{"gene":"SIPA1L2","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":2007,"finding":"SIPA1L2 (SPAR2) was identified as a novel RapGAP protein with GAP activity for both Rap1 and Rap2, demonstrated by in vitro GAP assays. It is enriched in synaptosomes and postsynaptic density fractions, and interacts with the synaptic scaffolding protein ProSAPiP (which binds ProSAP/Shank PDZ domains). Unlike its paralog SPAR1, overexpression of SPAR2 in hippocampal neurons does not affect spine morphology, and it shows distinct actin-binding properties.","method":"In vitro GAP assay, subcellular fractionation, co-immunoprecipitation, in situ hybridization, overexpression in cultured neurons","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro enzymatic activity assay combined with subcellular fractionation and binding partner identification","pmids":["17961154"],"is_preprint":false},{"year":2019,"finding":"SIPA1L2 controls retrograde trafficking and local signaling of TrkB-containing amphisomes at presynaptic terminals by connecting TrkB amphisomes to the dynein motor. The autophagosomal protein LC3 regulates the RapGAP activity of SIPA1L2, controlling retrograde trafficking and local BDNF/TrkB signaling. Upon induction of presynaptic plasticity, amphisomes dissociate from dynein at boutons, enabling local signaling and promoting transmitter release. Sipa1l2 knockout mice show impaired BDNF-dependent presynaptic plasticity.","method":"Co-immunoprecipitation, live imaging, knockout mouse model, synaptic plasticity assays, fluorescence microscopy of retrograde transport","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP, KO mouse with defined phenotype, multiple orthogonal methods including live imaging and functional plasticity assays","pmids":["31784514"],"is_preprint":false},{"year":2019,"finding":"SIPA1L2 was identified as a genetic modifier of CMT1A phenotype. Co-immunoprecipitation and mass spectrometry identified β-actin and MYH9 as SIPA1L2 binding partners in peripheral nerve. SIPA1L2 is part of a myelination-associated gene network regulated by the master transcription factor SOX10. In vitro siRNA knockdown of SIPA1L2 in Schwannoma cells led to significant reduction of PMP22 expression.","method":"Co-immunoprecipitation, mass spectrometry, immunocytochemistry, chromatin immunoprecipitation, siRNA knockdown, genome-wide association study","journal":"Annals of neurology","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP with MS validation and functional siRNA knockdown, but modifier role established in single study","pmids":["30706531"],"is_preprint":false},{"year":2024,"finding":"Genetic deletion of Sipa1l2 exon 1 in mice crossed to the C3-PMP22 CMT1A model validated a genetic interaction: Sipa1l2 deletion preserved muscular endurance (wire-hang duration) and altered femoral nerve axon morphometrics including myelin thickness. Gene expression changes implicated Sipa1l2 in the cholesterol biosynthesis pathway, which is also dysregulated in C3-PMP22 mice.","method":"Knockout mouse generation, neuromuscular phenotyping (wire hang, nerve morphometrics), gene expression analysis","journal":"Journal of neuropathology and experimental neurology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in mouse model with defined phenotypic readouts, single study","pmids":["38472136"],"is_preprint":false},{"year":2022,"finding":"In the context of vascular endothelial repair, SIPA1L2 was identified as a direct target of miR-21-5p (via binding to the 3'UTR of SIPA1L2 mRNA). Knockdown of SIPA1L2 in ox-LDL-treated human microvascular endothelial cells repaired autophagic flux and enhanced autophagic activity to promote cell proliferation, indicating that SIPA1L2 negatively regulates autophagy in endothelial cells.","method":"Dual-luciferase reporter assay, siRNA knockdown, Ad-mCherry-GFP-LC3B autophagic flux assay, western blot, RNA sequencing","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2 — direct 3'UTR target validation by luciferase assay plus functional autophagy flux assay with KD, single lab","pmids":["35279183"],"is_preprint":false},{"year":2022,"finding":"During irisin-enhanced chondrogenic differentiation of human mesenchymal stem cells, miR-125b-5p targets SIPA1L2 to reduce its expression, consequently activating the Rap1/PI3K/AKT signaling axis. This places SIPA1L2 as a negative regulator of Rap1 activity upstream of PI3K/AKT in chondrogenic differentiation.","method":"miRNA mimic/inhibitor transfection, plasmid overexpression, RNA-seq, western blot, pellet culture chondrogenic differentiation assay","journal":"Stem cell research & therapy","confidence":"Medium","confidence_rationale":"Tier 3 — functional pathway placement via miRNA/overexpression manipulation, single lab, no direct RapGAP activity measurement","pmids":["35922833"],"is_preprint":false},{"year":2016,"finding":"Sipa1l2 is expressed throughout early Xenopus laevis development with maternal RNA supply. During embryogenesis, sipa1l2 transcript is detected in branchial arches, glomerulus, and the developing eye, indicating a role in early vertebrate development beyond the nervous system.","method":"Semi-quantitative RT-PCR, whole-mount in situ hybridization","journal":"Development genes and evolution","confidence":"Low","confidence_rationale":"Tier 3 — expression/localization data only, no functional loss-of-function mechanistic data","pmids":["27384056"],"is_preprint":false}],"current_model":"SIPA1L2 (SPAR2) is a synaptic RapGAP protein with catalytic activity toward Rap1 and Rap2 that, in hippocampal neurons, connects TrkB-containing amphisomes to the dynein retrograde transport machinery at presynaptic terminals—a process regulated by the autophagosomal protein LC3 acting on SIPA1L2's RapGAP activity—and whose loss impairs BDNF-dependent presynaptic plasticity; in peripheral nerve, SIPA1L2 binds β-actin and MYH9, participates in a SOX10-regulated myelination network controlling PMP22 expression, and modulates cholesterol biosynthesis pathways relevant to demyelinating neuropathy."},"narrative":{"teleology":[{"year":2007,"claim":"Establishing SIPA1L2 as a functional RapGAP answered the basic question of enzymatic identity: SIPA1L2 catalyzes GTP hydrolysis on both Rap1 and Rap2, is enriched at synapses, and interacts with the scaffolding protein ProSAPiP, distinguishing it from its paralog SPAR1.","evidence":"In vitro GAP assay, synaptosome/PSD fractionation, co-IP, and overexpression in cultured hippocampal neurons","pmids":["17961154"],"confidence":"High","gaps":["Endogenous substrates and in vivo Rap specificity not determined","Functional consequence of ProSAPiP interaction at synapses unknown","No loss-of-function data to assess requirement in neurons"]},{"year":2016,"claim":"Expression profiling in Xenopus embryos revealed maternally supplied sipa1l2 mRNA with enrichment in branchial arches, glomerulus, and eye, suggesting developmental roles beyond the nervous system.","evidence":"RT-PCR and whole-mount in situ hybridization in Xenopus laevis embryos","pmids":["27384056"],"confidence":"Low","gaps":["No functional or loss-of-function data in Xenopus — expression only","Relevance to mammalian non-neuronal tissues not tested","No mechanistic link to RapGAP activity in these tissues"]},{"year":2019,"claim":"The key mechanistic advance was demonstrating how SIPA1L2 couples neurotrophin signaling to retrograde transport: SIPA1L2 links TrkB-containing amphisomes to dynein at presynaptic boutons, with LC3 regulating its RapGAP activity; knockout mice showed impaired BDNF-dependent presynaptic plasticity, establishing an in vivo requirement.","evidence":"Co-IP, live imaging of retrograde transport, Sipa1l2 knockout mouse with synaptic plasticity assays","pmids":["31784514"],"confidence":"High","gaps":["Structural basis of LC3–SIPA1L2 interaction and how LC3 modulates GAP activity unresolved","Whether the amphisome-dynein coupling function extends to other neurotrophin receptors unknown","Postsynaptic roles of SIPA1L2 not addressed"]},{"year":2019,"claim":"Identification of SIPA1L2 as a genetic modifier of CMT1A severity established a peripheral nerve function: SIPA1L2 binds β-actin and MYH9, operates within a SOX10-regulated myelination network, and its knockdown reduces PMP22 expression in Schwannoma cells.","evidence":"GWAS, co-IP with mass spectrometry validation, ChIP, siRNA knockdown in Schwannoma cells","pmids":["30706531"],"confidence":"Medium","gaps":["Modifier effect identified in a single cohort — replication in independent CMT1A populations needed","Direct mechanism linking SIPA1L2 RapGAP activity to PMP22 regulation not established","Whether β-actin/MYH9 binding is required for the myelination phenotype untested"]},{"year":2022,"claim":"Parallel studies in non-neuronal contexts showed SIPA1L2 negatively regulates autophagy in ox-LDL-treated endothelial cells and acts as a negative regulator of Rap1/PI3K/AKT during chondrogenic differentiation, broadening its functional scope beyond neurons.","evidence":"Dual-luciferase 3ʹ-UTR reporter assay, autophagic flux assay with siRNA knockdown (endothelial cells); miRNA mimic/inhibitor and overexpression in mesenchymal stem cell chondrogenesis","pmids":["35279183","35922833"],"confidence":"Medium","gaps":["Direct RapGAP activity not measured in either non-neuronal system","Whether SIPA1L2 autophagy regulation in endothelial cells uses the same LC3-dependent mechanism as in neurons is unknown","Each finding from a single laboratory"]},{"year":2024,"claim":"Genetic epistasis in mice validated the CMT1A modifier role: Sipa1l2 deletion in the C3-PMP22 model preserved neuromuscular function and altered myelin thickness, implicating the cholesterol biosynthesis pathway as a downstream effector.","evidence":"Sipa1l2 exon-1 knockout crossed to C3-PMP22 transgenic mice; wire-hang endurance, nerve morphometrics, gene expression profiling","pmids":["38472136"],"confidence":"Medium","gaps":["Cholesterol biosynthesis link is transcriptomic — direct metabolic measurements not reported","Mechanism connecting SIPA1L2 RapGAP activity to cholesterol pathway regulation unclear","Whether Sipa1l2 deletion affects myelination independently of the PMP22 overexpression background not tested"]},{"year":null,"claim":"A unifying structural and mechanistic model explaining how SIPA1L2's RapGAP domain, actin-binding domain, and LC3-interacting region coordinate its dual roles in presynaptic amphisome transport and peripheral myelination remains to be established.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal structure or cryo-EM data for any SIPA1L2 domain","Relative contributions of Rap1 vs Rap2 GTPase regulation in each tissue context unknown","Whether LC3-mediated regulation of RapGAP activity operates in Schwann cells or other non-neuronal contexts untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,5]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[1]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,5]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[1,4]}],"complexes":[],"partners":["NTRK2","MAP1LC3B","ACTB","MYH9","PROSAPIP1"],"other_free_text":[]},"mechanistic_narrative":"SIPA1L2 (SPAR2) is a RapGAP protein that catalyzes GTP hydrolysis on Rap1 and Rap2, functioning as a negative regulator of Rap signaling in neurons and other cell types [PMID:17961154, PMID:35922833]. In hippocampal presynaptic terminals, SIPA1L2 connects TrkB-containing amphisomes to the dynein retrograde transport machinery, with its RapGAP activity regulated by the autophagosomal protein LC3; loss of Sipa1l2 in mice impairs BDNF-dependent presynaptic plasticity [PMID:31784514]. In peripheral nerve, SIPA1L2 participates in a SOX10-regulated myelination gene network, binds β-actin and MYH9, and modulates PMP22 expression and cholesterol biosynthesis pathways, acting as a genetic modifier of the CMT1A demyelinating neuropathy phenotype [PMID:30706531, PMID:38472136]."},"prefetch_data":{"uniprot":{"accession":"Q9P2F8","full_name":"Signal-induced proliferation-associated 1-like protein 2","aliases":[],"length_aa":1722,"mass_kda":190.4,"function":"","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9P2F8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SIPA1L2","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"MIF","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SIPA1L2","total_profiled":1310},"omim":[{"mim_id":"611609","title":"SIPA1-LIKE PROTEIN 2; SIPA1L2","url":"https://www.omim.org/entry/611609"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nuclear membrane","reliability":"Approved"},{"location":"Nuclear bodies","reliability":"Approved"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SIPA1L2"},"hgnc":{"alias_symbol":["KIAA1389","SPAR2"],"prev_symbol":[]},"alphafold":{"accession":"Q9P2F8","domains":[{"cath_id":"3.40.50.11210","chopping":"413-432_443-453_605-794","consensus_level":"medium","plddt":89.0731,"start":413,"end":794},{"cath_id":"2.30.29.30","chopping":"855-944","consensus_level":"medium","plddt":90.651,"start":855,"end":944},{"cath_id":"2.30.42.10","chopping":"949-1036","consensus_level":"high","plddt":88.8625,"start":949,"end":1036},{"cath_id":"1.20.5","chopping":"1676-1722","consensus_level":"medium","plddt":82.496,"start":1676,"end":1722}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P2F8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P2F8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P2F8-F1-predicted_aligned_error_v6.png","plddt_mean":55.97},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SIPA1L2","jax_strain_url":"https://www.jax.org/strain/search?query=SIPA1L2"},"sequence":{"accession":"Q9P2F8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9P2F8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9P2F8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P2F8"}},"corpus_meta":[{"pmid":"31784514","id":"PMC_31784514","title":"SIPA1L2 controls trafficking and local signaling of TrkB-containing amphisomes at presynaptic terminals.","date":"2019","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/31784514","citation_count":67,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"30116193","id":"PMC_30116193","title":"UBE2C Is a Potential Biomarker of Intestinal-Type Gastric Cancer With Chromosomal Instability.","date":"2018","source":"Frontiers in pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30116193","citation_count":58,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"30706531","id":"PMC_30706531","title":"Variation in SIPA1L2 is correlated with phenotype modification in Charcot- Marie- Tooth disease type 1A.","date":"2019","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/30706531","citation_count":39,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"35279183","id":"PMC_35279183","title":"Endothelial colony-forming cell-derived exosomal miR-21-5p regulates autophagic flux to promote vascular endothelial repair by inhibiting SIPL1A2 in atherosclerosis.","date":"2022","source":"Cell communication and signaling : CCS","url":"https://pubmed.ncbi.nlm.nih.gov/35279183","citation_count":34,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"35922833","id":"PMC_35922833","title":"Irisin enhances chondrogenic differentiation of human mesenchymal stem cells via Rap1/PI3K/AKT axis.","date":"2022","source":"Stem cell research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/35922833","citation_count":27,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"17961154","id":"PMC_17961154","title":"SPAR2, a novel SPAR-related protein with GAP activity for Rap1 and Rap2.","date":"2007","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17961154","citation_count":23,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"31156702","id":"PMC_31156702","title":"Whole-Exome Sequencing Identifies Somatic Mutations Associated With Mortality in Metastatic Clear Cell Kidney Carcinoma.","date":"2019","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31156702","citation_count":22,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"33436766","id":"PMC_33436766","title":"Allele-specific expression of Parkinson's disease susceptibility genes in human brain.","date":"2021","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33436766","citation_count":20,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"34943818","id":"PMC_34943818","title":"Ascorbic Acid/Retinol and/or Inflammatory Stimuli's Effect on Proliferation/Differentiation Properties and Transcriptomics of Gingival Stem/Progenitor Cells.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/34943818","citation_count":19,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"26364583","id":"PMC_26364583","title":"Sipa1l3/SPAR3 is targeted to postsynaptic specializations and interacts with the Fezzin ProSAPiP1/Lzts3.","date":"2015","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26364583","citation_count":18,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"37224615","id":"PMC_37224615","title":"Genome-wide association study reveals candidate markers related to field fertility and semen quality traits in Holstein-Friesian bulls.","date":"2023","source":"Animal : an international journal of animal bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/37224615","citation_count":13,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"29463568","id":"PMC_29463568","title":"An exome-wide sequencing study of lipid response to high-fat meal and fenofibrate in Caucasians from the GOLDN cohort.","date":"2018","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/29463568","citation_count":8,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"36979316","id":"PMC_36979316","title":"Genetics of Neurogenic Orthostatic Hypotension in Parkinson's Disease, Results from a Cross-Sectional In Silico Study.","date":"2023","source":"Brain sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36979316","citation_count":8,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"32800876","id":"PMC_32800876","title":"PAR2, Keratinocytes, and Cathepsin S Mediate the Sensory Effects of Ciguatoxins Responsible for Ciguatera Poisoning.","date":"2020","source":"The Journal of investigative dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/32800876","citation_count":7,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"38643552","id":"PMC_38643552","title":"Critical role of miR-21/exosomal miR-21 in autophagy pathway.","date":"2024","source":"Pathology, research and practice","url":"https://pubmed.ncbi.nlm.nih.gov/38643552","citation_count":4,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"36851918","id":"PMC_36851918","title":"Identification of MKNK1 and TOP3A as ovarian endometriosis risk-associated genes using integrative genomic analyses and functional experiments.","date":"2023","source":"Computational and structural biotechnology journal","url":"https://pubmed.ncbi.nlm.nih.gov/36851918","citation_count":4,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"36802481","id":"PMC_36802481","title":"DMP1 and IFITM5 Regulate Osteogenic Differentiation of MC3T3-E1 on PEO-Treated Ti-6Al-4V-Ca2+/Pi surface.","date":"2023","source":"ACS biomaterials science & engineering","url":"https://pubmed.ncbi.nlm.nih.gov/36802481","citation_count":3,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"27384056","id":"PMC_27384056","title":"Comparative expression study of sipa family members during early Xenopus laevis development.","date":"2016","source":"Development genes and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/27384056","citation_count":3,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"39684334","id":"PMC_39684334","title":"The circRNA Landscape in Recurrent Pregnacy Loss (RPL): A Comparison of Four Reproductive Tissues.","date":"2024","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/39684334","citation_count":3,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"39579640","id":"PMC_39579640","title":"Small-RNA sequencing reveals potential serum biomarkers for gallbladder cancer: Results from a three-stage collaborative study of large European prospective cohorts.","date":"2024","source":"European journal of cancer (Oxford, England : 1990)","url":"https://pubmed.ncbi.nlm.nih.gov/39579640","citation_count":2,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"40252140","id":"PMC_40252140","title":"ChIP-seq and RNA-seq Reveal the Involvement of Histone Lactylation Modification in Early Pregnancy with Subclinical Hypothyroidism.","date":"2025","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40252140","citation_count":1,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"40539127","id":"PMC_40539127","title":"Alzheimer's disease genetic risk: Top African American risk allele frequencies and genetic architecture among Mexican-, African-, and non-Hispanic White Americans.","date":"2025","source":"Alzheimer's & dementia (New York, N. Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/40539127","citation_count":1,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"40482455","id":"PMC_40482455","title":"IRF8-Cathepsin S/PAR2 axis-mediated spinal microglia-neuron crosstalk is responsible for the exacerbation of postsurgical pain induced by preoperative stress.","date":"2025","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/40482455","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"38472136","id":"PMC_38472136","title":"Testing SIPA1L2 as a modifier of CMT1A using mouse models.","date":"2024","source":"Journal of neuropathology and experimental neurology","url":"https://pubmed.ncbi.nlm.nih.gov/38472136","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"38076977","id":"PMC_38076977","title":"Testing SIPA1L2 as a modifier of CMT1A using mouse models.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38076977","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"39649580","id":"PMC_39649580","title":"Multi-ancestry genome-wide association study reveals novel genetic signals for lung function decline.","date":"2024","source":"medRxiv : the preprint server for health sciences","url":"https://pubmed.ncbi.nlm.nih.gov/39649580","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"40183409","id":"PMC_40183409","title":"RNA‑seq analysis of predictive markers associated with glutamine metabolism in thyroid cancer.","date":"2025","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/40183409","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"41503462","id":"PMC_41503462","title":"Genome-wide association studies identify genetic determinants of synucleinopathy biomarkers.","date":"2025","source":"medRxiv : the preprint server for health sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41503462","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"25064009","id":"PMC_25064009","title":"Large-scale meta-analysis of genome-wide association data identifies six new risk loci for Parkinson's disease.","date":"2014","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25064009","citation_count":1512,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12477932","id":"PMC_12477932","title":"Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12477932","citation_count":1479,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"26186194","id":"PMC_26186194","title":"The BioPlex Network: A Systematic Exploration of the Human Interactome.","date":"2015","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/26186194","citation_count":1118,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28514442","id":"PMC_28514442","title":"Architecture of the human interactome defines protein communities and disease networks.","date":"2017","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/28514442","citation_count":1085,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"25416956","id":"PMC_25416956","title":"A proteome-scale map of the human interactome network.","date":"2014","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/25416956","citation_count":977,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32296183","id":"PMC_32296183","title":"A reference map of the human binary protein interactome.","date":"2020","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/32296183","citation_count":849,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29507755","id":"PMC_29507755","title":"VIRMA mediates preferential m6A mRNA methylation in 3'UTR and near stop codon and associates with alternative polyadenylation.","date":"2018","source":"Cell discovery","url":"https://pubmed.ncbi.nlm.nih.gov/29507755","citation_count":829,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"14702039","id":"PMC_14702039","title":"Complete sequencing and characterization of 21,243 full-length human cDNAs.","date":"2003","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/14702039","citation_count":754,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"33961781","id":"PMC_33961781","title":"Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.","date":"2021","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/33961781","citation_count":705,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21873635","id":"PMC_21873635","title":"Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium.","date":"2011","source":"Briefings in bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/21873635","citation_count":656,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29395067","id":"PMC_29395067","title":"High-Density Proximity Mapping Reveals the Subcellular Organization of mRNA-Associated Granules and Bodies.","date":"2018","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/29395067","citation_count":580,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15489334","id":"PMC_15489334","title":"The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).","date":"2004","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/15489334","citation_count":438,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"26638075","id":"PMC_26638075","title":"A Dynamic Protein Interaction Landscape of the Human Centrosome-Cilium Interface.","date":"2015","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/26638075","citation_count":433,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"35271311","id":"PMC_35271311","title":"OpenCell: Endogenous tagging for the cartography of human cellular organization.","date":"2022","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/35271311","citation_count":432,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"8889548","id":"PMC_8889548","title":"Normalization and subtraction: two approaches to facilitate gene discovery.","date":"1996","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/8889548","citation_count":401,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"24255178","id":"PMC_24255178","title":"Protein interaction network of the mammalian Hippo pathway reveals mechanisms of kinase-phosphatase interactions.","date":"2013","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/24255178","citation_count":383,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"34079125","id":"PMC_34079125","title":"A proximity-dependent biotinylation map of a human cell.","date":"2021","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/34079125","citation_count":339,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"22810586","id":"PMC_22810586","title":"Interpreting cancer genomes using systematic host network perturbations by tumour virus proteins.","date":"2012","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/22810586","citation_count":319,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15146197","id":"PMC_15146197","title":"Transcriptome characterization elucidates signaling networks that control human ES cell growth and differentiation.","date":"2004","source":"Nature biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/15146197","citation_count":266,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21988832","id":"PMC_21988832","title":"Toward an understanding of the protein interaction network of the human liver.","date":"2011","source":"Molecular systems biology","url":"https://pubmed.ncbi.nlm.nih.gov/21988832","citation_count":207,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"23602568","id":"PMC_23602568","title":"The protein interaction landscape of the human CMGC kinase group.","date":"2013","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/23602568","citation_count":174,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16710414","id":"PMC_16710414","title":"The DNA sequence and biological annotation of human chromosome 1.","date":"2006","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/16710414","citation_count":144,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20694011","id":"PMC_20694011","title":"Association of IFIH1 and other autoimmunity risk alleles with selective IgA deficiency.","date":"2010","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20694011","citation_count":118,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28718761","id":"PMC_28718761","title":"The human cytoplasmic dynein interactome reveals novel activators of motility.","date":"2017","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/28718761","citation_count":118,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"31753913","id":"PMC_31753913","title":"Systematic bromodomain protein screens identify homologous recombination and R-loop suppression pathways involved in genome integrity.","date":"2019","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/31753913","citation_count":110,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20379614","id":"PMC_20379614","title":"Personalized smoking cessation: interactions between nicotine dose, dependence and quit-success genotype score.","date":"2010","source":"Molecular medicine (Cambridge, Mass.)","url":"https://pubmed.ncbi.nlm.nih.gov/20379614","citation_count":108,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"30021884","id":"PMC_30021884","title":"Histone Interaction Landscapes Visualized by Crosslinking Mass Spectrometry in Intact Cell Nuclei.","date":"2018","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/30021884","citation_count":101,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"10718198","id":"PMC_10718198","title":"Prediction of the coding sequences of unidentified human genes. XVI. The complete sequences of 150 new cDNA clones from brain which code for large proteins in vitro.","date":"2000","source":"DNA research : an international journal for rapid publication of reports on genes and genomes","url":"https://pubmed.ncbi.nlm.nih.gov/10718198","citation_count":97,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"27107012","id":"PMC_27107012","title":"Pooled-matrix protein interaction screens using Barcode Fusion Genetics.","date":"2016","source":"Molecular systems biology","url":"https://pubmed.ncbi.nlm.nih.gov/27107012","citation_count":89,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32707033","id":"PMC_32707033","title":"Kinase Interaction Network Expands Functional and Disease Roles of Human Kinases.","date":"2020","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/32707033","citation_count":88,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17360,"output_tokens":2007,"usd":0.041092},"stage2":{"model":"claude-opus-4-6","input_tokens":5270,"output_tokens":2178,"usd":0.1212},"total_usd":0.345865,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":29452,"output_tokens":1996,"usd":0.059148},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":5515,"output_tokens":2215,"usd":0.124425}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"SIPA1L2 (SPAR2) connects TrkB-containing amphisomes to a dynein motor at presynaptic terminals, enabling retrograde transport to the soma. The autophagosomal protein LC3 regulates the RapGAP activity of SIPA1L2 and controls retrograde trafficking and local signaling of TrkB. Following induction of presynaptic plasticity, amphisomes dissociate from dynein at boutons, enabling local signaling and promoting transmitter release. sipa1l2 knockout mice show impaired BDNF-dependent presynaptic plasticity.\",\n      \"method\": \"Co-immunoprecipitation, live imaging, sipa1l2 knockout mouse phenotyping, in vitro RapGAP assays, retrograde transport assays in hippocampal neurons\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (Co-IP, live imaging, KO mice, in vitro assays) in a single rigorous study with functional validation\",\n      \"pmids\": [\"31784514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SIPA1L2 (SPAR2) is a GTPase-activating protein (GAP) with in vitro GAP activity for Rap1 and Rap2. It interacts with the synaptic scaffolding protein ProSAPiP (which binds ProSAP/Shank PDZ domains), and is enriched in synaptosomes and post-synaptic density fractions. Unlike SPAR, overexpression of SPAR2 in hippocampal neurons does not affect spine morphology, and it shows different actin-binding properties.\",\n      \"method\": \"In vitro GAP assay, subcellular fractionation, co-immunoprecipitation, overexpression in COS-7 cells and hippocampal neurons, in situ hybridization\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro enzymatic assay demonstrating RapGAP activity, replicated across multiple experimental approaches in one study\",\n      \"pmids\": [\"17961154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SIPA1L2 binds β-actin and MYH9 as interaction partners in peripheral nerve, and is part of a myelination-associated gene network regulated by the master transcription factor SOX10. Knockdown of SIPA1L2 in Schwannoma cells leads to a significant reduction of PMP22 expression.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, immunocytochemistry, chromatin immunoprecipitation, in vitro siRNA knockdown\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP/MS for binding partners and ChIP for transcriptional regulation, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"30706531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Genetic deletion of Sipa1l2 in C3-PMP22 mice (CMT1A model) preserved muscular endurance and altered femoral nerve axon morphometrics (myelin thickness), and gene expression changes implicated Sipa1l2 in cholesterol biosynthesis. This validates a genetic interaction between Sipa1l2 and PMP22 duplication in peripheral neuropathy.\",\n      \"method\": \"Sipa1l2 exon-1 knockout mouse crossed to C3-PMP22 CMT1A model, neuromuscular phenotyping (inverted wire hang), nerve morphometrics, gene expression analysis\",\n      \"journal\": \"Journal of neuropathology and experimental neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO crossed to disease model with defined neuromuscular and morphometric phenotypic readouts, single lab\",\n      \"pmids\": [\"38472136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SIPA1L2 is targeted by miR-21-5p delivered via ECFC-derived exosomes; miR-21-5p binds the 3' UTR of SIPA1L2 to inhibit its expression, and SIPA1L2 knockdown repairs autophagic flux and promotes endothelial cell proliferation and migration in ox-LDL-injured HMECs.\",\n      \"method\": \"Dual-luciferase reporter assay, RNA-sequencing, western blot, Ad-mCherry-GFP-LC3B autophagic flux assay, SIPA1L2 knockdown in HMECs, rat atherosclerosis model\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct 3' UTR luciferase validation of miR-21-5p targeting SIPA1L2, combined with KD phenotypic readout across multiple assays\",\n      \"pmids\": [\"35279183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In the context of chondrogenic differentiation of hMSCs, irisin upregulates miR-125b-5p, which targets SIPA1L2, consequently activating the Rap1/PI3K/AKT axis. This places SIPA1L2 as a negative regulator of Rap1 signaling upstream of PI3K/AKT in this differentiation context.\",\n      \"method\": \"RNA-seq, miRNA mimics and inhibitor transfection, plasmid overexpression, western blot, high-density pellet chondrogenic culture system\",\n      \"journal\": \"Stem cell research & therapy\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, pathway placement inferred from miRNA targeting and downstream signaling readouts without direct enzymatic validation of SIPA1L2 RapGAP activity in this context\",\n      \"pmids\": [\"35922833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Xenopus laevis sipa1l2 ortholog is maternally supplied (RNA detected by RT-PCR) and expressed during early embryonic development specifically in the branchial arches, glomerulus, and developing eye, suggesting a conserved role during vertebrate embryogenesis.\",\n      \"method\": \"Semi-quantitative RT-PCR, whole mount in situ hybridization in Xenopus laevis embryos\",\n      \"journal\": \"Development genes and evolution\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — localization/expression data only, no functional perturbation experiment performed\",\n      \"pmids\": [\"27384056\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SIPA1L2 (SPAR2) is a synaptic RapGAP that inactivates Rap1 and Rap2; in neurons it physically connects TrkB-containing amphisomes to the dynein retrograde transport machinery, with LC3 regulating its RapGAP activity to control local presynaptic BDNF/TrkB signaling and plasticity, while in peripheral nerve it binds β-actin and MYH9, participates in a SOX10-regulated myelination network, and regulates PMP22 expression, and in endothelial and other non-neuronal cells it acts downstream of miR-21-5p to modulate autophagic flux and Rap1/PI3K/AKT signaling.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"SIPA1L2 (SPAR2) was identified as a novel RapGAP protein with GAP activity for both Rap1 and Rap2, demonstrated by in vitro GAP assays. It is enriched in synaptosomes and postsynaptic density fractions, and interacts with the synaptic scaffolding protein ProSAPiP (which binds ProSAP/Shank PDZ domains). Unlike its paralog SPAR1, overexpression of SPAR2 in hippocampal neurons does not affect spine morphology, and it shows distinct actin-binding properties.\",\n      \"method\": \"In vitro GAP assay, subcellular fractionation, co-immunoprecipitation, in situ hybridization, overexpression in cultured neurons\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro enzymatic activity assay combined with subcellular fractionation and binding partner identification\",\n      \"pmids\": [\"17961154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SIPA1L2 controls retrograde trafficking and local signaling of TrkB-containing amphisomes at presynaptic terminals by connecting TrkB amphisomes to the dynein motor. The autophagosomal protein LC3 regulates the RapGAP activity of SIPA1L2, controlling retrograde trafficking and local BDNF/TrkB signaling. Upon induction of presynaptic plasticity, amphisomes dissociate from dynein at boutons, enabling local signaling and promoting transmitter release. Sipa1l2 knockout mice show impaired BDNF-dependent presynaptic plasticity.\",\n      \"method\": \"Co-immunoprecipitation, live imaging, knockout mouse model, synaptic plasticity assays, fluorescence microscopy of retrograde transport\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP, KO mouse with defined phenotype, multiple orthogonal methods including live imaging and functional plasticity assays\",\n      \"pmids\": [\"31784514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SIPA1L2 was identified as a genetic modifier of CMT1A phenotype. Co-immunoprecipitation and mass spectrometry identified β-actin and MYH9 as SIPA1L2 binding partners in peripheral nerve. SIPA1L2 is part of a myelination-associated gene network regulated by the master transcription factor SOX10. In vitro siRNA knockdown of SIPA1L2 in Schwannoma cells led to significant reduction of PMP22 expression.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, immunocytochemistry, chromatin immunoprecipitation, siRNA knockdown, genome-wide association study\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP with MS validation and functional siRNA knockdown, but modifier role established in single study\",\n      \"pmids\": [\"30706531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Genetic deletion of Sipa1l2 exon 1 in mice crossed to the C3-PMP22 CMT1A model validated a genetic interaction: Sipa1l2 deletion preserved muscular endurance (wire-hang duration) and altered femoral nerve axon morphometrics including myelin thickness. Gene expression changes implicated Sipa1l2 in the cholesterol biosynthesis pathway, which is also dysregulated in C3-PMP22 mice.\",\n      \"method\": \"Knockout mouse generation, neuromuscular phenotyping (wire hang, nerve morphometrics), gene expression analysis\",\n      \"journal\": \"Journal of neuropathology and experimental neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in mouse model with defined phenotypic readouts, single study\",\n      \"pmids\": [\"38472136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In the context of vascular endothelial repair, SIPA1L2 was identified as a direct target of miR-21-5p (via binding to the 3'UTR of SIPA1L2 mRNA). Knockdown of SIPA1L2 in ox-LDL-treated human microvascular endothelial cells repaired autophagic flux and enhanced autophagic activity to promote cell proliferation, indicating that SIPA1L2 negatively regulates autophagy in endothelial cells.\",\n      \"method\": \"Dual-luciferase reporter assay, siRNA knockdown, Ad-mCherry-GFP-LC3B autophagic flux assay, western blot, RNA sequencing\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct 3'UTR target validation by luciferase assay plus functional autophagy flux assay with KD, single lab\",\n      \"pmids\": [\"35279183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"During irisin-enhanced chondrogenic differentiation of human mesenchymal stem cells, miR-125b-5p targets SIPA1L2 to reduce its expression, consequently activating the Rap1/PI3K/AKT signaling axis. This places SIPA1L2 as a negative regulator of Rap1 activity upstream of PI3K/AKT in chondrogenic differentiation.\",\n      \"method\": \"miRNA mimic/inhibitor transfection, plasmid overexpression, RNA-seq, western blot, pellet culture chondrogenic differentiation assay\",\n      \"journal\": \"Stem cell research & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional pathway placement via miRNA/overexpression manipulation, single lab, no direct RapGAP activity measurement\",\n      \"pmids\": [\"35922833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Sipa1l2 is expressed throughout early Xenopus laevis development with maternal RNA supply. During embryogenesis, sipa1l2 transcript is detected in branchial arches, glomerulus, and the developing eye, indicating a role in early vertebrate development beyond the nervous system.\",\n      \"method\": \"Semi-quantitative RT-PCR, whole-mount in situ hybridization\",\n      \"journal\": \"Development genes and evolution\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — expression/localization data only, no functional loss-of-function mechanistic data\",\n      \"pmids\": [\"27384056\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SIPA1L2 (SPAR2) is a synaptic RapGAP protein with catalytic activity toward Rap1 and Rap2 that, in hippocampal neurons, connects TrkB-containing amphisomes to the dynein retrograde transport machinery at presynaptic terminals—a process regulated by the autophagosomal protein LC3 acting on SIPA1L2's RapGAP activity—and whose loss impairs BDNF-dependent presynaptic plasticity; in peripheral nerve, SIPA1L2 binds β-actin and MYH9, participates in a SOX10-regulated myelination network controlling PMP22 expression, and modulates cholesterol biosynthesis pathways relevant to demyelinating neuropathy.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SIPA1L2 (SPAR2) is a Rap GTPase-activating protein that inactivates Rap1 and Rap2, functioning as a signaling scaffold that links receptor trafficking to cytoskeletal and synaptic organization in neurons and glia. At presynaptic terminals, SIPA1L2 physically connects TrkB-containing amphisomes to the dynein retrograde transport machinery, with the autophagosomal protein LC3 regulating its RapGAP activity to control BDNF-dependent presynaptic plasticity; sipa1l2 knockout mice show impaired presynaptic plasticity and transmitter release [PMID:31784514, PMID:17961154]. In peripheral nerve, SIPA1L2 interacts with β-actin and MYH9, operates within a SOX10-regulated myelination gene network, and controls PMP22 expression; genetic deletion of Sipa1l2 in a CMT1A mouse model preserves muscular endurance and alters myelin thickness, validating a genetic interaction with PMP22 duplication in peripheral neuropathy [PMID:30706531, PMID:38472136]. In non-neuronal cells, SIPA1L2 functions as a negative regulator of Rap1/PI3K/AKT signaling and autophagic flux, and its expression is post-transcriptionally repressed by miR-21-5p and miR-125b-5p [PMID:35279183, PMID:35922833].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Establishing SIPA1L2 as a bona fide RapGAP resolved the question of whether this SPAR family paralog shares enzymatic activity with SPAR1, and its synaptic enrichment placed it at the postsynaptic density alongside scaffolding partners.\",\n      \"evidence\": \"In vitro GAP assays on Rap1/Rap2, subcellular fractionation of synaptosomes, co-immunoprecipitation with ProSAPiP in COS-7 cells and hippocampal neurons\",\n      \"pmids\": [\"17961154\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"In vivo relevance of SIPA1L2 RapGAP activity at synapses was not tested\",\n        \"Regulation of GAP activity by interacting proteins was unknown\",\n        \"No loss-of-function data in neurons\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The discovery that SIPA1L2 physically bridges TrkB-amphisomes to dynein and that LC3 regulates its RapGAP activity answered how presynaptic retrograde BDNF/TrkB signaling is mechanistically coupled to autophagosomal trafficking, and knockout mice established its necessity for presynaptic plasticity.\",\n      \"evidence\": \"Co-immunoprecipitation, live imaging of retrograde transport, in vitro RapGAP assays with LC3, sipa1l2 knockout mouse electrophysiology and presynaptic plasticity in hippocampal neurons\",\n      \"pmids\": [\"31784514\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for LC3-dependent regulation of the GAP domain is unresolved\",\n        \"Whether other SPAR family members compensate in the knockout is unknown\",\n        \"Mechanism by which amphisomes dissociate from dynein at boutons is not defined\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identification of β-actin and MYH9 as SIPA1L2 binding partners in peripheral nerve, together with SOX10-dependent transcriptional regulation and control of PMP22 expression, extended SIPA1L2 function beyond CNS synapses to peripheral myelination.\",\n      \"evidence\": \"Co-immunoprecipitation/mass spectrometry from nerve tissue, ChIP for SOX10 binding, siRNA knockdown in Schwannoma cells measuring PMP22 levels\",\n      \"pmids\": [\"30706531\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether SIPA1L2 regulates PMP22 through its RapGAP activity or a scaffolding function is unclear\",\n        \"No in vivo myelination phenotype from SIPA1L2 loss alone was shown\",\n        \"Mechanism linking SIPA1L2 to PMP22 transcription not defined\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrating that miR-21-5p directly targets the SIPA1L2 3′ UTR and that SIPA1L2 knockdown restores autophagic flux in injured endothelial cells established a non-neuronal role for SIPA1L2 in autophagy regulation and vascular biology.\",\n      \"evidence\": \"Dual-luciferase 3′ UTR reporter assay, mCherry-GFP-LC3B autophagic flux assay, SIPA1L2 knockdown in ox-LDL-injured HMECs\",\n      \"pmids\": [\"35279183\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether autophagic flux regulation depends on SIPA1L2 RapGAP activity or its scaffolding of LC3 is untested\",\n        \"In vivo validation in atherosclerosis models with SIPA1L2-specific perturbation is lacking\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Crossing the Sipa1l2 knockout to a CMT1A model validated a functional genetic interaction between Sipa1l2 and PMP22 duplication in vivo, implicating SIPA1L2 in cholesterol biosynthesis pathways relevant to peripheral neuropathy.\",\n      \"evidence\": \"Sipa1l2 exon-1 knockout crossed to C3-PMP22 mice, inverted wire hang endurance test, femoral nerve morphometrics, gene expression profiling\",\n      \"pmids\": [\"38472136\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct mechanistic link between SIPA1L2 and cholesterol biosynthesis is not established\",\n        \"Whether RapGAP activity is required for the protective phenotype is unknown\",\n        \"Single behavioral readout (wire hang) limits assessment of functional rescue\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis for LC3 regulation of SIPA1L2 RapGAP activity, the mechanism by which SIPA1L2 controls PMP22 expression, and whether its synaptic and myelination roles are both RapGAP-dependent remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No crystal or cryo-EM structure of SIPA1L2 or its LC3-bound form exists\",\n        \"Separation-of-function mutations distinguishing GAP from scaffolding roles have not been generated\",\n        \"Circuit-level consequences of SIPA1L2 loss in the CNS beyond presynaptic plasticity are unexplored\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 4, 5]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\n      \"TrkB-amphisome–dynein transport complex\"\n    ],\n    \"partners\": [\n      \"NTRK2\",\n      \"MAP1LC3B\",\n      \"DYNC1H1\",\n      \"ACTB\",\n      \"MYH9\",\n      \"PROSAPIP1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"SIPA1L2 (SPAR2) is a RapGAP protein that catalyzes GTP hydrolysis on Rap1 and Rap2, functioning as a negative regulator of Rap signaling in neurons and other cell types [PMID:17961154, PMID:35922833]. In hippocampal presynaptic terminals, SIPA1L2 connects TrkB-containing amphisomes to the dynein retrograde transport machinery, with its RapGAP activity regulated by the autophagosomal protein LC3; loss of Sipa1l2 in mice impairs BDNF-dependent presynaptic plasticity [PMID:31784514]. In peripheral nerve, SIPA1L2 participates in a SOX10-regulated myelination gene network, binds β-actin and MYH9, and modulates PMP22 expression and cholesterol biosynthesis pathways, acting as a genetic modifier of the CMT1A demyelinating neuropathy phenotype [PMID:30706531, PMID:38472136].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Establishing SIPA1L2 as a functional RapGAP answered the basic question of enzymatic identity: SIPA1L2 catalyzes GTP hydrolysis on both Rap1 and Rap2, is enriched at synapses, and interacts with the scaffolding protein ProSAPiP, distinguishing it from its paralog SPAR1.\",\n      \"evidence\": \"In vitro GAP assay, synaptosome/PSD fractionation, co-IP, and overexpression in cultured hippocampal neurons\",\n      \"pmids\": [\"17961154\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Endogenous substrates and in vivo Rap specificity not determined\",\n        \"Functional consequence of ProSAPiP interaction at synapses unknown\",\n        \"No loss-of-function data to assess requirement in neurons\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Expression profiling in Xenopus embryos revealed maternally supplied sipa1l2 mRNA with enrichment in branchial arches, glomerulus, and eye, suggesting developmental roles beyond the nervous system.\",\n      \"evidence\": \"RT-PCR and whole-mount in situ hybridization in Xenopus laevis embryos\",\n      \"pmids\": [\"27384056\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No functional or loss-of-function data in Xenopus — expression only\",\n        \"Relevance to mammalian non-neuronal tissues not tested\",\n        \"No mechanistic link to RapGAP activity in these tissues\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The key mechanistic advance was demonstrating how SIPA1L2 couples neurotrophin signaling to retrograde transport: SIPA1L2 links TrkB-containing amphisomes to dynein at presynaptic boutons, with LC3 regulating its RapGAP activity; knockout mice showed impaired BDNF-dependent presynaptic plasticity, establishing an in vivo requirement.\",\n      \"evidence\": \"Co-IP, live imaging of retrograde transport, Sipa1l2 knockout mouse with synaptic plasticity assays\",\n      \"pmids\": [\"31784514\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of LC3–SIPA1L2 interaction and how LC3 modulates GAP activity unresolved\",\n        \"Whether the amphisome-dynein coupling function extends to other neurotrophin receptors unknown\",\n        \"Postsynaptic roles of SIPA1L2 not addressed\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identification of SIPA1L2 as a genetic modifier of CMT1A severity established a peripheral nerve function: SIPA1L2 binds β-actin and MYH9, operates within a SOX10-regulated myelination network, and its knockdown reduces PMP22 expression in Schwannoma cells.\",\n      \"evidence\": \"GWAS, co-IP with mass spectrometry validation, ChIP, siRNA knockdown in Schwannoma cells\",\n      \"pmids\": [\"30706531\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Modifier effect identified in a single cohort — replication in independent CMT1A populations needed\",\n        \"Direct mechanism linking SIPA1L2 RapGAP activity to PMP22 regulation not established\",\n        \"Whether β-actin/MYH9 binding is required for the myelination phenotype untested\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Parallel studies in non-neuronal contexts showed SIPA1L2 negatively regulates autophagy in ox-LDL-treated endothelial cells and acts as a negative regulator of Rap1/PI3K/AKT during chondrogenic differentiation, broadening its functional scope beyond neurons.\",\n      \"evidence\": \"Dual-luciferase 3ʹ-UTR reporter assay, autophagic flux assay with siRNA knockdown (endothelial cells); miRNA mimic/inhibitor and overexpression in mesenchymal stem cell chondrogenesis\",\n      \"pmids\": [\"35279183\", \"35922833\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct RapGAP activity not measured in either non-neuronal system\",\n        \"Whether SIPA1L2 autophagy regulation in endothelial cells uses the same LC3-dependent mechanism as in neurons is unknown\",\n        \"Each finding from a single laboratory\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Genetic epistasis in mice validated the CMT1A modifier role: Sipa1l2 deletion in the C3-PMP22 model preserved neuromuscular function and altered myelin thickness, implicating the cholesterol biosynthesis pathway as a downstream effector.\",\n      \"evidence\": \"Sipa1l2 exon-1 knockout crossed to C3-PMP22 transgenic mice; wire-hang endurance, nerve morphometrics, gene expression profiling\",\n      \"pmids\": [\"38472136\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Cholesterol biosynthesis link is transcriptomic — direct metabolic measurements not reported\",\n        \"Mechanism connecting SIPA1L2 RapGAP activity to cholesterol pathway regulation unclear\",\n        \"Whether Sipa1l2 deletion affects myelination independently of the PMP22 overexpression background not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unifying structural and mechanistic model explaining how SIPA1L2's RapGAP domain, actin-binding domain, and LC3-interacting region coordinate its dual roles in presynaptic amphisome transport and peripheral myelination remains to be established.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No crystal structure or cryo-EM data for any SIPA1L2 domain\",\n        \"Relative contributions of Rap1 vs Rap2 GTPase regulation in each tissue context unknown\",\n        \"Whether LC3-mediated regulation of RapGAP activity operates in Schwann cells or other non-neuronal contexts untested\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"NTRK2\",\n      \"MAP1LC3B\",\n      \"ACTB\",\n      \"MYH9\",\n      \"PROSAPIP1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}