{"gene":"MYL12B","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":2011,"finding":"MYL12B (along with MYL12A and MYL9) associates with non-muscle myosin heavy chains MYH9 (NMHC IIA) and MYH10 (NMHC IIB), and with essential light chain MYL6, forming the non-muscle myosin II complex in NIH 3T3 fibroblasts. Knockdown of MYL12A/12B causes striking changes in cell morphology and dynamics, and significantly reduces the protein levels of MYH9, MYH10, and MYL6, demonstrating that RLCs are required to maintain myosin II stability.","method":"Proteomic co-immunoprecipitation/pulldown, siRNA knockdown with western blot and morphological readouts in NIH 3T3 fibroblasts","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal proteomic interaction analysis plus siRNA loss-of-function with multiple orthogonal readouts (protein levels, morphology); replicated across multiple cell/tissue types","pmids":["21126233"],"is_preprint":false},{"year":2021,"finding":"MYL12B is phosphorylated by smooth muscle myosin light chain kinase (smMLCK) in vitro. In cochlear hair cells, MYL12 phosphorylation by smMLCK contributes to apical constriction-like cellular shape changes; inhibition of smMLCK with ML-7 reduces MYL12 phosphorylation and is accompanied by expansion of outer hair cell area.","method":"In vitro kinase assay with purified MYL12B and smMLCK; immunofluorescence and ML-7 pharmacological inhibition in cochlear hair cells; droplet digital PCR for isoform expression","journal":"Journal of the Association for Research in Otolaryngology : JARO","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro phosphorylation assay with purified protein plus pharmacological loss-of-function in cells with defined morphological readout, single lab but multiple orthogonal methods","pmids":["33877471"],"is_preprint":false},{"year":2021,"finding":"The lncRNA MAFG-AS1 physically interacts with MYL12B (along with MYH9 and MYL6) as subunits of non-muscle myosin IIA. Knockdown of MAFG-AS1 inhibits the ATPase activity of MYH9 and disrupts the interaction among NM IIA subunits including MYL12B, indicating MYL12B's role in maintaining the functional NM IIA complex.","method":"RNA pulldown/co-immunoprecipitation identifying MAFG-AS1 interaction with MYL12B, MYH9, MYL6; ATPase activity assay after MAFG-AS1 knockdown; co-IP to assess subunit interactions","journal":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — RNA–protein interaction pulldown and functional ATPase assay, single lab, mechanistic follow-up but indirect for MYL12B specifically","pmids":["33813778"],"is_preprint":false},{"year":2015,"finding":"In a septic acute kidney injury mouse model, phosphorylated MYL12B (but not total MYL12B) is elevated in kidney tissue and plasma, as detected by 2D-DIGE and validated by western blot, indicating that phosphorylation is the regulated form of MYL12B in this pathological context.","method":"2D-DIGE proteomics on kidney tissue, MALDI-TOF/TOF MS identification, western blot validation of phosphorylated MYL12B in tissue and plasma","journal":"International journal of clinical and experimental pathology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — proteomics identification plus western blot validation of phosphorylated isoform, single lab, single method for mechanistic claim","pmids":["26823757"],"is_preprint":false},{"year":2024,"finding":"MYL12B functions as a target of miR-23a-3p carried in atherosclerotic plaque-derived extracellular vesicles. miR-23a-3p suppresses MYL12B expression, leading to inhibition of MRTFA nuclear translocation, reduced expression of contractile markers, and promotion of vascular smooth muscle cell phenotypic switching and carotid artery remodeling.","method":"miRNA analysis of EVs, identification of miR-23a-3p/Myl12b target relationship, engineered EVs loaded with miR-23a-3p, immunofluorescence and in vivo carotid artery model in Ldlr KO rats","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — miRNA target validation combined with in vivo functional readout (VSMC phenotypic switching, MRTFA localization), single lab, mechanistic pathway placement","pmids":["41784666"],"is_preprint":false},{"year":2024,"finding":"MYL12B serves as an essential and regulatory light chain for human Myosin 5c (Myo5c). Myo5c-HMM co-produced with CaM, essential light chain Myl6, and regulatory light chain Myl12b was purified and used to characterize Myo5c ATPase and motile activity, demonstrating that Myl12b is a functional light chain component of the Myo5c motor.","method":"Recombinant co-expression and purification of human Myo5c-HMM with Myl6 and Myl12b; actin-activated ATPase assay; in vitro motility assay","journal":"Frontiers in physiology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct in vitro reconstitution with purified proteins and functional assays, single lab, but MYL12B's specific contribution not mutagenically dissected","pmids":["38606007"],"is_preprint":false}],"current_model":"MYL12B is a non-muscle myosin II regulatory light chain that binds to non-muscle myosin heavy chains MYH9 and MYH10 and is required to maintain the stability and integrity of the myosin II complex; its phosphorylation by smooth muscle myosin light chain kinase (smMLCK) activates actomyosin contractility to drive cellular shape changes such as apical constriction in cochlear hair cells, and it also functions as a regulatory light chain for Myosin 5c; additionally, miR-23a-3p-mediated suppression of MYL12B inhibits MRTFA nuclear translocation and drives vascular smooth muscle cell phenotypic switching."},"narrative":{"mechanistic_narrative":"MYL12B is a non-muscle myosin II regulatory light chain that assembles with the non-muscle myosin heavy chains MYH9 and MYH10 and the essential light chain MYL6 to form the non-muscle myosin II complex, where it is required to maintain the stability of the holoenzyme and normal cell morphology and dynamics [PMID:21126233]. Its activity is controlled by phosphorylation: smooth muscle myosin light chain kinase (smMLCK) phosphorylates MYL12B in vitro, and in cochlear hair cells this phosphorylation drives apical constriction-like shape changes that are reversed by smMLCK inhibition [PMID:33877471]. Beyond conventional myosin II, MYL12B also serves as a functional regulatory light chain for the unconventional motor Myosin 5c, supporting its actin-activated ATPase and motile activity [PMID:38606007]. At the pathway level, MYL12B couples to vascular smooth muscle cell identity, as its suppression by miR-23a-3p blocks MRTFA nuclear translocation and promotes phenotypic switching [PMID:41784666].","teleology":[{"year":2011,"claim":"Established that MYL12B is a bona fide subunit of the non-muscle myosin II complex and that regulatory light chains are structurally required to keep the holoenzyme stable, rather than being passive accessory proteins.","evidence":"Proteomic co-IP/pulldown plus siRNA knockdown with western blot and morphological readouts in NIH 3T3 fibroblasts","pmids":["21126233"],"confidence":"High","gaps":["Does not distinguish the individual contribution of MYL12B from MYL12A or MYL9","Mechanism by which RLC loss destabilizes heavy chains not defined"]},{"year":2015,"claim":"Showed that phosphorylation, not total abundance, is the regulated state of MYL12B in a disease context, pointing to phospho-MYL12B as the functionally relevant species.","evidence":"2D-DIGE proteomics with MS identification and western blot validation in a septic acute kidney injury mouse model","pmids":["26823757"],"confidence":"Medium","gaps":["Single proteomic study without mechanistic dissection of the kinase or downstream effect","Causal role of phospho-MYL12B in kidney injury not tested"]},{"year":2021,"claim":"Identified smMLCK as a direct kinase for MYL12B and linked its phosphorylation to actomyosin-driven cell shape change, connecting molecular activation to a defined morphological output in hair cells.","evidence":"In vitro kinase assay with purified MYL12B and smMLCK plus ML-7 pharmacological inhibition with immunofluorescence in cochlear hair cells","pmids":["33877471"],"confidence":"High","gaps":["Phospho-site on MYL12B not mapped","ML-7 is not fully specific to smMLCK"]},{"year":2021,"claim":"Reinforced MYL12B's structural role by showing that an lncRNA scaffold is needed to hold the NM IIA subunits together and sustain heavy-chain ATPase activity.","evidence":"RNA pulldown/co-IP of MAFG-AS1 with MYL12B/MYH9/MYL6 and ATPase assay after MAFG-AS1 knockdown","pmids":["33813778"],"confidence":"Medium","gaps":["Effect on MYL12B is indirect through the complex rather than MYL12B-specific","Single lab, no reciprocal validation of the MYL12B contact"]},{"year":2024,"claim":"Expanded MYL12B's role beyond conventional myosin II by demonstrating it functions as a regulatory light chain for the unconventional motor Myosin 5c.","evidence":"Recombinant co-expression/purification of human Myo5c-HMM with Myl6 and Myl12b, actin-activated ATPase and in vitro motility assays","pmids":["38606007"],"confidence":"Medium","gaps":["MYL12B's specific contribution not isolated by mutagenesis","Physiological context of Myo5c regulation by MYL12B unknown"]},{"year":2024,"claim":"Placed MYL12B within a vascular signaling axis, showing its miR-23a-3p-mediated suppression controls MRTFA nuclear translocation and smooth muscle cell phenotype.","evidence":"miRNA target validation, engineered EVs loaded with miR-23a-3p, immunofluorescence and in vivo carotid artery model in Ldlr KO rats","pmids":["41784666"],"confidence":"Medium","gaps":["Mechanistic link from MYL12B to MRTFA localization not resolved","Single lab, target relationship not orthogonally confirmed"]},{"year":null,"claim":"How phosphorylation, motor partner selection (myosin II vs Myo5c), and transcriptional coupling to MRTFA are integrated by MYL12B remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of MYL12B bound to its distinct heavy-chain partners","Phospho-site identity and its differential effect across myosin classes unmapped","Mechanistic chain from MYL12B level to MRTFA nuclear translocation undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,5]}],"localization":[],"pathway":[{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[1]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4]}],"complexes":["non-muscle myosin II (NM IIA)"],"partners":["MYH9","MYH10","MYL6","MYO5C","SMMLCK"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O14950","full_name":"Myosin regulatory light chain 12B","aliases":["MLC-2A","MLC-2","Myosin regulatory light chain 2-B, smooth muscle isoform","Myosin regulatory light chain 20 kDa","MLC20","Myosin regulatory light chain MRLC2","SHUJUN-1"],"length_aa":172,"mass_kda":19.8,"function":"Myosin regulatory subunit that plays an important role in regulation of both smooth muscle and nonmuscle cell contractile activity via its phosphorylation. Phosphorylation triggers actin polymerization in vascular smooth muscle. Implicated in cytokinesis, receptor capping, and cell locomotion","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/O14950/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MYL12B","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000118680","cell_line_id":"CID000613","localizations":[{"compartment":"cytoskeleton","grade":3},{"compartment":"cytoplasmic","grade":2}],"interactors":[{"gene":"PPP6C","stoichiometry":10.0},{"gene":"MYL12A;MYL9","stoichiometry":10.0},{"gene":"MYH9","stoichiometry":10.0},{"gene":"MRPS18C","stoichiometry":10.0},{"gene":"MYL6B","stoichiometry":0.2},{"gene":"MYO18A","stoichiometry":0.2},{"gene":"MYL6","stoichiometry":0.2},{"gene":"POLR3A","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000613","total_profiled":1310},"omim":[{"mim_id":"609211","title":"MYOSIN, LIGHT CHAIN 12B, REGULATORY; MYL12B","url":"https://www.omim.org/entry/609211"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MYL12B"},"hgnc":{"alias_symbol":["MRLC2"],"prev_symbol":[]},"alphafold":{"accession":"O14950","domains":[{"cath_id":"1.10.238.10","chopping":"26-94","consensus_level":"high","plddt":91.1367,"start":26,"end":94},{"cath_id":"1.10.238.10","chopping":"99-164","consensus_level":"high","plddt":93.7303,"start":99,"end":164}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O14950","model_url":"https://alphafold.ebi.ac.uk/files/AF-O14950-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O14950-F1-predicted_aligned_error_v6.png","plddt_mean":83.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MYL12B","jax_strain_url":"https://www.jax.org/strain/search?query=MYL12B"},"sequence":{"accession":"O14950","fasta_url":"https://rest.uniprot.org/uniprotkb/O14950.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O14950/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O14950"}},"corpus_meta":[{"pmid":"21126233","id":"PMC_21126233","title":"Myosin regulatory light chains are required to maintain the stability of myosin II and cellular integrity.","date":"2011","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/21126233","citation_count":106,"is_preprint":false},{"pmid":"28321468","id":"PMC_28321468","title":"Hyperglycaemic memory affects the neurovascular unit of the retina in a diabetic mouse model.","date":"2017","source":"Diabetologia","url":"https://pubmed.ncbi.nlm.nih.gov/28321468","citation_count":30,"is_preprint":false},{"pmid":"33813778","id":"PMC_33813778","title":"HBx-upregulated MAFG-AS1 promotes cell proliferation and migration of hepatoma cells by enhancing MAFG expression and stabilizing nonmuscle myosin IIA.","date":"2021","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/33813778","citation_count":25,"is_preprint":false},{"pmid":"34611583","id":"PMC_34611583","title":"Transcriptional profiling of intervertebral disc in a post-traumatic early degeneration organ culture model.","date":"2021","source":"JOR spine","url":"https://pubmed.ncbi.nlm.nih.gov/34611583","citation_count":12,"is_preprint":false},{"pmid":"26823757","id":"PMC_26823757","title":"Identification of phosphorylated MYL12B as a potential plasma biomarker for septic acute kidney injury using a quantitative proteomic approach.","date":"2015","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/26823757","citation_count":11,"is_preprint":false},{"pmid":"38249550","id":"PMC_38249550","title":"Comparison of differentially expressed genes in longissimus dorsi muscle of Diannan small ears, Wujin and landrace pigs using RNA-seq.","date":"2024","source":"Frontiers in veterinary science","url":"https://pubmed.ncbi.nlm.nih.gov/38249550","citation_count":9,"is_preprint":false},{"pmid":"33877471","id":"PMC_33877471","title":"Phosphorylation of MYL12 by Myosin Light Chain Kinase Regulates Cellular Shape Changes in Cochlear Hair Cells.","date":"2021","source":"Journal of the Association for Research in Otolaryngology : JARO","url":"https://pubmed.ncbi.nlm.nih.gov/33877471","citation_count":7,"is_preprint":false},{"pmid":"23538510","id":"PMC_23538510","title":"Surface CD3 expression proceeds through both myosin regulatory light chain 9 (MYL9)-dependent and MYL9-independent pathways in Jurkat cells.","date":"2012","source":"Journal of smooth muscle research = Nihon Heikatsukin Gakkai kikanshi","url":"https://pubmed.ncbi.nlm.nih.gov/23538510","citation_count":6,"is_preprint":false},{"pmid":"39394698","id":"PMC_39394698","title":"Inter3D: Capture of TAD Reorganization Endows Variant Patterns of Gene Transcription.","date":"2024","source":"Genomics, proteomics & bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/39394698","citation_count":3,"is_preprint":false},{"pmid":"38606007","id":"PMC_38606007","title":"Motor properties of Myosin 5c are modulated by tropomyosin isoforms and inhibited by pentabromopseudilin.","date":"2024","source":"Frontiers in physiology","url":"https://pubmed.ncbi.nlm.nih.gov/38606007","citation_count":3,"is_preprint":false},{"pmid":"34674377","id":"PMC_34674377","title":"Proteomic and electron microscopy study of myogenic differentiation of alveolar mucosa multipotent mesenchymal stromal cells in three-dimensional culture.","date":"2021","source":"Proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/34674377","citation_count":2,"is_preprint":false},{"pmid":"40355769","id":"PMC_40355769","title":"An integrative analysis combining bioinformatics, network pharmacology and experimental methods identified key genes of EGCG targets in Nasopharyngeal Carcinoma.","date":"2025","source":"Discover oncology","url":"https://pubmed.ncbi.nlm.nih.gov/40355769","citation_count":2,"is_preprint":false},{"pmid":"40428155","id":"PMC_40428155","title":"Identification of Key Genes and Potential Therapeutic Targets in Sepsis-Associated Acute Kidney Injury Using Transformer and Machine Learning Approaches.","date":"2025","source":"Bioengineering (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/40428155","citation_count":1,"is_preprint":false},{"pmid":"39932158","id":"PMC_39932158","title":"Myosin Light Chain 12b and MASP1 as Novel Biomarker Candidates in Active Juvenile Idiopathic Arthritis─A Combined Proteomics/Bioinformatics Approach.","date":"2025","source":"Journal of proteome research","url":"https://pubmed.ncbi.nlm.nih.gov/39932158","citation_count":0,"is_preprint":false},{"pmid":"41784666","id":"PMC_41784666","title":"Atherosclerotic plaque-derived extracellular vesicles mediate smooth muscle cell phenotypic switching and promote vascular remodeling : EVs promote VSMC phenotypic switching.","date":"2026","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/41784666","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10780,"output_tokens":1904,"usd":0.03045,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8686,"output_tokens":2305,"usd":0.050528,"stage2_stop_reason":"end_turn"},"total_usd":0.080978,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"MYL12B (along with MYL12A and MYL9) associates with non-muscle myosin heavy chains MYH9 (NMHC IIA) and MYH10 (NMHC IIB), and with essential light chain MYL6, forming the non-muscle myosin II complex in NIH 3T3 fibroblasts. Knockdown of MYL12A/12B causes striking changes in cell morphology and dynamics, and significantly reduces the protein levels of MYH9, MYH10, and MYL6, demonstrating that RLCs are required to maintain myosin II stability.\",\n      \"method\": \"Proteomic co-immunoprecipitation/pulldown, siRNA knockdown with western blot and morphological readouts in NIH 3T3 fibroblasts\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal proteomic interaction analysis plus siRNA loss-of-function with multiple orthogonal readouts (protein levels, morphology); replicated across multiple cell/tissue types\",\n      \"pmids\": [\"21126233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MYL12B is phosphorylated by smooth muscle myosin light chain kinase (smMLCK) in vitro. In cochlear hair cells, MYL12 phosphorylation by smMLCK contributes to apical constriction-like cellular shape changes; inhibition of smMLCK with ML-7 reduces MYL12 phosphorylation and is accompanied by expansion of outer hair cell area.\",\n      \"method\": \"In vitro kinase assay with purified MYL12B and smMLCK; immunofluorescence and ML-7 pharmacological inhibition in cochlear hair cells; droplet digital PCR for isoform expression\",\n      \"journal\": \"Journal of the Association for Research in Otolaryngology : JARO\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro phosphorylation assay with purified protein plus pharmacological loss-of-function in cells with defined morphological readout, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"33877471\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The lncRNA MAFG-AS1 physically interacts with MYL12B (along with MYH9 and MYL6) as subunits of non-muscle myosin IIA. Knockdown of MAFG-AS1 inhibits the ATPase activity of MYH9 and disrupts the interaction among NM IIA subunits including MYL12B, indicating MYL12B's role in maintaining the functional NM IIA complex.\",\n      \"method\": \"RNA pulldown/co-immunoprecipitation identifying MAFG-AS1 interaction with MYL12B, MYH9, MYL6; ATPase activity assay after MAFG-AS1 knockdown; co-IP to assess subunit interactions\",\n      \"journal\": \"FASEB journal : official publication of the Federation of American Societies for Experimental Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — RNA–protein interaction pulldown and functional ATPase assay, single lab, mechanistic follow-up but indirect for MYL12B specifically\",\n      \"pmids\": [\"33813778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In a septic acute kidney injury mouse model, phosphorylated MYL12B (but not total MYL12B) is elevated in kidney tissue and plasma, as detected by 2D-DIGE and validated by western blot, indicating that phosphorylation is the regulated form of MYL12B in this pathological context.\",\n      \"method\": \"2D-DIGE proteomics on kidney tissue, MALDI-TOF/TOF MS identification, western blot validation of phosphorylated MYL12B in tissue and plasma\",\n      \"journal\": \"International journal of clinical and experimental pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — proteomics identification plus western blot validation of phosphorylated isoform, single lab, single method for mechanistic claim\",\n      \"pmids\": [\"26823757\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MYL12B functions as a target of miR-23a-3p carried in atherosclerotic plaque-derived extracellular vesicles. miR-23a-3p suppresses MYL12B expression, leading to inhibition of MRTFA nuclear translocation, reduced expression of contractile markers, and promotion of vascular smooth muscle cell phenotypic switching and carotid artery remodeling.\",\n      \"method\": \"miRNA analysis of EVs, identification of miR-23a-3p/Myl12b target relationship, engineered EVs loaded with miR-23a-3p, immunofluorescence and in vivo carotid artery model in Ldlr KO rats\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — miRNA target validation combined with in vivo functional readout (VSMC phenotypic switching, MRTFA localization), single lab, mechanistic pathway placement\",\n      \"pmids\": [\"41784666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MYL12B serves as an essential and regulatory light chain for human Myosin 5c (Myo5c). Myo5c-HMM co-produced with CaM, essential light chain Myl6, and regulatory light chain Myl12b was purified and used to characterize Myo5c ATPase and motile activity, demonstrating that Myl12b is a functional light chain component of the Myo5c motor.\",\n      \"method\": \"Recombinant co-expression and purification of human Myo5c-HMM with Myl6 and Myl12b; actin-activated ATPase assay; in vitro motility assay\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct in vitro reconstitution with purified proteins and functional assays, single lab, but MYL12B's specific contribution not mutagenically dissected\",\n      \"pmids\": [\"38606007\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MYL12B is a non-muscle myosin II regulatory light chain that binds to non-muscle myosin heavy chains MYH9 and MYH10 and is required to maintain the stability and integrity of the myosin II complex; its phosphorylation by smooth muscle myosin light chain kinase (smMLCK) activates actomyosin contractility to drive cellular shape changes such as apical constriction in cochlear hair cells, and it also functions as a regulatory light chain for Myosin 5c; additionally, miR-23a-3p-mediated suppression of MYL12B inhibits MRTFA nuclear translocation and drives vascular smooth muscle cell phenotypic switching.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MYL12B is a non-muscle myosin II regulatory light chain that assembles with the non-muscle myosin heavy chains MYH9 and MYH10 and the essential light chain MYL6 to form the non-muscle myosin II complex, where it is required to maintain the stability of the holoenzyme and normal cell morphology and dynamics [#0]. Its activity is controlled by phosphorylation: smooth muscle myosin light chain kinase (smMLCK) phosphorylates MYL12B in vitro, and in cochlear hair cells this phosphorylation drives apical constriction-like shape changes that are reversed by smMLCK inhibition [#1]. Beyond conventional myosin II, MYL12B also serves as a functional regulatory light chain for the unconventional motor Myosin 5c, supporting its actin-activated ATPase and motile activity [#5]. At the pathway level, MYL12B couples to vascular smooth muscle cell identity, as its suppression by miR-23a-3p blocks MRTFA nuclear translocation and promotes phenotypic switching [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Established that MYL12B is a bona fide subunit of the non-muscle myosin II complex and that regulatory light chains are structurally required to keep the holoenzyme stable, rather than being passive accessory proteins.\",\n      \"evidence\": \"Proteomic co-IP/pulldown plus siRNA knockdown with western blot and morphological readouts in NIH 3T3 fibroblasts\",\n      \"pmids\": [\"21126233\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Does not distinguish the individual contribution of MYL12B from MYL12A or MYL9\",\n        \"Mechanism by which RLC loss destabilizes heavy chains not defined\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed that phosphorylation, not total abundance, is the regulated state of MYL12B in a disease context, pointing to phospho-MYL12B as the functionally relevant species.\",\n      \"evidence\": \"2D-DIGE proteomics with MS identification and western blot validation in a septic acute kidney injury mouse model\",\n      \"pmids\": [\"26823757\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single proteomic study without mechanistic dissection of the kinase or downstream effect\",\n        \"Causal role of phospho-MYL12B in kidney injury not tested\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified smMLCK as a direct kinase for MYL12B and linked its phosphorylation to actomyosin-driven cell shape change, connecting molecular activation to a defined morphological output in hair cells.\",\n      \"evidence\": \"In vitro kinase assay with purified MYL12B and smMLCK plus ML-7 pharmacological inhibition with immunofluorescence in cochlear hair cells\",\n      \"pmids\": [\"33877471\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Phospho-site on MYL12B not mapped\",\n        \"ML-7 is not fully specific to smMLCK\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Reinforced MYL12B's structural role by showing that an lncRNA scaffold is needed to hold the NM IIA subunits together and sustain heavy-chain ATPase activity.\",\n      \"evidence\": \"RNA pulldown/co-IP of MAFG-AS1 with MYL12B/MYH9/MYL6 and ATPase assay after MAFG-AS1 knockdown\",\n      \"pmids\": [\"33813778\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Effect on MYL12B is indirect through the complex rather than MYL12B-specific\",\n        \"Single lab, no reciprocal validation of the MYL12B contact\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Expanded MYL12B's role beyond conventional myosin II by demonstrating it functions as a regulatory light chain for the unconventional motor Myosin 5c.\",\n      \"evidence\": \"Recombinant co-expression/purification of human Myo5c-HMM with Myl6 and Myl12b, actin-activated ATPase and in vitro motility assays\",\n      \"pmids\": [\"38606007\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"MYL12B's specific contribution not isolated by mutagenesis\",\n        \"Physiological context of Myo5c regulation by MYL12B unknown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placed MYL12B within a vascular signaling axis, showing its miR-23a-3p-mediated suppression controls MRTFA nuclear translocation and smooth muscle cell phenotype.\",\n      \"evidence\": \"miRNA target validation, engineered EVs loaded with miR-23a-3p, immunofluorescence and in vivo carotid artery model in Ldlr KO rats\",\n      \"pmids\": [\"41784666\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanistic link from MYL12B to MRTFA localization not resolved\",\n        \"Single lab, target relationship not orthogonally confirmed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How phosphorylation, motor partner selection (myosin II vs Myo5c), and transcriptional coupling to MRTFA are integrated by MYL12B remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural model of MYL12B bound to its distinct heavy-chain partners\",\n        \"Phospho-site identity and its differential effect across myosin classes unmapped\",\n        \"Mechanistic chain from MYL12B level to MRTFA nuclear translocation undefined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [\"non-muscle myosin II (NM IIA)\"],\n    \"partners\": [\"MYH9\", \"MYH10\", \"MYL6\", \"MYO5C\", \"smMLCK\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}