{"gene":"COL4A6","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":1994,"finding":"COL4A6 and COL4A5 are arranged head-to-head on chromosome Xq22 and share a common bidirectional promoter region; COL4A6 is transcribed from two alternative promoters in a tissue-specific manner, with one transcript (from exon 1') abundant in placenta and another (from exon 1) more frequent in kidney and lung.","method":"Genomic sequencing, 5' flanking sequence analysis, reverse transcription-PCR across tissue types","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — RT-PCR across multiple tissues with sequencing of promoter regions; replicated in multiple subsequent studies","pmids":["7972123"],"is_preprint":false},{"year":1995,"finding":"The alpha6(IV) chain (COL4A6 protein product) is present as 27-kD monomers and associated dimers of the NC1 domain; it localizes to basement membranes of Bowman's capsules and distal tubules in adult kidney but is absent from the glomerular basement membrane, whereas alpha5(IV) is present in the GBM. Both chains co-localize in skin, smooth muscle cells, and adipocytes but are absent or minimal in cardiac muscle and hepatic sinusoidal endothelial cells.","method":"Peptide-specific monoclonal antibody generation, Western blotting, immunofluorescence staining across multiple human tissues","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal chain-specific antibodies with Western blot and immunofluorescence across multiple tissues; foundational localization study replicated in subsequent work","pmids":["7657706"],"is_preprint":false},{"year":1995,"finding":"The COL4A6 gene spans >200 kb, contains 46 exons, with exons 1' and 1 encoding two alternative 5'-UTRs and distinct signal peptide N-termini, exons 2-7 encoding the 7S domain, exons 7-42 encoding the collagenous COL1 domain with Gly-X-Y repeats, and exons 43-45 encoding the NC1 domain. The exon size pattern is highly homologous to COL4A2.","method":"Genomic library screening, lambda phage clone characterization, exon/intron mapping, restriction analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — complete gene structure determination by direct sequencing and mapping; foundational structural paper","pmids":["7592929"],"is_preprint":false},{"year":1998,"finding":"Deletions spanning the 5' ends of both COL4A5 and COL4A6 cause diffuse leiomyomatosis (DL) in association with Alport syndrome; the COL4A6 breakpoints in DL/AS cases are clustered within intron 2 of COL4A6. Breakpoint sequences share homology with topoisomerase I and II consensus sequences, implicating topoisomerase-mediated recombination in deletion formation. Immunohistochemical analysis confirmed absence of alpha5(IV) and alpha6(IV) chains in basement membranes of affected smooth muscle tumor tissue.","method":"Breakpoint sequence characterization, DNA sequence homology analysis, immunohistochemistry with chain-specific antibodies, somatic mosaicism analysis","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct breakpoint sequencing with functional immunohistochemical validation; replicated across multiple DL/AS families","pmids":["9463311"],"is_preprint":false},{"year":2000,"finding":"The minimal promoters for COL4A5 and COL4A6 are functionally distinct, residing within 100 bp of their respective transcription start sites. A bidirectional positive regulatory element exists between the two genes that functions in multiple cell types but not in glomerular visceral epithelial cells, which selectively transcribe COL4A5. This element enables co-expression of both genes in keratinocytes but not in podocytes.","method":"Transient transfection with reporter gene constructs, RNase protection assays, gel shift assays, DNase I footprinting","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (reporter assays, gel shifts, footprinting) in cell lines with distinct expression patterns","pmids":["11096082"],"is_preprint":false},{"year":2005,"finding":"The bifunctional promoter between COL4A5 and COL4A6 regulates their expression in a cell-type-specific manner in response to growth factors. TGF-beta, EGF, VEGF, and PDGF significantly enhance expression from the alpha5(IV) gene in glomerular endothelial cells and mesangial cells but not from the alpha6(IV) gene; conversely, in tubular epithelial cells, these growth factors enhance expression from the alpha6(IV) gene but not the alpha5(IV) gene.","method":"Cloning of mouse bifunctional promoter into bidirectional reporter construct (CAT/Luciferase), transfection into glomerular endothelial cells, mesangial cells, and tubular epithelial cells, growth factor stimulation assays","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — bidirectional reporter construct with multiple growth factors across multiple cell types, single lab","pmids":["15598179"],"is_preprint":false},{"year":2010,"finding":"Alpha5(IV) and alpha6(IV) chains are specifically expressed in esophageal smooth muscle basement membranes within the gastrointestinal tract. Deletion of COL4A5-COL4A6 promoters leads to clonal overgrowth of esophageal smooth muscle cells, demonstrated by CAG repeat analysis of the androgen receptor gene showing X-inactivation on the non-affected allele in leiomyoma cells.","method":"Immunohistochemistry with chain-specific antibodies across gastrointestinal tract, CAG repeat analysis of androgen receptor gene for clonal X-inactivation analysis","journal":"Matrix biology : journal of the International Society for Matrix Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — immunohistochemistry plus clonality analysis by X-inactivation, single lab, two orthogonal methods","pmids":["20951201"],"is_preprint":false},{"year":2013,"finding":"A missense mutation (c.1771G>A, p.Gly591Ser) in COL4A6 causes X-linked nonsyndromic congenital hearing loss without Alport syndrome features. Expression of the COL4A6 homolog was confirmed in the zebrafish otic vesicle by in situ hybridization and in murine inner ear by immunostaining, establishing a role for COL4A6 in inner ear development and function.","method":"Next-generation sequencing, Sanger sequencing for segregation, in situ hybridization in zebrafish, immunostaining in mouse inner ear","journal":"European journal of human genetics : EJHG","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — mutation identified with segregation plus in situ hybridization and immunostaining in model organisms confirming expression; single lab","pmids":["23714752"],"is_preprint":false},{"year":2016,"finding":"COL4A6 is dispensable for autosomal recessive Alport syndrome: mice lacking both alpha3(IV) and alpha6(IV) chains showed no significant difference in renal function or survival compared to Col4a3 single knockout mice, indicating alpha6(IV) induction in the GBM in autosomal recessive Alport syndrome does not play a major compensatory role.","method":"Generation of Col4a3/Col4a6 double knockout mice, renal function measurement, survival analysis, immunostaining","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis via double KO mouse with defined functional phenotype, single lab","pmids":["27377778"],"is_preprint":false},{"year":2017,"finding":"AS-DL deletions arise predominantly through homologous recombination involving transposed elements (long and short interspersed repeats, DNA transposons, LTR retrotransposons) at sequences homologous between COL4A5 and COL4A6. Eight of nine deletion alleles involved such homologous sequences. The occurrence of leiomyomatosis requires inactivation of both COL4A5 and COL4A6, as all deletions involved the bidirectional promoter region.","method":"Breakpoint characterization by PCR and sequencing in five AS-DL patients, sequence homology analysis for transposed elements","journal":"Journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct breakpoint sequencing across multiple patients with mechanistic inference about promoter loss; single lab","pmids":["28275241"],"is_preprint":false},{"year":2021,"finding":"Col4a6 knockout mice do not develop hearing loss or cochlear malformation, in contrast to humans with the COL4A6 p.Gly591Ser missense mutation who do. Alpha6(IV) chain is distributed throughout cochlear subepithelial basement membranes in mice. This discrepancy indicates the hearing loss mechanism is likely due to dominant-negative effects of the aberrant alpha6(IV) chain or the alpha5-alpha6-alpha5(IV) heterotrimer, rather than simple loss of function.","method":"Col4a6 knockout mouse generation, auditory brainstem response (click-evoked ABR), micro-computed tomography, histology, immunohistochemistry","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with defined audiological and structural phenotype plus immunolocalization; single lab, multiple readouts","pmids":["33848312"],"is_preprint":false},{"year":2021,"finding":"A splicing variant in COL4A6 (c.951+1G>C) causes skipping of exon 15, demonstrated by in vitro minigene splicing assay, establishing a pathogenic mechanism for X-linked nonsyndromic hearing loss.","method":"In vitro minigene splicing assay","journal":"European journal of human genetics : EJHG","confidence":"Medium","confidence_rationale":"Tier 1-2 / Weak — direct functional splicing assay, single lab, single method","pmids":["33840813"],"is_preprint":false},{"year":2020,"finding":"Knockdown of COL4A6 in prostate cancer cells activates the p-FAK/MMP-9 signaling pathway, promoting cell invasion and migration as measured by wound healing and transwell assays. COL4A6 protein localizes extracellularly in prostate cancer cells.","method":"siRNA knockdown, wound healing assay, cell invasion transwell assay, Western blot, immunofluorescence staining","journal":"Genetic testing and molecular biomarkers","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single knockdown experiment with invasion assay; pathway assignment (p-FAK/MMP-9) lacks direct biochemical validation","pmids":["32551898"],"is_preprint":false},{"year":2026,"finding":"A synonymous COL4A6 variant (c.1767G>A, p.Pro589=) causes partial exon skipping, demonstrated by RNA studies, establishing it as pathogenic for X-linked nonsyndromic hearing loss. Structural modeling of missense variant p.Gly494Arg predicts impact on protein structure. Zebrafish spatial and temporal expression analysis confirmed col4a6 expression in the otic vesicle and developing ear from 1 to 5 days post-fertilization.","method":"Exome/genome sequencing, RNA splicing analysis, zebrafish expression analysis (spatial/temporal), structural modeling","journal":"QJM : monthly journal of the Association of Physicians","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct RNA evidence for splicing effect plus in vivo zebrafish expression validation; single lab, multiple methods","pmids":["41092388"],"is_preprint":false},{"year":2026,"finding":"COL4A6 produced by cancer-associated fibroblasts (CAFs) promotes tumor progression and stromal remodeling in gastric cancer by inducing CAF activation (upregulation of alpha-SMA and FAP, stress fiber remodeling) and promoting epithelial-mesenchymal transition (EMT) in gastric cancer cells.","method":"Single-cell sequencing, CAF-enriched fibroblast cultures, functional experiments measuring alpha-SMA/FAP upregulation and stress fiber remodeling, EMT assays in cancer cells","journal":"Scientific reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, cell culture functional experiments without reconstitution or in vivo validation; abstract lacks specific method detail","pmids":["41735371"],"is_preprint":false}],"current_model":"COL4A6 encodes the alpha6(IV) type IV collagen chain, which is expressed from two alternative promoters regulated by a bifunctional bidirectional promoter shared with COL4A5, with tissue-specific and growth factor-regulated expression controlled at the promoter level; the alpha6(IV) chain localizes extracellularly to distinct basement membranes (e.g., Bowman's capsule and distal tubules but not the glomerular basement membrane in kidney, and esophageal smooth muscle), forms heterotrimers with alpha5(IV) chains, and missense mutations in the collagenous domain cause X-linked nonsyndromic hearing loss likely through dominant-negative disruption of the heterotrimer rather than simple loss of function, while contiguous deletions of the COL4A5/COL4A6 bidirectional promoter region cause diffuse leiomyomatosis through loss of both gene products in esophageal smooth muscle."},"narrative":{"mechanistic_narrative":"COL4A6 encodes the alpha6(IV) type IV collagen chain, a basement membrane structural component whose expression is governed by a bidirectional promoter shared head-to-head with COL4A5 on chromosome Xq22 [PMID:7972123]. This shared regulatory region drives tissue-specific transcription from two alternative COL4A6 promoters and contains a bidirectional positive regulatory element that enables co-expression of both chains in keratinocytes and other cell types but is inactive in podocytes, which selectively transcribe COL4A5 [PMID:7972123, PMID:11096082]; growth factors including TGF-beta, EGF, VEGF, and PDGF further partition expression in a cell-type-specific manner, enhancing alpha6(IV) in tubular epithelial cells while enhancing alpha5(IV) in glomerular cells [PMID:15598179]. The alpha6(IV) chain assembles through its NC1 domain and deposits into select basement membranes—Bowman's capsule and distal tubules but notably not the glomerular basement membrane, as well as skin, smooth muscle, and esophageal smooth muscle—while co-localizing with alpha5(IV) [PMID:7657706, PMID:20951201]. Two distinct disease mechanisms arise from this gene: contiguous deletions removing the 5' ends and shared bidirectional promoter of both COL4A5 and COL4A6 cause diffuse leiomyomatosis through loss of both chains in esophageal smooth muscle, with deletion breakpoints clustering in COL4A6 intron 2 and arising via topoisomerase- and homologous-recombination-mediated rearrangement of transposed elements [PMID:9463311, PMID:20951201, PMID:28275241]; separately, missense and splicing variants in COL4A6 cause X-linked nonsyndromic congenital hearing loss [PMID:23714752, PMID:33840813, PMID:41092388]. Because Col4a6 knockout mice develop neither hearing loss nor cochlear malformation despite alpha6(IV) distribution throughout cochlear basement membranes, the hearing-loss mechanism is attributed to dominant-negative disruption of the heterotrimer by aberrant alpha6(IV) chains rather than simple loss of function [PMID:33848312]. Genetic epistasis in Col4a3/Col4a6 double-knockout mice shows alpha6(IV) is dispensable for autosomal recessive Alport syndrome progression [PMID:27377778].","teleology":[{"year":1994,"claim":"Established the genomic architecture underlying COL4A6 regulation by showing it is arranged head-to-head with COL4A5 and driven by a shared bidirectional promoter with two tissue-specific alternative start sites.","evidence":"Genomic sequencing, promoter analysis, and RT-PCR across tissues","pmids":["7972123"],"confidence":"High","gaps":["Did not define the cis-elements conferring tissue specificity","Functional consequence of the two transcript isoforms unresolved"]},{"year":1995,"claim":"Defined the alpha6(IV) protein product and its restricted basement-membrane distribution, distinguishing it from alpha5(IV) by its absence from the glomerular basement membrane.","evidence":"Chain-specific monoclonal antibodies, Western blot, and immunofluorescence across human tissues","pmids":["7657706"],"confidence":"High","gaps":["Heterotrimer stoichiometry not directly resolved","Functional role in each basement membrane not tested"]},{"year":1995,"claim":"Resolved the full gene structure including dual alternative first exons, the 7S, collagenous COL1, and NC1 domains, providing the framework for interpreting downstream mutations.","evidence":"Genomic library screening and exon/intron mapping","pmids":["7592929"],"confidence":"High","gaps":["Did not assign functional roles to individual domains"]},{"year":1998,"claim":"Linked contiguous deletions removing both COL4A5 and COL4A6 5' regions to diffuse leiomyomatosis with Alport syndrome and implicated topoisomerase-mediated recombination, explaining a co-deletion disease mechanism.","evidence":"Breakpoint sequencing, homology analysis, and immunohistochemistry in DL/AS families","pmids":["9463311"],"confidence":"High","gaps":["Did not establish how loss of both chains drives smooth muscle overgrowth"]},{"year":2000,"claim":"Dissected the bidirectional promoter to show distinct minimal promoters and a shared positive regulatory element that permits co-expression in some cell types but not podocytes, explaining cell-type-selective chain expression.","evidence":"Reporter assays, RNase protection, gel shift, and DNase I footprinting in cell lines","pmids":["11096082"],"confidence":"High","gaps":["Trans-acting factors binding the element not identified"]},{"year":2005,"claim":"Showed the bidirectional promoter responds to growth factors in a cell-type-specific manner, partitioning alpha5(IV) versus alpha6(IV) induction between glomerular and tubular cells.","evidence":"Bidirectional reporter constructs with growth factor stimulation across renal cell types","pmids":["15598179"],"confidence":"High","gaps":["Signal transduction pathways linking growth factors to the promoter not defined","Single lab"]},{"year":2010,"claim":"Demonstrated that promoter deletion causes clonal esophageal smooth muscle overgrowth, connecting the genetic lesion to a defined tumorigenic clonal expansion.","evidence":"Chain-specific immunohistochemistry and androgen receptor CAG-repeat X-inactivation clonality analysis","pmids":["20951201"],"confidence":"Medium","gaps":["Mechanism by which collagen chain loss triggers clonal growth unknown","Single lab"]},{"year":2013,"claim":"Identified COL4A6 missense mutation as a cause of X-linked nonsyndromic hearing loss and established inner-ear expression, defining a new disease association distinct from Alport syndrome.","evidence":"NGS with segregation, zebrafish in situ hybridization, mouse inner-ear immunostaining","pmids":["23714752"],"confidence":"Medium","gaps":["Mechanism by which the missense allele disrupts function not established","Single family"]},{"year":2016,"claim":"Tested whether alpha6(IV) compensates in autosomal recessive Alport syndrome and showed via genetic epistasis it is dispensable, ruling out a major compensatory GBM role.","evidence":"Col4a3/Col4a6 double-knockout mice with renal function and survival analysis","pmids":["27377778"],"confidence":"Medium","gaps":["Does not address alpha6(IV) function in non-renal basement membranes","Single lab"]},{"year":2021,"claim":"Reconciled the human-mouse discrepancy by showing Col4a6 knockout mice have normal hearing, indicating the human hearing-loss mutation acts through a dominant-negative mechanism rather than loss of function.","evidence":"Col4a6 knockout mice with ABR, micro-CT, histology, and immunohistochemistry","pmids":["33848312"],"confidence":"Medium","gaps":["Dominant-negative mechanism inferred, not biochemically demonstrated","Single lab"]},{"year":2021,"claim":"Expanded the pathogenic mutational spectrum for hearing loss by demonstrating a splice-site variant causes exon 15 skipping.","evidence":"In vitro minigene splicing assay","pmids":["33840813"],"confidence":"Medium","gaps":["Effect on protein assembly not tested","Single method"]},{"year":2026,"claim":"Further extended the hearing-loss spectrum to a synonymous variant causing partial exon skipping and reconfirmed conserved otic-vesicle expression, strengthening the developmental role.","evidence":"Exome/genome sequencing, RNA splicing analysis, zebrafish spatiotemporal expression, structural modeling","pmids":["41092388"],"confidence":"Medium","gaps":["Functional impact of structural model on heterotrimer not validated","Single lab"]},{"year":2020,"claim":"Implicated COL4A6 in cancer cell behavior, with knockdown activating p-FAK/MMP-9 signaling to promote prostate cancer invasion and migration.","evidence":"siRNA knockdown with wound healing, transwell invasion, Western blot, and immunofluorescence","pmids":["32551898"],"confidence":"Low","gaps":["Pathway assignment lacks direct biochemical validation","Single knockdown experiment, no in vivo validation"]},{"year":2026,"claim":"Implicated CAF-derived COL4A6 in gastric cancer progression through CAF activation and induction of epithelial-mesenchymal transition.","evidence":"Single-cell sequencing, CAF cultures, alpha-SMA/FAP and stress-fiber readouts, EMT assays","pmids":["41735371"],"confidence":"Low","gaps":["No reconstitution or in vivo validation","Mechanism linking secreted collagen to CAF activation undefined"]},{"year":null,"claim":"The biochemical basis of the inferred dominant-negative heterotrimer disruption in hearing loss, and the trans-acting factors that read the bidirectional promoter to achieve cell-type-specific chain expression, remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural or biochemical demonstration of mutant heterotrimer disruption","Transcription factors binding the bidirectional regulatory element unidentified","Functional role of alpha6(IV) in each specific basement membrane untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,2]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,6,12]},{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[1,6]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[1,6]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,4,5]}],"complexes":[],"partners":["COL4A5"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q14031","full_name":"Collagen alpha-6(IV) chain","aliases":[],"length_aa":1691,"mass_kda":163.8,"function":"Type IV collagen is the major structural component of glomerular basement membranes (GBM), forming a 'chicken-wire' meshwork together with laminins, proteoglycans and entactin/nidogen","subcellular_location":"Secreted, extracellular space, extracellular matrix, basement membrane","url":"https://www.uniprot.org/uniprotkb/Q14031/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/COL4A6","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/COL4A6","total_profiled":1310},"omim":[{"mim_id":"620536","title":"ALPORT SYNDROME 3B, AUTOSOMAL RECESSIVE; ATS3B","url":"https://www.omim.org/entry/620536"},{"mim_id":"308940","title":"LEIOMYOMATOSIS, DIFFUSE, WITH ALPORT SYNDROME; DL-ATS","url":"https://www.omim.org/entry/308940"},{"mim_id":"303631","title":"COLLAGEN, TYPE IV, ALPHA-6; COL4A6","url":"https://www.omim.org/entry/303631"},{"mim_id":"303630","title":"COLLAGEN, TYPE IV, ALPHA-5; COL4A5","url":"https://www.omim.org/entry/303630"},{"mim_id":"301050","title":"ALPORT SYNDROME 1, X-LINKED; ATS1","url":"https://www.omim.org/entry/301050"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"endometrium 1","ntpm":33.0},{"tissue":"urinary bladder","ntpm":40.3}],"url":"https://www.proteinatlas.org/search/COL4A6"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q14031","domains":[{"cath_id":"2.170.240.10","chopping":"1470-1662_1678-1690","consensus_level":"medium","plddt":93.3516,"start":1470,"end":1690}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14031","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q14031-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q14031-F1-predicted_aligned_error_v6.png","plddt_mean":47.41},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=COL4A6","jax_strain_url":"https://www.jax.org/strain/search?query=COL4A6"},"sequence":{"accession":"Q14031","fasta_url":"https://rest.uniprot.org/uniprotkb/Q14031.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q14031/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14031"}},"corpus_meta":[{"pmid":"7657706","id":"PMC_7657706","title":"Differential expression of two basement membrane collagen genes, COL4A6 and COL4A5, demonstrated by immunofluorescence staining using peptide-specific monoclonal antibodies.","date":"1995","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/7657706","citation_count":239,"is_preprint":false},{"pmid":"7972123","id":"PMC_7972123","title":"The genes COL4A5 and COL4A6, coding for basement membrane collagen chains alpha 5(IV) and alpha 6(IV), are located head-to-head in close proximity on human chromosome Xq22 and COL4A6 is transcribed from two alternative promoters.","date":"1994","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/7972123","citation_count":69,"is_preprint":false},{"pmid":"23714752","id":"PMC_23714752","title":"Novel form of X-linked nonsyndromic hearing loss with cochlear malformation caused by a mutation in the type IV collagen gene COL4A6.","date":"2013","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/23714752","citation_count":50,"is_preprint":false},{"pmid":"8738805","id":"PMC_8738805","title":"Identification of 17 mutations in ten exons in the COL4A5 collagen gene, but no mutations found in four exons in COL4A6: a study of 250 patients with hematuria and suspected of having Alport syndrome.","date":"1996","source":"Journal of the American Society of Nephrology : JASN","url":"https://pubmed.ncbi.nlm.nih.gov/8738805","citation_count":42,"is_preprint":false},{"pmid":"9463311","id":"PMC_9463311","title":"Topoisomerase I and II consensus sequences in a 17-kb deletion junction of the COL4A5 and COL4A6 genes and immunohistochemical analysis of esophageal leiomyomatosis associated with Alport syndrome.","date":"1998","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9463311","citation_count":40,"is_preprint":false},{"pmid":"9465897","id":"PMC_9465897","title":"Novel COL4A5/COL4A6 deletions and further characterization of the diffuse leiomyomatosis-Alport syndrome (DL-AS) locus define the DL critical region.","date":"1997","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9465897","citation_count":34,"is_preprint":false},{"pmid":"9502408","id":"PMC_9502408","title":"Somatic deletion of the 5' ends of both the COL4A5 and COL4A6 genes in a sporadic leiomyoma of the esophagus.","date":"1998","source":"The American journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/9502408","citation_count":29,"is_preprint":false},{"pmid":"7592929","id":"PMC_7592929","title":"Isolation and structure of the COL4A6 gene encoding the human alpha 6(IV) collagen chain and comparison with other type IV collagen genes.","date":"1995","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7592929","citation_count":27,"is_preprint":false},{"pmid":"11773466","id":"PMC_11773466","title":"Alport syndrome associated with diffuse leiomyomatosis: COL4A5-COL4A6 deletion associated with a mild form of Alport nephropathy.","date":"2002","source":"Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association","url":"https://pubmed.ncbi.nlm.nih.gov/11773466","citation_count":24,"is_preprint":false},{"pmid":"32551898","id":"PMC_32551898","title":"Downregulation of Collagen COL4A6 Is Associated with Prostate Cancer Progression and Metastasis.","date":"2020","source":"Genetic testing and molecular biomarkers","url":"https://pubmed.ncbi.nlm.nih.gov/32551898","citation_count":23,"is_preprint":false},{"pmid":"28275241","id":"PMC_28275241","title":"Characterization of contiguous gene deletions in COL4A6 and COL4A5 in Alport syndrome-diffuse leiomyomatosis.","date":"2017","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28275241","citation_count":20,"is_preprint":false},{"pmid":"15598179","id":"PMC_15598179","title":"Bifunctional promoter of type IV collagen COL4A5 and COL4A6 genes regulates the expression of alpha5 and alpha6 chains in a distinct cell-specific fashion.","date":"2005","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/15598179","citation_count":20,"is_preprint":false},{"pmid":"7833948","id":"PMC_7833948","title":"Deletion spanning the 5' ends of both the COL4A5 and COL4A6 genes in a patient with Alport's syndrome and leiomyomatosis.","date":"1994","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/7833948","citation_count":19,"is_preprint":false},{"pmid":"8661006","id":"PMC_8661006","title":"Structure of the human type IV collagen COL4A6 gene, which is mutated in Alport syndrome-associated leiomyomatosis.","date":"1996","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/8661006","citation_count":18,"is_preprint":false},{"pmid":"7607673","id":"PMC_7607673","title":"YAC contigs mapping the human COL4A5 and COL4A6 genes and DXS118 within Xq21.3-q22.","date":"1995","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/7607673","citation_count":17,"is_preprint":false},{"pmid":"27377778","id":"PMC_27377778","title":"COL4A6 is dispensable for autosomal recessive Alport syndrome.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27377778","citation_count":14,"is_preprint":false},{"pmid":"11096082","id":"PMC_11096082","title":"Regulation of the paired type IV collagen genes COL4A5 and COL4A6. Role of the proximal promoter region.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11096082","citation_count":13,"is_preprint":false},{"pmid":"23958657","id":"PMC_23958657","title":"Deletion of the 5'exons of COL4A6 is not needed for the development of diffuse leiomyomatosis in patients with Alport syndrome.","date":"2013","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23958657","citation_count":13,"is_preprint":false},{"pmid":"33840813","id":"PMC_33840813","title":"Confirmation of COL4A6 variants in X-linked nonsyndromic hearing loss and its clinical implications.","date":"2021","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/33840813","citation_count":10,"is_preprint":false},{"pmid":"34778325","id":"PMC_34778325","title":"Clinical Manifestations of Alport Syndrome-Diffuse Leiomyomatosis Patients With Contiguous Gene Deletions in COL4A6 and COL4A5.","date":"2021","source":"Frontiers in medicine","url":"https://pubmed.ncbi.nlm.nih.gov/34778325","citation_count":9,"is_preprint":false},{"pmid":"20951201","id":"PMC_20951201","title":"Clonal overgrowth of esophageal smooth muscle cells in diffuse leiomyomatosis-Alport syndrome caused by partial deletion in COL4A5 and COL4A6 genes.","date":"2010","source":"Matrix biology : journal of the International Society for Matrix Biology","url":"https://pubmed.ncbi.nlm.nih.gov/20951201","citation_count":9,"is_preprint":false},{"pmid":"26179878","id":"PMC_26179878","title":"Chinese family with diffuse oesophageal leiomyomatosis: a new COL4A5/COL4A6 deletion and a case of gonosomal mosaicism.","date":"2015","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26179878","citation_count":9,"is_preprint":false},{"pmid":"30045277","id":"PMC_30045277","title":"Missense mutations in COL4A5 or COL4A6 genes may cause cerebrovascular fibromuscular dysplasia: Case report and literature review.","date":"2018","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/30045277","citation_count":8,"is_preprint":false},{"pmid":"33848312","id":"PMC_33848312","title":"Lack of collagen α6(IV) chain in mice does not cause severe-to-profound hearing loss or cochlear malformation, a distinct phenotype from nonsyndromic hearing loss with COL4A6 missense mutation.","date":"2021","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/33848312","citation_count":6,"is_preprint":false},{"pmid":"41092388","id":"PMC_41092388","title":"Uncovering dual molecular diagnoses in families with complex phenotypes through structural and clinical studies of novel COL4A6 variants.","date":"2026","source":"QJM : monthly journal of the Association of Physicians","url":"https://pubmed.ncbi.nlm.nih.gov/41092388","citation_count":0,"is_preprint":false},{"pmid":"41735371","id":"PMC_41735371","title":"CAF-enriched COL4A6 promotes gastric cancer progression and stromal remodeling despite an inverse association in bulk transcriptomes.","date":"2026","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/41735371","citation_count":0,"is_preprint":false},{"pmid":"41743075","id":"PMC_41743075","title":"Temporal Transcriptomics Leads From Discovery to in Vivo Validation: COL4A3/COL4A6/ COL4A5 and ITGA8 as Novel Arthrofibrosis Biomarkers in Post-traumatic Joint Contracture.","date":"2026","source":"Dose-response : a publication of International Hormesis Society","url":"https://pubmed.ncbi.nlm.nih.gov/41743075","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15437,"output_tokens":3934,"usd":0.05266,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11772,"output_tokens":3970,"usd":0.079055,"stage2_stop_reason":"end_turn"},"total_usd":0.131715,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"COL4A6 and COL4A5 are arranged head-to-head on chromosome Xq22 and share a common bidirectional promoter region; COL4A6 is transcribed from two alternative promoters in a tissue-specific manner, with one transcript (from exon 1') abundant in placenta and another (from exon 1) more frequent in kidney and lung.\",\n      \"method\": \"Genomic sequencing, 5' flanking sequence analysis, reverse transcription-PCR across tissue types\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — RT-PCR across multiple tissues with sequencing of promoter regions; replicated in multiple subsequent studies\",\n      \"pmids\": [\"7972123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The alpha6(IV) chain (COL4A6 protein product) is present as 27-kD monomers and associated dimers of the NC1 domain; it localizes to basement membranes of Bowman's capsules and distal tubules in adult kidney but is absent from the glomerular basement membrane, whereas alpha5(IV) is present in the GBM. Both chains co-localize in skin, smooth muscle cells, and adipocytes but are absent or minimal in cardiac muscle and hepatic sinusoidal endothelial cells.\",\n      \"method\": \"Peptide-specific monoclonal antibody generation, Western blotting, immunofluorescence staining across multiple human tissues\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal chain-specific antibodies with Western blot and immunofluorescence across multiple tissues; foundational localization study replicated in subsequent work\",\n      \"pmids\": [\"7657706\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The COL4A6 gene spans >200 kb, contains 46 exons, with exons 1' and 1 encoding two alternative 5'-UTRs and distinct signal peptide N-termini, exons 2-7 encoding the 7S domain, exons 7-42 encoding the collagenous COL1 domain with Gly-X-Y repeats, and exons 43-45 encoding the NC1 domain. The exon size pattern is highly homologous to COL4A2.\",\n      \"method\": \"Genomic library screening, lambda phage clone characterization, exon/intron mapping, restriction analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — complete gene structure determination by direct sequencing and mapping; foundational structural paper\",\n      \"pmids\": [\"7592929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Deletions spanning the 5' ends of both COL4A5 and COL4A6 cause diffuse leiomyomatosis (DL) in association with Alport syndrome; the COL4A6 breakpoints in DL/AS cases are clustered within intron 2 of COL4A6. Breakpoint sequences share homology with topoisomerase I and II consensus sequences, implicating topoisomerase-mediated recombination in deletion formation. Immunohistochemical analysis confirmed absence of alpha5(IV) and alpha6(IV) chains in basement membranes of affected smooth muscle tumor tissue.\",\n      \"method\": \"Breakpoint sequence characterization, DNA sequence homology analysis, immunohistochemistry with chain-specific antibodies, somatic mosaicism analysis\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct breakpoint sequencing with functional immunohistochemical validation; replicated across multiple DL/AS families\",\n      \"pmids\": [\"9463311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The minimal promoters for COL4A5 and COL4A6 are functionally distinct, residing within 100 bp of their respective transcription start sites. A bidirectional positive regulatory element exists between the two genes that functions in multiple cell types but not in glomerular visceral epithelial cells, which selectively transcribe COL4A5. This element enables co-expression of both genes in keratinocytes but not in podocytes.\",\n      \"method\": \"Transient transfection with reporter gene constructs, RNase protection assays, gel shift assays, DNase I footprinting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (reporter assays, gel shifts, footprinting) in cell lines with distinct expression patterns\",\n      \"pmids\": [\"11096082\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The bifunctional promoter between COL4A5 and COL4A6 regulates their expression in a cell-type-specific manner in response to growth factors. TGF-beta, EGF, VEGF, and PDGF significantly enhance expression from the alpha5(IV) gene in glomerular endothelial cells and mesangial cells but not from the alpha6(IV) gene; conversely, in tubular epithelial cells, these growth factors enhance expression from the alpha6(IV) gene but not the alpha5(IV) gene.\",\n      \"method\": \"Cloning of mouse bifunctional promoter into bidirectional reporter construct (CAT/Luciferase), transfection into glomerular endothelial cells, mesangial cells, and tubular epithelial cells, growth factor stimulation assays\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — bidirectional reporter construct with multiple growth factors across multiple cell types, single lab\",\n      \"pmids\": [\"15598179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Alpha5(IV) and alpha6(IV) chains are specifically expressed in esophageal smooth muscle basement membranes within the gastrointestinal tract. Deletion of COL4A5-COL4A6 promoters leads to clonal overgrowth of esophageal smooth muscle cells, demonstrated by CAG repeat analysis of the androgen receptor gene showing X-inactivation on the non-affected allele in leiomyoma cells.\",\n      \"method\": \"Immunohistochemistry with chain-specific antibodies across gastrointestinal tract, CAG repeat analysis of androgen receptor gene for clonal X-inactivation analysis\",\n      \"journal\": \"Matrix biology : journal of the International Society for Matrix Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — immunohistochemistry plus clonality analysis by X-inactivation, single lab, two orthogonal methods\",\n      \"pmids\": [\"20951201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A missense mutation (c.1771G>A, p.Gly591Ser) in COL4A6 causes X-linked nonsyndromic congenital hearing loss without Alport syndrome features. Expression of the COL4A6 homolog was confirmed in the zebrafish otic vesicle by in situ hybridization and in murine inner ear by immunostaining, establishing a role for COL4A6 in inner ear development and function.\",\n      \"method\": \"Next-generation sequencing, Sanger sequencing for segregation, in situ hybridization in zebrafish, immunostaining in mouse inner ear\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — mutation identified with segregation plus in situ hybridization and immunostaining in model organisms confirming expression; single lab\",\n      \"pmids\": [\"23714752\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"COL4A6 is dispensable for autosomal recessive Alport syndrome: mice lacking both alpha3(IV) and alpha6(IV) chains showed no significant difference in renal function or survival compared to Col4a3 single knockout mice, indicating alpha6(IV) induction in the GBM in autosomal recessive Alport syndrome does not play a major compensatory role.\",\n      \"method\": \"Generation of Col4a3/Col4a6 double knockout mice, renal function measurement, survival analysis, immunostaining\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis via double KO mouse with defined functional phenotype, single lab\",\n      \"pmids\": [\"27377778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"AS-DL deletions arise predominantly through homologous recombination involving transposed elements (long and short interspersed repeats, DNA transposons, LTR retrotransposons) at sequences homologous between COL4A5 and COL4A6. Eight of nine deletion alleles involved such homologous sequences. The occurrence of leiomyomatosis requires inactivation of both COL4A5 and COL4A6, as all deletions involved the bidirectional promoter region.\",\n      \"method\": \"Breakpoint characterization by PCR and sequencing in five AS-DL patients, sequence homology analysis for transposed elements\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct breakpoint sequencing across multiple patients with mechanistic inference about promoter loss; single lab\",\n      \"pmids\": [\"28275241\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Col4a6 knockout mice do not develop hearing loss or cochlear malformation, in contrast to humans with the COL4A6 p.Gly591Ser missense mutation who do. Alpha6(IV) chain is distributed throughout cochlear subepithelial basement membranes in mice. This discrepancy indicates the hearing loss mechanism is likely due to dominant-negative effects of the aberrant alpha6(IV) chain or the alpha5-alpha6-alpha5(IV) heterotrimer, rather than simple loss of function.\",\n      \"method\": \"Col4a6 knockout mouse generation, auditory brainstem response (click-evoked ABR), micro-computed tomography, histology, immunohistochemistry\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with defined audiological and structural phenotype plus immunolocalization; single lab, multiple readouts\",\n      \"pmids\": [\"33848312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A splicing variant in COL4A6 (c.951+1G>C) causes skipping of exon 15, demonstrated by in vitro minigene splicing assay, establishing a pathogenic mechanism for X-linked nonsyndromic hearing loss.\",\n      \"method\": \"In vitro minigene splicing assay\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Weak — direct functional splicing assay, single lab, single method\",\n      \"pmids\": [\"33840813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Knockdown of COL4A6 in prostate cancer cells activates the p-FAK/MMP-9 signaling pathway, promoting cell invasion and migration as measured by wound healing and transwell assays. COL4A6 protein localizes extracellularly in prostate cancer cells.\",\n      \"method\": \"siRNA knockdown, wound healing assay, cell invasion transwell assay, Western blot, immunofluorescence staining\",\n      \"journal\": \"Genetic testing and molecular biomarkers\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single knockdown experiment with invasion assay; pathway assignment (p-FAK/MMP-9) lacks direct biochemical validation\",\n      \"pmids\": [\"32551898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"A synonymous COL4A6 variant (c.1767G>A, p.Pro589=) causes partial exon skipping, demonstrated by RNA studies, establishing it as pathogenic for X-linked nonsyndromic hearing loss. Structural modeling of missense variant p.Gly494Arg predicts impact on protein structure. Zebrafish spatial and temporal expression analysis confirmed col4a6 expression in the otic vesicle and developing ear from 1 to 5 days post-fertilization.\",\n      \"method\": \"Exome/genome sequencing, RNA splicing analysis, zebrafish expression analysis (spatial/temporal), structural modeling\",\n      \"journal\": \"QJM : monthly journal of the Association of Physicians\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct RNA evidence for splicing effect plus in vivo zebrafish expression validation; single lab, multiple methods\",\n      \"pmids\": [\"41092388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"COL4A6 produced by cancer-associated fibroblasts (CAFs) promotes tumor progression and stromal remodeling in gastric cancer by inducing CAF activation (upregulation of alpha-SMA and FAP, stress fiber remodeling) and promoting epithelial-mesenchymal transition (EMT) in gastric cancer cells.\",\n      \"method\": \"Single-cell sequencing, CAF-enriched fibroblast cultures, functional experiments measuring alpha-SMA/FAP upregulation and stress fiber remodeling, EMT assays in cancer cells\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, cell culture functional experiments without reconstitution or in vivo validation; abstract lacks specific method detail\",\n      \"pmids\": [\"41735371\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COL4A6 encodes the alpha6(IV) type IV collagen chain, which is expressed from two alternative promoters regulated by a bifunctional bidirectional promoter shared with COL4A5, with tissue-specific and growth factor-regulated expression controlled at the promoter level; the alpha6(IV) chain localizes extracellularly to distinct basement membranes (e.g., Bowman's capsule and distal tubules but not the glomerular basement membrane in kidney, and esophageal smooth muscle), forms heterotrimers with alpha5(IV) chains, and missense mutations in the collagenous domain cause X-linked nonsyndromic hearing loss likely through dominant-negative disruption of the heterotrimer rather than simple loss of function, while contiguous deletions of the COL4A5/COL4A6 bidirectional promoter region cause diffuse leiomyomatosis through loss of both gene products in esophageal smooth muscle.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"COL4A6 encodes the alpha6(IV) type IV collagen chain, a basement membrane structural component whose expression is governed by a bidirectional promoter shared head-to-head with COL4A5 on chromosome Xq22 [#0]. This shared regulatory region drives tissue-specific transcription from two alternative COL4A6 promoters and contains a bidirectional positive regulatory element that enables co-expression of both chains in keratinocytes and other cell types but is inactive in podocytes, which selectively transcribe COL4A5 [#0, #4]; growth factors including TGF-beta, EGF, VEGF, and PDGF further partition expression in a cell-type-specific manner, enhancing alpha6(IV) in tubular epithelial cells while enhancing alpha5(IV) in glomerular cells [#5]. The alpha6(IV) chain assembles through its NC1 domain and deposits into select basement membranes—Bowman's capsule and distal tubules but notably not the glomerular basement membrane, as well as skin, smooth muscle, and esophageal smooth muscle—while co-localizing with alpha5(IV) [#1, #6]. Two distinct disease mechanisms arise from this gene: contiguous deletions removing the 5' ends and shared bidirectional promoter of both COL4A5 and COL4A6 cause diffuse leiomyomatosis through loss of both chains in esophageal smooth muscle, with deletion breakpoints clustering in COL4A6 intron 2 and arising via topoisomerase- and homologous-recombination-mediated rearrangement of transposed elements [#3, #6, #9]; separately, missense and splicing variants in COL4A6 cause X-linked nonsyndromic congenital hearing loss [#7, #11, #13]. Because Col4a6 knockout mice develop neither hearing loss nor cochlear malformation despite alpha6(IV) distribution throughout cochlear basement membranes, the hearing-loss mechanism is attributed to dominant-negative disruption of the heterotrimer by aberrant alpha6(IV) chains rather than simple loss of function [#10]. Genetic epistasis in Col4a3/Col4a6 double-knockout mice shows alpha6(IV) is dispensable for autosomal recessive Alport syndrome progression [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established the genomic architecture underlying COL4A6 regulation by showing it is arranged head-to-head with COL4A5 and driven by a shared bidirectional promoter with two tissue-specific alternative start sites.\",\n      \"evidence\": \"Genomic sequencing, promoter analysis, and RT-PCR across tissues\",\n      \"pmids\": [\"7972123\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the cis-elements conferring tissue specificity\", \"Functional consequence of the two transcript isoforms unresolved\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defined the alpha6(IV) protein product and its restricted basement-membrane distribution, distinguishing it from alpha5(IV) by its absence from the glomerular basement membrane.\",\n      \"evidence\": \"Chain-specific monoclonal antibodies, Western blot, and immunofluorescence across human tissues\",\n      \"pmids\": [\"7657706\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Heterotrimer stoichiometry not directly resolved\", \"Functional role in each basement membrane not tested\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Resolved the full gene structure including dual alternative first exons, the 7S, collagenous COL1, and NC1 domains, providing the framework for interpreting downstream mutations.\",\n      \"evidence\": \"Genomic library screening and exon/intron mapping\",\n      \"pmids\": [\"7592929\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not assign functional roles to individual domains\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Linked contiguous deletions removing both COL4A5 and COL4A6 5' regions to diffuse leiomyomatosis with Alport syndrome and implicated topoisomerase-mediated recombination, explaining a co-deletion disease mechanism.\",\n      \"evidence\": \"Breakpoint sequencing, homology analysis, and immunohistochemistry in DL/AS families\",\n      \"pmids\": [\"9463311\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish how loss of both chains drives smooth muscle overgrowth\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Dissected the bidirectional promoter to show distinct minimal promoters and a shared positive regulatory element that permits co-expression in some cell types but not podocytes, explaining cell-type-selective chain expression.\",\n      \"evidence\": \"Reporter assays, RNase protection, gel shift, and DNase I footprinting in cell lines\",\n      \"pmids\": [\"11096082\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trans-acting factors binding the element not identified\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showed the bidirectional promoter responds to growth factors in a cell-type-specific manner, partitioning alpha5(IV) versus alpha6(IV) induction between glomerular and tubular cells.\",\n      \"evidence\": \"Bidirectional reporter constructs with growth factor stimulation across renal cell types\",\n      \"pmids\": [\"15598179\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signal transduction pathways linking growth factors to the promoter not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated that promoter deletion causes clonal esophageal smooth muscle overgrowth, connecting the genetic lesion to a defined tumorigenic clonal expansion.\",\n      \"evidence\": \"Chain-specific immunohistochemistry and androgen receptor CAG-repeat X-inactivation clonality analysis\",\n      \"pmids\": [\"20951201\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which collagen chain loss triggers clonal growth unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified COL4A6 missense mutation as a cause of X-linked nonsyndromic hearing loss and established inner-ear expression, defining a new disease association distinct from Alport syndrome.\",\n      \"evidence\": \"NGS with segregation, zebrafish in situ hybridization, mouse inner-ear immunostaining\",\n      \"pmids\": [\"23714752\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which the missense allele disrupts function not established\", \"Single family\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Tested whether alpha6(IV) compensates in autosomal recessive Alport syndrome and showed via genetic epistasis it is dispensable, ruling out a major compensatory GBM role.\",\n      \"evidence\": \"Col4a3/Col4a6 double-knockout mice with renal function and survival analysis\",\n      \"pmids\": [\"27377778\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address alpha6(IV) function in non-renal basement membranes\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Reconciled the human-mouse discrepancy by showing Col4a6 knockout mice have normal hearing, indicating the human hearing-loss mutation acts through a dominant-negative mechanism rather than loss of function.\",\n      \"evidence\": \"Col4a6 knockout mice with ABR, micro-CT, histology, and immunohistochemistry\",\n      \"pmids\": [\"33848312\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Dominant-negative mechanism inferred, not biochemically demonstrated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Expanded the pathogenic mutational spectrum for hearing loss by demonstrating a splice-site variant causes exon 15 skipping.\",\n      \"evidence\": \"In vitro minigene splicing assay\",\n      \"pmids\": [\"33840813\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Effect on protein assembly not tested\", \"Single method\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Further extended the hearing-loss spectrum to a synonymous variant causing partial exon skipping and reconfirmed conserved otic-vesicle expression, strengthening the developmental role.\",\n      \"evidence\": \"Exome/genome sequencing, RNA splicing analysis, zebrafish spatiotemporal expression, structural modeling\",\n      \"pmids\": [\"41092388\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional impact of structural model on heterotrimer not validated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Implicated COL4A6 in cancer cell behavior, with knockdown activating p-FAK/MMP-9 signaling to promote prostate cancer invasion and migration.\",\n      \"evidence\": \"siRNA knockdown with wound healing, transwell invasion, Western blot, and immunofluorescence\",\n      \"pmids\": [\"32551898\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathway assignment lacks direct biochemical validation\", \"Single knockdown experiment, no in vivo validation\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Implicated CAF-derived COL4A6 in gastric cancer progression through CAF activation and induction of epithelial-mesenchymal transition.\",\n      \"evidence\": \"Single-cell sequencing, CAF cultures, alpha-SMA/FAP and stress-fiber readouts, EMT assays\",\n      \"pmids\": [\"41735371\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No reconstitution or in vivo validation\", \"Mechanism linking secreted collagen to CAF activation undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The biochemical basis of the inferred dominant-negative heterotrimer disruption in hearing loss, and the trans-acting factors that read the bidirectional promoter to achieve cell-type-specific chain expression, remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural or biochemical demonstration of mutant heterotrimer disruption\", \"Transcription factors binding the bidirectional regulatory element unidentified\", \"Functional role of alpha6(IV) in each specific basement membrane untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 6, 12]},\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [1, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 4, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"COL4A5\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}