{"gene":"SGCD","run_date":"2026-06-10T07:46:31","timeline":{"discoveries":[{"year":1996,"finding":"Delta-sarcoglycan (SGCD) encodes a novel 35-kDa component of the sarcoglycan (SG) complex at the muscle membrane, where dystrophin associates with the dystroglycan (DG) and sarcoglycan (SG) subcomplexes. A homozygous frameshift mutation (single nucleotide deletion) in SGCD causes LGMD2F, establishing SGCD as a structural component of the dystrophin-associated protein complex.","method":"Chromosomal mapping, mutation identification by sequencing, protein complex membership inferred from co-localization with known SG complex components","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic identification with protein complex assignment, single lab but converging genetic and biochemical evidence","pmids":["8841194"],"is_preprint":false},{"year":2019,"finding":"Loss of delta-sarcoglycan (Sgcd knockout mouse) results in decreased or absent expression of other sarcoglycan complex partners (α-, β-, γ-, ε-sarcoglycan, and sarcospan) in the retina, with a significant compensatory increase in α-sarcoglycan subunit, demonstrating that SGCD is required for the stability and normal expression of the sarcoglycan-sarcospan complex in retinal tissue.","method":"Immunofluorescence and Western blot analysis of Sgcd-/- mouse retina; electroretinography","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein-level analysis by Western blot and immunofluorescence in KO model with defined molecular consequence, single lab","pmids":["31689918"],"is_preprint":false},{"year":2025,"finding":"In Sgcd-/- mice, loss of delta-sarcoglycan destabilizes the dystrophin-associated glycoprotein complex at the sarcolemma, rendering muscle fibers vulnerable to contraction-induced damage. This is accompanied by early dysregulation of the ATX-LPA signaling axis and the YAP/TAZ signaling pathway, which are concomitant with inflammatory infiltrate, fibrosis, impaired force generation, and reduced resistance to mechanical damage in skeletal muscles.","method":"Sgcd-/- mouse model; measurement of contractile properties, ATX-LPA pathway components, YAP/TAZ pathway markers, inflammatory and fibrotic markers across multiple skeletal muscles at 1 and 2 months of age","journal":"Skeletal muscle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function model with defined molecular pathway readouts and functional phenotype, single lab, multiple muscles and timepoints","pmids":["40050938"],"is_preprint":false},{"year":2018,"finding":"In Sgcd-/- mice, GRK2 and NF-κB are NOT upregulated (in contrast to mdx dystrophin-deficient mice), indicating that SGCD-deficient cardiomyopathy does not involve the same adrenergic dysregulation pathway as dystrophin deficiency. AAV9-mediated βARKct gene therapy (GRK2 inhibitor) provided only mild cardiac benefit in Sgcd-/- mice, consistent with the absence of GRK2 upregulation.","method":"AAV9-mediated gene delivery in Sgcd-/- mice; echocardiographic assessment of left ventricular function; molecular analysis of GRK2 and NF-κB expression","journal":"Neuromuscular disorders : NMD","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — negative mechanistic finding confirmed by molecular and functional readouts in KO model, single lab","pmids":["30782477"],"is_preprint":false},{"year":2013,"finding":"Expression of SGCD in transfected PC12 cells augmented chromogranin A (CHGA) trafficking into the exocytotic regulated secretory pathway, suggesting SGCD plays a role in catecholamine exocytosis regulation.","method":"Transfection of PC12 cells with SGCD and chimeric regulated secretory pathway photoprotein (CHGA-EAP); measurement of exocytotic pathway activity","journal":"Journal of neurochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single cell-based overexpression assay, single lab, no mutagenesis or mechanistic follow-up","pmids":["23786442"],"is_preprint":false},{"year":2017,"finding":"In Boston terriers with LGMD2F caused by SGCD mutations, absence of SGCD protein results in loss of the entire sarcoglycan-sarcospan complex at the sarcolemma, as confirmed by immunostaining and immunohistochemistry, demonstrating that SGCD is required for sarcolemmal localization of the sarcoglycan-sarcospan complex.","method":"Whole exome sequencing, immunostaining, immunohistochemistry for sarcoglycan-sarcospan complex in canine muscle","journal":"Skeletal muscle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein localization by immunostaining in loss-of-function animal model, confirms human findings in independent species","pmids":["28697784"],"is_preprint":false}],"current_model":"SGCD encodes delta-sarcoglycan, a 35-kDa transmembrane component of the sarcoglycan-sarcospan subcomplex of the dystrophin-associated glycoprotein complex (DGC) at the sarcolemma; loss of SGCD destabilizes the entire sarcoglycan-sarcospan complex, renders muscle fibers vulnerable to contraction-induced damage, and triggers downstream inflammatory and fibrotic signaling (ATX-LPA, YAP/TAZ pathways), with SGCD-deficient cardiomyopathy operating through a GRK2/NF-κB-independent mechanism distinct from dystrophin deficiency."},"narrative":{"mechanistic_narrative":"SGCD encodes delta-sarcoglycan, a 35-kDa structural component of the sarcoglycan-sarcospan subcomplex within the dystrophin-associated protein complex at the muscle membrane, where loss-of-function mutations cause limb-girdle muscular dystrophy type 2F [PMID:8841194]. SGCD is required for assembly and sarcolemmal localization of the entire sarcoglycan-sarcospan complex: its absence in knockout mice and in naturally occurring canine LGMD2F leads to loss or destabilization of the other sarcoglycan subunits and sarcospan [PMID:31689918, PMID:28697784]. Without an intact complex, the dystrophin-associated glycoprotein complex is destabilized at the sarcolemma, rendering muscle fibers vulnerable to contraction-induced damage and driving inflammatory infiltration, fibrosis, and impaired force generation through early dysregulation of the ATX-LPA and YAP/TAZ signaling axes [PMID:40050938]. In the heart, SGCD-deficient cardiomyopathy proceeds through a mechanism distinct from dystrophin deficiency, without upregulation of GRK2 or NF-κB [PMID:30782477].","teleology":[{"year":1996,"claim":"Established SGCD as a distinct gene encoding a structural membrane component and linked its loss to human muscular dystrophy, answering what disease the gene causes and where its product acts.","evidence":"Chromosomal mapping and sequencing identifying a homozygous frameshift mutation causing LGMD2F, with complex membership inferred from co-localization","pmids":["8841194"],"confidence":"Medium","gaps":["Complex membership inferred from co-localization rather than direct biochemical reconstitution","Structural role within the complex not resolved at residue level"]},{"year":2017,"claim":"Demonstrated in an independent species that SGCD is required for sarcolemmal localization of the whole sarcoglycan-sarcospan complex, confirming its assembly-anchoring role beyond a single human pedigree.","evidence":"Whole exome sequencing and immunostaining/immunohistochemistry of muscle from Boston terriers with SGCD-mutant LGMD2F","pmids":["28697784"],"confidence":"Medium","gaps":["Does not define which subunit interactions SGCD directly mediates","Mechanism of complex destabilization not dissected"]},{"year":2018,"claim":"Distinguished SGCD-deficient cardiomyopathy from dystrophin deficiency by showing it does not engage the GRK2/NF-κB adrenergic dysregulation pathway, refining the cardiac mechanism.","evidence":"AAV9 βARKct gene therapy and molecular analysis of GRK2/NF-κB in Sgcd-/- mice with echocardiography","pmids":["30782477"],"confidence":"Medium","gaps":["Positive driver of the cardiac phenotype not identified","Why βARKct gives mild benefit despite absent GRK2 upregulation unexplained"]},{"year":2019,"claim":"Extended the complex-stabilizing requirement to non-muscle (retinal) tissue, showing SGCD loss collapses partner subunit expression with selective α-sarcoglycan compensation.","evidence":"Immunofluorescence, Western blot, and electroretinography in Sgcd-/- mouse retina","pmids":["31689918"],"confidence":"Medium","gaps":["Functional consequence of complex loss in retina incompletely defined","Basis of selective α-sarcoglycan compensation unknown"]},{"year":2025,"claim":"Connected SGCD loss to specific downstream signaling, identifying early ATX-LPA and YAP/TAZ dysregulation as drivers of inflammation, fibrosis, and mechanical fragility in skeletal muscle.","evidence":"Sgcd-/- mouse contractile, pathway, inflammatory, and fibrotic readouts across multiple muscles at 1 and 2 months","pmids":["40050938"],"confidence":"Medium","gaps":["Causal link between complex loss and ATX-LPA/YAP/TAZ activation not mechanistically resolved","Whether targeting these pathways rescues phenotype untested"]},{"year":null,"claim":"How SGCD physically organizes the sarcoglycan-sarcospan complex and how complex loss is transduced into specific signaling cascades remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of SGCD within the complex","Direct binding partners within the complex not mapped biochemically","Mechanistic chain from sarcolemmal instability to ATX-LPA/YAP/TAZ unestablished"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,5]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2,5]}],"pathway":[],"complexes":["dystrophin-associated glycoprotein complex","sarcoglycan-sarcospan complex"],"partners":["SGCA","SGCB","SGCG","SGCE","SSPN"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q92629","full_name":"Delta-sarcoglycan","aliases":["35 kDa dystrophin-associated glycoprotein","35DAG"],"length_aa":289,"mass_kda":32.1,"function":"Component of the sarcoglycan complex, a subcomplex of the dystrophin-glycoprotein complex which forms a link between the F-actin cytoskeleton and the extracellular matrix","subcellular_location":"Cell membrane, sarcolemma; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/Q92629/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SGCD","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SGCD","total_profiled":1310},"omim":[{"mim_id":"608113","title":"SARCOGLYCAN, ZETA; SGCZ","url":"https://www.omim.org/entry/608113"},{"mim_id":"607155","title":"MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (LIMB-GIRDLE), TYPE C, 5; MDDGC5","url":"https://www.omim.org/entry/607155"},{"mim_id":"606685","title":"CARDIOMYOPATHY, DILATED, 1L; CMD1L","url":"https://www.omim.org/entry/606685"},{"mim_id":"604286","title":"MUSCULAR DYSTROPHY, LIMB-GIRDLE, AUTOSOMAL RECESSIVE 4; LGMDR4","url":"https://www.omim.org/entry/604286"},{"mim_id":"601411","title":"SARCOGLYCAN, DELTA; SGCD","url":"https://www.omim.org/entry/601411"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"heart muscle","ntpm":36.6},{"tissue":"skeletal muscle","ntpm":40.2},{"tissue":"tongue","ntpm":31.1}],"url":"https://www.proteinatlas.org/search/SGCD"},"hgnc":{"alias_symbol":["DAGD","LGMD2F","CMD1L"],"prev_symbol":[]},"alphafold":{"accession":"Q92629","domains":[{"cath_id":"-","chopping":"102-170","consensus_level":"medium","plddt":91.3268,"start":102,"end":170},{"cath_id":"-","chopping":"249-289","consensus_level":"medium","plddt":73.8373,"start":249,"end":289},{"cath_id":"1.20.5","chopping":"24-80","consensus_level":"medium","plddt":83.1914,"start":24,"end":80}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92629","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q92629-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q92629-F1-predicted_aligned_error_v6.png","plddt_mean":81.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SGCD","jax_strain_url":"https://www.jax.org/strain/search?query=SGCD"},"sequence":{"accession":"Q92629","fasta_url":"https://rest.uniprot.org/uniprotkb/Q92629.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q92629/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92629"}},"corpus_meta":[{"pmid":"8841194","id":"PMC_8841194","title":"Autosomal recessive limb-girdle muscular dystrophy, LGMD2F, is caused by a mutation in the delta-sarcoglycan gene.","date":"1996","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8841194","citation_count":363,"is_preprint":false},{"pmid":"8776597","id":"PMC_8776597","title":"Linkage analysis in autosomal recessive limb-girdle muscular dystrophy (AR LGMD) maps a sixth form to 5q33-34 (LGMD2F) and indicates that there is at least one more subtype of AR LGMD.","date":"1996","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8776597","citation_count":93,"is_preprint":false},{"pmid":"9832045","id":"PMC_9832045","title":"A first missense mutation in the delta sarcoglycan gene associated with a severe phenotype and frequency of limb-girdle muscular dystrophy type 2F (LGMD2F) in Brazilian sarcoglycanopathies.","date":"1998","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9832045","citation_count":40,"is_preprint":false},{"pmid":"30733730","id":"PMC_30733730","title":"SGCD Homozygous Nonsense Mutation (p.Arg97∗) Causing Limb-Girdle Muscular Dystrophy Type 2F (LGMD2F) in a Consanguineous Family, a Case Report.","date":"2019","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30733730","citation_count":20,"is_preprint":false},{"pmid":"31689918","id":"PMC_31689918","title":"Lack of Delta-Sarcoglycan (Sgcd) Results in Retinal Degeneration.","date":"2019","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/31689918","citation_count":19,"is_preprint":false},{"pmid":"28697784","id":"PMC_28697784","title":"Exome sequencing reveals independent SGCD deletions causing limb girdle muscular dystrophy in Boston terriers.","date":"2017","source":"Skeletal muscle","url":"https://pubmed.ncbi.nlm.nih.gov/28697784","citation_count":17,"is_preprint":false},{"pmid":"10838250","id":"PMC_10838250","title":"A homozygous nonsense mutation in delta-sarcoglycan exon 3 in a case of LGMD2F.","date":"2000","source":"Neuromuscular disorders : NMD","url":"https://pubmed.ncbi.nlm.nih.gov/10838250","citation_count":16,"is_preprint":false},{"pmid":"30782477","id":"PMC_30782477","title":"Various effects of AAV9-mediated βARKct gene therapy on the heart in dystrophin-deficient (mdx) mice and δ-sarcoglycan-deficient (Sgcd-/-) mice.","date":"2018","source":"Neuromuscular disorders : NMD","url":"https://pubmed.ncbi.nlm.nih.gov/30782477","citation_count":11,"is_preprint":false},{"pmid":"28412737","id":"PMC_28412737","title":"Whole-exome sequencing identifies SGCD and ACVRL1 mutations associated with total anomalous pulmonary venous return (TAPVR) in Chinese population.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/28412737","citation_count":11,"is_preprint":false},{"pmid":"36505894","id":"PMC_36505894","title":"Identification of FERMT1 and SGCD as key marker in acute aortic dissection from the perspective of predictive, preventive, and personalized medicine.","date":"2022","source":"The EPMA journal","url":"https://pubmed.ncbi.nlm.nih.gov/36505894","citation_count":7,"is_preprint":false},{"pmid":"40050938","id":"PMC_40050938","title":"Dysregulated ATX-LPA and YAP/TAZ signaling in dystrophic Sgcd-/- mice with early fibrosis and inflammation.","date":"2025","source":"Skeletal muscle","url":"https://pubmed.ncbi.nlm.nih.gov/40050938","citation_count":3,"is_preprint":false},{"pmid":"30257524","id":"PMC_30257524","title":"Significant Association Between Variant in SGCD and Age-Related Macular Degeneration.","date":"2018","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/30257524","citation_count":3,"is_preprint":false},{"pmid":"37628692","id":"PMC_37628692","title":"SGCD Missense Variant in a Lagotto Romagnolo Dog with Autosomal Recessively Inherited Limb-Girdle Muscular Dystrophy.","date":"2023","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/37628692","citation_count":3,"is_preprint":false},{"pmid":"18763146","id":"PMC_18763146","title":"Cloning, expression and characterization of gene sgcD involved in the biosynthesis of novel antitumor lidamycin.","date":"2003","source":"Science in China. Series C, Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/18763146","citation_count":2,"is_preprint":false},{"pmid":"23786442","id":"PMC_23786442","title":"Genetic variation at the delta-sarcoglycan (SGCD) locus elevates heritable sympathetic nerve activity in human twin pairs.","date":"2013","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23786442","citation_count":2,"is_preprint":false},{"pmid":"35999027","id":"PMC_35999027","title":"Identification of a SGCD × Discrimination Interaction Effect on Systolic Blood Pressure in African American Adults in the Jackson Heart Study.","date":"2022","source":"American journal of hypertension","url":"https://pubmed.ncbi.nlm.nih.gov/35999027","citation_count":2,"is_preprint":false},{"pmid":"40539696","id":"PMC_40539696","title":"SGCD: High-Resolution Spatial Domain Characterization via Data Interpolation and Cell-Type Deconvolution.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/40539696","citation_count":1,"is_preprint":false},{"pmid":"41840602","id":"PMC_41840602","title":"From gene to heart: the impact of a novel SGCD variant in familial dilated cardiomyopathy.","date":"2026","source":"BMC medical genomics","url":"https://pubmed.ncbi.nlm.nih.gov/41840602","citation_count":0,"is_preprint":false},{"pmid":"41721539","id":"PMC_41721539","title":"Clinical and Genetic Analysis of Limb-Girdle Muscular Dystrophy Type 2F with A Novel SGCD Mutation: A Case Report.","date":"2026","source":"Cell journal","url":"https://pubmed.ncbi.nlm.nih.gov/41721539","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11524,"output_tokens":1661,"usd":0.029743,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8546,"output_tokens":2019,"usd":0.046602,"stage2_stop_reason":"end_turn"},"total_usd":0.076345,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1996,\n      \"finding\": \"Delta-sarcoglycan (SGCD) encodes a novel 35-kDa component of the sarcoglycan (SG) complex at the muscle membrane, where dystrophin associates with the dystroglycan (DG) and sarcoglycan (SG) subcomplexes. A homozygous frameshift mutation (single nucleotide deletion) in SGCD causes LGMD2F, establishing SGCD as a structural component of the dystrophin-associated protein complex.\",\n      \"method\": \"Chromosomal mapping, mutation identification by sequencing, protein complex membership inferred from co-localization with known SG complex components\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic identification with protein complex assignment, single lab but converging genetic and biochemical evidence\",\n      \"pmids\": [\"8841194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Loss of delta-sarcoglycan (Sgcd knockout mouse) results in decreased or absent expression of other sarcoglycan complex partners (α-, β-, γ-, ε-sarcoglycan, and sarcospan) in the retina, with a significant compensatory increase in α-sarcoglycan subunit, demonstrating that SGCD is required for the stability and normal expression of the sarcoglycan-sarcospan complex in retinal tissue.\",\n      \"method\": \"Immunofluorescence and Western blot analysis of Sgcd-/- mouse retina; electroretinography\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein-level analysis by Western blot and immunofluorescence in KO model with defined molecular consequence, single lab\",\n      \"pmids\": [\"31689918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Sgcd-/- mice, loss of delta-sarcoglycan destabilizes the dystrophin-associated glycoprotein complex at the sarcolemma, rendering muscle fibers vulnerable to contraction-induced damage. This is accompanied by early dysregulation of the ATX-LPA signaling axis and the YAP/TAZ signaling pathway, which are concomitant with inflammatory infiltrate, fibrosis, impaired force generation, and reduced resistance to mechanical damage in skeletal muscles.\",\n      \"method\": \"Sgcd-/- mouse model; measurement of contractile properties, ATX-LPA pathway components, YAP/TAZ pathway markers, inflammatory and fibrotic markers across multiple skeletal muscles at 1 and 2 months of age\",\n      \"journal\": \"Skeletal muscle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function model with defined molecular pathway readouts and functional phenotype, single lab, multiple muscles and timepoints\",\n      \"pmids\": [\"40050938\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In Sgcd-/- mice, GRK2 and NF-κB are NOT upregulated (in contrast to mdx dystrophin-deficient mice), indicating that SGCD-deficient cardiomyopathy does not involve the same adrenergic dysregulation pathway as dystrophin deficiency. AAV9-mediated βARKct gene therapy (GRK2 inhibitor) provided only mild cardiac benefit in Sgcd-/- mice, consistent with the absence of GRK2 upregulation.\",\n      \"method\": \"AAV9-mediated gene delivery in Sgcd-/- mice; echocardiographic assessment of left ventricular function; molecular analysis of GRK2 and NF-κB expression\",\n      \"journal\": \"Neuromuscular disorders : NMD\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — negative mechanistic finding confirmed by molecular and functional readouts in KO model, single lab\",\n      \"pmids\": [\"30782477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Expression of SGCD in transfected PC12 cells augmented chromogranin A (CHGA) trafficking into the exocytotic regulated secretory pathway, suggesting SGCD plays a role in catecholamine exocytosis regulation.\",\n      \"method\": \"Transfection of PC12 cells with SGCD and chimeric regulated secretory pathway photoprotein (CHGA-EAP); measurement of exocytotic pathway activity\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single cell-based overexpression assay, single lab, no mutagenesis or mechanistic follow-up\",\n      \"pmids\": [\"23786442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In Boston terriers with LGMD2F caused by SGCD mutations, absence of SGCD protein results in loss of the entire sarcoglycan-sarcospan complex at the sarcolemma, as confirmed by immunostaining and immunohistochemistry, demonstrating that SGCD is required for sarcolemmal localization of the sarcoglycan-sarcospan complex.\",\n      \"method\": \"Whole exome sequencing, immunostaining, immunohistochemistry for sarcoglycan-sarcospan complex in canine muscle\",\n      \"journal\": \"Skeletal muscle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein localization by immunostaining in loss-of-function animal model, confirms human findings in independent species\",\n      \"pmids\": [\"28697784\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SGCD encodes delta-sarcoglycan, a 35-kDa transmembrane component of the sarcoglycan-sarcospan subcomplex of the dystrophin-associated glycoprotein complex (DGC) at the sarcolemma; loss of SGCD destabilizes the entire sarcoglycan-sarcospan complex, renders muscle fibers vulnerable to contraction-induced damage, and triggers downstream inflammatory and fibrotic signaling (ATX-LPA, YAP/TAZ pathways), with SGCD-deficient cardiomyopathy operating through a GRK2/NF-κB-independent mechanism distinct from dystrophin deficiency.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SGCD encodes delta-sarcoglycan, a 35-kDa structural component of the sarcoglycan-sarcospan subcomplex within the dystrophin-associated protein complex at the muscle membrane, where loss-of-function mutations cause limb-girdle muscular dystrophy type 2F [#0]. SGCD is required for assembly and sarcolemmal localization of the entire sarcoglycan-sarcospan complex: its absence in knockout mice and in naturally occurring canine LGMD2F leads to loss or destabilization of the other sarcoglycan subunits and sarcospan [#1, #5]. Without an intact complex, the dystrophin-associated glycoprotein complex is destabilized at the sarcolemma, rendering muscle fibers vulnerable to contraction-induced damage and driving inflammatory infiltration, fibrosis, and impaired force generation through early dysregulation of the ATX-LPA and YAP/TAZ signaling axes [#2]. In the heart, SGCD-deficient cardiomyopathy proceeds through a mechanism distinct from dystrophin deficiency, without upregulation of GRK2 or NF-\\u03baB [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established SGCD as a distinct gene encoding a structural membrane component and linked its loss to human muscular dystrophy, answering what disease the gene causes and where its product acts.\",\n      \"evidence\": \"Chromosomal mapping and sequencing identifying a homozygous frameshift mutation causing LGMD2F, with complex membership inferred from co-localization\",\n      \"pmids\": [\"8841194\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Complex membership inferred from co-localization rather than direct biochemical reconstitution\", \"Structural role within the complex not resolved at residue level\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated in an independent species that SGCD is required for sarcolemmal localization of the whole sarcoglycan-sarcospan complex, confirming its assembly-anchoring role beyond a single human pedigree.\",\n      \"evidence\": \"Whole exome sequencing and immunostaining/immunohistochemistry of muscle from Boston terriers with SGCD-mutant LGMD2F\",\n      \"pmids\": [\"28697784\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not define which subunit interactions SGCD directly mediates\", \"Mechanism of complex destabilization not dissected\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Distinguished SGCD-deficient cardiomyopathy from dystrophin deficiency by showing it does not engage the GRK2/NF-\\u03baB adrenergic dysregulation pathway, refining the cardiac mechanism.\",\n      \"evidence\": \"AAV9 \\u03b2ARKct gene therapy and molecular analysis of GRK2/NF-\\u03baB in Sgcd-/- mice with echocardiography\",\n      \"pmids\": [\"30782477\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Positive driver of the cardiac phenotype not identified\", \"Why \\u03b2ARKct gives mild benefit despite absent GRK2 upregulation unexplained\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended the complex-stabilizing requirement to non-muscle (retinal) tissue, showing SGCD loss collapses partner subunit expression with selective \\u03b1-sarcoglycan compensation.\",\n      \"evidence\": \"Immunofluorescence, Western blot, and electroretinography in Sgcd-/- mouse retina\",\n      \"pmids\": [\"31689918\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of complex loss in retina incompletely defined\", \"Basis of selective \\u03b1-sarcoglycan compensation unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected SGCD loss to specific downstream signaling, identifying early ATX-LPA and YAP/TAZ dysregulation as drivers of inflammation, fibrosis, and mechanical fragility in skeletal muscle.\",\n      \"evidence\": \"Sgcd-/- mouse contractile, pathway, inflammatory, and fibrotic readouts across multiple muscles at 1 and 2 months\",\n      \"pmids\": [\"40050938\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal link between complex loss and ATX-LPA/YAP/TAZ activation not mechanistically resolved\", \"Whether targeting these pathways rescues phenotype untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SGCD physically organizes the sarcoglycan-sarcospan complex and how complex loss is transduced into specific signaling cascades remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of SGCD within the complex\", \"Direct binding partners within the complex not mapped biochemically\", \"Mechanistic chain from sarcolemmal instability to ATX-LPA/YAP/TAZ unestablished\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 5]}\n    ],\n    \"pathway\": [],\n    \"complexes\": [\"dystrophin-associated glycoprotein complex\", \"sarcoglycan-sarcospan complex\"],\n    \"partners\": [\"SGCA\", \"SGCB\", \"SGCG\", \"SGCE\", \"SSPN\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}