{"gene":"REEP1","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2010,"finding":"REEP1 is structurally related to the DP1/Yop1p family of ER-shaping proteins and localizes to the tubular ER in neurons, where it forms protein complexes with atlastin-1 and spastin via hydrophobic hairpin domains in each protein.","method":"Co-immunoprecipitation in COS7 cells, co-localization in cultured rat cerebral cortical neurons, domain mutagenesis","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP with domain mutagenesis, replicated across cell types and confirmed with functional readouts","pmids":["20200447"],"is_preprint":false},{"year":2010,"finding":"REEP1 binds microtubules and promotes ER alignment along the microtubule cytoskeleton; a SPG31 mutant REEP1 lacking the C-terminal cytoplasmic region lost microtubule binding and disrupted the ER network.","method":"Overexpression and mutant analysis in COS7 cells, in vitro ER network formation assay, microtubule binding assay","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro reconstitution combined with loss-of-function mutagenesis and cellular imaging","pmids":["20200447"],"is_preprint":false},{"year":2010,"finding":"REEP proteins are required for ER network formation in vitro, establishing a direct role in tubular ER shaping.","method":"In vitro ER network formation assay with REEP protein depletion/addition","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro assay with direct functional readout","pmids":["20200447"],"is_preprint":false},{"year":2013,"finding":"REEP1 is a neuron-specific, membrane-binding, and membrane curvature-inducing protein that resides in the ER; REEP1-deficient cortical motor neurons show reduced complexity of the peripheral ER by ultrastructural analysis.","method":"Mouse knockout model (heterozygous and homozygous Reep1 exon 2 deletion), ultrastructural EM analysis of neuronal ER, membrane curvature assays","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1-2 — mouse KO with ultrastructural EM, membrane curvature induction assay, neuron-specific readout","pmids":["24051375"],"is_preprint":false},{"year":2015,"finding":"REEP1 is present at the ER-mitochondria interface, contains subdomains for both mitochondrial and ER localization, and facilitates ER-mitochondria interactions; disease-associated mutations diminish this function and cause neuritic growth defects and degeneration.","method":"Cellular imaging and biochemical fractionation, split-RLuc8 assay for ER-mitochondria proximity, knockdown and mutant expression in mouse cortical neurons","journal":"Annals of neurology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including novel proximity assay, biochemical fractionation, and neuronal loss-of-function with defined phenotype","pmids":["26201691"],"is_preprint":false},{"year":2016,"finding":"REEP1 co-immunoprecipitates with seipin in cells, and Reep1-null mouse embryonic fibroblasts and cortical neurons show lipid droplet abnormalities, linking REEP1 to lipid droplet regulation.","method":"Co-immunoprecipitation, Reep1 null mouse model, lipid droplet imaging in fibroblasts and neurons","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — Co-IP combined with null mouse model and cellular phenotypic readout","pmids":["27638887"],"is_preprint":false},{"year":2014,"finding":"The N-terminus of REEP1 is necessary for proper ER targeting; HSP-associated N-terminal missense variants abolish ER targeting and cause accumulation at lipid droplets. Co-overexpression of REEP1 with atlastins increases lipid droplet size synergistically.","method":"Mutant and deletion overexpression in cell lines, fluorescence microscopy, lipid droplet size measurement","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2-3 — systematic mutant analysis with imaging, but single lab","pmids":["24478229"],"is_preprint":false},{"year":2017,"finding":"REEP1 interacts with mitochondrial phosphatase PGAM5; impaired REEP1-PGAM5 interaction in SPG31 patient fibroblasts leads to DRP1 hyperphosphorylation at Ser637, inhibiting mitochondrial fission and causing highly tubular mitochondrial morphology.","method":"Primary patient fibroblasts, co-immunoprecipitation, phospho-DRP1 immunoblotting, genetic and pharmacological rescue of DRP1-S637 phosphorylation","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — Co-IP, phosphorylation analysis, and rescue experiments in patient cells with multiple orthogonal methods","pmids":["28007911"],"is_preprint":false},{"year":2017,"finding":"Mutant REEP1 proteins (carrying pathological mutations) localize to mitochondria and sequester mitochondria to the perinuclear region of neurons, impairing mitochondrial transport along the axon.","method":"Ectopic expression of pathological mutant REEP1 in primary neuronal cultures, live-cell imaging of mitochondrial distribution","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct localization experiment with functional consequence in neurons, single lab","pmids":["28007911"],"is_preprint":false},{"year":2017,"finding":"A nonstop variant in REEP1 produces a C-terminally extended protein whose extension triggers self-aggregation of REEP1, representing a toxic gain-of-function mechanism distinct from the loss-of-function mechanism underlying HSP.","method":"Minigene and protein expression assays, aggregation assays with REEP1 and reporter constructs","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2-3 — functional protein aggregation assay with reporters, single lab","pmids":["29124833"],"is_preprint":false},{"year":2022,"finding":"REEP1 associates with NDUFA4 and plays a role in preserving the integrity of mitochondrial complex IV; overexpression of REEP1 in SOD1G93A mice augments mitochondrial function and is neuroprotective.","method":"Co-immunoprecipitation of REEP1 with NDUFA4, viral overexpression in SOD1G93A mouse spinal cord, mitochondrial complex IV activity assays","journal":"Neuroscience bulletin","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP and in vivo overexpression with functional mitochondrial readout, single lab","pmids":["36520405"],"is_preprint":false},{"year":2014,"finding":"Downregulation of the Drosophila REEP1 homolog enhances Tau toxicity and formation of insoluble Tau aggregates, while overexpression of Drosophila or human REEP1 reverses these phenotypes and promotes neuronal resistance to ER stress.","method":"RNAi knockdown and overexpression in Drosophila Tau toxicity model, insoluble aggregate assay, ER stress assay","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo Drosophila genetic epistasis with defined molecular readouts, ortholog confirmed functional","pmids":["25096240"],"is_preprint":false},{"year":2023,"finding":"In fission yeast, Yep1 (ortholog of human REEP1-4) is essential for ER-phagy and nucleophagy; its ER-phagy role requires self-interaction, membrane-shaping ability, and C-terminal amphipathic helices. Human REEP1-4 can functionally substitute for Yep1 in ER-phagy.","method":"Imaging-based screen in S. pombe, deletion and domain mutant analysis, complementation with human REEP1-4","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 1-2 — systematic genetic and domain analysis with human protein complementation, multiple orthogonal methods","pmids":["37939137"],"is_preprint":false},{"year":2024,"finding":"REEP1 localizes within mitochondria-associated ER membranes (MAM) and its increased presence at MAM/mitochondria enhances interaction with NDPK-D, reducing cardiolipin externalization and supporting autophagosome biogenesis.","method":"Fluorescent co-localization, cardiolipin probe assay, Co-immunoprecipitation of REEP1 with NDPK-D, monodansylcadaverine staining for autophagosomes in SH-SY5Y cells","journal":"Phytomedicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP and co-localization with functional readout, single lab","pmids":["39178680"],"is_preprint":false},{"year":2012,"finding":"An internally deleted REEP1 mutant (p.102_139del) shows a subcellular localization defect and recruits atlastin-1 to the altered localization sites, whereas an HSP missense mutant (p.Ala20Glu) does not, indicating distinct pathomechanisms for different REEP1 mutations.","method":"Overexpression of mutant REEP1 in cell lines, co-localization imaging with atlastin-1","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 — co-localization and overexpression, single lab, no reciprocal Co-IP","pmids":["22703882"],"is_preprint":false}],"current_model":"REEP1 is a neuron-enriched, membrane curvature-inducing protein of the tubular ER that shapes the ER network through hydrophobic hairpin domains, interacts directly with atlastin-1 and spastin via these domains, binds microtubules through its C-terminal cytoplasmic region to align ER along the cytoskeleton, localizes to ER-mitochondria contact sites (MAM) where it facilitates ER-mitochondria tethering, interacts with PGAM5 to regulate DRP1-S637 phosphorylation and mitochondrial fission, interacts with NDUFA4 to support mitochondrial complex IV integrity, co-operates with seipin in lipid droplet regulation, and is required for ER-phagy autophagosomal enclosure; loss-of-function mutations cause haploinsufficiency with ER morphology defects and axonal degeneration, while certain gain-of-function mutations produce aggregation-prone or mislocalized proteins with distinct toxic effects on lower motor neurons."},"narrative":{"teleology":[{"year":2010,"claim":"Establishing REEP1 as an ER-shaping protein that cooperates with atlastin-1 and spastin answered how three HSP-linked gene products converge on a shared membrane-remodeling function at the tubular ER.","evidence":"Reciprocal co-IP in COS7 cells, domain mutagenesis, in vitro ER network reconstitution, and neuronal co-localization","pmids":["20200447"],"confidence":"High","gaps":["Stoichiometry and direct binding interfaces between REEP1, atlastin-1, and spastin remain unresolved","No structural model of the REEP1 hairpin domains in a lipid bilayer"]},{"year":2010,"claim":"Demonstrating that REEP1 binds microtubules through its C-terminal cytoplasmic region and that SPG31 truncation mutants lose this activity explained how ER–cytoskeleton coupling fails in disease.","evidence":"Microtubule binding assay, overexpression of wild-type versus C-terminally truncated REEP1 in COS7 cells","pmids":["20200447"],"confidence":"High","gaps":["Identity of the microtubule-binding motif within the C-terminus is not mapped at residue level","Whether REEP1 binds microtubules directly or through adaptors in vivo is unresolved"]},{"year":2013,"claim":"A mouse knockout confirmed REEP1 is essential for peripheral ER complexity in cortical motor neurons in vivo, grounding prior in vitro findings in a physiological model of axonal vulnerability.","evidence":"Reep1 exon-2 deletion mouse, ultrastructural EM of neuronal ER, membrane curvature assays","pmids":["24051375"],"confidence":"High","gaps":["Whether ER complexity defects are cell-autonomous or influenced by non-neuronal cells is unknown","Behavioral and electrophysiological progression in Reep1-null mice was not fully characterized at this stage"]},{"year":2014,"claim":"Analysis of distinct REEP1 mutations revealed that an internal deletion mislocalizes REEP1 and recruits atlastin-1, whereas a missense mutant does not, establishing that different pathological mutations drive distinct cellular pathomechanisms.","evidence":"Overexpression of deletion and missense REEP1 mutants in cell lines with atlastin-1 co-localization imaging","pmids":["22703882"],"confidence":"Medium","gaps":["No reciprocal co-IP was performed to validate the altered interaction","Only two mutations were compared; broader allelic series needed"]},{"year":2014,"claim":"A Drosophila Tau toxicity model showed that REEP1 ortholog depletion enhances protein aggregation and ER stress, while overexpression rescues, linking REEP1 to neuronal proteostasis.","evidence":"RNAi knockdown and overexpression in Drosophila, insoluble aggregate and ER stress assays","pmids":["25096240"],"confidence":"Medium","gaps":["Whether the anti-aggregation effect is direct or secondary to ER morphology changes is unclear","Has not been independently replicated in mammalian Tau models"]},{"year":2015,"claim":"Identification of REEP1 at ER–mitochondria contact sites with subdomains targeting each organelle expanded its role beyond ER shaping to inter-organelle communication relevant to axonal maintenance.","evidence":"Split-RLuc8 ER–mitochondria proximity assay, biochemical fractionation, knockdown and mutant expression in mouse cortical neurons","pmids":["26201691"],"confidence":"High","gaps":["The molecular tethering mechanism at the MAM is not defined","Functional consequences of disrupted MAM contacts on calcium or lipid transfer were not measured"]},{"year":2016,"claim":"Discovery of a REEP1–seipin interaction and lipid droplet abnormalities in Reep1-null cells connected ER shaping to lipid droplet homeostasis.","evidence":"Co-IP in cells, lipid droplet imaging in Reep1-null MEFs and cortical neurons","pmids":["27638887"],"confidence":"High","gaps":["Whether REEP1 acts on lipid droplet budding, growth, or turnover is unresolved","Direct versus seipin-mediated mechanism not distinguished"]},{"year":2017,"claim":"The REEP1–PGAM5 interaction and its control of DRP1-S637 phosphorylation provided a mechanistic link between ER morphology and mitochondrial fission regulation, explaining hypertubular mitochondria in SPG31 patient cells.","evidence":"Co-IP, phospho-DRP1 immunoblotting, genetic and pharmacological rescue in SPG31 patient fibroblasts","pmids":["28007911"],"confidence":"High","gaps":["Whether REEP1 modulates PGAM5 phosphatase activity directly or through scaffolding is unknown","Not tested in motor neurons or in vivo"]},{"year":2017,"claim":"A nonstop REEP1 variant was shown to produce a C-terminally extended, aggregation-prone protein, establishing a gain-of-function toxicity mechanism distinct from haploinsufficiency.","evidence":"Minigene expression, protein aggregation assay with reporter constructs","pmids":["29124833"],"confidence":"Medium","gaps":["Single lab finding; aggregation has not been confirmed in patient-derived cells or in vivo","Whether the aggregates are toxic through proteostasis disruption or sequestration of partners is unclear"]},{"year":2022,"claim":"Association of REEP1 with NDUFA4 and enhancement of complex IV activity upon REEP1 overexpression in an ALS mouse model extended its mitochondrial role to respiratory chain integrity and neuroprotection.","evidence":"Co-IP of REEP1 with NDUFA4, viral overexpression in SOD1G93A mouse spinal cord, complex IV activity assay","pmids":["36520405"],"confidence":"Medium","gaps":["Single lab; the REEP1–NDUFA4 interaction awaits reciprocal validation","Whether the neuroprotective effect is mediated through complex IV or additional pathways is unresolved"]},{"year":2023,"claim":"Demonstration that REEP1 ortholog Yep1 is essential for ER-phagy in fission yeast—and that human REEP1 complements this function—established ER-phagy as a conserved REEP1-dependent process requiring self-interaction and membrane-shaping activity.","evidence":"Imaging-based screen in S. pombe, domain deletion mutant analysis, human REEP1-4 complementation","pmids":["37939137"],"confidence":"High","gaps":["The mammalian ER-phagy receptor(s) that cooperate with REEP1 are not identified","Whether REEP1 ER-phagy function is relevant to HSP pathogenesis has not been tested"]},{"year":2024,"claim":"REEP1 at MAM was linked to NDPK-D interaction, cardiolipin externalization control, and autophagosome biogenesis, providing a MAM-localized mechanism connecting REEP1 to autophagy signaling.","evidence":"Co-IP of REEP1 with NDPK-D, cardiolipin probe assay, autophagosome staining in SH-SY5Y cells","pmids":["39178680"],"confidence":"Medium","gaps":["Single lab; NDPK-D interaction not validated by reciprocal approach","Whether cardiolipin externalization changes are a direct or secondary effect of REEP1 is unclear"]},{"year":null,"claim":"It remains unknown how REEP1's multiple functions—ER shaping, microtubule coupling, MAM tethering, mitochondrial fission regulation, lipid droplet homeostasis, and ER-phagy—are coordinated in motor neurons and which deficit is the primary driver of axonal degeneration in SPG31.","evidence":"","pmids":[],"confidence":"High","gaps":["No high-resolution structure of REEP1 in a membrane context exists","Relative contributions of ER-phagy versus ER morphology versus mitochondrial fission defects to HSP pathogenesis are undefined","Cell-type-specific interactome of REEP1 in motor neurons has not been systematically mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[3,6]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,2,3]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,2,3,6]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[4,7,8,10]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1]},{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[5,6]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,2,3]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[12,13]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[7,9]}],"complexes":[],"partners":["ATL1","SPAST","PGAM5","BSCL2","NDUFA4","DRP1","NME4"],"other_free_text":[]},"mechanistic_narrative":"REEP1 is a neuron-enriched ER-shaping protein that generates membrane curvature through hydrophobic hairpin domains to build and maintain the tubular ER network, and couples ER tubules to the microtubule cytoskeleton via its C-terminal cytoplasmic region [PMID:20200447, PMID:24051375]. It forms complexes with atlastin-1 and spastin through its hairpin domains, cooperates with seipin in lipid droplet regulation, and resides at ER–mitochondria contact sites where it interacts with PGAM5 to regulate DRP1-S637 phosphorylation and mitochondrial fission, and with NDUFA4 to support complex IV integrity [PMID:20200447, PMID:27638887, PMID:26201691, PMID:28007911, PMID:36520405]. REEP1 is functionally required for ER-phagy, as demonstrated by conservation of this role from fission yeast to human, dependent on its self-interaction and membrane-shaping activity [PMID:37939137]. Loss-of-function mutations in REEP1 cause hereditary spastic paraplegia (SPG31) through haploinsufficiency with ER morphology defects, while certain gain-of-function mutations produce mislocalized or aggregation-prone proteins with distinct neurotoxic effects [PMID:24051375, PMID:29124833, PMID:28007911]."},"prefetch_data":{"uniprot":{"accession":"Q9H902","full_name":"Receptor expression-enhancing protein 1","aliases":["Spastic paraplegia 31 protein"],"length_aa":201,"mass_kda":22.3,"function":"Required for endoplasmic reticulum (ER) network formation, shaping and remodeling; it links ER tubules to the cytoskeleton. May also enhance the cell surface expression of odorant receptors (PubMed:20200447). May play a role in long-term axonal maintenance (PubMed:24478229)","subcellular_location":"Membrane; Mitochondrion membrane; Endoplasmic reticulum","url":"https://www.uniprot.org/uniprotkb/Q9H902/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/REEP1","classification":"Not Classified","n_dependent_lines":25,"n_total_lines":1208,"dependency_fraction":0.020695364238410598},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/REEP1","total_profiled":1310},"omim":[{"mim_id":"620011","title":"NEURONOPATHY, DISTAL HEREDITARY MOTOR, AUTOSOMAL RECESSIVE 6; HMNR6","url":"https://www.omim.org/entry/620011"},{"mim_id":"614751","title":"NEURONOPATHY, DISTAL HEREDITARY MOTOR, AUTOSOMAL DOMINANT 12; HMND12","url":"https://www.omim.org/entry/614751"},{"mim_id":"613564","title":"CHROMOSOME 2p12-p11.2 DELETION SYNDROME","url":"https://www.omim.org/entry/613564"},{"mim_id":"610250","title":"SPASTIC PARAPLEGIA 31, AUTOSOMAL DOMINANT; SPG31","url":"https://www.omim.org/entry/610250"},{"mim_id":"610243","title":"ZINC FINGER FYVE DOMAIN-CONTAINING PROTEIN 27; ZFYVE27","url":"https://www.omim.org/entry/610243"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"testis","ntpm":42.3}],"url":"https://www.proteinatlas.org/search/REEP1"},"hgnc":{"alias_symbol":["FLJ13110","SPG31","Yip2a"],"prev_symbol":["C2orf23"]},"alphafold":{"accession":"Q9H902","domains":[{"cath_id":"-","chopping":"1-80","consensus_level":"medium","plddt":70.4655,"start":1,"end":80}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H902","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H902-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H902-F1-predicted_aligned_error_v6.png","plddt_mean":67.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=REEP1","jax_strain_url":"https://www.jax.org/strain/search?query=REEP1"},"sequence":{"accession":"Q9H902","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H902.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H902/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H902"}},"corpus_meta":[{"pmid":"20200447","id":"PMC_20200447","title":"Hereditary spastic paraplegia proteins REEP1, spastin, and atlastin-1 coordinate microtubule interactions with the tubular ER network.","date":"2010","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/20200447","citation_count":317,"is_preprint":false},{"pmid":"16826527","id":"PMC_16826527","title":"Mutations in the novel mitochondrial protein REEP1 cause hereditary spastic paraplegia type 31.","date":"2006","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/16826527","citation_count":190,"is_preprint":false},{"pmid":"18321925","id":"PMC_18321925","title":"REEP1 mutation spectrum and genotype/phenotype correlation in hereditary spastic paraplegia type 31.","date":"2008","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/18321925","citation_count":146,"is_preprint":false},{"pmid":"26201691","id":"PMC_26201691","title":"Hereditary spastic paraplegia-linked REEP1 modulates endoplasmic reticulum/mitochondria contacts.","date":"2015","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/26201691","citation_count":85,"is_preprint":false},{"pmid":"27638887","id":"PMC_27638887","title":"Reep1 null mice reveal a converging role for hereditary spastic paraplegia proteins in lipid droplet regulation.","date":"2016","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27638887","citation_count":81,"is_preprint":false},{"pmid":"21618648","id":"PMC_21618648","title":"REEP1 mutations in SPG31: frequency, mutational spectrum, and potential association with mitochondrial morpho-functional dysfunction.","date":"2011","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/21618648","citation_count":79,"is_preprint":false},{"pmid":"22703882","id":"PMC_22703882","title":"Exome sequencing identifies a REEP1 mutation involved in distal hereditary motor neuropathy type V.","date":"2012","source":"American journal of human 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the phenotype of REEP1-associated hereditary spastic paraplegia (HSP).","date":"2008","source":"Neurogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/19034539","citation_count":38,"is_preprint":false},{"pmid":"18644145","id":"PMC_18644145","title":"Autosomal dominant hereditary spastic paraplegia: novel mutations in the REEP1 gene (SPG31).","date":"2008","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/18644145","citation_count":35,"is_preprint":false},{"pmid":"28007911","id":"PMC_28007911","title":"Mitochondrial morphology and cellular distribution are altered in SPG31 patients and are linked to DRP1 hyperphosphorylation.","date":"2017","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28007911","citation_count":33,"is_preprint":false},{"pmid":"24355597","id":"PMC_24355597","title":"REEP1 and REEP2 proteins are preferentially expressed in neuronal and neuronal-like exocytotic tissues.","date":"2013","source":"Brain 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neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/31913854","citation_count":10,"is_preprint":false},{"pmid":"29107646","id":"PMC_29107646","title":"Spastic paraplegia type 31: A novel REEP1 splice site donor variant and expansion of the phenotype variability.","date":"2017","source":"Parkinsonism & related disorders","url":"https://pubmed.ncbi.nlm.nih.gov/29107646","citation_count":10,"is_preprint":false},{"pmid":"36520405","id":"PMC_36520405","title":"REEP1 Preserves Motor Function in SOD1G93A Mice by Improving Mitochondrial Function via Interaction with NDUFA4.","date":"2022","source":"Neuroscience bulletin","url":"https://pubmed.ncbi.nlm.nih.gov/36520405","citation_count":9,"is_preprint":false},{"pmid":"39178680","id":"PMC_39178680","title":"Phillyrin promotes autophagosome formation in A53T-αSyn-induced Parkinson's disease model via modulation of REEP1.","date":"2024","source":"Phytomedicine : international journal of phytotherapy and phytopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/39178680","citation_count":8,"is_preprint":false},{"pmid":"24986827","id":"PMC_24986827","title":"A recurrent deletion syndrome at chromosome bands 2p11.2-2p12 flanked by segmental duplications at the breakpoints and including REEP1.","date":"2014","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/24986827","citation_count":8,"is_preprint":false},{"pmid":"28099355","id":"PMC_28099355","title":"Hereditary spastic paraplegia due to a novel mutation of the REEP1 gene: Case report and literature review.","date":"2017","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28099355","citation_count":7,"is_preprint":false},{"pmid":"36834939","id":"PMC_36834939","title":"Converging Role for REEP1/SPG31 in Oxidative Stress.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36834939","citation_count":6,"is_preprint":false},{"pmid":"32655478","id":"PMC_32655478","title":"Screening for REEP1 Mutations in 31 Chinese Hereditary Spastic Paraplegia Families.","date":"2020","source":"Frontiers in neurology","url":"https://pubmed.ncbi.nlm.nih.gov/32655478","citation_count":5,"is_preprint":false},{"pmid":"38889632","id":"PMC_38889632","title":"Generation of a human induced pluripotent stem cell line (FSMi001-A) from fibroblasts of a patient carrying heterozygous mutation in the REEP1 gene.","date":"2024","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/38889632","citation_count":3,"is_preprint":false},{"pmid":"35132160","id":"PMC_35132160","title":"A clinical and genetic study of SPG31 in Japan.","date":"2022","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/35132160","citation_count":2,"is_preprint":false},{"pmid":"38479332","id":"PMC_38479332","title":"Generation of homozygous and heterozygous REEP1 knockout induced pluripotent stem cell lines by CRISPR/Cas9 gene editing.","date":"2024","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/38479332","citation_count":1,"is_preprint":false},{"pmid":"31055810","id":"PMC_31055810","title":"[Deletional variant of REEP1 gene in a pedigree affected with spastic paraplegia type 31].","date":"2019","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31055810","citation_count":1,"is_preprint":false},{"pmid":"38525447","id":"PMC_38525447","title":"Phenotypic variability in a large kindred with spastic paraplegia associated with a novel REEP1 variant.","date":"2024","source":"eNeurologicalSci","url":"https://pubmed.ncbi.nlm.nih.gov/38525447","citation_count":0,"is_preprint":false},{"pmid":"32905827","id":"PMC_32905827","title":"A novel REEP1 splicing mutation with broad clinical variability in a family with hereditary spastic paraplegia.","date":"2020","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/32905827","citation_count":0,"is_preprint":false},{"pmid":"41018230","id":"PMC_41018230","title":"Double gene mutations of LRSAM1 and REEP1 and a new REEP1 mutation site found in a patient with amyotrophic lateral sclerosis with subjective paresthesia: A case report.","date":"2023","source":"Ibrain","url":"https://pubmed.ncbi.nlm.nih.gov/41018230","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18573,"output_tokens":3269,"usd":0.052377},"stage2":{"model":"claude-opus-4-6","input_tokens":6666,"output_tokens":3249,"usd":0.171832},"total_usd":0.224209,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"REEP1 is structurally related to the DP1/Yop1p family of ER-shaping proteins and localizes to the tubular ER in neurons, where it forms protein complexes with atlastin-1 and spastin via hydrophobic hairpin domains in each protein.\",\n      \"method\": \"Co-immunoprecipitation in COS7 cells, co-localization in cultured rat cerebral cortical neurons, domain mutagenesis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP with domain mutagenesis, replicated across cell types and confirmed with functional readouts\",\n      \"pmids\": [\"20200447\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"REEP1 binds microtubules and promotes ER alignment along the microtubule cytoskeleton; a SPG31 mutant REEP1 lacking the C-terminal cytoplasmic region lost microtubule binding and disrupted the ER network.\",\n      \"method\": \"Overexpression and mutant analysis in COS7 cells, in vitro ER network formation assay, microtubule binding assay\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro reconstitution combined with loss-of-function mutagenesis and cellular imaging\",\n      \"pmids\": [\"20200447\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"REEP proteins are required for ER network formation in vitro, establishing a direct role in tubular ER shaping.\",\n      \"method\": \"In vitro ER network formation assay with REEP protein depletion/addition\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro assay with direct functional readout\",\n      \"pmids\": [\"20200447\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"REEP1 is a neuron-specific, membrane-binding, and membrane curvature-inducing protein that resides in the ER; REEP1-deficient cortical motor neurons show reduced complexity of the peripheral ER by ultrastructural analysis.\",\n      \"method\": \"Mouse knockout model (heterozygous and homozygous Reep1 exon 2 deletion), ultrastructural EM analysis of neuronal ER, membrane curvature assays\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mouse KO with ultrastructural EM, membrane curvature induction assay, neuron-specific readout\",\n      \"pmids\": [\"24051375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"REEP1 is present at the ER-mitochondria interface, contains subdomains for both mitochondrial and ER localization, and facilitates ER-mitochondria interactions; disease-associated mutations diminish this function and cause neuritic growth defects and degeneration.\",\n      \"method\": \"Cellular imaging and biochemical fractionation, split-RLuc8 assay for ER-mitochondria proximity, knockdown and mutant expression in mouse cortical neurons\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including novel proximity assay, biochemical fractionation, and neuronal loss-of-function with defined phenotype\",\n      \"pmids\": [\"26201691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"REEP1 co-immunoprecipitates with seipin in cells, and Reep1-null mouse embryonic fibroblasts and cortical neurons show lipid droplet abnormalities, linking REEP1 to lipid droplet regulation.\",\n      \"method\": \"Co-immunoprecipitation, Reep1 null mouse model, lipid droplet imaging in fibroblasts and neurons\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP combined with null mouse model and cellular phenotypic readout\",\n      \"pmids\": [\"27638887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The N-terminus of REEP1 is necessary for proper ER targeting; HSP-associated N-terminal missense variants abolish ER targeting and cause accumulation at lipid droplets. Co-overexpression of REEP1 with atlastins increases lipid droplet size synergistically.\",\n      \"method\": \"Mutant and deletion overexpression in cell lines, fluorescence microscopy, lipid droplet size measurement\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — systematic mutant analysis with imaging, but single lab\",\n      \"pmids\": [\"24478229\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"REEP1 interacts with mitochondrial phosphatase PGAM5; impaired REEP1-PGAM5 interaction in SPG31 patient fibroblasts leads to DRP1 hyperphosphorylation at Ser637, inhibiting mitochondrial fission and causing highly tubular mitochondrial morphology.\",\n      \"method\": \"Primary patient fibroblasts, co-immunoprecipitation, phospho-DRP1 immunoblotting, genetic and pharmacological rescue of DRP1-S637 phosphorylation\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, phosphorylation analysis, and rescue experiments in patient cells with multiple orthogonal methods\",\n      \"pmids\": [\"28007911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mutant REEP1 proteins (carrying pathological mutations) localize to mitochondria and sequester mitochondria to the perinuclear region of neurons, impairing mitochondrial transport along the axon.\",\n      \"method\": \"Ectopic expression of pathological mutant REEP1 in primary neuronal cultures, live-cell imaging of mitochondrial distribution\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct localization experiment with functional consequence in neurons, single lab\",\n      \"pmids\": [\"28007911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A nonstop variant in REEP1 produces a C-terminally extended protein whose extension triggers self-aggregation of REEP1, representing a toxic gain-of-function mechanism distinct from the loss-of-function mechanism underlying HSP.\",\n      \"method\": \"Minigene and protein expression assays, aggregation assays with REEP1 and reporter constructs\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — functional protein aggregation assay with reporters, single lab\",\n      \"pmids\": [\"29124833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"REEP1 associates with NDUFA4 and plays a role in preserving the integrity of mitochondrial complex IV; overexpression of REEP1 in SOD1G93A mice augments mitochondrial function and is neuroprotective.\",\n      \"method\": \"Co-immunoprecipitation of REEP1 with NDUFA4, viral overexpression in SOD1G93A mouse spinal cord, mitochondrial complex IV activity assays\",\n      \"journal\": \"Neuroscience bulletin\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and in vivo overexpression with functional mitochondrial readout, single lab\",\n      \"pmids\": [\"36520405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Downregulation of the Drosophila REEP1 homolog enhances Tau toxicity and formation of insoluble Tau aggregates, while overexpression of Drosophila or human REEP1 reverses these phenotypes and promotes neuronal resistance to ER stress.\",\n      \"method\": \"RNAi knockdown and overexpression in Drosophila Tau toxicity model, insoluble aggregate assay, ER stress assay\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo Drosophila genetic epistasis with defined molecular readouts, ortholog confirmed functional\",\n      \"pmids\": [\"25096240\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In fission yeast, Yep1 (ortholog of human REEP1-4) is essential for ER-phagy and nucleophagy; its ER-phagy role requires self-interaction, membrane-shaping ability, and C-terminal amphipathic helices. Human REEP1-4 can functionally substitute for Yep1 in ER-phagy.\",\n      \"method\": \"Imaging-based screen in S. pombe, deletion and domain mutant analysis, complementation with human REEP1-4\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — systematic genetic and domain analysis with human protein complementation, multiple orthogonal methods\",\n      \"pmids\": [\"37939137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"REEP1 localizes within mitochondria-associated ER membranes (MAM) and its increased presence at MAM/mitochondria enhances interaction with NDPK-D, reducing cardiolipin externalization and supporting autophagosome biogenesis.\",\n      \"method\": \"Fluorescent co-localization, cardiolipin probe assay, Co-immunoprecipitation of REEP1 with NDPK-D, monodansylcadaverine staining for autophagosomes in SH-SY5Y cells\",\n      \"journal\": \"Phytomedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and co-localization with functional readout, single lab\",\n      \"pmids\": [\"39178680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"An internally deleted REEP1 mutant (p.102_139del) shows a subcellular localization defect and recruits atlastin-1 to the altered localization sites, whereas an HSP missense mutant (p.Ala20Glu) does not, indicating distinct pathomechanisms for different REEP1 mutations.\",\n      \"method\": \"Overexpression of mutant REEP1 in cell lines, co-localization imaging with atlastin-1\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-localization and overexpression, single lab, no reciprocal Co-IP\",\n      \"pmids\": [\"22703882\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"REEP1 is a neuron-enriched, membrane curvature-inducing protein of the tubular ER that shapes the ER network through hydrophobic hairpin domains, interacts directly with atlastin-1 and spastin via these domains, binds microtubules through its C-terminal cytoplasmic region to align ER along the cytoskeleton, localizes to ER-mitochondria contact sites (MAM) where it facilitates ER-mitochondria tethering, interacts with PGAM5 to regulate DRP1-S637 phosphorylation and mitochondrial fission, interacts with NDUFA4 to support mitochondrial complex IV integrity, co-operates with seipin in lipid droplet regulation, and is required for ER-phagy autophagosomal enclosure; loss-of-function mutations cause haploinsufficiency with ER morphology defects and axonal degeneration, while certain gain-of-function mutations produce aggregation-prone or mislocalized proteins with distinct toxic effects on lower motor neurons.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"REEP1 is a neuron-enriched ER-shaping protein that generates membrane curvature through hydrophobic hairpin domains to build and maintain the tubular ER network, and couples ER tubules to the microtubule cytoskeleton via its C-terminal cytoplasmic region [PMID:20200447, PMID:24051375]. It forms complexes with atlastin-1 and spastin through its hairpin domains, cooperates with seipin in lipid droplet regulation, and resides at ER–mitochondria contact sites where it interacts with PGAM5 to regulate DRP1-S637 phosphorylation and mitochondrial fission, and with NDUFA4 to support complex IV integrity [PMID:20200447, PMID:27638887, PMID:26201691, PMID:28007911, PMID:36520405]. REEP1 is functionally required for ER-phagy, as demonstrated by conservation of this role from fission yeast to human, dependent on its self-interaction and membrane-shaping activity [PMID:37939137]. Loss-of-function mutations in REEP1 cause hereditary spastic paraplegia (SPG31) through haploinsufficiency with ER morphology defects, while certain gain-of-function mutations produce mislocalized or aggregation-prone proteins with distinct neurotoxic effects [PMID:24051375, PMID:29124833, PMID:28007911].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Establishing REEP1 as an ER-shaping protein that cooperates with atlastin-1 and spastin answered how three HSP-linked gene products converge on a shared membrane-remodeling function at the tubular ER.\",\n      \"evidence\": \"Reciprocal co-IP in COS7 cells, domain mutagenesis, in vitro ER network reconstitution, and neuronal co-localization\",\n      \"pmids\": [\"20200447\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Stoichiometry and direct binding interfaces between REEP1, atlastin-1, and spastin remain unresolved\",\n        \"No structural model of the REEP1 hairpin domains in a lipid bilayer\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrating that REEP1 binds microtubules through its C-terminal cytoplasmic region and that SPG31 truncation mutants lose this activity explained how ER–cytoskeleton coupling fails in disease.\",\n      \"evidence\": \"Microtubule binding assay, overexpression of wild-type versus C-terminally truncated REEP1 in COS7 cells\",\n      \"pmids\": [\"20200447\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Identity of the microtubule-binding motif within the C-terminus is not mapped at residue level\",\n        \"Whether REEP1 binds microtubules directly or through adaptors in vivo is unresolved\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"A mouse knockout confirmed REEP1 is essential for peripheral ER complexity in cortical motor neurons in vivo, grounding prior in vitro findings in a physiological model of axonal vulnerability.\",\n      \"evidence\": \"Reep1 exon-2 deletion mouse, ultrastructural EM of neuronal ER, membrane curvature assays\",\n      \"pmids\": [\"24051375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ER complexity defects are cell-autonomous or influenced by non-neuronal cells is unknown\",\n        \"Behavioral and electrophysiological progression in Reep1-null mice was not fully characterized at this stage\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Analysis of distinct REEP1 mutations revealed that an internal deletion mislocalizes REEP1 and recruits atlastin-1, whereas a missense mutant does not, establishing that different pathological mutations drive distinct cellular pathomechanisms.\",\n      \"evidence\": \"Overexpression of deletion and missense REEP1 mutants in cell lines with atlastin-1 co-localization imaging\",\n      \"pmids\": [\"22703882\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No reciprocal co-IP was performed to validate the altered interaction\",\n        \"Only two mutations were compared; broader allelic series needed\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A Drosophila Tau toxicity model showed that REEP1 ortholog depletion enhances protein aggregation and ER stress, while overexpression rescues, linking REEP1 to neuronal proteostasis.\",\n      \"evidence\": \"RNAi knockdown and overexpression in Drosophila, insoluble aggregate and ER stress assays\",\n      \"pmids\": [\"25096240\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether the anti-aggregation effect is direct or secondary to ER morphology changes is unclear\",\n        \"Has not been independently replicated in mammalian Tau models\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identification of REEP1 at ER–mitochondria contact sites with subdomains targeting each organelle expanded its role beyond ER shaping to inter-organelle communication relevant to axonal maintenance.\",\n      \"evidence\": \"Split-RLuc8 ER–mitochondria proximity assay, biochemical fractionation, knockdown and mutant expression in mouse cortical neurons\",\n      \"pmids\": [\"26201691\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The molecular tethering mechanism at the MAM is not defined\",\n        \"Functional consequences of disrupted MAM contacts on calcium or lipid transfer were not measured\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Discovery of a REEP1–seipin interaction and lipid droplet abnormalities in Reep1-null cells connected ER shaping to lipid droplet homeostasis.\",\n      \"evidence\": \"Co-IP in cells, lipid droplet imaging in Reep1-null MEFs and cortical neurons\",\n      \"pmids\": [\"27638887\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether REEP1 acts on lipid droplet budding, growth, or turnover is unresolved\",\n        \"Direct versus seipin-mediated mechanism not distinguished\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The REEP1–PGAM5 interaction and its control of DRP1-S637 phosphorylation provided a mechanistic link between ER morphology and mitochondrial fission regulation, explaining hypertubular mitochondria in SPG31 patient cells.\",\n      \"evidence\": \"Co-IP, phospho-DRP1 immunoblotting, genetic and pharmacological rescue in SPG31 patient fibroblasts\",\n      \"pmids\": [\"28007911\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether REEP1 modulates PGAM5 phosphatase activity directly or through scaffolding is unknown\",\n        \"Not tested in motor neurons or in vivo\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"A nonstop REEP1 variant was shown to produce a C-terminally extended, aggregation-prone protein, establishing a gain-of-function toxicity mechanism distinct from haploinsufficiency.\",\n      \"evidence\": \"Minigene expression, protein aggregation assay with reporter constructs\",\n      \"pmids\": [\"29124833\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab finding; aggregation has not been confirmed in patient-derived cells or in vivo\",\n        \"Whether the aggregates are toxic through proteostasis disruption or sequestration of partners is unclear\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Association of REEP1 with NDUFA4 and enhancement of complex IV activity upon REEP1 overexpression in an ALS mouse model extended its mitochondrial role to respiratory chain integrity and neuroprotection.\",\n      \"evidence\": \"Co-IP of REEP1 with NDUFA4, viral overexpression in SOD1G93A mouse spinal cord, complex IV activity assay\",\n      \"pmids\": [\"36520405\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab; the REEP1–NDUFA4 interaction awaits reciprocal validation\",\n        \"Whether the neuroprotective effect is mediated through complex IV or additional pathways is unresolved\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstration that REEP1 ortholog Yep1 is essential for ER-phagy in fission yeast—and that human REEP1 complements this function—established ER-phagy as a conserved REEP1-dependent process requiring self-interaction and membrane-shaping activity.\",\n      \"evidence\": \"Imaging-based screen in S. pombe, domain deletion mutant analysis, human REEP1-4 complementation\",\n      \"pmids\": [\"37939137\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The mammalian ER-phagy receptor(s) that cooperate with REEP1 are not identified\",\n        \"Whether REEP1 ER-phagy function is relevant to HSP pathogenesis has not been tested\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"REEP1 at MAM was linked to NDPK-D interaction, cardiolipin externalization control, and autophagosome biogenesis, providing a MAM-localized mechanism connecting REEP1 to autophagy signaling.\",\n      \"evidence\": \"Co-IP of REEP1 with NDPK-D, cardiolipin probe assay, autophagosome staining in SH-SY5Y cells\",\n      \"pmids\": [\"39178680\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab; NDPK-D interaction not validated by reciprocal approach\",\n        \"Whether cardiolipin externalization changes are a direct or secondary effect of REEP1 is unclear\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown how REEP1's multiple functions—ER shaping, microtubule coupling, MAM tethering, mitochondrial fission regulation, lipid droplet homeostasis, and ER-phagy—are coordinated in motor neurons and which deficit is the primary driver of axonal degeneration in SPG31.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No high-resolution structure of REEP1 in a membrane context exists\",\n        \"Relative contributions of ER-phagy versus ER morphology versus mitochondrial fission defects to HSP pathogenesis are undefined\",\n        \"Cell-type-specific interactome of REEP1 in motor neurons has not been systematically mapped\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [3, 6]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 2, 3, 6]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [4, 7, 8, 10]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [5, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [12, 13]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ATL1\",\n      \"SPAST\",\n      \"PGAM5\",\n      \"BSCL2\",\n      \"NDUFA4\",\n      \"DRP1\",\n      \"NME4\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}