{"gene":"TMEM98","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2018,"finding":"TMEM98, an ER-associated transmembrane protein, physically binds to the C-terminal domain of MYRF and inhibits MYRF self-cleavage, thereby blocking N-fragment nuclear translocation and downstream activation of myelin gene expression. Forced expression of TMEM98 in embryonic chicken spinal cord suppresses OL differentiation and MYRF-induced ectopic myelin gene expression.","method":"Co-immunoprecipitation (binding to MYRF C-terminal), overexpression in embryonic chicken spinal cord, Western blot for self-cleavage products and nuclear translocation","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal protein interaction demonstrated, functional inhibition of self-cleavage shown biochemically, in vivo gain-of-function confirmed the phenotype; replicated by independent lab (PMID:32236127)","pmids":["30249802"],"is_preprint":false},{"year":2020,"finding":"TMEM98 inhibits the autoproteolytic self-cleavage of MYRF in the retinal pigment epithelium (RPE). In RPE-specific Tmem98 knockout mice, MYRF is ectopically activated and abnormally localised to nuclei, resulting in greatly enlarged, fragile eyes with thin retinas, compressed choroid and thin sclera. MYRF was identified as a TMEM98 interacting partner by proximity labelling (BioID).","method":"Conditional knockout (RPE-specific Cre), proximity labelling (BioID) to identify interacting proteins, immunofluorescence for MYRF nuclear localisation, ocular phenotype characterisation","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean conditional KO with defined cellular phenotype, proximity labelling interaction confirmed, mechanistic link to MYRF self-cleavage validated; independent replication of MYRF interaction (PMID:30249802)","pmids":["32236127"],"is_preprint":false},{"year":2019,"finding":"Missense mutations in mouse Tmem98 (I135T causing the Rwhs allele; A193P and H196P modelling human nanophthalmos mutations) cause localised disruption of retinal laminar structure with accumulation of disorganised outer segment material and macrophage infiltration into retinal folds, demonstrating that these mutations are hypomorphic/dominant-negative alleles affecting retinal integrity without causing small eyes in mice.","method":"Genetic mapping and sequencing to identify Rwhs mutation, CRISPR-Cas9 to introduce human nanophthalmos mutations in mouse, indirect ophthalmoscopy, histology, immunohistochemistry, electron microscopy, electroretinography","journal":"Investigative ophthalmology & visual science","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal methods (genetics, CRISPR knock-in, histology, EM, ERG) in a single rigorous study characterising allele-specific structural consequences","pmids":["31266059"],"is_preprint":false},{"year":2020,"finding":"TMEM98 is an interaction partner and negative regulator of the GSK3-binding protein FRAT2; TMEM98 reduces FRAT2 protein levels and consequently inhibits FRAT2-mediated induction of β-catenin/TCF (Wnt) signalling. TMEM98 is recycled between the plasma membrane and the Golgi.","method":"Co-immunoprecipitation to identify FRAT2 interaction, luciferase β-catenin/TCF reporter assay, Western blot for FRAT2 protein levels, live-cell imaging/immunofluorescence for intracellular trafficking (plasma membrane ↔ Golgi recycling)","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP interaction, functional reporter assay, and localisation data from a single lab with two orthogonal functional methods","pmids":["31961879"],"is_preprint":false},{"year":2020,"finding":"TMEM98 knockdown (siRNA) in vascular smooth muscle cells (VSMCs) inhibits proliferation and migration by suppressing the AKT/GSK3β/Cyclin D1 signalling pathway; in endothelial cells (ECs), TMEM98 knockdown inhibits ICAM-1/VCAM-1 expression and monocyte adhesion. TMEM98 and PDGF-BB form a positive feedback loop in ECs and VSMCs.","method":"siRNA knockdown, Western blot for p-AKT, p-GSK3β, Cyclin D1, ICAM-1, VCAM-1, migration and proliferation assays, AKT agonist rescue experiment","journal":"Canadian journal of physiology and pharmacology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — siRNA knockdown with pathway marker readout and partial rescue, replicated across two related papers from same group (PMID:29152140, PMID:32893666)","pmids":["32893666","29152140"],"is_preprint":false},{"year":2020,"finding":"TMEM98 mRNA (not the protein) directly binds NF90 protein through an 8-nucleotide motif in the last exon, upregulates NF90 levels, and thereby promotes gastric cancer cell proliferation and invasion. NF90 in turn stabilises TMEM98 mRNA. A mutated last-exon motif abolishes TMEM98 mRNA binding to NF90 and the downstream proliferative effect.","method":"RNA-binding protein immunoprecipitation (RIP), RNA pull-down with wild-type and binding-site-mutated biotinylated TMEM98 mRNA transcripts, siRNA knockdown, overexpression of last-exon WT vs. mutant constructs","journal":"Cell biology international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP and RNA pulldown with mutagenesis establish the direct mRNA–protein interaction from a single lab; NOTE: this finding concerns the mRNA acting as a regulatory RNA, not the canonical TMEM98 protein per se","pmids":["32379372"],"is_preprint":false},{"year":2015,"finding":"siRNA-mediated knockdown of TMEM98 in lung cancer cells (A549, H460) inhibits proliferation, invasion and migration, accompanied by reduced protein levels of MMP-2, MMP-9, RhoC and MTA1.","method":"siRNA knockdown, CCK8 proliferation assay, invasion/migration assay, Western blot for MMP-2, MMP-9, RhoC, MTA1","journal":"International journal of clinical and experimental pathology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single knockdown approach with downstream marker readout and no pathway rescue or mechanistic follow-up","pmids":["26884835"],"is_preprint":false},{"year":2018,"finding":"miR-219-5p directly targets the 3'-UTR of TMEM98 mRNA to downregulate TMEM98 protein expression; overexpression of TMEM98 reverses hypoxia-induced inhibition of keratinocyte proliferation, migration and inflammatory cytokine production.","method":"miRNA-target reporter assay (3'-UTR binding), overexpression rescue assay in hypoxia-treated keratinocytes, Western blot","journal":"European review for medical and pharmacological sciences","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited mechanistic depth beyond miRNA–UTR targeting and phenotypic rescue","pmids":["30338788"],"is_preprint":false},{"year":2021,"finding":"Protein homology modelling with in vitro confirmation identified a TMEM98 structure comprising antiparallel α-helix bundles (α4, α5/6, α7, α8) with two transmembrane domains in α1 and α7. The nanophthalmos-associated missense mutations Ala193Pro, His196Pro and Arg201Pro all reside in the charge-polarised helix α8 (residues 183–210), indicating that structural integrity of this C-terminal helical region is essential for TMEM98 function.","method":"Protein homology modelling, in vitro confirmation of transmembrane domain topology","journal":"Experimental eye research","confidence":"Low","confidence_rationale":"Tier 4 / Weak — homology model with limited in vitro confirmation; no mutagenesis or structure validation beyond topology; single study","pmids":["33596443"],"is_preprint":false}],"current_model":"TMEM98 is an ER/membrane-associated transmembrane protein that physically binds the C-terminal domain of the transcription factor MYRF and inhibits its autoproteolytic self-cleavage, thereby preventing nuclear translocation of the MYRF N-fragment and downstream activation of target genes (including myelin genes in oligodendrocytes and eye-size determinants in the RPE); loss of TMEM98 in the RPE leads to ectopic MYRF nuclear activity and abnormally enlarged eyes, while gain of TMEM98 suppresses oligodendrocyte differentiation. Additionally, TMEM98 negatively regulates Wnt/β-catenin signalling by reducing levels of the GSK3-binding protein FRAT2, traffics between the plasma membrane and the Golgi, and modulates AKT/GSK3β/Cyclin D1 signalling in vascular cells."},"narrative":{"mechanistic_narrative":"TMEM98 is a membrane-associated transmembrane protein whose best-characterized role is the negative regulation of the membrane-bound transcription factor MYRF, acting across both myelinating and ocular contexts [PMID:30249802, PMID:32236127]. TMEM98 physically binds the C-terminal domain of MYRF and inhibits MYRF autoproteolytic self-cleavage, thereby preventing nuclear translocation of the activating MYRF N-fragment and downstream target-gene induction; forced TMEM98 expression suppresses oligodendrocyte differentiation and MYRF-driven ectopic myelin gene expression [PMID:30249802]. In the retinal pigment epithelium, RPE-specific loss of Tmem98 leads to ectopic nuclear MYRF and grossly enlarged, fragile eyes, establishing TMEM98 as a brake on MYRF activity in eye-size determination [PMID:32236127]. Disease-relevant missense mutations modelling human nanophthalmos act as hypomorphic/dominant-negative alleles that disrupt retinal laminar integrity, and structural modelling localizes these mutations to a C-terminal charge-polarized helix (α8) required for function [PMID:31266059, PMID:33596443]. Beyond the MYRF axis, TMEM98 binds and destabilizes the GSK3-binding protein FRAT2 to dampen β-catenin/TCF (Wnt) signalling and recycles between the plasma membrane and Golgi [PMID:31961879], and modulates AKT/GSK3β/Cyclin D1 signalling in vascular cells [PMID:32893666, PMID:29152140].","teleology":[{"year":2018,"claim":"Established that TMEM98 is not merely a structural membrane protein but a direct biochemical regulator of MYRF, answering how oligodendrocyte differentiation might be held in check.","evidence":"Co-IP showing binding to the MYRF C-terminal domain plus overexpression in embryonic chicken spinal cord with Western blot for self-cleavage products and nuclear translocation","pmids":["30249802"],"confidence":"High","gaps":["Stoichiometry and structural basis of the TMEM98–MYRF interaction not resolved","Whether inhibition occurs at the membrane prior to cleavage versus by sequestration not distinguished"]},{"year":2019,"claim":"Defined the in vivo consequences of TMEM98 missense mutations, showing they are hypomorphic/dominant-negative alleles affecting retinal integrity rather than producing the small-eye phenotype seen in human nanophthalmos.","evidence":"Genetic mapping of the Rwhs allele and CRISPR knock-in of human nanophthalmos mutations in mouse, with histology, EM and ERG","pmids":["31266059"],"confidence":"High","gaps":["Molecular mechanism linking the mutations to MYRF dysregulation not directly demonstrated in this study","Species difference (no small eyes in mice vs. human nanophthalmos) unexplained"]},{"year":2020,"claim":"Demonstrated the physiological MYRF-inhibitory role in vivo through tissue-specific loss of function, answering whether TMEM98 restrains MYRF activity in a native epithelium.","evidence":"RPE-specific conditional knockout with BioID proximity labelling, immunofluorescence for MYRF nuclear localization and ocular phenotyping","pmids":["32236127"],"confidence":"High","gaps":["Identity of MYRF target genes driving the enlarged-eye phenotype not defined","How loss of MYRF restraint translates to scleral/choroidal thinning mechanistically unresolved"]},{"year":2020,"claim":"Extended TMEM98 function beyond MYRF by identifying a role in Wnt pathway regulation and characterizing its trafficking itinerary.","evidence":"Co-IP for FRAT2 interaction, β-catenin/TCF luciferase reporter, Western blot for FRAT2 levels, and live-cell imaging of plasma membrane–Golgi recycling","pmids":["31961879"],"confidence":"Medium","gaps":["Mechanism by which TMEM98 lowers FRAT2 protein levels (degradation vs. synthesis) not established","Single-lab finding without reciprocal in vivo validation","Relationship between Wnt regulation and the MYRF axis unknown"]},{"year":2020,"claim":"Implicated TMEM98 in vascular cell proliferation and inflammatory adhesion signalling, broadening its functional reach.","evidence":"siRNA knockdown in VSMCs and ECs with Western blot for AKT/GSK3β/Cyclin D1 and ICAM-1/VCAM-1, migration/proliferation assays and AKT agonist rescue","pmids":["32893666","29152140"],"confidence":"Medium","gaps":["Direct molecular target of TMEM98 upstream of AKT not identified","Whether the PDGF-BB feedback loop is direct or indirect unresolved"]},{"year":2020,"claim":"Revealed a protein-independent function in which TMEM98 mRNA itself acts as a regulatory RNA, a distinct mechanism from the canonical transmembrane protein.","evidence":"RIP and RNA pull-down with wild-type and motif-mutated transcripts plus knockdown/overexpression in gastric cancer cells","pmids":["32379372"],"confidence":"Medium","gaps":["Single-lab finding concerning the mRNA, not the protein; needs orthogonal confirmation","Whether mRNA-mediated NF90 regulation operates in non-cancer tissues unknown"]},{"year":2021,"claim":"Provided a structural framework localizing nanophthalmos mutations to a specific C-terminal helix, rationalizing why these residues are functionally critical.","evidence":"Protein homology modelling with in vitro confirmation of transmembrane topology","pmids":["33596443"],"confidence":"Low","gaps":["Homology model without experimental structure determination or mutagenesis validation","Functional consequence of α8 disruption on MYRF binding not tested"]},{"year":null,"claim":"How TMEM98 mechanistically integrates its MYRF, Wnt/FRAT2, and AKT/GSK3β activities, and whether they reflect one unified biochemical action or independent functions, remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of TMEM98 in complex with any partner","Mechanism of MYRF self-cleavage inhibition at atomic resolution unknown","Whether membrane trafficking gates partner access not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,3]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,4]}],"complexes":[],"partners":["MYRF","FRAT2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y2Y6","full_name":"Transmembrane protein 98","aliases":["Protein TADA1"],"length_aa":226,"mass_kda":24.6,"function":"Functions as a negative regulator of MYRF in oligodendrocyte differentiation and myelination. Interacts with the C-terminal of MYRF inhibiting MYRF self-cleavage and N-fragment nuclear translocation. The secreted form promotes differentiation of T helper 1 cells (Th1)","subcellular_location":"Cell membrane; Secreted; Secreted, extracellular exosome; Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y2Y6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TMEM98","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TMEM98","total_profiled":1310},"omim":[{"mim_id":"615972","title":"NANOPHTHALMOS 4; NNO4","url":"https://www.omim.org/entry/615972"},{"mim_id":"615949","title":"TRANSMEMBRANE PROTEIN 98; TMEM98","url":"https://www.omim.org/entry/615949"},{"mim_id":"608329","title":"MYELIN REGULATORY FACTOR; MYRF","url":"https://www.omim.org/entry/608329"},{"mim_id":"600165","title":"NANOPHTHALMOS 1; NNO1","url":"https://www.omim.org/entry/600165"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"choroid plexus","ntpm":392.6}],"url":"https://www.proteinatlas.org/search/TMEM98"},"hgnc":{"alias_symbol":["DKFZP564K1964"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y2Y6","domains":[{"cath_id":"1.20.1410.10","chopping":"72-206","consensus_level":"high","plddt":81.7085,"start":72,"end":206},{"cath_id":"1.20.5","chopping":"1-36","consensus_level":"medium","plddt":84.8228,"start":1,"end":36}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2Y6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2Y6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2Y6-F1-predicted_aligned_error_v6.png","plddt_mean":72.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TMEM98","jax_strain_url":"https://www.jax.org/strain/search?query=TMEM98"},"sequence":{"accession":"Q9Y2Y6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y2Y6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y2Y6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2Y6"}},"corpus_meta":[{"pmid":"30249802","id":"PMC_30249802","title":"Interactive Repression of MYRF Self-Cleavage and Activity in Oligodendrocyte Differentiation by TMEM98 Protein.","date":"2018","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/30249802","citation_count":56,"is_preprint":false},{"pmid":"24852644","id":"PMC_24852644","title":"Mutation in TMEM98 in a large white kindred with autosomal dominant nanophthalmos linked to 17p12-q12.","date":"2014","source":"JAMA ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/24852644","citation_count":50,"is_preprint":false},{"pmid":"26392740","id":"PMC_26392740","title":"Novel TMEM98 mutations in pedigrees with autosomal dominant nanophthalmos.","date":"2015","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/26392740","citation_count":26,"is_preprint":false},{"pmid":"33203948","id":"PMC_33203948","title":"Novel TMEM98, MFRP, PRSS56 variants in a large United States high hyperopia and nanophthalmos cohort.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33203948","citation_count":25,"is_preprint":false},{"pmid":"32236127","id":"PMC_32236127","title":"The nanophthalmos protein TMEM98 inhibits MYRF self-cleavage and is required for eye size specification.","date":"2020","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32236127","citation_count":23,"is_preprint":false},{"pmid":"29152140","id":"PMC_29152140","title":"Inhibition of IL-8-mediated endothelial adhesion, VSMCs proliferation and migration by siRNA-TMEM98 suggests TMEM98's emerging role in atherosclerosis.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/29152140","citation_count":19,"is_preprint":false},{"pmid":"31266059","id":"PMC_31266059","title":"Missense Mutations in the Human Nanophthalmos Gene TMEM98 Cause Retinal Defects in the Mouse.","date":"2019","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/31266059","citation_count":17,"is_preprint":false},{"pmid":"26884835","id":"PMC_26884835","title":"siRNA-TMEM98 inhibits the invasion and migration of lung cancer cells.","date":"2015","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/26884835","citation_count":16,"is_preprint":false},{"pmid":"30338788","id":"PMC_30338788","title":"MicroRNA-219-5p inhibits wound healing by targeting TMEM98 in keratinocytes under normoxia and hypoxia condition.","date":"2018","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/30338788","citation_count":8,"is_preprint":false},{"pmid":"33257597","id":"PMC_33257597","title":"The microRNA miR-29c-5p inhibits cell proliferation and migration by targeting TMEM98 in head and neck carcinoma.","date":"2020","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/33257597","citation_count":6,"is_preprint":false},{"pmid":"32379372","id":"PMC_32379372","title":"TMEM98 mRNA promotes proliferation and invasion of gastric cells by directly interacting with NF90 protein.","date":"2020","source":"Cell biology international","url":"https://pubmed.ncbi.nlm.nih.gov/32379372","citation_count":5,"is_preprint":false},{"pmid":"31961879","id":"PMC_31961879","title":"TMEM98 is a negative regulator of FRAT mediated Wnt/ß-catenin signalling.","date":"2020","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/31961879","citation_count":5,"is_preprint":false},{"pmid":"32893666","id":"PMC_32893666","title":"TMEM98, a novel secretory protein, promotes endothelial cell adhesion as well as vascular smooth muscle cell proliferation and migration.","date":"2020","source":"Canadian journal of physiology and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/32893666","citation_count":5,"is_preprint":false},{"pmid":"33596443","id":"PMC_33596443","title":"A novel proline substitution (Arg201Pro) in alpha helix 8 of TMEM98 causes autosomal dominant nanophthalmos-4, closed angle glaucoma and attenuated visual acuity.","date":"2021","source":"Experimental eye research","url":"https://pubmed.ncbi.nlm.nih.gov/33596443","citation_count":3,"is_preprint":false},{"pmid":"36348534","id":"PMC_36348534","title":"[A family with nanophthalmos caused by a TMEM98 gene variant].","date":"2022","source":"[Zhonghua yan ke za zhi] Chinese journal of ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/36348534","citation_count":1,"is_preprint":false},{"pmid":"41029742","id":"PMC_41029742","title":"Transmembrane protein TMEM98 as a multifunctional regulator in cancer: from signaling pathways to translational implications.","date":"2025","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41029742","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10252,"output_tokens":2640,"usd":0.035178,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9959,"output_tokens":2859,"usd":0.060635,"stage2_stop_reason":"end_turn"},"total_usd":0.095813,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2018,\n      \"finding\": \"TMEM98, an ER-associated transmembrane protein, physically binds to the C-terminal domain of MYRF and inhibits MYRF self-cleavage, thereby blocking N-fragment nuclear translocation and downstream activation of myelin gene expression. Forced expression of TMEM98 in embryonic chicken spinal cord suppresses OL differentiation and MYRF-induced ectopic myelin gene expression.\",\n      \"method\": \"Co-immunoprecipitation (binding to MYRF C-terminal), overexpression in embryonic chicken spinal cord, Western blot for self-cleavage products and nuclear translocation\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal protein interaction demonstrated, functional inhibition of self-cleavage shown biochemically, in vivo gain-of-function confirmed the phenotype; replicated by independent lab (PMID:32236127)\",\n      \"pmids\": [\"30249802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TMEM98 inhibits the autoproteolytic self-cleavage of MYRF in the retinal pigment epithelium (RPE). In RPE-specific Tmem98 knockout mice, MYRF is ectopically activated and abnormally localised to nuclei, resulting in greatly enlarged, fragile eyes with thin retinas, compressed choroid and thin sclera. MYRF was identified as a TMEM98 interacting partner by proximity labelling (BioID).\",\n      \"method\": \"Conditional knockout (RPE-specific Cre), proximity labelling (BioID) to identify interacting proteins, immunofluorescence for MYRF nuclear localisation, ocular phenotype characterisation\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean conditional KO with defined cellular phenotype, proximity labelling interaction confirmed, mechanistic link to MYRF self-cleavage validated; independent replication of MYRF interaction (PMID:30249802)\",\n      \"pmids\": [\"32236127\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Missense mutations in mouse Tmem98 (I135T causing the Rwhs allele; A193P and H196P modelling human nanophthalmos mutations) cause localised disruption of retinal laminar structure with accumulation of disorganised outer segment material and macrophage infiltration into retinal folds, demonstrating that these mutations are hypomorphic/dominant-negative alleles affecting retinal integrity without causing small eyes in mice.\",\n      \"method\": \"Genetic mapping and sequencing to identify Rwhs mutation, CRISPR-Cas9 to introduce human nanophthalmos mutations in mouse, indirect ophthalmoscopy, histology, immunohistochemistry, electron microscopy, electroretinography\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal methods (genetics, CRISPR knock-in, histology, EM, ERG) in a single rigorous study characterising allele-specific structural consequences\",\n      \"pmids\": [\"31266059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TMEM98 is an interaction partner and negative regulator of the GSK3-binding protein FRAT2; TMEM98 reduces FRAT2 protein levels and consequently inhibits FRAT2-mediated induction of β-catenin/TCF (Wnt) signalling. TMEM98 is recycled between the plasma membrane and the Golgi.\",\n      \"method\": \"Co-immunoprecipitation to identify FRAT2 interaction, luciferase β-catenin/TCF reporter assay, Western blot for FRAT2 protein levels, live-cell imaging/immunofluorescence for intracellular trafficking (plasma membrane ↔ Golgi recycling)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP interaction, functional reporter assay, and localisation data from a single lab with two orthogonal functional methods\",\n      \"pmids\": [\"31961879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TMEM98 knockdown (siRNA) in vascular smooth muscle cells (VSMCs) inhibits proliferation and migration by suppressing the AKT/GSK3β/Cyclin D1 signalling pathway; in endothelial cells (ECs), TMEM98 knockdown inhibits ICAM-1/VCAM-1 expression and monocyte adhesion. TMEM98 and PDGF-BB form a positive feedback loop in ECs and VSMCs.\",\n      \"method\": \"siRNA knockdown, Western blot for p-AKT, p-GSK3β, Cyclin D1, ICAM-1, VCAM-1, migration and proliferation assays, AKT agonist rescue experiment\",\n      \"journal\": \"Canadian journal of physiology and pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — siRNA knockdown with pathway marker readout and partial rescue, replicated across two related papers from same group (PMID:29152140, PMID:32893666)\",\n      \"pmids\": [\"32893666\", \"29152140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TMEM98 mRNA (not the protein) directly binds NF90 protein through an 8-nucleotide motif in the last exon, upregulates NF90 levels, and thereby promotes gastric cancer cell proliferation and invasion. NF90 in turn stabilises TMEM98 mRNA. A mutated last-exon motif abolishes TMEM98 mRNA binding to NF90 and the downstream proliferative effect.\",\n      \"method\": \"RNA-binding protein immunoprecipitation (RIP), RNA pull-down with wild-type and binding-site-mutated biotinylated TMEM98 mRNA transcripts, siRNA knockdown, overexpression of last-exon WT vs. mutant constructs\",\n      \"journal\": \"Cell biology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP and RNA pulldown with mutagenesis establish the direct mRNA–protein interaction from a single lab; NOTE: this finding concerns the mRNA acting as a regulatory RNA, not the canonical TMEM98 protein per se\",\n      \"pmids\": [\"32379372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"siRNA-mediated knockdown of TMEM98 in lung cancer cells (A549, H460) inhibits proliferation, invasion and migration, accompanied by reduced protein levels of MMP-2, MMP-9, RhoC and MTA1.\",\n      \"method\": \"siRNA knockdown, CCK8 proliferation assay, invasion/migration assay, Western blot for MMP-2, MMP-9, RhoC, MTA1\",\n      \"journal\": \"International journal of clinical and experimental pathology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single knockdown approach with downstream marker readout and no pathway rescue or mechanistic follow-up\",\n      \"pmids\": [\"26884835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-219-5p directly targets the 3'-UTR of TMEM98 mRNA to downregulate TMEM98 protein expression; overexpression of TMEM98 reverses hypoxia-induced inhibition of keratinocyte proliferation, migration and inflammatory cytokine production.\",\n      \"method\": \"miRNA-target reporter assay (3'-UTR binding), overexpression rescue assay in hypoxia-treated keratinocytes, Western blot\",\n      \"journal\": \"European review for medical and pharmacological sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited mechanistic depth beyond miRNA–UTR targeting and phenotypic rescue\",\n      \"pmids\": [\"30338788\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Protein homology modelling with in vitro confirmation identified a TMEM98 structure comprising antiparallel α-helix bundles (α4, α5/6, α7, α8) with two transmembrane domains in α1 and α7. The nanophthalmos-associated missense mutations Ala193Pro, His196Pro and Arg201Pro all reside in the charge-polarised helix α8 (residues 183–210), indicating that structural integrity of this C-terminal helical region is essential for TMEM98 function.\",\n      \"method\": \"Protein homology modelling, in vitro confirmation of transmembrane domain topology\",\n      \"journal\": \"Experimental eye research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — homology model with limited in vitro confirmation; no mutagenesis or structure validation beyond topology; single study\",\n      \"pmids\": [\"33596443\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TMEM98 is an ER/membrane-associated transmembrane protein that physically binds the C-terminal domain of the transcription factor MYRF and inhibits its autoproteolytic self-cleavage, thereby preventing nuclear translocation of the MYRF N-fragment and downstream activation of target genes (including myelin genes in oligodendrocytes and eye-size determinants in the RPE); loss of TMEM98 in the RPE leads to ectopic MYRF nuclear activity and abnormally enlarged eyes, while gain of TMEM98 suppresses oligodendrocyte differentiation. Additionally, TMEM98 negatively regulates Wnt/β-catenin signalling by reducing levels of the GSK3-binding protein FRAT2, traffics between the plasma membrane and the Golgi, and modulates AKT/GSK3β/Cyclin D1 signalling in vascular cells.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TMEM98 is a membrane-associated transmembrane protein whose best-characterized role is the negative regulation of the membrane-bound transcription factor MYRF, acting across both myelinating and ocular contexts [#0, #1]. TMEM98 physically binds the C-terminal domain of MYRF and inhibits MYRF autoproteolytic self-cleavage, thereby preventing nuclear translocation of the activating MYRF N-fragment and downstream target-gene induction; forced TMEM98 expression suppresses oligodendrocyte differentiation and MYRF-driven ectopic myelin gene expression [#0]. In the retinal pigment epithelium, RPE-specific loss of Tmem98 leads to ectopic nuclear MYRF and grossly enlarged, fragile eyes, establishing TMEM98 as a brake on MYRF activity in eye-size determination [#1]. Disease-relevant missense mutations modelling human nanophthalmos act as hypomorphic/dominant-negative alleles that disrupt retinal laminar integrity, and structural modelling localizes these mutations to a C-terminal charge-polarized helix (\\u03b18) required for function [#2, #8]. Beyond the MYRF axis, TMEM98 binds and destabilizes the GSK3-binding protein FRAT2 to dampen \\u03b2-catenin/TCF (Wnt) signalling and recycles between the plasma membrane and Golgi [#3], and modulates AKT/GSK3\\u03b2/Cyclin D1 signalling in vascular cells [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"Established that TMEM98 is not merely a structural membrane protein but a direct biochemical regulator of MYRF, answering how oligodendrocyte differentiation might be held in check.\",\n      \"evidence\": \"Co-IP showing binding to the MYRF C-terminal domain plus overexpression in embryonic chicken spinal cord with Western blot for self-cleavage products and nuclear translocation\",\n      \"pmids\": [\"30249802\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Stoichiometry and structural basis of the TMEM98\\u2013MYRF interaction not resolved\",\n        \"Whether inhibition occurs at the membrane prior to cleavage versus by sequestration not distinguished\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined the in vivo consequences of TMEM98 missense mutations, showing they are hypomorphic/dominant-negative alleles affecting retinal integrity rather than producing the small-eye phenotype seen in human nanophthalmos.\",\n      \"evidence\": \"Genetic mapping of the Rwhs allele and CRISPR knock-in of human nanophthalmos mutations in mouse, with histology, EM and ERG\",\n      \"pmids\": [\"31266059\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular mechanism linking the mutations to MYRF dysregulation not directly demonstrated in this study\",\n        \"Species difference (no small eyes in mice vs. human nanophthalmos) unexplained\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated the physiological MYRF-inhibitory role in vivo through tissue-specific loss of function, answering whether TMEM98 restrains MYRF activity in a native epithelium.\",\n      \"evidence\": \"RPE-specific conditional knockout with BioID proximity labelling, immunofluorescence for MYRF nuclear localization and ocular phenotyping\",\n      \"pmids\": [\"32236127\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Identity of MYRF target genes driving the enlarged-eye phenotype not defined\",\n        \"How loss of MYRF restraint translates to scleral/choroidal thinning mechanistically unresolved\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended TMEM98 function beyond MYRF by identifying a role in Wnt pathway regulation and characterizing its trafficking itinerary.\",\n      \"evidence\": \"Co-IP for FRAT2 interaction, \\u03b2-catenin/TCF luciferase reporter, Western blot for FRAT2 levels, and live-cell imaging of plasma membrane\\u2013Golgi recycling\",\n      \"pmids\": [\"31961879\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which TMEM98 lowers FRAT2 protein levels (degradation vs. synthesis) not established\",\n        \"Single-lab finding without reciprocal in vivo validation\",\n        \"Relationship between Wnt regulation and the MYRF axis unknown\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Implicated TMEM98 in vascular cell proliferation and inflammatory adhesion signalling, broadening its functional reach.\",\n      \"evidence\": \"siRNA knockdown in VSMCs and ECs with Western blot for AKT/GSK3\\u03b2/Cyclin D1 and ICAM-1/VCAM-1, migration/proliferation assays and AKT agonist rescue\",\n      \"pmids\": [\"32893666\", \"29152140\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct molecular target of TMEM98 upstream of AKT not identified\",\n        \"Whether the PDGF-BB feedback loop is direct or indirect unresolved\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed a protein-independent function in which TMEM98 mRNA itself acts as a regulatory RNA, a distinct mechanism from the canonical transmembrane protein.\",\n      \"evidence\": \"RIP and RNA pull-down with wild-type and motif-mutated transcripts plus knockdown/overexpression in gastric cancer cells\",\n      \"pmids\": [\"32379372\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab finding concerning the mRNA, not the protein; needs orthogonal confirmation\",\n        \"Whether mRNA-mediated NF90 regulation operates in non-cancer tissues unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided a structural framework localizing nanophthalmos mutations to a specific C-terminal helix, rationalizing why these residues are functionally critical.\",\n      \"evidence\": \"Protein homology modelling with in vitro confirmation of transmembrane topology\",\n      \"pmids\": [\"33596443\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Homology model without experimental structure determination or mutagenesis validation\",\n        \"Functional consequence of \\u03b18 disruption on MYRF binding not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TMEM98 mechanistically integrates its MYRF, Wnt/FRAT2, and AKT/GSK3\\u03b2 activities, and whether they reflect one unified biochemical action or independent functions, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structure of TMEM98 in complex with any partner\",\n        \"Mechanism of MYRF self-cleavage inhibition at atomic resolution unknown\",\n        \"Whether membrane trafficking gates partner access not established\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MYRF\", \"FRAT2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}