id: A0A8N7TEH3 gene_symbol: exoc3l2a product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:7955 label: Danio rerio description: exoc3l2a (exocyst complex component 3-like 2a) is one of two zebrafish co-orthologs of vertebrate EXOC3L2, retained from the teleost-specific genome duplication; its paralog is exoc3l2b. It encodes a 932-aa member of the EXOC3/Sec6 family with an N-terminal region and a C-terminal Sec6 helical-bundle domain. By sequence it is much closer to EXOC3L2 than to EXOC3, EXOC3L1, EXOC3L4 or TNFAIP2 (M-Sec). Mammalian EXOC3L2 is expressed in endothelial cells and co-precipitates with the exocyst subunit EXOC4. In cultured human endothelial cells it is needed for VEGFA-induced VEGFR2 phosphorylation and for directional migration. Mouse Exoc3l2 knockouts die in utero with hemorrhage and heart and brain defects, and human biallelic EXOC3L2 mutations cause a hindbrain, kidney and bone-marrow syndrome. In zebrafish, exoc3l2a is expressed in an endothelial-specific pattern at 24 hpf and belongs to the endothelial gene signature of the caudal hematopoietic tissue niche. No zebrafish loss-of-function or biochemical study of exoc3l2a has been published. existing_annotations: - term: id: GO:0000145 label: exocyst evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: part_of supporting_entities: - AGI_LocusCode:AT1G71820 - FB:FBgn0266671 - MGI:MGI:3041195 - PANTHER:PTN000480155 - PomBase:SPCC1235.10c - SGD:S000001330 - dictyBase:DDB_G0293520 review: summary: Exocyst (IBA) from the EXOC3/Sec6 family node PTN000480155, seeded by Sec6/EXOC3 orthologs from budding and fission yeast, Arabidopsis, Dictyostelium, fly and mouse. action: ACCEPT reason: exoc3l2a keeps a complete Sec6 domain and is an EXOC3L2 co-ortholog. Mammalian EXOC3L2 is the only member of this subfamily studied biochemically. A tagged EXOC3L2 co-precipitates with EXOC4 and colocalises with EXOC4 and EXOC7, which supports association with the exocyst, the claim the propagated term makes. Whether EXOC3L2 is a stoichiometric subunit that replaces EXOC3, or a separate partner, has not been settled, so the term is kept at the complex level. supported_by: - reference_id: PMID:21566143 supporting_text: Myc-tagged EXOC3L2 co-precipitates with the exocyst protein EXOC4, and immunofluorescence detection of EXOC3L2 shows partial subcellular colocalization with EXOC4 and EXOC7. - reference_id: PMID:30086153 supporting_text: Therefore, it will be relevant to determine whether EXOC3 paralogs, particularly M-Sec and EXOC3L2, are interchangeable subunits that are selectively assembled into different functional variants of the exocyst complex, or independent operators. - reference_id: file:DANRE/exoc3l2a/exoc3l2a-bioinformatics/RESULTS.md supporting_text: Both copies keep a full-length Sec6 domain and the N-terminal region; neither is truncated. - term: id: GO:0000145 label: exocyst evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: part_of supporting_entities: - InterPro:IPR010326 review: summary: Exocyst from the InterPro EXOC3/Sec6 entry (IPR010326) mapping. action: ACCEPT reason: Same claim as the IBA row. The Sec6 domain is intact, and the mammalian ortholog associates with the exocyst. supported_by: - reference_id: PMID:21566143 supporting_text: The subcellular localization and the colocalization with EXOC4 indicate an association between EXOC3l2 and the exocyst complex. - term: id: GO:0000149 label: SNARE binding evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: enables supporting_entities: - PANTHER:PTN000480155 - SGD:S000001330 review: summary: SNARE binding (IBA) from node PTN000480155, with budding-yeast Sec6 as the only experimental donor. action: MARK_AS_OVER_ANNOTATED reason: SNARE binding has been shown only for yeast Sec6. The node spans the whole EXOC3/Sec6 family, including the vertebrate EXOC3-like paralogs (EXOC3L1, EXOC3L2, EXOC3L4, TNFAIP2), and none of these paralogs has been tested for SNARE binding. exoc3l2a is only 19.7% identical to human EXOC3 and is the faster-evolving copy of its pair. The one EXOC3L2 interaction studied is with the exocyst core subunit EXOC4. The function could have been inherited from Sec6, but no data support it for the EXOC3L2 lineage. exoc3l2b carries no IBA rows, because the accession in the PANTHER tree (A0A8M3B147) has since been deleted from UniProt. supported_by: - reference_id: file:DANRE/exoc3l2a/exoc3l2a-bioinformatics/RESULTS.md supporting_text: The two zebrafish proteins are 50.9% identical to each other, 35-36% identical to human EXOC3L2 and only 19.7-21.9% identical to human EXOC3 (the Sec6 ortholog), EXOC3L1, EXOC3L4 and TNFAIP2. - reference_id: file:DANRE/exoc3l2a/exoc3l2a-bioinformatics/RESULTS.md supporting_text: exoc3l2a is the faster-evolving copy. - reference_id: PMID:21566143 supporting_text: Myc-tagged EXOC3L2 co-precipitates with the exocyst protein EXOC4, and immunofluorescence detection of EXOC3L2 shows partial subcellular colocalization with EXOC4 and EXOC7. propagation_review: root_cause: UNRESOLVED source_entities: - source_id: PANTHER:PTN000480155 source_status: UNRESOLVED comment: Family-wide EXOC3/Sec6 node; its only SNARE-binding evidence is yeast Sec6, and it is unknown whether the vertebrate EXOC3-like paralogs kept this activity. - source_id: SGD:S000001330 source_label: SEC6 (budding yeast) source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET comment: Sec6 binding to SNAREs is sound for yeast Sec6, but the EXOC3L2 lineage diverged far from EXOC3/Sec6 (about 20% identity) and has not been tested. - term: id: GO:0006887 label: exocytosis evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in supporting_entities: - FB:FBgn0266671 - MGI:MGI:3041195 - PANTHER:PTN000480155 - SGD:S000001330 - WB:WBGene00017284 review: summary: Exocytosis (IBA) from the EXOC3/Sec6 family node. action: KEEP_AS_NON_CORE reason: An exocyst-associated protein is plausibly involved in exocytosis, and the proposed model for EXOC3L2 is exocyst-dependent delivery of VEGFR2 to the cell surface. But no secretion or exocytosis assay has been done for EXOC3L2 in any species; the measured effects are on VEGFR2 phosphorylation and directional migration. The term is kept as a plausible family-level process, not as a demonstrated core function. supported_by: - reference_id: PMID:21566143 supporting_text: We hypothesized that EXOC3L2 may be involved in the exocytosis of VEGFR2, and that a down-regulation of EXOC3L2 expression thus could have an effect on VEGFR2 phosphorylation. - reference_id: PMID:21566143 supporting_text: Finally, we show that exoc3l2 silencing inhibits VEGF receptor 2 phosphorylation and VEGFA-directed migration of cultured endothelial cells. - term: id: GO:0006887 label: exocytosis evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: involved_in supporting_entities: - InterPro:IPR010326 review: summary: Exocytosis from the InterPro EXOC3/Sec6 mapping. action: KEEP_AS_NON_CORE reason: Same reasoning as the IBA row. The process is plausible for an exocyst-associated protein but has not been measured for EXOC3L2. supported_by: - reference_id: PMID:21566143 supporting_text: We hypothesized that EXOC3L2 may be involved in the exocytosis of VEGFR2, and that a down-regulation of EXOC3L2 expression thus could have an effect on VEGFR2 phosphorylation. core_functions: - description: EXOC3/Sec6-family protein and EXOC3L2 co-ortholog, expressed in embryonic endothelial cells, including the endothelium of the caudal hematopoietic tissue niche. By analogy with mammalian EXOC3L2 it probably associates with the exocyst and may support VEGF receptor signalling and directional migration of endothelial cells. None of these activities has been tested for the zebrafish protein. in_complex: id: GO:0000145 label: exocyst supported_by: - reference_id: PMID:40613926 supporting_text: In situ hybridization for three of these genes– exoc3l2a, slc22a7b.1, and bpifc–, confirmed their endothelial-specific expression pattern - reference_id: PMID:37119815 supporting_text: 'There are numerous genes identified by this study that were not previously associated with the HSPC niche, including several with activities related to endocytosis and membrane trafficking: ap1b1, dab2, pxk, exoc3l2a and snx8.' - reference_id: PMID:21566143 supporting_text: Myc-tagged EXOC3L2 co-precipitates with the exocyst protein EXOC4, and immunofluorescence detection of EXOC3L2 shows partial subcellular colocalization with EXOC4 and EXOC7. references: - id: GO_REF:0000002 title: Gene Ontology annotation through association of InterPro records with GO terms findings: [] - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: PMID:21566143 title: Exocyst complex component 3-like 2 (EXOC3L2) associates with the exocyst complex and mediates directional migration of endothelial cells. findings: [] reference_review: relevance: HIGH correctness: VERIFIED review_notes: Full text; the founding functional study of human EXOC3L2 (EXOC4 co-precipitation, VEGFR2 phosphorylation, directional migration). Human and mouse cells, not zebrafish. - id: PMID:36362885 title: Essential Roles of Exocyst Complex Component 3-like 2 on Cardiovascular Development in Mice. findings: [] reference_review: relevance: HIGH correctness: VERIFIED review_notes: Full text; mouse Exoc3l2 knockout, Tie2-Cre conditional and inducible endothelial deletion. - id: PMID:30327448 title: Biallelic mutations in EXOC3L2 cause a novel syndrome that affects the brain, kidney and blood. findings: [] reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: Abstract only; human patients with biallelic EXOC3L2 variants. - id: PMID:30086153 title: Modeling the structural implications of an alternatively spliced Exoc3l2, a paralog of the tunneling nanotube-forming M-Sec. findings: [] reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: Full text; homology model of mouse EXOC3L2 built on M-Sec. Its "Exoc3l2a" is a mouse splice variant, not the zebrafish gene. - id: PMID:40613926 title: In vivo profiling of the endothelium using 'AngioTag' zebrafish. findings: [] reference_review: relevance: HIGH correctness: VERIFIED review_notes: Full text; exoc3l2a enriched in endothelial TRAP-seq and endothelial-specific by whole-mount in situ at 24 hpf (the figure legend misspells it "exoc312a"). - id: PMID:37119815 title: Transcription factor induction of vascular blood stem cell niches in vivo. findings: [] reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: Full text; exoc3l2a named among the CHT niche endothelial signature genes (discussion only). - id: file:DANRE/exoc3l2a/exoc3l2a-bioinformatics/RESULTS.md title: exoc3l2a / exoc3l2b orthology, protein, expression and synteny comparison reference_review: relevance: HIGH correctness: VERIFIED review_notes: Manual audit verified the sidecar supports both copies as EXOC3L2 co-orthologs retaining the full Sec6 domain; its expression comparison is compatible with subfunctionalization but is not a functional assay. findings: [] suggested_questions: - question: Is exoc3l2a required for vascular development in zebrafish, as Exoc3l2 is in mouse? Do exoc3l2a mutants show hemorrhage, sprouting defects or an abnormal caudal hematopoietic tissue niche? - question: Is exoc3l2b also expressed in endothelium, or is the endothelial domain carried by exoc3l2a alone? - question: PANTHER lists EXOC3L4 as the human ortholog and places the gene in a TNFAIP2-named subfamily, while sequence identity, synteny and Ensembl Compara support EXOC3L2. Should the PANTHER tree for PTHR21292 be revisited? suggested_experiments: - description: Make exoc3l2a, exoc3l2b and double mutants, including an RNA-less or promoter-deletion allele to avoid transcriptional adaptation. Score vascular patterning, hemorrhage and CHT hematopoiesis in kdrl and gata1 reporter backgrounds. - description: Do two-colour in situ hybridization (HCR) for exoc3l2a and exoc3l2b with kdrl and sox10 at 12-48 hpf, to test whether the endothelial and neural-crest domains are split between the copies. - description: Co-immunoprecipitate tagged Exoc3l2a with zebrafish exocyst subunits (Exoc4, Exoc7) and with RalA.