{"gene":"NSDHL","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":2000,"finding":"NSDHL encodes a 3β-hydroxysteroid dehydrogenase functioning in the cholesterol biosynthetic pathway; loss-of-function mutations in NSDHL cause CHILD syndrome, and the protein functions upstream of EBP (delta8-delta7 sterol isomerase) in cholesterol biosynthesis.","method":"SSCA and genomic sequence analysis of NSDHL in CHILD syndrome patients; genetic epistasis with EBP (CDPX2 gene) established pathway position","journal":"American journal of medical genetics","confidence":"High","confidence_rationale":"Tier 2 — foundational mutation identification with pathway placement, replicated across multiple patients and consistent with mouse models","pmids":["10710235"],"is_preprint":false},{"year":2003,"finding":"NSDHL protein localizes to ER membranes and to the surface of lipid droplets, and trafficking through the Golgi is necessary for ER membrane localization; the dual localization was demonstrated using tagged wild-type and mutant murine Nsdhl alleles.","method":"Confocal microscopy of tagged NSDHL constructs (wild-type and mutant); Golgi trafficking disruption experiments","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — direct subcellular localization with functional consequence (Golgi trafficking required for ER localization), multiple alleles tested","pmids":["14506130"],"is_preprint":false},{"year":2003,"finding":"Mouse NSDHL protein can rescue lethality of erg26-deficient Saccharomyces cerevisiae cells (lacking the yeast ortholog), confirming NSDHL functions as a C-3 sterol dehydrogenase; hypomorphic alleles showed partial complementation while null alleles showed none.","method":"Functional complementation assay in Erg26-deficient yeast; in vivo rescue of yeast lethality","journal":"Molecular genetics and metabolism","confidence":"High","confidence_rationale":"Tier 1 — in vivo complementation assay in yeast with multiple alleles tested, directly establishes enzymatic function","pmids":["14567972"],"is_preprint":false},{"year":2005,"finding":"Nsdhl-deficient male mouse embryos die in midgestation (E10.5–13.5) with placental labyrinth defects: thinner labyrinth layer, fewer fetal vessels, and decreased proliferation of labyrinth trophoblast cells, implicating NSDHL in placental vascular development.","method":"Analysis of Nsdhl mutant mouse embryos by histology; trophoblast proliferation assays","journal":"Molecular genetics and metabolism","confidence":"High","confidence_rationale":"Tier 2 — loss-of-function with defined cellular phenotype in multiple alleles, consistent with subsequent studies","pmids":["15639195"],"is_preprint":false},{"year":2006,"finding":"NSDHL deficiency in mouse embryos disrupts Indian hedgehog (Ihh) signaling in the placenta; Ptch1-lacZ reporter expression was markedly decreased in Nsdhl mutant placentas, and Ihh-expressing cells failed to migrate into allantoic mesoderm, establishing a role for NSDHL-dependent cholesterol biosynthesis in placental hedgehog signaling.","method":"Transgenic Ptch1-lacZ reporter mouse; X-linked lacZ mosaic analysis; histology of mutant placentas","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis using reporter mouse, multiple complementary methods establishing pathway position","pmids":["17028112"],"is_preprint":false},{"year":2009,"finding":"NSDHL-deficient cells in heterozygous Bpa(1H)/+ female mice are subject to negative selection over time; clonal NSDHL-negative cells decline from ~50% to ~20% in liver and brain over the first year of life, demonstrating a cell-autonomous requirement for NSDHL in neuronal and hepatocyte survival.","method":"Immunohistochemistry for NSDHL across multiple tissue types and developmental stages in wild-type and Bpa(1H) mice","journal":"Molecular genetics and metabolism","confidence":"Medium","confidence_rationale":"Tier 3 — direct localization/cell-proportion quantification with functional inference, single lab","pmids":["19631568"],"is_preprint":false},{"year":2009,"finding":"Trophoblast-lineage expression of Nsdhl (from the maternally inherited allele) has the largest effect on placental area in Nsdhl mutant conceptuses; maternal genotype independently contributes a smaller effect on placental development, demonstrating non-cell-autonomous and imprinting-related roles for NSDHL in placentation.","method":"Transgenic rescue experiments (human NSDHL transgene rescuing male lethality); placental area measurements at E10.5 comparing maternal vs. paternal transmission","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 — transgenic rescue with quantitative phenotypic analysis, single lab","pmids":["19880419"],"is_preprint":false},{"year":2010,"finding":"Hypomorphic NSDHL mutations (p.Lys232del and p.Arg367SerfsX33) cause CK syndrome through temperature-sensitive protein instability; these mutations alter protein folding and show complementation in Erg26-deficient yeast; methylsterol accumulation (not cholesterol deficiency) is hypothesized as the pathogenic mechanism, as CSF and plasma cholesterol levels are normal in CKS patients.","method":"Yeast complementation assay; temperature-sensitive protein stability assays; sterol analysis of CSF and plasma","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1–2 — yeast complementation plus biochemical sterol analysis, multiple orthogonal methods","pmids":["21129721"],"is_preprint":false},{"year":2015,"finding":"Conditional ablation of Nsdhl in radial glia (GFAP-cre) causes defective SHH signaling in cerebellar granule cell precursors, resulting in proliferation defects that are rescued by exogenous cholesterol supplementation; methylsterol accumulation above the enzymatic block is associated with increased cell death, establishing that NSDHL-derived cholesterol is required for SHH signaling in postnatal CNS.","method":"Conditional knockout mouse (Nsdhl(tm1.1Hrm) × GFAP-cre); in vitro granule cell precursor proliferation assay; cholesterol rescue experiment; sterol level measurements","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1–2 — conditional KO with defined phenotype, in vitro rescue by cholesterol supplementation, multiple orthogonal methods","pmids":["25652406"],"is_preprint":false},{"year":2015,"finding":"FR171456 specifically inhibits NSDHL (and its yeast ortholog Erg26p) enzymatic activity; multiple ERG26 mutations confer resistance to FR171456 in growth and enzyme assays, identifying the binding site on the enzyme.","method":"Genome-wide yeast haploinsufficiency profiling; enzyme inhibition assays; resistance mutation mapping; sterol intermediate profiling in human and yeast cells","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — direct enzyme inhibition assay with resistance mutation mapping and genome-wide target identification","pmids":["26456460"],"is_preprint":false},{"year":2020,"finding":"Two X-ray crystal structures of human NSDHL were solved, revealing a coenzyme-binding site and a unique conformational change upon coenzyme binding; structure-based virtual screening identified a novel NSDHL inhibitor with suppressive activity toward EGFR trafficking, establishing that NSDHL regulates EGFR trafficking pathways.","method":"X-ray crystallography; structure-based virtual screening; biochemical inhibition assays; cell-based EGFR trafficking assays","journal":"Cellular and molecular life sciences : CMLS","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus functional biochemical and cell-based validation","pmids":["32140747"],"is_preprint":false},{"year":2021,"finding":"NSDHL promotes triple-negative breast cancer metastasis by inhibiting endosomal degradation of TGFβR2, thereby activating the TGFβ signaling pathway; this function depends on NSDHL's enzymatic activity in cholesterol biosynthesis, as the catalytically inactive Y151X mutant did not rescue migration or TGFβR2 expression; blocking upstream NSDHL metabolism with ketoconazole rescued cancer metastasis.","method":"CRISPR pooled in vivo screen; Transwell migration assay; animal experiments; NSDHL knockdown and catalytic mutant (Y151X); TGFβR2 degradation assay; ketoconazole treatment","journal":"Breast cancer research and treatment","confidence":"High","confidence_rationale":"Tier 2 — in vivo CRISPR screen, catalytic mutant validation, and pathway rescue, multiple orthogonal methods","pmids":["33864166"],"is_preprint":false},{"year":2020,"finding":"NSDHL knockdown in 3T3-L1 cells attenuates adipogenesis, reduces lipid accumulation, downregulates PPARγ expression, and decreases LXR-SREBP1 signaling pathway activity, identifying NSDHL as a regulator of adipogenic differentiation through the LXR-SREBP1 axis.","method":"NSDHL knockdown in 3T3-L1 cells; quantitative RT-PCR; Oil Red O lipid staining; LXR-SREBP1 pathway analysis","journal":"Bioscience, biotechnology, and biochemistry","confidence":"Medium","confidence_rationale":"Tier 3 — single lab KD with defined phenotype and partial pathway placement","pmids":["31985358"],"is_preprint":false},{"year":2024,"finding":"NSDHL binds to STING protein and facilitates its degradation via ubiquitination, thereby inhibiting the cGAS-STING signaling pathway and reducing IFNβ synthesis in cholangiocarcinoma cells.","method":"Co-immunoprecipitation (NSDHL-STING binding); ubiquitination assay; IFNβ measurement; NSDHL overexpression in cells","journal":"Heliyon","confidence":"Medium","confidence_rationale":"Tier 3 — single Co-IP with ubiquitination assay and functional readout, single lab","pmids":["39290276"],"is_preprint":false},{"year":2024,"finding":"NSDHL knockdown in MCF-7 tumor spheroids reduces TGF-β1 and TGF-β3 secretion, decreases Smad2/3 phosphorylation, and reduces SOX2 expression, suppressing breast cancer stem-like cell populations and tumor-initiating capacity in orthotopic xenograft models.","method":"NSDHL knockdown; tumor spheroid formation assay; RNA sequencing; flow cytometry for BCSC markers; orthotopic xenograft model; ELISA for TGF-β","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (RNA-seq, flow cytometry, in vivo xenograft), single lab","pmids":["39516821"],"is_preprint":false}],"current_model":"NSDHL is a 3β-hydroxysterol dehydrogenase/decarboxylase that removes C-4 methyl groups in post-squalene cholesterol biosynthesis, localizes to ER membranes and lipid droplet surfaces via Golgi trafficking, and—beyond its metabolic role—regulates multiple signaling pathways including SHH (by supplying cholesterol for ligand activity), TGFβ (by preventing endosomal degradation of TGFβR2), cGAS-STING (by binding and ubiquitin-mediated degradation of STING), and EGFR trafficking, with loss-of-function causing methyl sterol accumulation that drives the pathology of CHILD syndrome and CK syndrome."},"narrative":{"teleology":[{"year":2000,"claim":"Identification of NSDHL as the gene mutated in CHILD syndrome established it as a cholesterol biosynthetic enzyme acting upstream of EBP, answering the long-standing question of the molecular basis of this X-linked ichthyosis.","evidence":"SSCA and genomic sequencing of CHILD syndrome patients with epistasis analysis relative to EBP/CDPX2","pmids":["10710235"],"confidence":"High","gaps":["Precise enzymatic reaction mechanism not yet defined","Substrate specificity not characterized biochemically","Subcellular site of action unknown"]},{"year":2003,"claim":"Functional complementation of ERG26-deficient yeast by mouse NSDHL confirmed C-3 sterol dehydrogenase activity, while subcellular localization studies revealed dual ER membrane/lipid droplet targeting dependent on Golgi trafficking, establishing both enzymatic identity and cellular compartmentalization.","evidence":"Yeast rescue assays with multiple alleles; confocal microscopy of tagged NSDHL constructs with Golgi-disruption experiments","pmids":["14567972","14506130"],"confidence":"High","gaps":["No structural information on NSDHL at this stage","Mechanism of Golgi-dependent ER targeting not defined","Functional role of lipid droplet localization unclear"]},{"year":2005,"claim":"Analysis of Nsdhl-null mouse embryos revealed midgestational lethality with placental labyrinth defects, demonstrating that NSDHL is essential for trophoblast proliferation and placental vascular development in vivo.","evidence":"Histological analysis and trophoblast proliferation assays in Nsdhl mutant mouse embryos","pmids":["15639195"],"confidence":"High","gaps":["Molecular pathway linking NSDHL to trophoblast proliferation not identified","Whether cholesterol deficiency or sterol intermediate accumulation drives phenotype not resolved"]},{"year":2006,"claim":"Demonstration that NSDHL deficiency disrupts Indian hedgehog signaling in the placenta linked the cholesterol biosynthetic role to a specific developmental signaling pathway, explaining the trophoblast proliferation defect.","evidence":"Ptch1-lacZ reporter analysis in Nsdhl mutant placentas; mosaic analysis in heterozygous females","pmids":["17028112"],"confidence":"High","gaps":["Whether cholesterol supply for Hh ligand modification is the direct mechanism not proven","Cell-autonomous vs. non-cell-autonomous signaling not fully dissected"]},{"year":2009,"claim":"Longitudinal mosaic analysis in heterozygous female mice showed progressive loss of NSDHL-negative cells in brain and liver, establishing a cell-autonomous survival requirement; transgenic rescue experiments further demonstrated that trophoblast-intrinsic NSDHL expression drives the placental phenotype.","evidence":"Immunohistochemistry across developmental stages in Bpa(1H)/+ mice; human NSDHL transgene rescue with placental area measurements","pmids":["19631568","19880419"],"confidence":"Medium","gaps":["Mechanism of cell death in NSDHL-negative neurons not characterized","Contribution of imprinting vs. X-inactivation to phenotype not separated"]},{"year":2010,"claim":"Identification of CK syndrome mutations as hypomorphic, temperature-sensitive NSDHL alleles with normal cholesterol but methylsterol accumulation reframed the pathogenic mechanism from cholesterol deficiency to toxic sterol intermediate accumulation.","evidence":"Yeast complementation; temperature-sensitive protein stability assays; CSF and plasma sterol analysis in CK syndrome patients","pmids":["21129721"],"confidence":"High","gaps":["Specific toxic methylsterol species not identified","Downstream targets of methylsterol toxicity unknown","Why CKS and CHILD syndrome differ phenotypically despite same gene not fully explained"]},{"year":2015,"claim":"Conditional CNS knockout revealed that NSDHL-derived cholesterol is required for SHH signaling in cerebellar granule cell precursors, with exogenous cholesterol rescuing proliferation defects — directly linking the enzyme's metabolic product to postnatal brain development and hedgehog pathway activation.","evidence":"Conditional Nsdhl knockout (GFAP-cre); in vitro GCP proliferation assay with cholesterol rescue; sterol measurements","pmids":["25652406"],"confidence":"High","gaps":["Whether cholesterol acts via SHH ligand modification or smoothened activation not resolved","Whether methylsterol accumulation contributes independently to cell death not separated from cholesterol deficiency"]},{"year":2015,"claim":"Genome-wide haploinsufficiency profiling identified FR171456 as a direct NSDHL/Erg26p inhibitor, with resistance mutations mapping the enzyme's active site and providing the first pharmacological tool for NSDHL.","evidence":"Yeast haploinsufficiency screen; enzyme inhibition assays; resistance mutation mapping; sterol profiling","pmids":["26456460"],"confidence":"High","gaps":["Inhibitor selectivity in mammalian systems not fully characterized","No co-crystal structure of NSDHL with inhibitor"]},{"year":2020,"claim":"Crystal structures of human NSDHL revealed the coenzyme-binding site and a conformational change upon binding, enabling structure-based discovery of a novel inhibitor that suppresses EGFR trafficking — expanding NSDHL's functional scope beyond cholesterol synthesis to receptor trafficking regulation.","evidence":"X-ray crystallography; structure-based virtual screening; EGFR trafficking cell-based assays","pmids":["32140747"],"confidence":"High","gaps":["Mechanism by which NSDHL activity controls EGFR trafficking not defined","Whether EGFR regulation is direct or mediated by sterol intermediates unknown"]},{"year":2021,"claim":"In vivo CRISPR screening and catalytic-mutant rescue experiments demonstrated that NSDHL's enzymatic activity prevents endosomal degradation of TGFβR2, thereby sustaining TGFβ signaling and promoting breast cancer metastasis — establishing a catalysis-dependent, non-canonical signaling function.","evidence":"Pooled in vivo CRISPR screen; NSDHL knockdown and Y151X catalytic mutant; TGFβR2 degradation assays; ketoconazole rescue; orthotopic models","pmids":["33864166"],"confidence":"High","gaps":["Whether sterol intermediates or cholesterol membrane composition mediates TGFβR2 stabilization unknown","Endosomal sorting mechanism not characterized"]},{"year":2024,"claim":"Co-immunoprecipitation and ubiquitination studies showed NSDHL physically binds STING and promotes its ubiquitin-dependent degradation, identifying a non-enzymatic role in suppressing cGAS-STING innate immune signaling.","evidence":"Co-IP of NSDHL-STING; ubiquitination assays; IFNβ measurements in cholangiocarcinoma cells","pmids":["39290276"],"confidence":"Medium","gaps":["No reciprocal IP or endogenous IP reported","E3 ligase mediating STING ubiquitination in this context not identified","Whether this function is independent of NSDHL enzymatic activity not tested"]},{"year":null,"claim":"Key unresolved questions include the precise sterol intermediate(s) responsible for toxicity in CHILD/CK syndrome, the mechanism by which NSDHL metabolic activity controls receptor trafficking (TGFβR2, EGFR), and whether the STING-binding function represents a bona fide non-enzymatic role or is secondary to altered membrane sterol composition.","evidence":"","pmids":[],"confidence":"High","gaps":["Toxic methylsterol species identity unknown","Structural basis for NSDHL-STING interaction not defined","No systematic separation of enzymatic vs. non-enzymatic functions across signaling phenotypes"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[0,2,7,9]},{"term_id":"GO:0016829","term_label":"lyase activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1]},{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[1]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,2,7,8,9,12]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,8,11,14]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[3,4,6,8]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,7,11,14]}],"complexes":[],"partners":["STING1","TGFBR2"],"other_free_text":[]},"mechanistic_narrative":"NSDHL is a 3β-hydroxysterol dehydrogenase/C-3 sterol dehydrogenase that catalyzes the removal of C-4 methyl groups during post-squalene cholesterol biosynthesis, functioning upstream of EBP in the pathway; its enzymatic activity is confirmed by rescue of ERG26-deficient yeast and by direct enzyme inhibition studies with FR171456 [PMID:10710235, PMID:14567972, PMID:26456460]. The protein localizes to ER membranes and lipid droplet surfaces via Golgi-dependent trafficking, and loss-of-function mutations cause CHILD syndrome while hypomorphic alleles with temperature-sensitive instability cause CK syndrome, with methylsterol accumulation rather than cholesterol deficiency implicated as the primary pathogenic mechanism [PMID:14506130, PMID:21129721]. Beyond its metabolic role, NSDHL-derived cholesterol is essential for Hedgehog signaling in placental and cerebellar development, and NSDHL enzymatic activity sustains TGFβ signaling by preventing endosomal degradation of TGFβR2 and regulates EGFR trafficking [PMID:17028112, PMID:25652406, PMID:33864166, PMID:32140747]. NSDHL also binds STING and promotes its ubiquitin-mediated degradation, thereby attenuating cGAS-STING innate immune signaling [PMID:39290276]."},"prefetch_data":{"uniprot":{"accession":"Q15738","full_name":"Sterol-4-alpha-carboxylate 3-dehydrogenase, decarboxylating","aliases":["Protein H105e3"],"length_aa":373,"mass_kda":41.9,"function":"Catalyzes the NAD(P)(+)-dependent oxidative decarboxylation of the C4 methyl groups of 4-alpha-carboxysterols in post-squalene cholesterol biosynthesis (By similarity). Also plays a role in the regulation of the endocytic trafficking of EGFR (By similarity)","subcellular_location":"Endoplasmic reticulum membrane; Lipid droplet","url":"https://www.uniprot.org/uniprotkb/Q15738/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NSDHL","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000147383","cell_line_id":"CID000288","localizations":[{"compartment":"er","grade":3},{"compartment":"vesicles","grade":2}],"interactors":[{"gene":"CDS1","stoichiometry":0.2},{"gene":"CLTA","stoichiometry":0.2},{"gene":"COPA","stoichiometry":0.2},{"gene":"COPB2","stoichiometry":0.2},{"gene":"COPE","stoichiometry":0.2},{"gene":"FASN","stoichiometry":0.2},{"gene":"IDI1","stoichiometry":0.2},{"gene":"MVD","stoichiometry":0.2},{"gene":"POMT1","stoichiometry":0.2},{"gene":"HSD17B12","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000288","total_profiled":1310},"omim":[{"mim_id":"616834","title":"MICROCEPHALY, CONGENITAL CATARACT, AND PSORIASIFORM DERMATITIS; MCCPD","url":"https://www.omim.org/entry/616834"},{"mim_id":"308300","title":"INCONTINENTIA PIGMENTI; IP","url":"https://www.omim.org/entry/308300"},{"mim_id":"308050","title":"CONGENITAL HEMIDYSPLASIA WITH ICHTHYOSIFORM ERYTHRODERMA AND LIMB DEFECTS","url":"https://www.omim.org/entry/308050"},{"mim_id":"300831","title":"CK SYNDROME; CKS","url":"https://www.omim.org/entry/300831"},{"mim_id":"300275","title":"NAD(P)H STEROID DEHYDROGENASE-LIKE PROTEIN; NSDHL","url":"https://www.omim.org/entry/300275"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Endoplasmic reticulum","reliability":"Enhanced"},{"location":"Lipid droplets","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/NSDHL"},"hgnc":{"alias_symbol":["XAP104","H105e3","SDR31E1"],"prev_symbol":[]},"alphafold":{"accession":"Q15738","domains":[{"cath_id":"3.40.50.720","chopping":"29-368","consensus_level":"medium","plddt":93.1647,"start":29,"end":368}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15738","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15738-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15738-F1-predicted_aligned_error_v6.png","plddt_mean":88.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NSDHL","jax_strain_url":"https://www.jax.org/strain/search?query=NSDHL"},"sequence":{"accession":"Q15738","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15738.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15738/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15738"}},"corpus_meta":[{"pmid":"10710235","id":"PMC_10710235","title":"Mutations in the NSDHL gene, encoding a 3beta-hydroxysteroid dehydrogenase, cause CHILD syndrome.","date":"2000","source":"American journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10710235","citation_count":191,"is_preprint":false},{"pmid":"14506130","id":"PMC_14506130","title":"NSDHL, an enzyme involved in cholesterol biosynthesis, traffics through the Golgi and accumulates on ER membranes and on the surface of lipid droplets.","date":"2003","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/14506130","citation_count":84,"is_preprint":false},{"pmid":"21129721","id":"PMC_21129721","title":"Hypomorphic temperature-sensitive alleles of NSDHL cause CK syndrome.","date":"2010","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21129721","citation_count":43,"is_preprint":false},{"pmid":"11907515","id":"PMC_11907515","title":"A novel missense mutation of NSDHL in an unusual case of CHILD syndrome showing bilateral, almost symmetric involvement.","date":"2002","source":"Journal of the American Academy of Dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/11907515","citation_count":37,"is_preprint":false},{"pmid":"33864166","id":"PMC_33864166","title":"NSDHL promotes triple-negative breast cancer metastasis through the TGFβ signaling pathway and cholesterol biosynthesis.","date":"2021","source":"Breast cancer research and treatment","url":"https://pubmed.ncbi.nlm.nih.gov/33864166","citation_count":33,"is_preprint":false},{"pmid":"25652406","id":"PMC_25652406","title":"Analysis of hedgehog signaling in cerebellar granule cell precursors in a conditional Nsdhl allele demonstrates an essential role for cholesterol in postnatal CNS development.","date":"2015","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25652406","citation_count":28,"is_preprint":false},{"pmid":"12966526","id":"PMC_12966526","title":"Left-sided CHILD syndrome caused by a nonsense mutation in the NSDHL gene.","date":"2003","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/12966526","citation_count":28,"is_preprint":false},{"pmid":"30582412","id":"PMC_30582412","title":"RNA-Seq analysis reveals a negative role of MSMO1 with a synergized NSDHL expression during adipogenesis of 3T3-L1.","date":"2018","source":"Bioscience, biotechnology, and biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30582412","citation_count":23,"is_preprint":false},{"pmid":"17028112","id":"PMC_17028112","title":"Analysis of Nsdhl-deficient embryos reveals a role for Hedgehog signaling in early placental development.","date":"2006","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17028112","citation_count":21,"is_preprint":false},{"pmid":"15639195","id":"PMC_15639195","title":"Placental defects are associated with male lethality in bare patches and striated embryos deficient in the NAD(P)H Steroid Dehydrogenase-like (NSDHL) Enzyme.","date":"2005","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/15639195","citation_count":20,"is_preprint":false},{"pmid":"16088165","id":"PMC_16088165","title":"CHILD syndrome caused by a deletion of exons 6-8 of the NSDHL gene.","date":"2005","source":"Dermatology (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/16088165","citation_count":18,"is_preprint":false},{"pmid":"14567972","id":"PMC_14567972","title":"Identification of two novel mutations in the murine Nsdhl sterol dehydrogenase gene and development of a functional complementation assay in yeast.","date":"2003","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/14567972","citation_count":17,"is_preprint":false},{"pmid":"36669362","id":"PMC_36669362","title":"Regorafenib enhances anti-tumor efficacy of immune checkpoint inhibitor by regulating IFN-γ/NSDHL/SREBP1/TGF-β1 axis in hepatocellular carcinoma.","date":"2023","source":"Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie","url":"https://pubmed.ncbi.nlm.nih.gov/36669362","citation_count":17,"is_preprint":false},{"pmid":"28739597","id":"PMC_28739597","title":"A Large Deletion in the NSDHL Gene in Labrador Retrievers with a Congenital Cornification Disorder.","date":"2017","source":"G3 (Bethesda, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/28739597","citation_count":16,"is_preprint":false},{"pmid":"19631568","id":"PMC_19631568","title":"Developmental expression pattern of the cholesterogenic enzyme NSDHL and negative selection of NSDHL-deficient cells in the heterozygous Bpa(1H)/+ mouse.","date":"2009","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/19631568","citation_count":16,"is_preprint":false},{"pmid":"32140747","id":"PMC_32140747","title":"Crystal structures of human NSDHL and development of its novel inhibitor with the potential to suppress EGFR activity.","date":"2020","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/32140747","citation_count":14,"is_preprint":false},{"pmid":"26456460","id":"PMC_26456460","title":"FR171456 is a specific inhibitor of mammalian NSDHL and yeast Erg26p.","date":"2015","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/26456460","citation_count":13,"is_preprint":false},{"pmid":"19906044","id":"PMC_19906044","title":"CHILD syndrome: the NSDHL gene and its role in CHILD syndrome, a rare hereditary disorder.","date":"2009","source":"Journal of the European Academy of Dermatology and Venereology : JEADV","url":"https://pubmed.ncbi.nlm.nih.gov/19906044","citation_count":13,"is_preprint":false},{"pmid":"31078502","id":"PMC_31078502","title":"Identification of NSDHL mutations associated with CHILD syndrome in oral verruciform xanthoma.","date":"2019","source":"Oral surgery, oral medicine, oral pathology and oral radiology","url":"https://pubmed.ncbi.nlm.nih.gov/31078502","citation_count":10,"is_preprint":false},{"pmid":"31571289","id":"PMC_31571289","title":"A missense variant in the NSDHL gene in a Chihuahua with a congenital cornification disorder resembling inflammatory linear verrucous epidermal nevi.","date":"2019","source":"Animal genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31571289","citation_count":8,"is_preprint":false},{"pmid":"32819291","id":"PMC_32819291","title":"Novel variant in NSDHL gene associated with CHILD syndrome and syndactyly- a case report.","date":"2020","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32819291","citation_count":7,"is_preprint":false},{"pmid":"25900314","id":"PMC_25900314","title":"A novel missense mutation in the NSDHL gene identified in a Lithuanian family by targeted next-generation sequencing causes CK syndrome.","date":"2015","source":"American journal of medical genetics. 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loss-of-function mutations in NSDHL cause CHILD syndrome, and the protein functions upstream of EBP (delta8-delta7 sterol isomerase) in cholesterol biosynthesis.\",\n      \"method\": \"SSCA and genomic sequence analysis of NSDHL in CHILD syndrome patients; genetic epistasis with EBP (CDPX2 gene) established pathway position\",\n      \"journal\": \"American journal of medical genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — foundational mutation identification with pathway placement, replicated across multiple patients and consistent with mouse models\",\n      \"pmids\": [\"10710235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"NSDHL protein localizes to ER membranes and to the surface of lipid droplets, and trafficking through the Golgi is necessary for ER membrane localization; the dual localization was demonstrated using tagged wild-type and mutant murine Nsdhl alleles.\",\n      \"method\": \"Confocal microscopy of tagged NSDHL constructs (wild-type and mutant); Golgi trafficking disruption experiments\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct subcellular localization with functional consequence (Golgi trafficking required for ER localization), multiple alleles tested\",\n      \"pmids\": [\"14506130\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mouse NSDHL protein can rescue lethality of erg26-deficient Saccharomyces cerevisiae cells (lacking the yeast ortholog), confirming NSDHL functions as a C-3 sterol dehydrogenase; hypomorphic alleles showed partial complementation while null alleles showed none.\",\n      \"method\": \"Functional complementation assay in Erg26-deficient yeast; in vivo rescue of yeast lethality\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vivo complementation assay in yeast with multiple alleles tested, directly establishes enzymatic function\",\n      \"pmids\": [\"14567972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Nsdhl-deficient male mouse embryos die in midgestation (E10.5–13.5) with placental labyrinth defects: thinner labyrinth layer, fewer fetal vessels, and decreased proliferation of labyrinth trophoblast cells, implicating NSDHL in placental vascular development.\",\n      \"method\": \"Analysis of Nsdhl mutant mouse embryos by histology; trophoblast proliferation assays\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with defined cellular phenotype in multiple alleles, consistent with subsequent studies\",\n      \"pmids\": [\"15639195\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NSDHL deficiency in mouse embryos disrupts Indian hedgehog (Ihh) signaling in the placenta; Ptch1-lacZ reporter expression was markedly decreased in Nsdhl mutant placentas, and Ihh-expressing cells failed to migrate into allantoic mesoderm, establishing a role for NSDHL-dependent cholesterol biosynthesis in placental hedgehog signaling.\",\n      \"method\": \"Transgenic Ptch1-lacZ reporter mouse; X-linked lacZ mosaic analysis; histology of mutant placentas\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis using reporter mouse, multiple complementary methods establishing pathway position\",\n      \"pmids\": [\"17028112\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"NSDHL-deficient cells in heterozygous Bpa(1H)/+ female mice are subject to negative selection over time; clonal NSDHL-negative cells decline from ~50% to ~20% in liver and brain over the first year of life, demonstrating a cell-autonomous requirement for NSDHL in neuronal and hepatocyte survival.\",\n      \"method\": \"Immunohistochemistry for NSDHL across multiple tissue types and developmental stages in wild-type and Bpa(1H) mice\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct localization/cell-proportion quantification with functional inference, single lab\",\n      \"pmids\": [\"19631568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Trophoblast-lineage expression of Nsdhl (from the maternally inherited allele) has the largest effect on placental area in Nsdhl mutant conceptuses; maternal genotype independently contributes a smaller effect on placental development, demonstrating non-cell-autonomous and imprinting-related roles for NSDHL in placentation.\",\n      \"method\": \"Transgenic rescue experiments (human NSDHL transgene rescuing male lethality); placental area measurements at E10.5 comparing maternal vs. paternal transmission\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic rescue with quantitative phenotypic analysis, single lab\",\n      \"pmids\": [\"19880419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Hypomorphic NSDHL mutations (p.Lys232del and p.Arg367SerfsX33) cause CK syndrome through temperature-sensitive protein instability; these mutations alter protein folding and show complementation in Erg26-deficient yeast; methylsterol accumulation (not cholesterol deficiency) is hypothesized as the pathogenic mechanism, as CSF and plasma cholesterol levels are normal in CKS patients.\",\n      \"method\": \"Yeast complementation assay; temperature-sensitive protein stability assays; sterol analysis of CSF and plasma\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — yeast complementation plus biochemical sterol analysis, multiple orthogonal methods\",\n      \"pmids\": [\"21129721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Conditional ablation of Nsdhl in radial glia (GFAP-cre) causes defective SHH signaling in cerebellar granule cell precursors, resulting in proliferation defects that are rescued by exogenous cholesterol supplementation; methylsterol accumulation above the enzymatic block is associated with increased cell death, establishing that NSDHL-derived cholesterol is required for SHH signaling in postnatal CNS.\",\n      \"method\": \"Conditional knockout mouse (Nsdhl(tm1.1Hrm) × GFAP-cre); in vitro granule cell precursor proliferation assay; cholesterol rescue experiment; sterol level measurements\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — conditional KO with defined phenotype, in vitro rescue by cholesterol supplementation, multiple orthogonal methods\",\n      \"pmids\": [\"25652406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FR171456 specifically inhibits NSDHL (and its yeast ortholog Erg26p) enzymatic activity; multiple ERG26 mutations confer resistance to FR171456 in growth and enzyme assays, identifying the binding site on the enzyme.\",\n      \"method\": \"Genome-wide yeast haploinsufficiency profiling; enzyme inhibition assays; resistance mutation mapping; sterol intermediate profiling in human and yeast cells\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct enzyme inhibition assay with resistance mutation mapping and genome-wide target identification\",\n      \"pmids\": [\"26456460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Two X-ray crystal structures of human NSDHL were solved, revealing a coenzyme-binding site and a unique conformational change upon coenzyme binding; structure-based virtual screening identified a novel NSDHL inhibitor with suppressive activity toward EGFR trafficking, establishing that NSDHL regulates EGFR trafficking pathways.\",\n      \"method\": \"X-ray crystallography; structure-based virtual screening; biochemical inhibition assays; cell-based EGFR trafficking assays\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus functional biochemical and cell-based validation\",\n      \"pmids\": [\"32140747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NSDHL promotes triple-negative breast cancer metastasis by inhibiting endosomal degradation of TGFβR2, thereby activating the TGFβ signaling pathway; this function depends on NSDHL's enzymatic activity in cholesterol biosynthesis, as the catalytically inactive Y151X mutant did not rescue migration or TGFβR2 expression; blocking upstream NSDHL metabolism with ketoconazole rescued cancer metastasis.\",\n      \"method\": \"CRISPR pooled in vivo screen; Transwell migration assay; animal experiments; NSDHL knockdown and catalytic mutant (Y151X); TGFβR2 degradation assay; ketoconazole treatment\",\n      \"journal\": \"Breast cancer research and treatment\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo CRISPR screen, catalytic mutant validation, and pathway rescue, multiple orthogonal methods\",\n      \"pmids\": [\"33864166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"NSDHL knockdown in 3T3-L1 cells attenuates adipogenesis, reduces lipid accumulation, downregulates PPARγ expression, and decreases LXR-SREBP1 signaling pathway activity, identifying NSDHL as a regulator of adipogenic differentiation through the LXR-SREBP1 axis.\",\n      \"method\": \"NSDHL knockdown in 3T3-L1 cells; quantitative RT-PCR; Oil Red O lipid staining; LXR-SREBP1 pathway analysis\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab KD with defined phenotype and partial pathway placement\",\n      \"pmids\": [\"31985358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NSDHL binds to STING protein and facilitates its degradation via ubiquitination, thereby inhibiting the cGAS-STING signaling pathway and reducing IFNβ synthesis in cholangiocarcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation (NSDHL-STING binding); ubiquitination assay; IFNβ measurement; NSDHL overexpression in cells\",\n      \"journal\": \"Heliyon\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP with ubiquitination assay and functional readout, single lab\",\n      \"pmids\": [\"39290276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NSDHL knockdown in MCF-7 tumor spheroids reduces TGF-β1 and TGF-β3 secretion, decreases Smad2/3 phosphorylation, and reduces SOX2 expression, suppressing breast cancer stem-like cell populations and tumor-initiating capacity in orthotopic xenograft models.\",\n      \"method\": \"NSDHL knockdown; tumor spheroid formation assay; RNA sequencing; flow cytometry for BCSC markers; orthotopic xenograft model; ELISA for TGF-β\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (RNA-seq, flow cytometry, in vivo xenograft), single lab\",\n      \"pmids\": [\"39516821\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NSDHL is a 3β-hydroxysterol dehydrogenase/decarboxylase that removes C-4 methyl groups in post-squalene cholesterol biosynthesis, localizes to ER membranes and lipid droplet surfaces via Golgi trafficking, and—beyond its metabolic role—regulates multiple signaling pathways including SHH (by supplying cholesterol for ligand activity), TGFβ (by preventing endosomal degradation of TGFβR2), cGAS-STING (by binding and ubiquitin-mediated degradation of STING), and EGFR trafficking, with loss-of-function causing methyl sterol accumulation that drives the pathology of CHILD syndrome and CK syndrome.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NSDHL is a 3β-hydroxysterol dehydrogenase/C-3 sterol dehydrogenase that catalyzes the removal of C-4 methyl groups during post-squalene cholesterol biosynthesis, functioning upstream of EBP in the pathway; its enzymatic activity is confirmed by rescue of ERG26-deficient yeast and by direct enzyme inhibition studies with FR171456 [PMID:10710235, PMID:14567972, PMID:26456460]. The protein localizes to ER membranes and lipid droplet surfaces via Golgi-dependent trafficking, and loss-of-function mutations cause CHILD syndrome while hypomorphic alleles with temperature-sensitive instability cause CK syndrome, with methylsterol accumulation rather than cholesterol deficiency implicated as the primary pathogenic mechanism [PMID:14506130, PMID:21129721]. Beyond its metabolic role, NSDHL-derived cholesterol is essential for Hedgehog signaling in placental and cerebellar development, and NSDHL enzymatic activity sustains TGFβ signaling by preventing endosomal degradation of TGFβR2 and regulates EGFR trafficking [PMID:17028112, PMID:25652406, PMID:33864166, PMID:32140747]. NSDHL also binds STING and promotes its ubiquitin-mediated degradation, thereby attenuating cGAS-STING innate immune signaling [PMID:39290276].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Identification of NSDHL as the gene mutated in CHILD syndrome established it as a cholesterol biosynthetic enzyme acting upstream of EBP, answering the long-standing question of the molecular basis of this X-linked ichthyosis.\",\n      \"evidence\": \"SSCA and genomic sequencing of CHILD syndrome patients with epistasis analysis relative to EBP/CDPX2\",\n      \"pmids\": [\"10710235\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise enzymatic reaction mechanism not yet defined\", \"Substrate specificity not characterized biochemically\", \"Subcellular site of action unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Functional complementation of ERG26-deficient yeast by mouse NSDHL confirmed C-3 sterol dehydrogenase activity, while subcellular localization studies revealed dual ER membrane/lipid droplet targeting dependent on Golgi trafficking, establishing both enzymatic identity and cellular compartmentalization.\",\n      \"evidence\": \"Yeast rescue assays with multiple alleles; confocal microscopy of tagged NSDHL constructs with Golgi-disruption experiments\",\n      \"pmids\": [\"14567972\", \"14506130\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural information on NSDHL at this stage\", \"Mechanism of Golgi-dependent ER targeting not defined\", \"Functional role of lipid droplet localization unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Analysis of Nsdhl-null mouse embryos revealed midgestational lethality with placental labyrinth defects, demonstrating that NSDHL is essential for trophoblast proliferation and placental vascular development in vivo.\",\n      \"evidence\": \"Histological analysis and trophoblast proliferation assays in Nsdhl mutant mouse embryos\",\n      \"pmids\": [\"15639195\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular pathway linking NSDHL to trophoblast proliferation not identified\", \"Whether cholesterol deficiency or sterol intermediate accumulation drives phenotype not resolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstration that NSDHL deficiency disrupts Indian hedgehog signaling in the placenta linked the cholesterol biosynthetic role to a specific developmental signaling pathway, explaining the trophoblast proliferation defect.\",\n      \"evidence\": \"Ptch1-lacZ reporter analysis in Nsdhl mutant placentas; mosaic analysis in heterozygous females\",\n      \"pmids\": [\"17028112\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether cholesterol supply for Hh ligand modification is the direct mechanism not proven\", \"Cell-autonomous vs. non-cell-autonomous signaling not fully dissected\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Longitudinal mosaic analysis in heterozygous female mice showed progressive loss of NSDHL-negative cells in brain and liver, establishing a cell-autonomous survival requirement; transgenic rescue experiments further demonstrated that trophoblast-intrinsic NSDHL expression drives the placental phenotype.\",\n      \"evidence\": \"Immunohistochemistry across developmental stages in Bpa(1H)/+ mice; human NSDHL transgene rescue with placental area measurements\",\n      \"pmids\": [\"19631568\", \"19880419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of cell death in NSDHL-negative neurons not characterized\", \"Contribution of imprinting vs. X-inactivation to phenotype not separated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identification of CK syndrome mutations as hypomorphic, temperature-sensitive NSDHL alleles with normal cholesterol but methylsterol accumulation reframed the pathogenic mechanism from cholesterol deficiency to toxic sterol intermediate accumulation.\",\n      \"evidence\": \"Yeast complementation; temperature-sensitive protein stability assays; CSF and plasma sterol analysis in CK syndrome patients\",\n      \"pmids\": [\"21129721\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific toxic methylsterol species not identified\", \"Downstream targets of methylsterol toxicity unknown\", \"Why CKS and CHILD syndrome differ phenotypically despite same gene not fully explained\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Conditional CNS knockout revealed that NSDHL-derived cholesterol is required for SHH signaling in cerebellar granule cell precursors, with exogenous cholesterol rescuing proliferation defects — directly linking the enzyme's metabolic product to postnatal brain development and hedgehog pathway activation.\",\n      \"evidence\": \"Conditional Nsdhl knockout (GFAP-cre); in vitro GCP proliferation assay with cholesterol rescue; sterol measurements\",\n      \"pmids\": [\"25652406\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether cholesterol acts via SHH ligand modification or smoothened activation not resolved\", \"Whether methylsterol accumulation contributes independently to cell death not separated from cholesterol deficiency\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Genome-wide haploinsufficiency profiling identified FR171456 as a direct NSDHL/Erg26p inhibitor, with resistance mutations mapping the enzyme's active site and providing the first pharmacological tool for NSDHL.\",\n      \"evidence\": \"Yeast haploinsufficiency screen; enzyme inhibition assays; resistance mutation mapping; sterol profiling\",\n      \"pmids\": [\"26456460\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Inhibitor selectivity in mammalian systems not fully characterized\", \"No co-crystal structure of NSDHL with inhibitor\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Crystal structures of human NSDHL revealed the coenzyme-binding site and a conformational change upon binding, enabling structure-based discovery of a novel inhibitor that suppresses EGFR trafficking — expanding NSDHL's functional scope beyond cholesterol synthesis to receptor trafficking regulation.\",\n      \"evidence\": \"X-ray crystallography; structure-based virtual screening; EGFR trafficking cell-based assays\",\n      \"pmids\": [\"32140747\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which NSDHL activity controls EGFR trafficking not defined\", \"Whether EGFR regulation is direct or mediated by sterol intermediates unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"In vivo CRISPR screening and catalytic-mutant rescue experiments demonstrated that NSDHL's enzymatic activity prevents endosomal degradation of TGFβR2, thereby sustaining TGFβ signaling and promoting breast cancer metastasis — establishing a catalysis-dependent, non-canonical signaling function.\",\n      \"evidence\": \"Pooled in vivo CRISPR screen; NSDHL knockdown and Y151X catalytic mutant; TGFβR2 degradation assays; ketoconazole rescue; orthotopic models\",\n      \"pmids\": [\"33864166\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether sterol intermediates or cholesterol membrane composition mediates TGFβR2 stabilization unknown\", \"Endosomal sorting mechanism not characterized\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Co-immunoprecipitation and ubiquitination studies showed NSDHL physically binds STING and promotes its ubiquitin-dependent degradation, identifying a non-enzymatic role in suppressing cGAS-STING innate immune signaling.\",\n      \"evidence\": \"Co-IP of NSDHL-STING; ubiquitination assays; IFNβ measurements in cholangiocarcinoma cells\",\n      \"pmids\": [\"39290276\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reciprocal IP or endogenous IP reported\", \"E3 ligase mediating STING ubiquitination in this context not identified\", \"Whether this function is independent of NSDHL enzymatic activity not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the precise sterol intermediate(s) responsible for toxicity in CHILD/CK syndrome, the mechanism by which NSDHL metabolic activity controls receptor trafficking (TGFβR2, EGFR), and whether the STING-binding function represents a bona fide non-enzymatic role or is secondary to altered membrane sterol composition.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Toxic methylsterol species identity unknown\", \"Structural basis for NSDHL-STING interaction not defined\", \"No systematic separation of enzymatic vs. non-enzymatic functions across signaling phenotypes\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [0, 2, 7, 9]},\n      {\"term_id\": \"GO:0016829\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 2, 7, 8, 9, 12]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 8, 11, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [3, 4, 6, 8]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 7, 11, 14]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"STING1\",\n      \"TGFBR2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}