{"gene":"SGCA","run_date":"2026-06-10T07:46:31","timeline":{"discoveries":[{"year":1993,"finding":"SGCA (adhalin/50-DAG) is a component of the dystrophin-glycoprotein complex (DGC), which links the muscle cytoskeleton to the extracellular matrix. It has a predicted 17-amino acid signal sequence, one transmembrane domain, and two potential N-linked glycosylation sites. Expression is restricted to skeletal, cardiac, and selected smooth muscles. Down-regulation in DMD/mdx muscle is a post-translational event, as mRNA is present.","method":"cDNA cloning, deduced amino acid sequence analysis, affinity-purified antibody immunoblot/immunofluorescence, mRNA expression analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — cDNA cloning with primary structure determination, antibody validation, and expression profiling; foundational structural characterization replicated across subsequent studies","pmids":["8226900"],"is_preprint":false},{"year":1994,"finding":"Missense mutations within the adhalin gene cause autosomal recessive muscular dystrophy (SCARMD/LGMD2D). The adhalin gene maps to chromosome 17q12-q21.33, distinct from the 13q-linked SCARMD locus.","method":"cDNA cloning, microsatellite linkage analysis, genomic sequencing to identify missense mutations","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct mutation identification by sequencing plus genetic linkage in affected families; independently replicated in multiple subsequent studies","pmids":["8069911"],"is_preprint":false},{"year":1994,"finding":"Human adhalin is alternatively spliced, producing a 35-kDa non-transmembrane isoform in addition to the full-length transmembrane form. Both isoforms are exclusively expressed in striated muscle.","method":"cDNA characterization, alternative splice form identification, chromosomal mapping to 17q21","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single lab, direct molecular characterization of splice variants with expression profiling","pmids":["7937874"],"is_preprint":false},{"year":1996,"finding":"Adhalin localizes to the plasma membrane with the majority of protein on the outer face of the sarcolemma, as determined by immunogold electron microscopy. Alpha-dystroglycan projects from the outer face and forms strands reaching the basal lamina. In DMD, adhalin labeling is severely reduced but the vestige remains in normal position, while merosin is expressed normally, indicating that merosin incorporation is independent of dystrophin and its associated proteins.","method":"Single and double immunogold labeling electron microscopy on normal and DMD human skeletal muscle","journal":"Neuropathology and applied neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct ultrastructural localization with functional implication; single lab, two orthogonal labeling approaches","pmids":["8866780"],"is_preprint":false},{"year":1996,"finding":"Triple immunogold labeling electron microscopy on normal human skeletal myofibers demonstrated that dystrophin, beta-dystroglycan, and adhalin are closely associated with each other at the muscle plasma membrane, consistent with biochemical evidence for their complex assembly.","method":"Triple immunogold labeling electron microscopy","journal":"Acta neuropathologica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct ultrastructural co-localization; single lab, single method but rigorous EM approach","pmids":["8960314"],"is_preprint":false},{"year":1999,"finding":"Alpha-sarcoglycan (adhalin) has ecto-ATPase activity: it binds ATP in a Mg2+-dependent, Ca2+-independent manner, and the binding is inhibited by BzATP and ADP. A consensus nucleotide-binding site exists in the extracellular domain. An antibody against this sequence inhibits ATP binding. A dystrophin-DAP preparation shows Mg-ATPase activity inhibited by this antibody but not by endo-ATPase inhibitors. A P2X-type purinergic receptor is present in the sarcolemmal membrane, suggesting that alpha-sarcoglycan modulates P2X receptor activity by buffering extracellular ATP concentration.","method":"ATP binding assay (Mg2+-dependent), ATPase activity assay with inhibitory antibody, purinergic receptor identification, sequence analysis of nucleotide-binding site","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay with antibody inhibition and sequence-based active site identification; multiple orthogonal methods in single study","pmids":["10075685"],"is_preprint":false},{"year":1997,"finding":"Most SGCA missense mutations (including the common R77C) are located in the extracellular domain of the protein. Mutation severity correlates at least in part with the amount of residual protein. The R77C substitution accounts for 32% of mutated chromosomes and the R284C substitution is associated with a benign disease course.","method":"Mutation screening of 31 unrelated patients by sequencing; genotype-phenotype correlation analysis","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Strong — systematic mutational survey with genotype-phenotype correlation; replicated across multiple independent families","pmids":["9192266"],"is_preprint":false},{"year":1997,"finding":"Primary defect in any one of the four sarcoglycan proteins (alpha, beta, gamma, delta) leads to reduced expression of the whole sarcoglycan complex (secondary deficiency of the other sarcoglycans), as shown by immunohistochemical analysis of alpha-SG-deficient patients who also show concomitant deficiency of beta- and gamma-sarcoglycans.","method":"Immunohistochemistry on 20 alpha-SG-deficient patient muscle biopsies","journal":"Acta neuropathologica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic immunohistochemical analysis across 20 patients; single method but large patient cohort demonstrating complex interdependence","pmids":["9224527"],"is_preprint":false},{"year":1997,"finding":"Mouse adhalin is expressed specifically in striated muscle cells and their immediate precursors. Proper localization to the muscle cell membrane occurs only during late stages of myotube maturation, coincident with redistribution of caveolin-3 and dystrophin, indicating that adhalin membrane targeting is linked to formation of a fully functional muscle fiber.","method":"cDNA cloning, peptide-specific antibody generation, immunofluorescence and mRNA expression analysis during myogenic differentiation in vitro and in vivo","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization with functional context during differentiation; single lab, multiple orthogonal approaches (mRNA + protein + localization)","pmids":["9196068"],"is_preprint":false},{"year":1998,"finding":"Epsilon-sarcoglycan is a newly identified sarcoglycan with high homology to alpha-sarcoglycan and an identical intron-exon structure, but more broadly expressed, indicating functional redundancy within the DGC sarcoglycan subcomplex.","method":"Gene cloning and sequence analysis, intron-exon structure comparison, expression profiling","journal":"FEBS letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — characterization of a paralog (epsilon-sarcoglycan) informing alpha-sarcoglycan biology only by inference; single lab, molecular cloning only","pmids":["9475163"],"is_preprint":false},{"year":2000,"finding":"A mutation in alpha-SG close to the transmembrane domain resulted in partial deficiency of alpha-SG alone without reducing the other three sarcoglycans, suggesting that mutations near the transmembrane domain are less critical for sarcoglycan complex integrity than mutations elsewhere.","method":"Immunohistochemistry and Western blot analysis in a LGMD2D family with genotype-phenotype analysis","journal":"Muscle & nerve","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single family observation; single lab, immunohistochemistry only without in vitro reconstitution","pmids":["10842281"],"is_preprint":false},{"year":2014,"finding":"The V247M alpha-sarcoglycan mutant (LGMD2D) is degraded via the ER quality control-proteasome pathway, specifically through the E3 ubiquitin ligases HRD1 and RFP2. Pharmacological inhibition of HRD1 rescues V247M alpha-sarcoglycan expression both in heterologous cell models and in patient-derived myotubes (carrying L31P/V247M mutations), demonstrating that inappropriate proteasomal degradation is the pathogenetic mechanism of missense sarcoglycanopathy.","method":"Cell-based degradation assay, E3 ligase identification (HRD1, RFP2), pharmacological HRD1 inhibition in heterologous cells and LGMD2D patient myotubes, protein rescue quantification","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mechanistic pathway dissection with identification of specific E3 ligases, confirmed by pharmacological rescue in disease-relevant patient cells; multiple orthogonal methods","pmids":["24565866"],"is_preprint":false},{"year":2020,"finding":"Combined administration of CFTR correctors (including compound C17) to LGMD2D patient-derived myotubes rescues defective alpha-sarcoglycan complex expression and promotes sarcolemma localization of the mutant protein. The data suggest that a misfolded alpha-sarcoglycan can still assemble into the sarcoglycan complex if assisted in cell trafficking, and that CFTR correctors act as proteostasis modulators.","method":"Biotinylation assays, Western blot analysis, treatment of patient-derived differentiated myogenic cells with CFTR correctors","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional rescue in patient-derived cells with multiple compound combinations; single lab, two orthogonal biochemical methods","pmids":["32155735"],"is_preprint":false},{"year":2007,"finding":"AAV1-mediated gene transfer of human alpha-sarcoglycan (sgca) into tibialis anterior of sgca(-/-) mice restored sarcoglycan complex localization to the sarcolemma, reduced muscle fiber damage (decreased Evans blue dye accumulation), prevented disease progression measured by T2-weighted MRI, and improved in vitro force mechanics of isolated EDL muscles.","method":"AAV gene transfer in sgca KO mice, Evans blue dye exclusion assay, MRI, in vitro force mechanics on isolated muscle","journal":"Molecular therapy : the journal of the American Society of Gene Therapy","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function rescue with defined molecular and functional phenotypic readouts; multiple orthogonal methods (histology, imaging, functional mechanics)","pmids":["17653106"],"is_preprint":false},{"year":2021,"finding":"A synonymous SGCA variant (c.157G>A) at the last coding nucleotide of exon 2 causes exonic splicing mutation that induces skipping of two co-regulated exons. Adenine base editing corrected the mutation in patient muscle stem cells with >90% efficiency, rescuing the splicing defect and alpha-sarcoglycan expression. Base-edited patient cells regenerated muscle and contributed to the Pax7+ satellite cell compartment in mouse xenografts.","method":"RNA splicing analysis, adenine base editing in primary human muscle stem cells, alpha-sarcoglycan protein expression rescue, in vivo mouse xenograft engraftment","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mechanistic splicing characterization combined with gene correction and in vivo functional validation; multiple orthogonal methods in a single rigorous study","pmids":["33848270"],"is_preprint":false},{"year":2025,"finding":"A synonymous SGCA variant located distant from canonical splice sites disrupts normal mRNA splicing, producing aberrant transcripts and presumably a nonfunctional/structurally altered alpha-sarcoglycan protein. This manifests as prominent cardiac involvement (left ventricular dysfunction, arrhythmias, dilated cardiomyopathy) in addition to skeletal muscle disease, broadening the recognized phenotypic spectrum of SGCA mutations.","method":"Exome sequencing, mRNA splicing analysis, cardiac assessment (echocardiography, Holter monitoring, cardiac MRI) in five consanguineous families","journal":"European journal of human genetics : EJHG","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional splicing characterization with multi-family clinical correlation; peer-reviewed with orthogonal molecular and clinical methods","pmids":["41345255"],"is_preprint":false},{"year":1996,"finding":"Adhalin (alpha-sarcoglycan) is not required for anchoring NOS I (neuronal nitric oxide synthase) to the sarcolemma in non-mammalian species: chicken and turtle skeletal muscle lacks adhalin immunoreactivity but retains NOS I sarcolemmal localization, indicating that the sarcoglycan subcomplex is not essential for NOS I positioning in these species.","method":"Comparative immunohistochemistry of NOS I, dystrophin, DAG, and adhalin across rat, chicken, and turtle skeletal muscle","journal":"Acta histochemica","confidence":"Low","confidence_rationale":"Tier 3 / Weak — negative/comparative result in non-mammalian species; single lab, immunohistochemistry only","pmids":["8863863"],"is_preprint":false}],"current_model":"SGCA (alpha-sarcoglycan/adhalin) is a type I transmembrane glycoprotein of the sarcoglycan subcomplex within the dystrophin-glycoprotein complex (DGC), where it localizes to the outer face of the sarcolemma and links the cytoskeleton to the extracellular matrix; it possesses ecto-ATPase activity in its extracellular domain that may regulate P2X purinergic receptor signaling by buffering extracellular ATP; missense mutations—predominantly in the extracellular domain—cause LGMD2D/R3 by triggering ER quality control-mediated proteasomal degradation via E3 ligases HRD1 and RFP2, which secondarily depletes the entire sarcoglycan complex; primary deficiency of any single sarcoglycan destabilizes the full complex; and proper membrane targeting of SGCA occurs only during late myotube maturation coincident with dystrophin/caveolin-3 redistribution."},"narrative":{"mechanistic_narrative":"SGCA (alpha-sarcoglycan/adhalin) is a striated muscle-restricted, type I transmembrane glycoprotein of the dystrophin-glycoprotein complex (DGC) that links the muscle cytoskeleton to the extracellular matrix at the sarcolemma [PMID:8226900]. Immunogold electron microscopy places the bulk of the protein on the outer face of the sarcolemma in close association with dystrophin and beta-dystroglycan, consistent with its assembly into the membrane-spanning complex [PMID:8866780, PMID:8960314]. Its extracellular domain carries a consensus nucleotide-binding site and exhibits Mg2+-dependent, Ca2+-independent ecto-ATPase activity, positioning it to modulate sarcolemmal P2X purinergic receptor signaling by buffering extracellular ATP [PMID:10075685]. Proper membrane targeting occurs only during late myotube maturation, coincident with redistribution of caveolin-3 and dystrophin [PMID:9196068], and alpha-sarcoglycan does not function in isolation: loss of any one sarcoglycan destabilizes the entire subcomplex, producing secondary deficiency of the others [PMID:9224527]. Missense mutations in SGCA, predominantly in the extracellular domain, cause autosomal recessive limb-girdle muscular dystrophy (LGMD2D/SCARMD), with severity correlating with residual protein [PMID:8069911, PMID:9192266]. Pathogenic missense alleles are recognized as misfolded by ER quality control and degraded via the proteasome through the E3 ubiquitin ligases HRD1 and RFP2; inhibiting this pathway or applying proteostasis-modulating CFTR correctors rescues mutant protein expression and sarcolemmal assembly in patient myotubes [PMID:24565866, PMID:32155735]. Restoration of SGCA by AAV gene transfer, base editing of splicing-disrupting variants, or correction of cryptic splice mutations rescues complex localization and muscle function [PMID:17653106, PMID:33848270], and splicing-disrupting variants additionally produce a phenotype spanning skeletal and cardiac muscle disease [PMID:41345255].","teleology":[{"year":1993,"claim":"Established that adhalin/SGCA is an intrinsic component of the dystrophin-glycoprotein complex, defining its place in the cytoskeleton-to-matrix linkage and showing its loss in dystrophy is post-transcriptional.","evidence":"cDNA cloning, primary structure deduction, and antibody immunoblot/immunofluorescence with mRNA profiling in normal and DMD/mdx muscle","pmids":["8226900"],"confidence":"High","gaps":["No direct demonstration of the binding partners that recruit SGCA into the complex","Function of the cytoplasmic and transmembrane domains not addressed"]},{"year":1994,"claim":"Identified SGCA as a disease gene, showing missense mutations cause autosomal recessive muscular dystrophy and mapping the locus distinct from the 13q SCARMD locus.","evidence":"cDNA cloning, microsatellite linkage, and genomic sequencing of affected families","pmids":["8069911"],"confidence":"High","gaps":["Did not establish how missense mutations mechanistically destabilize the protein or complex","Genotype-phenotype relationships not yet resolved"]},{"year":1996,"claim":"Defined the ultrastructural position of SGCA on the outer sarcolemmal face in tight association with dystrophin and beta-dystroglycan, anchoring biochemical complex models in physical co-localization.","evidence":"Single, double, and triple immunogold labeling electron microscopy on normal and DMD human muscle","pmids":["8866780","8960314"],"confidence":"Medium","gaps":["Does not resolve the stoichiometry or direct contact interfaces within the complex","Topology of the ecto-ATPase site relative to the basal lamina not mapped"]},{"year":1997,"claim":"Showed that the sarcoglycan subcomplex behaves as an interdependent unit, with primary loss of one member causing secondary depletion of the others, and that mutation severity tracks residual protein with the extracellular domain as a mutational hotspot.","evidence":"Immunohistochemistry across 20 alpha-SG-deficient biopsies and mutation screening with genotype-phenotype correlation in 31 patients","pmids":["9224527","9192266"],"confidence":"Medium","gaps":["Molecular basis of complex co-destabilization not yet defined","Did not identify the degradation machinery responsible for the loss"]},{"year":1997,"claim":"Linked SGCA membrane targeting to muscle maturation, showing correct sarcolemmal localization arises only late in myotube differentiation alongside caveolin-3 and dystrophin redistribution.","evidence":"cDNA cloning, peptide antibody, and immunofluorescence/mRNA analysis during myogenic differentiation in vitro and in vivo (mouse)","pmids":["9196068"],"confidence":"Medium","gaps":["Trafficking signals and chaperones driving late targeting not identified","Relationship between maturation timing and disease onset unexplored"]},{"year":1999,"claim":"Assigned a biochemical activity to SGCA, demonstrating Mg2+-dependent ecto-ATPase function via an extracellular nucleotide-binding site and proposing modulation of P2X purinergic signaling by ATP buffering.","evidence":"ATP binding and ATPase assays with inhibitory antibody, sequence-based active site mapping, and P2X receptor identification in sarcolemmal membranes","pmids":["10075685"],"confidence":"High","gaps":["Physiological consequence of ATP buffering on P2X signaling not demonstrated in vivo","Whether ecto-ATPase activity is lost in disease mutants untested"]},{"year":2007,"claim":"Provided causal in vivo proof that restoring SGCA rescues the dystrophic phenotype, validating it as a therapeutic target.","evidence":"AAV1-mediated human SGCA gene transfer in sgca-/- mice with Evans blue dye, T2 MRI, and isolated muscle force mechanics","pmids":["17653106"],"confidence":"High","gaps":["Durability and immune response of gene transfer not addressed here","Does not dissect which SGCA molecular activity drives functional rescue"]},{"year":2014,"claim":"Defined the pathogenetic mechanism of missense sarcoglycanopathy as ER quality control-mediated proteasomal degradation, identifying HRD1 and RFP2 as the responsible E3 ligases and showing pharmacological rescue in patient cells.","evidence":"Cell-based degradation assays, E3 ligase identification, and HRD1 inhibition in heterologous cells and LGMD2D patient myotubes","pmids":["24565866"],"confidence":"High","gaps":["Generalizability across the full spectrum of missense mutations not established","Long-term safety of HRD1 inhibition not assessed"]},{"year":2020,"claim":"Extended the proteostasis rescue concept by showing CFTR correctors restore mutant alpha-sarcoglycan trafficking and complex assembly, indicating misfolded protein retains assembly competence if escorted to the membrane.","evidence":"Biotinylation and Western blot analysis of CFTR-corrector-treated patient-derived myotubes","pmids":["32155735"],"confidence":"Medium","gaps":["In vivo efficacy and functional muscle recovery not demonstrated","Mechanism by which CFTR correctors act on SGCA not directly defined"]},{"year":2021,"claim":"Identified a synonymous exonic splicing mutation as a distinct pathogenic mechanism and demonstrated base-editing correction restoring splicing, protein, and regenerative capacity.","evidence":"RNA splicing analysis, adenine base editing in primary human muscle stem cells, and in vivo mouse xenograft engraftment","pmids":["33848270"],"confidence":"High","gaps":["Off-target editing and durability in vivo not fully resolved","Frequency of splicing-class mutations among patients not quantified"]},{"year":2025,"claim":"Broadened the SGCA phenotypic spectrum, showing a splicing-disrupting synonymous variant produces prominent cardiac involvement alongside skeletal disease.","evidence":"Exome sequencing, mRNA splicing analysis, and cardiac assessment in five consanguineous families","pmids":["41345255"],"confidence":"Medium","gaps":["Mechanism by which SGCA loss drives cardiomyopathy not dissected","Aberrant protein product not directly characterized"]},{"year":null,"claim":"How SGCA ecto-ATPase activity and P2X modulation contribute to sarcolemmal physiology and disease, and the structural basis of complex assembly, remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of the assembled sarcoglycan subcomplex","Physiological role of ecto-ATPase activity in vivo untested","Direct contact partners of SGCA within the complex not mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[5]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[5]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,3,4]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,3,4]}],"pathway":[{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[0,13]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,11,14]}],"complexes":["dystrophin-glycoprotein complex (DGC)","sarcoglycan subcomplex"],"partners":["DMD","DAG1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q16586","full_name":"Alpha-sarcoglycan","aliases":["50 kDa dystrophin-associated glycoprotein","50DAG","Adhalin","Dystroglycan-2"],"length_aa":387,"mass_kda":42.9,"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/Q16586/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SGCA","classification":"Not Classified","n_dependent_lines":24,"n_total_lines":1208,"dependency_fraction":0.019867549668874173},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SGCA","total_profiled":1310},"omim":[{"mim_id":"619040","title":"MYOFIBRILLAR MYOPATHY 10; MFM10","url":"https://www.omim.org/entry/619040"},{"mim_id":"616832","title":"MYOMESIN 3; MYOM3","url":"https://www.omim.org/entry/616832"},{"mim_id":"608896","title":"SARCOGLYCAN, GAMMA; SGCG","url":"https://www.omim.org/entry/608896"},{"mim_id":"608101","title":"SPERMATID-SPECIFIC LINKER HISTONE H1-LIKE PROTEIN","url":"https://www.omim.org/entry/608101"},{"mim_id":"608099","title":"MUSCULAR DYSTROPHY, LIMB-GIRDLE, AUTOSOMAL RECESSIVE 3; LGMDR3","url":"https://www.omim.org/entry/608099"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"blood vessel","ntpm":168.4},{"tissue":"heart muscle","ntpm":118.7},{"tissue":"skeletal muscle","ntpm":435.8},{"tissue":"tongue","ntpm":202.7}],"url":"https://www.proteinatlas.org/search/SGCA"},"hgnc":{"alias_symbol":["SCARMD1","LGMD2D","adhalin","DMDA2","A2"],"prev_symbol":["ADL"]},"alphafold":{"accession":"Q16586","domains":[{"cath_id":"2.60.40.10","chopping":"22-127","consensus_level":"medium","plddt":86.9752,"start":22,"end":127},{"cath_id":"3.30.70","chopping":"129-255","consensus_level":"medium","plddt":90.2197,"start":129,"end":255}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q16586","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q16586-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q16586-F1-predicted_aligned_error_v6.png","plddt_mean":80.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SGCA","jax_strain_url":"https://www.jax.org/strain/search?query=SGCA"},"sequence":{"accession":"Q16586","fasta_url":"https://rest.uniprot.org/uniprotkb/Q16586.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q16586/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q16586"}},"corpus_meta":[{"pmid":"8069911","id":"PMC_8069911","title":"Missense mutations in the adhalin gene linked to autosomal recessive muscular dystrophy.","date":"1994","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/8069911","citation_count":426,"is_preprint":false},{"pmid":"8226900","id":"PMC_8226900","title":"Primary structure and muscle-specific expression of the 50-kDa dystrophin-associated glycoprotein (adhalin).","date":"1993","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8226900","citation_count":148,"is_preprint":false},{"pmid":"10087042","id":"PMC_10087042","title":"Loperamide (ADL 2-1294), an opioid antihyperalgesic agent with peripheral selectivity.","date":"1999","source":"The Journal of pharmacology and experimental therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/10087042","citation_count":119,"is_preprint":false},{"pmid":"8534387","id":"PMC_8534387","title":"ADL structure for stroke patients in Japan based on the functional independence measure.","date":"1995","source":"American journal of physical medicine & rehabilitation","url":"https://pubmed.ncbi.nlm.nih.gov/8534387","citation_count":116,"is_preprint":false},{"pmid":"9475163","id":"PMC_9475163","title":"Human epsilon-sarcoglycan is highly related to alpha-sarcoglycan (adhalin), the limb girdle muscular dystrophy 2D gene.","date":"1998","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/9475163","citation_count":115,"is_preprint":false},{"pmid":"9192266","id":"PMC_9192266","title":"Mutational diversity and hot spots in the alpha-sarcoglycan gene in autosomal recessive muscular dystrophy (LGMD2D).","date":"1997","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9192266","citation_count":101,"is_preprint":false},{"pmid":"7937874","id":"PMC_7937874","title":"Human adhalin is alternatively spliced and the gene is located on chromosome 17q21.","date":"1994","source":"Proceedings of the National Academy of Sciences of the United States of 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Cardiomyopathy","date":"2025-02-12","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.10.25320701","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":44855,"output_tokens":4223,"usd":0.098955,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12331,"output_tokens":3800,"usd":0.078327,"stage2_stop_reason":"end_turn"},"total_usd":0.177282,"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\": 1993,\n      \"finding\": \"SGCA (adhalin/50-DAG) is a component of the dystrophin-glycoprotein complex (DGC), which links the muscle cytoskeleton to the extracellular matrix. It has a predicted 17-amino acid signal sequence, one transmembrane domain, and two potential N-linked glycosylation sites. Expression is restricted to skeletal, cardiac, and selected smooth muscles. Down-regulation in DMD/mdx muscle is a post-translational event, as mRNA is present.\",\n      \"method\": \"cDNA cloning, deduced amino acid sequence analysis, affinity-purified antibody immunoblot/immunofluorescence, mRNA expression analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cDNA cloning with primary structure determination, antibody validation, and expression profiling; foundational structural characterization replicated across subsequent studies\",\n      \"pmids\": [\"8226900\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Missense mutations within the adhalin gene cause autosomal recessive muscular dystrophy (SCARMD/LGMD2D). The adhalin gene maps to chromosome 17q12-q21.33, distinct from the 13q-linked SCARMD locus.\",\n      \"method\": \"cDNA cloning, microsatellite linkage analysis, genomic sequencing to identify missense mutations\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct mutation identification by sequencing plus genetic linkage in affected families; independently replicated in multiple subsequent studies\",\n      \"pmids\": [\"8069911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Human adhalin is alternatively spliced, producing a 35-kDa non-transmembrane isoform in addition to the full-length transmembrane form. Both isoforms are exclusively expressed in striated muscle.\",\n      \"method\": \"cDNA characterization, alternative splice form identification, chromosomal mapping to 17q21\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab, direct molecular characterization of splice variants with expression profiling\",\n      \"pmids\": [\"7937874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Adhalin localizes to the plasma membrane with the majority of protein on the outer face of the sarcolemma, as determined by immunogold electron microscopy. Alpha-dystroglycan projects from the outer face and forms strands reaching the basal lamina. In DMD, adhalin labeling is severely reduced but the vestige remains in normal position, while merosin is expressed normally, indicating that merosin incorporation is independent of dystrophin and its associated proteins.\",\n      \"method\": \"Single and double immunogold labeling electron microscopy on normal and DMD human skeletal muscle\",\n      \"journal\": \"Neuropathology and applied neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct ultrastructural localization with functional implication; single lab, two orthogonal labeling approaches\",\n      \"pmids\": [\"8866780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Triple immunogold labeling electron microscopy on normal human skeletal myofibers demonstrated that dystrophin, beta-dystroglycan, and adhalin are closely associated with each other at the muscle plasma membrane, consistent with biochemical evidence for their complex assembly.\",\n      \"method\": \"Triple immunogold labeling electron microscopy\",\n      \"journal\": \"Acta neuropathologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct ultrastructural co-localization; single lab, single method but rigorous EM approach\",\n      \"pmids\": [\"8960314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Alpha-sarcoglycan (adhalin) has ecto-ATPase activity: it binds ATP in a Mg2+-dependent, Ca2+-independent manner, and the binding is inhibited by BzATP and ADP. A consensus nucleotide-binding site exists in the extracellular domain. An antibody against this sequence inhibits ATP binding. A dystrophin-DAP preparation shows Mg-ATPase activity inhibited by this antibody but not by endo-ATPase inhibitors. A P2X-type purinergic receptor is present in the sarcolemmal membrane, suggesting that alpha-sarcoglycan modulates P2X receptor activity by buffering extracellular ATP concentration.\",\n      \"method\": \"ATP binding assay (Mg2+-dependent), ATPase activity assay with inhibitory antibody, purinergic receptor identification, sequence analysis of nucleotide-binding site\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay with antibody inhibition and sequence-based active site identification; multiple orthogonal methods in single study\",\n      \"pmids\": [\"10075685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Most SGCA missense mutations (including the common R77C) are located in the extracellular domain of the protein. Mutation severity correlates at least in part with the amount of residual protein. The R77C substitution accounts for 32% of mutated chromosomes and the R284C substitution is associated with a benign disease course.\",\n      \"method\": \"Mutation screening of 31 unrelated patients by sequencing; genotype-phenotype correlation analysis\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic mutational survey with genotype-phenotype correlation; replicated across multiple independent families\",\n      \"pmids\": [\"9192266\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Primary defect in any one of the four sarcoglycan proteins (alpha, beta, gamma, delta) leads to reduced expression of the whole sarcoglycan complex (secondary deficiency of the other sarcoglycans), as shown by immunohistochemical analysis of alpha-SG-deficient patients who also show concomitant deficiency of beta- and gamma-sarcoglycans.\",\n      \"method\": \"Immunohistochemistry on 20 alpha-SG-deficient patient muscle biopsies\",\n      \"journal\": \"Acta neuropathologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic immunohistochemical analysis across 20 patients; single method but large patient cohort demonstrating complex interdependence\",\n      \"pmids\": [\"9224527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Mouse adhalin is expressed specifically in striated muscle cells and their immediate precursors. Proper localization to the muscle cell membrane occurs only during late stages of myotube maturation, coincident with redistribution of caveolin-3 and dystrophin, indicating that adhalin membrane targeting is linked to formation of a fully functional muscle fiber.\",\n      \"method\": \"cDNA cloning, peptide-specific antibody generation, immunofluorescence and mRNA expression analysis during myogenic differentiation in vitro and in vivo\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization with functional context during differentiation; single lab, multiple orthogonal approaches (mRNA + protein + localization)\",\n      \"pmids\": [\"9196068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Epsilon-sarcoglycan is a newly identified sarcoglycan with high homology to alpha-sarcoglycan and an identical intron-exon structure, but more broadly expressed, indicating functional redundancy within the DGC sarcoglycan subcomplex.\",\n      \"method\": \"Gene cloning and sequence analysis, intron-exon structure comparison, expression profiling\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — characterization of a paralog (epsilon-sarcoglycan) informing alpha-sarcoglycan biology only by inference; single lab, molecular cloning only\",\n      \"pmids\": [\"9475163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"A mutation in alpha-SG close to the transmembrane domain resulted in partial deficiency of alpha-SG alone without reducing the other three sarcoglycans, suggesting that mutations near the transmembrane domain are less critical for sarcoglycan complex integrity than mutations elsewhere.\",\n      \"method\": \"Immunohistochemistry and Western blot analysis in a LGMD2D family with genotype-phenotype analysis\",\n      \"journal\": \"Muscle & nerve\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single family observation; single lab, immunohistochemistry only without in vitro reconstitution\",\n      \"pmids\": [\"10842281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The V247M alpha-sarcoglycan mutant (LGMD2D) is degraded via the ER quality control-proteasome pathway, specifically through the E3 ubiquitin ligases HRD1 and RFP2. Pharmacological inhibition of HRD1 rescues V247M alpha-sarcoglycan expression both in heterologous cell models and in patient-derived myotubes (carrying L31P/V247M mutations), demonstrating that inappropriate proteasomal degradation is the pathogenetic mechanism of missense sarcoglycanopathy.\",\n      \"method\": \"Cell-based degradation assay, E3 ligase identification (HRD1, RFP2), pharmacological HRD1 inhibition in heterologous cells and LGMD2D patient myotubes, protein rescue quantification\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mechanistic pathway dissection with identification of specific E3 ligases, confirmed by pharmacological rescue in disease-relevant patient cells; multiple orthogonal methods\",\n      \"pmids\": [\"24565866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Combined administration of CFTR correctors (including compound C17) to LGMD2D patient-derived myotubes rescues defective alpha-sarcoglycan complex expression and promotes sarcolemma localization of the mutant protein. The data suggest that a misfolded alpha-sarcoglycan can still assemble into the sarcoglycan complex if assisted in cell trafficking, and that CFTR correctors act as proteostasis modulators.\",\n      \"method\": \"Biotinylation assays, Western blot analysis, treatment of patient-derived differentiated myogenic cells with CFTR correctors\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional rescue in patient-derived cells with multiple compound combinations; single lab, two orthogonal biochemical methods\",\n      \"pmids\": [\"32155735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"AAV1-mediated gene transfer of human alpha-sarcoglycan (sgca) into tibialis anterior of sgca(-/-) mice restored sarcoglycan complex localization to the sarcolemma, reduced muscle fiber damage (decreased Evans blue dye accumulation), prevented disease progression measured by T2-weighted MRI, and improved in vitro force mechanics of isolated EDL muscles.\",\n      \"method\": \"AAV gene transfer in sgca KO mice, Evans blue dye exclusion assay, MRI, in vitro force mechanics on isolated muscle\",\n      \"journal\": \"Molecular therapy : the journal of the American Society of Gene Therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function rescue with defined molecular and functional phenotypic readouts; multiple orthogonal methods (histology, imaging, functional mechanics)\",\n      \"pmids\": [\"17653106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A synonymous SGCA variant (c.157G>A) at the last coding nucleotide of exon 2 causes exonic splicing mutation that induces skipping of two co-regulated exons. Adenine base editing corrected the mutation in patient muscle stem cells with >90% efficiency, rescuing the splicing defect and alpha-sarcoglycan expression. Base-edited patient cells regenerated muscle and contributed to the Pax7+ satellite cell compartment in mouse xenografts.\",\n      \"method\": \"RNA splicing analysis, adenine base editing in primary human muscle stem cells, alpha-sarcoglycan protein expression rescue, in vivo mouse xenograft engraftment\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mechanistic splicing characterization combined with gene correction and in vivo functional validation; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"33848270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A synonymous SGCA variant located distant from canonical splice sites disrupts normal mRNA splicing, producing aberrant transcripts and presumably a nonfunctional/structurally altered alpha-sarcoglycan protein. This manifests as prominent cardiac involvement (left ventricular dysfunction, arrhythmias, dilated cardiomyopathy) in addition to skeletal muscle disease, broadening the recognized phenotypic spectrum of SGCA mutations.\",\n      \"method\": \"Exome sequencing, mRNA splicing analysis, cardiac assessment (echocardiography, Holter monitoring, cardiac MRI) in five consanguineous families\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional splicing characterization with multi-family clinical correlation; peer-reviewed with orthogonal molecular and clinical methods\",\n      \"pmids\": [\"41345255\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Adhalin (alpha-sarcoglycan) is not required for anchoring NOS I (neuronal nitric oxide synthase) to the sarcolemma in non-mammalian species: chicken and turtle skeletal muscle lacks adhalin immunoreactivity but retains NOS I sarcolemmal localization, indicating that the sarcoglycan subcomplex is not essential for NOS I positioning in these species.\",\n      \"method\": \"Comparative immunohistochemistry of NOS I, dystrophin, DAG, and adhalin across rat, chicken, and turtle skeletal muscle\",\n      \"journal\": \"Acta histochemica\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — negative/comparative result in non-mammalian species; single lab, immunohistochemistry only\",\n      \"pmids\": [\"8863863\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SGCA (alpha-sarcoglycan/adhalin) is a type I transmembrane glycoprotein of the sarcoglycan subcomplex within the dystrophin-glycoprotein complex (DGC), where it localizes to the outer face of the sarcolemma and links the cytoskeleton to the extracellular matrix; it possesses ecto-ATPase activity in its extracellular domain that may regulate P2X purinergic receptor signaling by buffering extracellular ATP; missense mutations—predominantly in the extracellular domain—cause LGMD2D/R3 by triggering ER quality control-mediated proteasomal degradation via E3 ligases HRD1 and RFP2, which secondarily depletes the entire sarcoglycan complex; primary deficiency of any single sarcoglycan destabilizes the full complex; and proper membrane targeting of SGCA occurs only during late myotube maturation coincident with dystrophin/caveolin-3 redistribution.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SGCA (alpha-sarcoglycan/adhalin) is a striated muscle-restricted, type I transmembrane glycoprotein of the dystrophin-glycoprotein complex (DGC) that links the muscle cytoskeleton to the extracellular matrix at the sarcolemma [#0]. Immunogold electron microscopy places the bulk of the protein on the outer face of the sarcolemma in close association with dystrophin and beta-dystroglycan, consistent with its assembly into the membrane-spanning complex [#3, #4]. Its extracellular domain carries a consensus nucleotide-binding site and exhibits Mg2+-dependent, Ca2+-independent ecto-ATPase activity, positioning it to modulate sarcolemmal P2X purinergic receptor signaling by buffering extracellular ATP [#5]. Proper membrane targeting occurs only during late myotube maturation, coincident with redistribution of caveolin-3 and dystrophin [#8], and alpha-sarcoglycan does not function in isolation: loss of any one sarcoglycan destabilizes the entire subcomplex, producing secondary deficiency of the others [#7]. Missense mutations in SGCA, predominantly in the extracellular domain, cause autosomal recessive limb-girdle muscular dystrophy (LGMD2D/SCARMD), with severity correlating with residual protein [#1, #6]. Pathogenic missense alleles are recognized as misfolded by ER quality control and degraded via the proteasome through the E3 ubiquitin ligases HRD1 and RFP2; inhibiting this pathway or applying proteostasis-modulating CFTR correctors rescues mutant protein expression and sarcolemmal assembly in patient myotubes [#11, #12]. Restoration of SGCA by AAV gene transfer, base editing of splicing-disrupting variants, or correction of cryptic splice mutations rescues complex localization and muscle function [#13, #14], and splicing-disrupting variants additionally produce a phenotype spanning skeletal and cardiac muscle disease [#15].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Established that adhalin/SGCA is an intrinsic component of the dystrophin-glycoprotein complex, defining its place in the cytoskeleton-to-matrix linkage and showing its loss in dystrophy is post-transcriptional.\",\n      \"evidence\": \"cDNA cloning, primary structure deduction, and antibody immunoblot/immunofluorescence with mRNA profiling in normal and DMD/mdx muscle\",\n      \"pmids\": [\"8226900\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No direct demonstration of the binding partners that recruit SGCA into the complex\", \"Function of the cytoplasmic and transmembrane domains not addressed\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Identified SGCA as a disease gene, showing missense mutations cause autosomal recessive muscular dystrophy and mapping the locus distinct from the 13q SCARMD locus.\",\n      \"evidence\": \"cDNA cloning, microsatellite linkage, and genomic sequencing of affected families\",\n      \"pmids\": [\"8069911\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish how missense mutations mechanistically destabilize the protein or complex\", \"Genotype-phenotype relationships not yet resolved\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Defined the ultrastructural position of SGCA on the outer sarcolemmal face in tight association with dystrophin and beta-dystroglycan, anchoring biochemical complex models in physical co-localization.\",\n      \"evidence\": \"Single, double, and triple immunogold labeling electron microscopy on normal and DMD human muscle\",\n      \"pmids\": [\"8866780\", \"8960314\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not resolve the stoichiometry or direct contact interfaces within the complex\", \"Topology of the ecto-ATPase site relative to the basal lamina not mapped\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showed that the sarcoglycan subcomplex behaves as an interdependent unit, with primary loss of one member causing secondary depletion of the others, and that mutation severity tracks residual protein with the extracellular domain as a mutational hotspot.\",\n      \"evidence\": \"Immunohistochemistry across 20 alpha-SG-deficient biopsies and mutation screening with genotype-phenotype correlation in 31 patients\",\n      \"pmids\": [\"9224527\", \"9192266\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of complex co-destabilization not yet defined\", \"Did not identify the degradation machinery responsible for the loss\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Linked SGCA membrane targeting to muscle maturation, showing correct sarcolemmal localization arises only late in myotube differentiation alongside caveolin-3 and dystrophin redistribution.\",\n      \"evidence\": \"cDNA cloning, peptide antibody, and immunofluorescence/mRNA analysis during myogenic differentiation in vitro and in vivo (mouse)\",\n      \"pmids\": [\"9196068\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking signals and chaperones driving late targeting not identified\", \"Relationship between maturation timing and disease onset unexplored\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Assigned a biochemical activity to SGCA, demonstrating Mg2+-dependent ecto-ATPase function via an extracellular nucleotide-binding site and proposing modulation of P2X purinergic signaling by ATP buffering.\",\n      \"evidence\": \"ATP binding and ATPase assays with inhibitory antibody, sequence-based active site mapping, and P2X receptor identification in sarcolemmal membranes\",\n      \"pmids\": [\"10075685\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological consequence of ATP buffering on P2X signaling not demonstrated in vivo\", \"Whether ecto-ATPase activity is lost in disease mutants untested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Provided causal in vivo proof that restoring SGCA rescues the dystrophic phenotype, validating it as a therapeutic target.\",\n      \"evidence\": \"AAV1-mediated human SGCA gene transfer in sgca-/- mice with Evans blue dye, T2 MRI, and isolated muscle force mechanics\",\n      \"pmids\": [\"17653106\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Durability and immune response of gene transfer not addressed here\", \"Does not dissect which SGCA molecular activity drives functional rescue\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the pathogenetic mechanism of missense sarcoglycanopathy as ER quality control-mediated proteasomal degradation, identifying HRD1 and RFP2 as the responsible E3 ligases and showing pharmacological rescue in patient cells.\",\n      \"evidence\": \"Cell-based degradation assays, E3 ligase identification, and HRD1 inhibition in heterologous cells and LGMD2D patient myotubes\",\n      \"pmids\": [\"24565866\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generalizability across the full spectrum of missense mutations not established\", \"Long-term safety of HRD1 inhibition not assessed\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended the proteostasis rescue concept by showing CFTR correctors restore mutant alpha-sarcoglycan trafficking and complex assembly, indicating misfolded protein retains assembly competence if escorted to the membrane.\",\n      \"evidence\": \"Biotinylation and Western blot analysis of CFTR-corrector-treated patient-derived myotubes\",\n      \"pmids\": [\"32155735\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo efficacy and functional muscle recovery not demonstrated\", \"Mechanism by which CFTR correctors act on SGCA not directly defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified a synonymous exonic splicing mutation as a distinct pathogenic mechanism and demonstrated base-editing correction restoring splicing, protein, and regenerative capacity.\",\n      \"evidence\": \"RNA splicing analysis, adenine base editing in primary human muscle stem cells, and in vivo mouse xenograft engraftment\",\n      \"pmids\": [\"33848270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Off-target editing and durability in vivo not fully resolved\", \"Frequency of splicing-class mutations among patients not quantified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Broadened the SGCA phenotypic spectrum, showing a splicing-disrupting synonymous variant produces prominent cardiac involvement alongside skeletal disease.\",\n      \"evidence\": \"Exome sequencing, mRNA splicing analysis, and cardiac assessment in five consanguineous families\",\n      \"pmids\": [\"41345255\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which SGCA loss drives cardiomyopathy not dissected\", \"Aberrant protein product not directly characterized\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SGCA ecto-ATPase activity and P2X modulation contribute to sarcolemmal physiology and disease, and the structural basis of complex assembly, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structure of the assembled sarcoglycan subcomplex\", \"Physiological role of ecto-ATPase activity in vivo untested\", \"Direct contact partners of SGCA within the complex not mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 3, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [0, 13]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 11, 14]}\n    ],\n    \"complexes\": [\"dystrophin-glycoprotein complex (DGC)\", \"sarcoglycan subcomplex\"],\n    \"partners\": [\"DMD\", \"DAG1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}