","method":"NaPB treatment of MDCK cells stably expressing MCT8 mutants; T3 transport assay, protein expression analysis, kinetic analysis","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 1 — pharmacological rescue with kinetic characterization across multiple mutants","pmids":["27977298"],"is_preprint":false},{"year":2018,"finding":"MCT8 and OATP1C1 are expressed in activated skeletal muscle satellite cells (SCs) and act as gatekeepers of TH entry; Mct8/Oatp1c1 double KO mice show strongly reduced SC differentiation and impaired skeletal muscle regeneration, phenocopied by SC-specific conditional double KO.","method":"Conditional and global double KO mice; SC isolation; tissue TH content; TH-regulated gene expression; muscle regeneration assay","journal":"Stem cell reports","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific conditional KO with defined regeneration phenotype","pmids":["29706500"],"is_preprint":false},{"year":2016,"finding":"In mct8-deficient zebrafish, MCT8 is required for oligodendrocyte progenitor cell (OPC) differentiation into mature oligodendrocytes; mosaic expression of Mct8-tagRFP specifically in blood-brain barrier endothelial cells completely rescued CNS hypomyelination, demonstrating that MCT8 at the BBB is sufficient to restore myelination.","method":"mct8-/- zebrafish model; quantification of OPC and oligodendrocyte markers; live imaging of glial cells; BBB-targeted transgenic rescue with Mct8-tagRFP","journal":"Disease models & mechanisms","confidence":"High","confidence_rationale":"Tier 2 — genetic rescue with cell-type-specific transgene identifying BBB as critical site","pmids":["27664134"],"is_preprint":false},{"year":2016,"finding":"MCT8 deficiency in Purkinje cell precursors (via RNAi electroporation in chicken embryo) causes cell-autonomous defects: downregulation of TH-responsive gene RORα and Purkinje cell marker LHX1/5, reduced dendritic complexity; and non-autonomous effects on granule cell precursor proliferation and radial migration.","method":"MCT8-RNAi electroporation into chicken cerebellar anlage; immunostaining for differentiation markers; TRIAC rescue experiment","journal":"The Journal of endocrinology","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific KD with cell-autonomous and non-autonomous phenotypic readouts and partial rescue","pmids":["27879339"],"is_preprint":false},{"year":2019,"finding":"Human, mouse, and zebrafish MCT8 orthologues all transport T3, T4, rT3, and 3,3'-T2 by facilitated diffusion; zebrafish Mct8 has 1.5–4-fold higher initial uptake rates and 3–50-fold lower IC50 values for substrates than human or mouse MCT8, with different substrate preference; His192 in human MCT8, replaced by Gln in zebrafish, does not underlie these kinetic differences.","method":"Comparative transport assays in transiently transfected COS-1 and JEG-3 cells; surface biotinylation; immunoblotting; structural modeling; H192Q mutagenesis","journal":"Thyroid","confidence":"High","confidence_rationale":"Tier 1 — systematic comparative biochemistry with mutagenesis across three orthologues","pmids":["31436139"],"is_preprint":false},{"year":2021,"finding":"Both MCT8 and OATP1C1 are expressed in adult mouse subventricular zone neural stem cells (NSCs); Mct8/Oatp1c1 double KO severely impairs NSC proliferation and neuronal fate determination but not oligodendrocyte progenitor generation, identifying TH transport as a regulator of NSC function and glial-neuron cell fate in the adult brain.","method":"Immunohistochemical localization of MCT8/OATP1C1 in SVZ; analysis of Mct8/Oatp1c1 DKO mice for NSC proliferation (BrdU), fate markers, and progenitor numbers","journal":"Stem cell reports","confidence":"High","confidence_rationale":"Tier 2 — direct localization plus genetic KO with cell-type-specific fate phenotype","pmids":["33450189"],"is_preprint":false},{"year":2021,"finding":"MCT8 in osteoblast and osteoclast progenitors mediates T3 uptake in a cell-intrinsic manner; conditional Mct8 KO in osteoprogenitors increases trabecular bone volume and alters osteoblast/osteoclast numbers independently of systemic T3 elevation.","method":"Conditional Mct8 KO mouse lines targeting osteoclast precursors, osteoprogenitors, and mature osteoblasts/osteocytes; bone microarchitecture, turnover, ex vivo T3 uptake in bone marrow-derived cells","journal":"Thyroid","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific conditional KO with direct T3 uptake measurement ex vivo","pmids":["31910109"],"is_preprint":false},{"year":2024,"finding":"MCT8-deficient human cerebral organoids (from patient iPSCs) show impaired T3 transport into developing neural cells (assessed by deiodinase-3-mediated T3 catabolism assay), smaller neural rosettes with thinner cortical units, reduced cortex development gene expression, and reduced T3-inducibility of TH-regulated genes; TH analogs DITPA and TRIAC bypass MCT8 and restore normal TH-responsive gene induction.","method":"Human iPSC-derived cerebral organoids from MCT8-deficient patients; D3-mediated T3 catabolism as transport proxy; gene expression analysis; TH analog rescue experiments","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 1–2 — human patient-derived organoid model with functional transport assay and pharmacological rescue","pmids":["38376950"],"is_preprint":false},{"year":2016,"finding":"MCT8 mediates TH transport and is required for TH-dependent OPC maturation in a cell-autonomous manner; MCT8-deficient iPSC-derived OPCs transplanted into a hypothyroid triple KO mouse (mct8-/-; oatp1c1-/-; rag2-/-) fail to mature into oligodendrocytes, demonstrating that functional TH transport across brain barriers is also required for in vivo oligodendrocyte maturation.","method":"iPSC differentiation to OPCs; transplantation into shiverer and hypothyroid triple KO mice; behavioral and myelination assessment","journal":"Glia","confidence":"High","confidence_rationale":"Tier 2 — cell transplantation into defined in vivo environment separating cell-autonomous from systemic TH effects","pmids":["33956384"],"is_preprint":false},{"year":2023,"finding":"MCT8 deficiency (in Mct8/Dio2 KO mice and in human AHDS brain tissue) causes neurovascular unit disruption and blood-brain barrier leakage, including increased transcytosis, IgG extravasation, and reduced brain vessel density, identifying BBB structural integrity as an additional MCT8-dependent mechanism.","method":"Transmission electron microscopy of BBB; non-permeable dye (sodium fluorescein, Evans Blue) infiltration assays; IgG immunohistochemistry; MR angiography; angiogenesis gene expression by qRT-PCR in Mct8/Dio2KO mice and human AHDS brain sections","journal":"Fluids and barriers of the CNS","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods in mouse model and human tissue","pmids":["37924081"],"is_preprint":false}],"current_model":"SLC16A2/MCT8 is a twelve-transmembrane-domain facilitated transporter that mediates bidirectional, Na+-independent cellular uptake and efflux of thyroid hormones (predominantly T3 and T4), operating at the blood-brain barrier endothelium, neurons, oligodendrocyte progenitors, and other cell types; substrate recognition requires His192, His415, Arg301, Arg445, and Asp498 within the transmembrane channel; its trafficking to the plasma membrane is regulated by interacting proteins (including PBF) and is transcriptionally induced by retinoic acid via a RAR-binding element; inactivating mutations cause loss of function through reduced protein stability/trafficking or impaired substrate binding, leading to brain thyroid hormone deficiency and peripheral thyrotoxicosis (Allan-Herndon-Dudley syndrome), with BBB-targeted MCT8 delivery being sufficient to restore brain T3 levels and neurological function."},"narrative":{"teleology":[{"year":1994,"claim":"The initial cloning of SLC16A2 (XPCT) established it as a twelve-transmembrane-domain protein with transporter-family topology, providing the structural framework for subsequent functional characterization.","evidence":"Positional cloning with hydropathy-based structural prediction from the X chromosome","pmids":["7981683"],"confidence":"Medium","gaps":["No transport substrate identified","Single study without functional assay","Predicted topology not experimentally validated"]},{"year":2005,"claim":"Identification of inactivating MCT8 mutations in families with Allan–Herndon–Dudley syndrome, together with in vitro transport assays, established MCT8 as a specific T3 transporter whose loss causes elevated serum T3 and reduced T4, linking the gene to a Mendelian neurological disorder.","evidence":"Mutation analysis in six AHDS families; ¹²⁵I-T3 uptake assays and immunolocalization of wild-type and mutant MCT8 in transfected cells","pmids":["15889350","16131597","15980113"],"confidence":"High","gaps":["Mechanism of neurological damage not yet resolved","T4 transport by MCT8 not yet characterized","In vivo tissue-specific requirements unknown"]},{"year":2008,"claim":"Systematic characterization of patient-derived mutations revealed three distinct loss-of-function mechanisms — reduced expression, impaired trafficking, and reduced substrate affinity — and showed that MCT8 localizes to blood–brain barrier endothelium (luminal and abluminal) and choroid plexus apically, positioning it as the brain's thyroid hormone gatekeeper.","evidence":"Affinity labeling, Western blot, immunocytochemistry of mutants in JEG3/COS1 cells; protein immunolocalization in human/mouse/rat brain microvasculature and choroid plexus","pmids":["18187543","18687783"],"confidence":"High","gaps":["Why human neurons are more vulnerable than mouse neurons not yet explained","Structural basis of substrate translocation unknown"]},{"year":2009,"claim":"Transport assays in primary neurons and patient fibroblasts demonstrated that MCT8 mediates both T3 uptake and efflux, that LAT2 provides functional compensation in mouse but not human neurons, and that trafficking and function of MCT8 mutants are cell-type dependent.","evidence":"Primary cortical neuron uptake assays with pharmacological dissection; bidirectional transport in patient fibroblasts; surface biotinylation in JEG1 vs MDCK1 cells","pmids":["19641107","18636565","19648159"],"confidence":"High","gaps":["Identity of cell-type-specific trafficking cofactors unknown","In vivo significance of bidirectional transport not tested"]},{"year":2010,"claim":"Discovery that retinoic acid transcriptionally induces MCT8 expression >300-fold through a RAR/RXR-binding element upstream of the gene established a transcriptional regulatory axis for MCT8.","evidence":"ChIP for RAR/RXR binding, promoter-reporter assay, T3/T4 uptake after RA treatment in F9 cells","pmids":["20573951"],"confidence":"High","gaps":["Physiological relevance during brain development not tested in vivo","Other transcriptional regulators not mapped"]},{"year":2013,"claim":"Site-directed mutagenesis and chemical modification identified a substrate recognition mechanism comprising His192, His415, Arg301, Arg445, and Asp498 within the transmembrane channel, with a His–Arg clamp analogous to the thyroid hormone receptor and a functionally essential Arg445–Asp498 charge pair.","evidence":"DEPC modification with substrate protection; charge-swap double mutants; transport kinetics in MDCK1 cells and Xenopus oocytes; homology modeling","pmids":["23610131","23592749","24265446"],"confidence":"High","gaps":["No high-resolution experimental structure","Conformational cycle (inward-open to outward-open) not characterized","Residues governing T3 vs T4 selectivity not identified"]},{"year":2012,"claim":"Identification of PTTG1IP (PBF) as a physical interactor that redirects MCT8 away from the plasma membrane provided the first named protein partner that regulates MCT8 surface availability.","evidence":"Co-immunoprecipitation/pulldown; surface biotinylation; PBF-transgenic mouse thyroid phenocopy of Mct8 KO","pmids":["22535767"],"confidence":"High","gaps":["Binding interface not mapped","Whether PBF regulates MCT8 at the BBB unknown","Other trafficking regulators not identified"]},{"year":2014,"claim":"The Mct8/Oatp1c1 double-knockout mouse established that combined loss of both brain thyroid hormone transporters is required to recapitulate human AHDS neuropathology — including cerebellar delay, hypomyelination, and GABAergic interneuron defects — explaining why single Mct8 KO mice lack a brain phenotype.","evidence":"DKO mouse generation; brain TH content, deiodinase activity, histology, behavioral testing","pmids":["24691440"],"confidence":"High","gaps":["Relative contributions of individual cell types (neuron vs glia vs endothelium) not dissected","Postnatal rescue window not defined"]},{"year":2016,"claim":"BBB-targeted MCT8 re-expression (by AAV9 IV injection in mice and BBB-endothelial transgene in zebrafish) was sufficient to restore brain T3 content and rescue hypomyelination, proving that MCT8 at the blood–brain barrier is the critical site for brain thyroid hormone supply; separately, chemical chaperone NaPB rescued destabilized MCT8 mutants, and silychristin was identified as a nanomolar-potency MCT8-specific inhibitor.","evidence":"AAV9-MCT8 IV/ICV injection in Mct8 KO mice; BBB-targeted Mct8-tagRFP transgenic rescue in mct8⁻/⁻ zebrafish; NaPB dose–response with kinetic analysis in MDCK cells; silychristin IC₅₀ determination","pmids":["27432638","27664134","27977298","26910310"],"confidence":"High","gaps":["Long-term neurological rescue not assessed","NaPB efficacy in vivo not demonstrated","Silychristin mechanism of inhibition not defined"]},{"year":2016,"claim":"TRIAC was shown to bypass MCT8, entering neurons and OPCs via alternative transporters and restoring TH-dependent differentiation in MCT8-deficient models, providing a pharmacological bypass strategy.","evidence":"Radiolabeled transport assays in MCT8-deficient cells; in vivo TRIAC treatment of Mct8/Oatp1c1-DKO mice; RNAi of MCT8 in chicken cerebellum with TRIAC rescue","pmids":["25389909","27879339"],"confidence":"High","gaps":["TRIAC efficacy in human clinical trials not yet fully evaluated","Alternative transporter identity for TRIAC not definitively established"]},{"year":2021,"claim":"Cell-type-specific conditional knockouts extended MCT8's functional role beyond neurons and glia to adult neural stem cells and bone cells, showing that MCT8-mediated T3 uptake cell-autonomously controls NSC proliferation/neuronal fate and osteoblast-osteoclast homeostasis.","evidence":"Mct8/Oatp1c1 DKO SVZ analysis with BrdU and fate markers; conditional Mct8 KO in osteoprogenitors with bone microarchitecture and ex vivo T3 uptake","pmids":["33450189","31910109"],"confidence":"High","gaps":["Whether skeletal phenotype contributes to AHDS morbidity unknown","Signaling pathways downstream of T3 in NSCs not mapped"]},{"year":2023,"claim":"MCT8 deficiency was found to compromise blood–brain barrier structural integrity itself — causing increased transcytosis, IgG leakage, and reduced vessel density — revealing a neurovascular dimension of AHDS pathology beyond simple T3 deprivation.","evidence":"TEM of BBB, sodium fluorescein/Evans Blue infiltration, IgG immunohistochemistry, MR angiography in Mct8/Dio2 KO mice and human AHDS brain sections","pmids":["37924081"],"confidence":"High","gaps":["Whether BBB leakage is a direct consequence of local T3 deficiency or an independent MCT8 function is unclear","Reversibility of BBB damage not tested"]},{"year":2024,"claim":"Human iPSC-derived cerebral organoids from AHDS patients confirmed that MCT8 deficiency impairs T3 transport into developing neural tissue and reduces cortical development, and validated TRIAC and DITPA as compounds that restore TH-responsive gene expression independently of MCT8.","evidence":"Patient iPSC-derived cerebral organoids; D3-mediated T3 catabolism transport assay; gene expression profiling; TH analog rescue","pmids":["38376950"],"confidence":"High","gaps":["Long-term cortical maturation in organoids not assessed","Whether early prenatal treatment could prevent human AHDS neuropathology remains unknown"]},{"year":null,"claim":"Key unresolved questions include the high-resolution structure of MCT8, the conformational mechanism of substrate translocation, the identity of cell-type-specific trafficking cofactors that modulate MCT8 surface expression, and the therapeutic window for brain-targeted MCT8 gene therapy or TH analog treatment in AHDS patients.","evidence":"","pmids":[],"confidence":"High","gaps":["No experimental three-dimensional structure solved","Conformational cycle during transport not characterized","Optimal postnatal therapeutic window for neurological rescue not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[1,2,3,4,7,10,26]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,4,5,8,11,15]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[15]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[1,3,4,7,10,26]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[17,24,25,27,29]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,4,15,29,31]}],"complexes":[],"partners":["PTTG1IP","SLCO1C1"],"other_free_text":[]},"mechanistic_narrative":"SLC16A2 (MCT8) is a twelve-transmembrane-domain facilitated transporter that mediates bidirectional, Na⁺-independent cellular uptake and efflux of thyroid hormones — principally T3 and T4, but also rT3 and 3,3′-T2 — and is the dominant thyroid hormone transporter at the blood–brain barrier, in neurons, oligodendrocyte progenitors, and skeletal muscle satellite cells [PMID:15889350, PMID:18687783, PMID:19641107, PMID:27664134, PMID:29706500]. Substrate recognition within the transport channel depends on a His192–His415–Arg301 clamp and a functionally paired Arg445–Asp498 charge relay, while loss-of-function mutations impair transport through three mechanisms: reduced protein stability, defective trafficking to the plasma membrane, or diminished substrate affinity [PMID:23592749, PMID:24265446, PMID:18187543, PMID:23550058]. At the blood–brain barrier, MCT8 is the rate-limiting gateway for T3 entry; its absence causes brain thyroid hormone deficiency with impaired myelination, Purkinje cell differentiation, neural stem cell proliferation, and neurovascular integrity, while peripheral tissues exhibit thyrotoxicosis — the hallmark of Allan–Herndon–Dudley syndrome [PMID:24691440, PMID:37924081, PMID:15889350, PMID:38376950]. The thyroid hormone analogues TRIAC and DITPA bypass MCT8 to reach neural cells, providing a pharmacological rationale for treatment of MCT8-deficient patients [PMID:25389909, PMID:38376950]."},"prefetch_data":{"uniprot":{"accession":"P36021","full_name":"Monocarboxylate transporter 8","aliases":["Monocarboxylate transporter 7","MCT 7","Solute carrier family 16 member 2","X-linked PEST-containing transporter"],"length_aa":539,"mass_kda":59.5,"function":"Specific thyroid hormone transmembrane transporter, that mediates both uptake and efflux of thyroid hormones across the cell membrane independently of pH or a Na(+) gradient. Major substrates are the iodothyronines T3 and T4 and to a lesser extent rT3 and 3,3-diiodothyronine (3,3'-T2) (PubMed:16887882, PubMed:18337592, PubMed:20628049, PubMed:23550058, PubMed:26426690, PubMed:27805744, PubMed:31436139). 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the molecular, supramolecular and evolutionary aspects of chromosome biology","url":"https://pubmed.ncbi.nlm.nih.gov/16235118","citation_count":12,"is_preprint":false},{"pmid":"31910109","id":"PMC_31910109","title":"Lack of the Thyroid Hormone Transporter Mct8 in Osteoblast and Osteoclast Progenitors Increases Trabecular Bone in Male Mice.","date":"2020","source":"Thyroid : official journal of the American Thyroid Association","url":"https://pubmed.ncbi.nlm.nih.gov/31910109","citation_count":12,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":54163,"output_tokens":7513,"usd":0.137592},"stage2":{"model":"claude-opus-4-6","input_tokens":11254,"output_tokens":3520,"usd":0.216405},"total_usd":0.353997,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"SLC16A2 (then called XPCT) encodes a predicted 67 kDa protein containing twelve hydrophobic transmembrane domains characteristic of transporter proteins, with an N-terminal PEST domain, and is subject to X chromosome inactivation despite proximity to XIST.\",\n      \"method\": \"Positional cloning, expression studies, structural prediction\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — original positional cloning with structural characterization; single study\",\n      \"pmids\": [\"7981683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MCT8 (SLC16A2) functions as a specific transporter of triiodothyronine (T3) into neurons; inactivating mutations cause elevated free T3 and lowered free T4 in blood, indicating loss of T3 transport function.\",\n      \"method\": \"Mutation analysis in six families with Allan-Herndon-Dudley syndrome, biochemical thyroid hormone measurements\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — replicated across six independent families with consistent biochemical phenotype\",\n      \"pmids\": [\"15889350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The MCT8 A150V missense mutation in transmembrane domain 2 abolishes T3 uptake and causes intracellular retention of the protein rather than plasma membrane expression; wild-type MCT8 forms multimers.\",\n      \"method\": \"125I-T3 uptake assay, immunofluorescence, dimerization studies in transfected cells\",\n      \"journal\": \"European journal of endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro transport assay plus subcellular localization and dimerization studies in single rigorous paper\",\n      \"pmids\": [\"16131597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"A frameshift MCT8 mutation (c.1834delC) decreases cellular T3 uptake and intracellular T3 metabolism, demonstrating that MCT8 is required for both substrate entry and subsequent metabolism by deiodinases.\",\n      \"method\": \"In vitro T3 uptake assay and T3 metabolism assay in transfected cells\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro transport and metabolism assays with defined mutation\",\n      \"pmids\": [\"15980113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MCT8 mutations cause loss of thyroid hormone transport function through three distinct mechanisms: reduced protein expression, impaired trafficking to the plasma membrane, or reduced substrate affinity; mutants with residual transport activity (L434W, L568P, S194F, ~20–37% of WT) correlate with milder psychomotor phenotype.\",\n      \"method\": \"T3/T4 uptake assay, T3 metabolism assay, Western blotting, affinity labeling with N-bromoacetyl-T3, immunocytochemistry, quantitative RT-PCR in transfected JEG3 and COS1 cells\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal methods (transport, affinity labeling, localization) in a single rigorous study\",\n      \"pmids\": [\"18187543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MCT8 mRNA and protein are expressed in cerebral microvessels (blood-brain barrier) in human, mouse, and rat in addition to neurons; in rat, Mct8 localizes to both luminal and abluminal microvessel membranes; in choroid plexus MCT8 is concentrated on the apical surface.\",\n      \"method\": \"mRNA expression analysis, protein immunolocalization in cerebral microvessels and choroid plexus of human, mouse, and rat\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct protein localization across three species with membrane-domain specificity\",\n      \"pmids\": [\"18687783\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The majority of T3 uptake in primary cortical neurons is mediated by Mct8; pharmacological inhibition and mRNA profiling show that L-type amino acid transporters (LATs, including Lat2) are co-expressed in mouse neurons and provide functional complementation in Mct8-deficient mice but not in developing human neurons where LAT2 is expressed in microglia rather than neurons.\",\n      \"method\": \"Primary cortical neuron T3 uptake assay, pharmacological inhibition, mRNA profiling, immunolocalization in murine and human brain\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct neuronal uptake assays with pharmacological dissection plus human/mouse comparative localization\",\n      \"pmids\": [\"19641107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"MCT8 mutations can impair both T3 uptake and T3 efflux in patient fibroblasts; the F501del mutation causes a milder phenotype because it reduces T3 uptake only modestly while strongly reducing T3 efflux, potentially retaining T3 in cells.\",\n      \"method\": \"T3 uptake and efflux assays in patient-derived fibroblasts, type 3 deiodinase activity measurements, T3-responsive gene expression analysis\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — bidirectional transport characterization in primary patient cells with multiple functional readouts\",\n      \"pmids\": [\"18636565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Functional activity and plasma membrane surface translocation of MCT8 missense mutants (e.g., ins235V, L568P, R271H) are cell-type dependent, suggesting tissue-specific interacting proteins influence MCT8 trafficking and function.\",\n      \"method\": \"Stable cell lines in JEG1 and MDCK1 cells: T3 transport assay, surface biotinylation, kinetic analysis, immunocytochemistry\",\n      \"journal\": \"Journal of molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted transport with surface biotinylation across two cell systems\",\n      \"pmids\": [\"19648159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Tyrosine kinase inhibitors (sunitinib, imatinib, dasatinib, bosutinib) dose-dependently inhibit MCT8-mediated T3 and T4 uptake in a noncompetitive manner, with IC50 values of 13–38 µM.\",\n      \"method\": \"125I-T3 uptake and efflux assay in MDCK1 cells stably expressing human MCT8; kinetic analysis of inhibition mode\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro transport assay with defined kinetics and mode-of-inhibition characterization\",\n      \"pmids\": [\"22031512\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Zebrafish Slc16a2 (Mct8) transports T3 in a saturable, Na+-independent, temperature-dependent manner (Km ~0.8 µM at 26°C); at 26°C it does not transport T4, but does so at 37°C; it is highly expressed in brain, gills, pancreas, liver, pituitary, and heart, and expressed from mid-blastula stage.\",\n      \"method\": \"Cloning, heterologous expression, 125I-T3 uptake kinetics in transfected cells; tissue expression by qPCR\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted transport with Michaelis-Menten kinetics and substrate specificity characterization\",\n      \"pmids\": [\"21952246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PTTG-binding factor (PBF/PTTG1IP) physically binds MCT8 in vitro (co-immunoprecipitation/pulldown), shifts MCT8 subcellular localization away from the plasma membrane, and reduces MCT8 surface expression; PBF overexpression in mouse thyroid in vivo causes enhanced thyroidal TH accumulation and reduced TH secretion, phenocopying Mct8 knockout.\",\n      \"method\": \"Co-IP/pulldown, cell surface biotinylation assay, immunolocalization in PBF-transgenic mice, thyroid TH accumulation assay\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal interaction validated in vitro and confirmed by in vivo phenocopy in transgenic mice\",\n      \"pmids\": [\"22535767\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Arg445 (TM8) and Asp498 (TM10) of MCT8 are critical for thyroid hormone transport; mutations altering the charge at either position nearly abolish TH uptake without affecting protein expression, stability, or localization; charge-exchange double mutant (R445D+D498R) partially restores T4 uptake, indicating a functionally important charge pair between these residues.\",\n      \"method\": \"Site-directed mutagenesis, T3/T4 uptake assay, Western blotting, confocal microscopy in transfected cells\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis with charge-swap rescue experiment\",\n      \"pmids\": [\"24265446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"His192, located at the border of TM1 and ECL1, is critical for TH uptake: DEPC modification of His residues inhibits T3/T4 uptake (but not efflux), and this inhibition is blocked by pre-incubation with substrate; H192A mutation reduces TH uptake and abolishes DEPC sensitivity, placing His192 near the substrate recognition site.\",\n      \"method\": \"Chemical modification with DEPC, site-directed mutagenesis (H192A, H260A, H450A), T3/T4 uptake assay in transfected cells\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — chemical modification plus mutagenesis with substrate-protection control\",\n      \"pmids\": [\"23610131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"His192 and His415, together with Arg301, form a substrate recognition motif within the MCT8 transport channel; mutations at His192, His415, and Arg301 significantly alter substrate transport kinetics; molecular modeling places T3 between His415 and Arg301 analogous to the His-Arg clamp in the T3 receptor.\",\n      \"method\": \"Site-directed mutagenesis, T3 transport kinetics in MDCK-1 cells and Xenopus oocytes, molecular modeling\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis in two independent expression systems plus structural modeling\",\n      \"pmids\": [\"23592749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MCT8 mutations can be classified into two mechanistic groups: those causing partial or complete loss of transport activity while retaining plasma membrane localization (G221R, P321L, D453V, P537L), and those that mainly disrupt protein expression and trafficking causing ER retention (insV236, G282C, G558D).\",\n      \"method\": \"Live-cell imaging of MCT8-CFP fusion constructs in Flp-in 293 cells, T3/T4 uptake assay in multiple cell types, FRAP analysis\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — live-cell imaging combined with functional transport assays in multiple cell models\",\n      \"pmids\": [\"23550058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Mct10 (Slc16a10) facilitates thyroid hormone efflux from liver and kidney, contributing to the elevated serum T4 phenotype of Mct8-deficient mice; Mct10/Mct8 double knockout partially restores serum T4 levels compared with Mct8 single KO, demonstrating that Mct10 contributes to TH efflux from peripheral tissues in vivo.\",\n      \"method\": \"Mct10 KO and Mct8/Mct10 double KO mouse generation; serum TH measurements, tissue TH content analysis\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in vivo using double KO mice with direct TH measurements\",\n      \"pmids\": [\"24248460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Combined deficiency of MCT8 and OATP1C1 in mice strongly reduces brain uptake of both T3 and T4, causing cerebral hypothyroidism, delayed cerebellar development, reduced myelination, and compromised differentiation of GABAergic interneurons; single Mct8 KO mice do not show these neurological phenotypes because residual T4 entry via OATP1C1 compensates.\",\n      \"method\": \"Mct8/Oatp1c1 double KO mouse generation; brain TH content, deiodinase activity, TH target gene expression, histological and behavioral analysis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with double KO plus multiple mechanistic readouts; landmark study\",\n      \"pmids\": [\"24691440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Triiodothyroacetic acid (TRIAC/TA3) is not significantly transported by MCT8; it bypasses MCT8 in neuronal and oligodendrocyte cell lines and in patient fibroblasts, and can replace T3 to promote neural differentiation in cerebellum and cerebral cortex of MCT8-deficient mice.\",\n      \"method\": \"Radiolabeled substrate uptake in SH-SY5Y and MO3.13 cells and patient fibroblasts; TRIAC transport assay in MCT8-transfected cells; in vivo treatment of Pax8-KO and Mct8/Oatp1c1-DKO mice with assessment of TH-dependent gene expression and cerebellar/cortical development\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro transport assays in multiple cell types plus in vivo rescue experiment\",\n      \"pmids\": [\"25389909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Retinoic acid (RA), acting through retinoic acid receptor (RAR) binding to a consensus RA-response element 6.6 kb upstream of the Mct8 coding region, transcriptionally induces Mct8 expression >300-fold in F9 cells, increasing T3 and T4 uptake; this was abolished by a selective MCT8 inhibitor.\",\n      \"method\": \"Promoter-reporter assay, chromatin immunoprecipitation (RAR/RXR binding), T3/T4 uptake assay, pharmacological inhibition in F9 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP plus functional promoter assay plus direct transport measurement\",\n      \"pmids\": [\"20573951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Silychristin (a flavonolignan from milk thistle) inhibits MCT8-mediated T3 uptake with an IC50 of ~100 nM, at least 1 order of magnitude below other known MCT8 inhibitors, and shows specificity for MCT8 over MCT10 in overexpressing cells and endogenous Mct8 in primary murine astrocytes.\",\n      \"method\": \"Non-radioactive T3 uptake assay in MCT8-overexpressing MDCK1 cells and primary murine astrocytes; IC50 determination; MCT10-specificity control\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — quantitative in vitro inhibitor characterization with specificity controls in primary cells\",\n      \"pmids\": [\"26910310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"AAV9-mediated delivery of human MCT8 to brain barriers via intravenous (but not intracerebroventricular) injection in Mct8 KO mice increases brain T3 content and expression of T3-responsive genes (Hairless), demonstrating that MCT8 at brain barriers (including choroid plexus) is the critical site for T3 entry into the brain.\",\n      \"method\": \"IV and ICV AAV9 injection in Mct8 KO mice; brain T3 content measurement, Hairless gene expression, MCT8 protein localization by immunohistochemistry\",\n      \"journal\": \"Thyroid\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo gene delivery with functional readouts demonstrating route-specific mechanism\",\n      \"pmids\": [\"27432638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Chemical chaperone sodium phenylbutyrate (NaPB) rescues protein expression and transport function of several destabilized MCT8 mutants (S194F, S290F, L434W, R445C, L492P, L568P, delF501) in a dose-dependent manner; kinetic analysis shows these mutants have near-normal substrate affinity (Km for T3), indicating destabilization rather than active-site disruption as the primary defect.\",\n      \"method\": \"NaPB treatment of MDCK cells stably expressing MCT8 mutants; T3 transport assay, protein expression analysis, kinetic analysis\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — pharmacological rescue with kinetic characterization across multiple mutants\",\n      \"pmids\": [\"27977298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MCT8 and OATP1C1 are expressed in activated skeletal muscle satellite cells (SCs) and act as gatekeepers of TH entry; Mct8/Oatp1c1 double KO mice show strongly reduced SC differentiation and impaired skeletal muscle regeneration, phenocopied by SC-specific conditional double KO.\",\n      \"method\": \"Conditional and global double KO mice; SC isolation; tissue TH content; TH-regulated gene expression; muscle regeneration assay\",\n      \"journal\": \"Stem cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific conditional KO with defined regeneration phenotype\",\n      \"pmids\": [\"29706500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In mct8-deficient zebrafish, MCT8 is required for oligodendrocyte progenitor cell (OPC) differentiation into mature oligodendrocytes; mosaic expression of Mct8-tagRFP specifically in blood-brain barrier endothelial cells completely rescued CNS hypomyelination, demonstrating that MCT8 at the BBB is sufficient to restore myelination.\",\n      \"method\": \"mct8-/- zebrafish model; quantification of OPC and oligodendrocyte markers; live imaging of glial cells; BBB-targeted transgenic rescue with Mct8-tagRFP\",\n      \"journal\": \"Disease models & mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic rescue with cell-type-specific transgene identifying BBB as critical site\",\n      \"pmids\": [\"27664134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MCT8 deficiency in Purkinje cell precursors (via RNAi electroporation in chicken embryo) causes cell-autonomous defects: downregulation of TH-responsive gene RORα and Purkinje cell marker LHX1/5, reduced dendritic complexity; and non-autonomous effects on granule cell precursor proliferation and radial migration.\",\n      \"method\": \"MCT8-RNAi electroporation into chicken cerebellar anlage; immunostaining for differentiation markers; TRIAC rescue experiment\",\n      \"journal\": \"The Journal of endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific KD with cell-autonomous and non-autonomous phenotypic readouts and partial rescue\",\n      \"pmids\": [\"27879339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Human, mouse, and zebrafish MCT8 orthologues all transport T3, T4, rT3, and 3,3'-T2 by facilitated diffusion; zebrafish Mct8 has 1.5–4-fold higher initial uptake rates and 3–50-fold lower IC50 values for substrates than human or mouse MCT8, with different substrate preference; His192 in human MCT8, replaced by Gln in zebrafish, does not underlie these kinetic differences.\",\n      \"method\": \"Comparative transport assays in transiently transfected COS-1 and JEG-3 cells; surface biotinylation; immunoblotting; structural modeling; H192Q mutagenesis\",\n      \"journal\": \"Thyroid\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic comparative biochemistry with mutagenesis across three orthologues\",\n      \"pmids\": [\"31436139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Both MCT8 and OATP1C1 are expressed in adult mouse subventricular zone neural stem cells (NSCs); Mct8/Oatp1c1 double KO severely impairs NSC proliferation and neuronal fate determination but not oligodendrocyte progenitor generation, identifying TH transport as a regulator of NSC function and glial-neuron cell fate in the adult brain.\",\n      \"method\": \"Immunohistochemical localization of MCT8/OATP1C1 in SVZ; analysis of Mct8/Oatp1c1 DKO mice for NSC proliferation (BrdU), fate markers, and progenitor numbers\",\n      \"journal\": \"Stem cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization plus genetic KO with cell-type-specific fate phenotype\",\n      \"pmids\": [\"33450189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MCT8 in osteoblast and osteoclast progenitors mediates T3 uptake in a cell-intrinsic manner; conditional Mct8 KO in osteoprogenitors increases trabecular bone volume and alters osteoblast/osteoclast numbers independently of systemic T3 elevation.\",\n      \"method\": \"Conditional Mct8 KO mouse lines targeting osteoclast precursors, osteoprogenitors, and mature osteoblasts/osteocytes; bone microarchitecture, turnover, ex vivo T3 uptake in bone marrow-derived cells\",\n      \"journal\": \"Thyroid\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific conditional KO with direct T3 uptake measurement ex vivo\",\n      \"pmids\": [\"31910109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MCT8-deficient human cerebral organoids (from patient iPSCs) show impaired T3 transport into developing neural cells (assessed by deiodinase-3-mediated T3 catabolism assay), smaller neural rosettes with thinner cortical units, reduced cortex development gene expression, and reduced T3-inducibility of TH-regulated genes; TH analogs DITPA and TRIAC bypass MCT8 and restore normal TH-responsive gene induction.\",\n      \"method\": \"Human iPSC-derived cerebral organoids from MCT8-deficient patients; D3-mediated T3 catabolism as transport proxy; gene expression analysis; TH analog rescue experiments\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — human patient-derived organoid model with functional transport assay and pharmacological rescue\",\n      \"pmids\": [\"38376950\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MCT8 mediates TH transport and is required for TH-dependent OPC maturation in a cell-autonomous manner; MCT8-deficient iPSC-derived OPCs transplanted into a hypothyroid triple KO mouse (mct8-/-; oatp1c1-/-; rag2-/-) fail to mature into oligodendrocytes, demonstrating that functional TH transport across brain barriers is also required for in vivo oligodendrocyte maturation.\",\n      \"method\": \"iPSC differentiation to OPCs; transplantation into shiverer and hypothyroid triple KO mice; behavioral and myelination assessment\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell transplantation into defined in vivo environment separating cell-autonomous from systemic TH effects\",\n      \"pmids\": [\"33956384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MCT8 deficiency (in Mct8/Dio2 KO mice and in human AHDS brain tissue) causes neurovascular unit disruption and blood-brain barrier leakage, including increased transcytosis, IgG extravasation, and reduced brain vessel density, identifying BBB structural integrity as an additional MCT8-dependent mechanism.\",\n      \"method\": \"Transmission electron microscopy of BBB; non-permeable dye (sodium fluorescein, Evans Blue) infiltration assays; IgG immunohistochemistry; MR angiography; angiogenesis gene expression by qRT-PCR in Mct8/Dio2KO mice and human AHDS brain sections\",\n      \"journal\": \"Fluids and barriers of the CNS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in mouse model and human tissue\",\n      \"pmids\": [\"37924081\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SLC16A2/MCT8 is a twelve-transmembrane-domain facilitated transporter that mediates bidirectional, Na+-independent cellular uptake and efflux of thyroid hormones (predominantly T3 and T4), operating at the blood-brain barrier endothelium, neurons, oligodendrocyte progenitors, and other cell types; substrate recognition requires His192, His415, Arg301, Arg445, and Asp498 within the transmembrane channel; its trafficking to the plasma membrane is regulated by interacting proteins (including PBF) and is transcriptionally induced by retinoic acid via a RAR-binding element; inactivating mutations cause loss of function through reduced protein stability/trafficking or impaired substrate binding, leading to brain thyroid hormone deficiency and peripheral thyrotoxicosis (Allan-Herndon-Dudley syndrome), with BBB-targeted MCT8 delivery being sufficient to restore brain T3 levels and neurological function.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SLC16A2 (MCT8) is a twelve-transmembrane-domain facilitated transporter that mediates bidirectional, Na⁺-independent cellular uptake and efflux of thyroid hormones — principally T3 and T4, but also rT3 and 3,3′-T2 — and is the dominant thyroid hormone transporter at the blood–brain barrier, in neurons, oligodendrocyte progenitors, and skeletal muscle satellite cells [PMID:15889350, PMID:18687783, PMID:19641107, PMID:27664134, PMID:29706500]. Substrate recognition within the transport channel depends on a His192–His415–Arg301 clamp and a functionally paired Arg445–Asp498 charge relay, while loss-of-function mutations impair transport through three mechanisms: reduced protein stability, defective trafficking to the plasma membrane, or diminished substrate affinity [PMID:23592749, PMID:24265446, PMID:18187543, PMID:23550058]. At the blood–brain barrier, MCT8 is the rate-limiting gateway for T3 entry; its absence causes brain thyroid hormone deficiency with impaired myelination, Purkinje cell differentiation, neural stem cell proliferation, and neurovascular integrity, while peripheral tissues exhibit thyrotoxicosis — the hallmark of Allan–Herndon–Dudley syndrome [PMID:24691440, PMID:37924081, PMID:15889350, PMID:38376950]. The thyroid hormone analogues TRIAC and DITPA bypass MCT8 to reach neural cells, providing a pharmacological rationale for treatment of MCT8-deficient patients [PMID:25389909, PMID:38376950].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"The initial cloning of SLC16A2 (XPCT) established it as a twelve-transmembrane-domain protein with transporter-family topology, providing the structural framework for subsequent functional characterization.\",\n      \"evidence\": \"Positional cloning with hydropathy-based structural prediction from the X chromosome\",\n      \"pmids\": [\"7981683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No transport substrate identified\", \"Single study without functional assay\", \"Predicted topology not experimentally validated\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identification of inactivating MCT8 mutations in families with Allan–Herndon–Dudley syndrome, together with in vitro transport assays, established MCT8 as a specific T3 transporter whose loss causes elevated serum T3 and reduced T4, linking the gene to a Mendelian neurological disorder.\",\n      \"evidence\": \"Mutation analysis in six AHDS families; ¹²⁵I-T3 uptake assays and immunolocalization of wild-type and mutant MCT8 in transfected cells\",\n      \"pmids\": [\"15889350\", \"16131597\", \"15980113\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of neurological damage not yet resolved\", \"T4 transport by MCT8 not yet characterized\", \"In vivo tissue-specific requirements unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Systematic characterization of patient-derived mutations revealed three distinct loss-of-function mechanisms — reduced expression, impaired trafficking, and reduced substrate affinity — and showed that MCT8 localizes to blood–brain barrier endothelium (luminal and abluminal) and choroid plexus apically, positioning it as the brain's thyroid hormone gatekeeper.\",\n      \"evidence\": \"Affinity labeling, Western blot, immunocytochemistry of mutants in JEG3/COS1 cells; protein immunolocalization in human/mouse/rat brain microvasculature and choroid plexus\",\n      \"pmids\": [\"18187543\", \"18687783\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why human neurons are more vulnerable than mouse neurons not yet explained\", \"Structural basis of substrate translocation unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Transport assays in primary neurons and patient fibroblasts demonstrated that MCT8 mediates both T3 uptake and efflux, that LAT2 provides functional compensation in mouse but not human neurons, and that trafficking and function of MCT8 mutants are cell-type dependent.\",\n      \"evidence\": \"Primary cortical neuron uptake assays with pharmacological dissection; bidirectional transport in patient fibroblasts; surface biotinylation in JEG1 vs MDCK1 cells\",\n      \"pmids\": [\"19641107\", \"18636565\", \"19648159\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of cell-type-specific trafficking cofactors unknown\", \"In vivo significance of bidirectional transport not tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Discovery that retinoic acid transcriptionally induces MCT8 expression >300-fold through a RAR/RXR-binding element upstream of the gene established a transcriptional regulatory axis for MCT8.\",\n      \"evidence\": \"ChIP for RAR/RXR binding, promoter-reporter assay, T3/T4 uptake after RA treatment in F9 cells\",\n      \"pmids\": [\"20573951\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological relevance during brain development not tested in vivo\", \"Other transcriptional regulators not mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Site-directed mutagenesis and chemical modification identified a substrate recognition mechanism comprising His192, His415, Arg301, Arg445, and Asp498 within the transmembrane channel, with a His–Arg clamp analogous to the thyroid hormone receptor and a functionally essential Arg445–Asp498 charge pair.\",\n      \"evidence\": \"DEPC modification with substrate protection; charge-swap double mutants; transport kinetics in MDCK1 cells and Xenopus oocytes; homology modeling\",\n      \"pmids\": [\"23610131\", \"23592749\", \"24265446\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution experimental structure\", \"Conformational cycle (inward-open to outward-open) not characterized\", \"Residues governing T3 vs T4 selectivity not identified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identification of PTTG1IP (PBF) as a physical interactor that redirects MCT8 away from the plasma membrane provided the first named protein partner that regulates MCT8 surface availability.\",\n      \"evidence\": \"Co-immunoprecipitation/pulldown; surface biotinylation; PBF-transgenic mouse thyroid phenocopy of Mct8 KO\",\n      \"pmids\": [\"22535767\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding interface not mapped\", \"Whether PBF regulates MCT8 at the BBB unknown\", \"Other trafficking regulators not identified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"The Mct8/Oatp1c1 double-knockout mouse established that combined loss of both brain thyroid hormone transporters is required to recapitulate human AHDS neuropathology — including cerebellar delay, hypomyelination, and GABAergic interneuron defects — explaining why single Mct8 KO mice lack a brain phenotype.\",\n      \"evidence\": \"DKO mouse generation; brain TH content, deiodinase activity, histology, behavioral testing\",\n      \"pmids\": [\"24691440\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of individual cell types (neuron vs glia vs endothelium) not dissected\", \"Postnatal rescue window not defined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"BBB-targeted MCT8 re-expression (by AAV9 IV injection in mice and BBB-endothelial transgene in zebrafish) was sufficient to restore brain T3 content and rescue hypomyelination, proving that MCT8 at the blood–brain barrier is the critical site for brain thyroid hormone supply; separately, chemical chaperone NaPB rescued destabilized MCT8 mutants, and silychristin was identified as a nanomolar-potency MCT8-specific inhibitor.\",\n      \"evidence\": \"AAV9-MCT8 IV/ICV injection in Mct8 KO mice; BBB-targeted Mct8-tagRFP transgenic rescue in mct8⁻/⁻ zebrafish; NaPB dose–response with kinetic analysis in MDCK cells; silychristin IC₅₀ determination\",\n      \"pmids\": [\"27432638\", \"27664134\", \"27977298\", \"26910310\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Long-term neurological rescue not assessed\", \"NaPB efficacy in vivo not demonstrated\", \"Silychristin mechanism of inhibition not defined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"TRIAC was shown to bypass MCT8, entering neurons and OPCs via alternative transporters and restoring TH-dependent differentiation in MCT8-deficient models, providing a pharmacological bypass strategy.\",\n      \"evidence\": \"Radiolabeled transport assays in MCT8-deficient cells; in vivo TRIAC treatment of Mct8/Oatp1c1-DKO mice; RNAi of MCT8 in chicken cerebellum with TRIAC rescue\",\n      \"pmids\": [\"25389909\", \"27879339\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"TRIAC efficacy in human clinical trials not yet fully evaluated\", \"Alternative transporter identity for TRIAC not definitively established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Cell-type-specific conditional knockouts extended MCT8's functional role beyond neurons and glia to adult neural stem cells and bone cells, showing that MCT8-mediated T3 uptake cell-autonomously controls NSC proliferation/neuronal fate and osteoblast-osteoclast homeostasis.\",\n      \"evidence\": \"Mct8/Oatp1c1 DKO SVZ analysis with BrdU and fate markers; conditional Mct8 KO in osteoprogenitors with bone microarchitecture and ex vivo T3 uptake\",\n      \"pmids\": [\"33450189\", \"31910109\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether skeletal phenotype contributes to AHDS morbidity unknown\", \"Signaling pathways downstream of T3 in NSCs not mapped\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"MCT8 deficiency was found to compromise blood–brain barrier structural integrity itself — causing increased transcytosis, IgG leakage, and reduced vessel density — revealing a neurovascular dimension of AHDS pathology beyond simple T3 deprivation.\",\n      \"evidence\": \"TEM of BBB, sodium fluorescein/Evans Blue infiltration, IgG immunohistochemistry, MR angiography in Mct8/Dio2 KO mice and human AHDS brain sections\",\n      \"pmids\": [\"37924081\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether BBB leakage is a direct consequence of local T3 deficiency or an independent MCT8 function is unclear\", \"Reversibility of BBB damage not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Human iPSC-derived cerebral organoids from AHDS patients confirmed that MCT8 deficiency impairs T3 transport into developing neural tissue and reduces cortical development, and validated TRIAC and DITPA as compounds that restore TH-responsive gene expression independently of MCT8.\",\n      \"evidence\": \"Patient iPSC-derived cerebral organoids; D3-mediated T3 catabolism transport assay; gene expression profiling; TH analog rescue\",\n      \"pmids\": [\"38376950\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Long-term cortical maturation in organoids not assessed\", \"Whether early prenatal treatment could prevent human AHDS neuropathology remains unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the high-resolution structure of MCT8, the conformational mechanism of substrate translocation, the identity of cell-type-specific trafficking cofactors that modulate MCT8 surface expression, and the therapeutic window for brain-targeted MCT8 gene therapy or TH analog treatment in AHDS patients.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No experimental three-dimensional structure solved\", \"Conformational cycle during transport not characterized\", \"Optimal postnatal therapeutic window for neurological rescue not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [1, 2, 3, 4, 7, 10, 26]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 4, 5, 8, 11, 15]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [1, 3, 4, 7, 10, 26]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [17, 24, 25, 27, 29]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 4, 15, 29, 31]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PTTG1IP\",\n      \"SLCO1C1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}