{"gene":"TG_290620","gene_symbol":"CEP250L1","run_date":"2026-09-08T14:08:30","timeline":{"discoveries":[{"year":2015,"finding":"CEP250L1 (a distant ortholog of the CEP250/C-Nap protein family) localizes to the inner core of the bipartite Toxoplasma gondii centrosome, which is closely aligned with the unique spindle pole (centrocone) and is spatially distinct from the outer core. The inner core and outer core duplicate sequentially (outer first, inner second) during S phase, ensuring each daughter inherits one copy of each core type.","method":"Fluorescence microscopy (localization), genetic analysis of temperature-sensitive mutants establishing spatial and functional separation of inner vs. outer centrosome cores","journal":"PLoS biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment plus genetic epistasis in ts mutants, single lab, two orthogonal methods","pmids":["25734885"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"finding":"Conditional degradation of TgCEP250L1 causes lethality in T. gondii, with severe nuclear segregation defects: daughter cells form but nuclei fail to segregate, accumulating at the residual body. The centriole-containing outer/middle centrosome disconnects from the nucleus in the absence of TgCEP250L1.","method":"Conditional protein degradation (auxin-inducible degron or similar), fluorescence microscopy of nuclear segregation and centrosome positioning","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional loss-of-function with defined lethal phenotype and specific nuclear segregation defect, multiple orthogonal readouts (viability, nuclear accumulation, centrosome disconnection), single lab","pmids":["36069445"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"finding":"In the absence of TgCEP250L1, the microtubule-binding protein TgEB1 fails to localize at the mitotic spindle, and the intranuclear mitotic spindle does not assemble (or is unstable), directly linking TgCEP250L1 inner-core function to mitotic spindle nucleation or stabilization.","method":"Conditional protein degradation of TgCEP250L1 combined with localization analysis of TgEB1 by fluorescence microscopy and ultrastructure expansion microscopy","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with specific downstream marker (TgEB1) mislocalization and ultrastructure expansion microscopy, multiple orthogonal methods in a single rigorous study","pmids":["36069445"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"finding":"TgCEP250L1's localization within the centrosome changes relative to other markers during the cell cycle, specifically encompassing the transition to mitotic spindle formation, indicating it undergoes dynamic repositioning as division progresses.","method":"Ultrastructure expansion microscopy (U-ExM) combined with multi-marker co-localization across cell cycle stages","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with high-resolution expansion microscopy, single lab, single method for this specific finding","pmids":["36069445"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgCEP250L1 is an essential component of the inner core of the bipartite Toxoplasma gondii centrosome that, by remaining proximal to the nucleus and tethering the centrosome to it, is required for assembly or stabilization of the intranuclear mitotic spindle (evidenced by TgEB1 mislocalization upon its loss) and thereby for nuclear segregation during endodyogeny, while being dispensable for daughter cell budding per se."},"narrative":{"mechanistic_narrative":"TgCEP250L1 is an essential structural component of the bipartite Toxoplasma gondii centrosome that couples centrosome function to nuclear segregation during endodyogeny [PMID:25734885, PMID:36069445]. A distant ortholog of the CEP250/C-Nap protein family, it localizes to the inner core of the centrosome, which is closely aligned with the spindle pole (centrocone) and duplicates sequentially after the outer core during S phase [PMID:25734885]. Conditional degradation of TgCEP250L1 is lethal: daughter cells still form but nuclei fail to segregate and accumulate at the residual body, while the centriole-containing outer/middle centrosome disconnects from the nucleus [PMID:36069445]. Loss of TgCEP250L1 abolishes proper localization of the microtubule-binding protein TgEB1 and prevents assembly or stabilization of the intranuclear mitotic spindle, linking its inner-core function directly to spindle nucleation [PMID:36069445]. TgCEP250L1 repositions within the centrosome across the cell cycle, coincident with the transition to mitotic spindle formation [PMID:36069445].","teleology":[{"year":2015,"claim":"Establishing that the T. gondii centrosome is bipartite required identifying markers of its distinct cores; TgCEP250L1 defined the inner core aligned with the spindle pole, showing the two cores are spatially and functionally separable and duplicate sequentially.","evidence":"Fluorescence microscopy localization plus genetic epistasis in temperature-sensitive mutants","pmids":["25734885"],"confidence":"Medium","gaps":["Functional consequence of inner-core loss not tested","Molecular partners of TgCEP250L1 within the inner core not identified","Mechanism of sequential core duplication unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"claim":"Whether the inner core is functionally essential was unknown; conditional degradation showed TgCEP250L1 loss is lethal and specifically blocks nuclear segregation while daughter buds still form, establishing it as a nuclear-centrosome tether rather than a budding factor.","evidence":"Conditional protein degradation with fluorescence microscopy of nuclear segregation and centrosome positioning in T. gondii","pmids":["36069445"],"confidence":"High","gaps":["Direct molecular tether to the nuclear envelope not identified","How TgCEP250L1 maintains outer-core to nucleus connection mechanistically unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"claim":"The downstream consequence of inner-core loss for the spindle was untested; TgEB1 mislocalization and failed intranuclear spindle assembly upon TgCEP250L1 depletion tied inner-core function to mitotic spindle nucleation or stabilization.","evidence":"Conditional degradation plus TgEB1 localization by fluorescence and ultrastructure expansion microscopy","pmids":["36069445"],"confidence":"High","gaps":["Whether TgCEP250L1 acts in spindle nucleation versus stabilization not distinguished","No direct biochemical link between TgCEP250L1 and TgEB1 or spindle microtubules"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"claim":"Whether TgCEP250L1 is a static or dynamic centrosome component was open; U-ExM showed its position shifts relative to other markers coincident with spindle formation, indicating cell-cycle-regulated repositioning.","evidence":"Ultrastructure expansion microscopy with multi-marker co-localization across cell cycle stages","pmids":["36069445"],"confidence":"Medium","gaps":["Signals driving repositioning unknown","Post-translational regulation of TgCEP250L1 not characterized"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The direct molecular partners and biochemical mechanism by which TgCEP250L1 tethers the centrosome to the nucleus and enables spindle assembly remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No identified binding partners at the nuclear envelope","No structural model of the inner core","Mechanism connecting TgCEP250L1 loss to TgEB1 mislocalization not established"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Inner core of the bipartite Toxoplasma gondii centrosome"],"partners":["TGEB1 (LOCALIZATION DEPENDENT ON TGCEP250L1, NOT A DEMONSTRATED DIRECT INTERACTION)"],"other_free_text":["Distant ortholog of the CEP250/C-Nap protein family [#0]","Essential gene: conditional degradation is lethal in T. gondii [#1]","Required for nuclear segregation but dispensable for daughter cell budding during endodyogeny [#1]","Inner core duplicates after the outer core during S phase [#0]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"25734885","id":"PMC_25734885","title":"A novel bipartite centrosome coordinates the apicomplexan cell cycle.","date":"2015","source":"PLoS biology","url":"https://pubmed.ncbi.nlm.nih.gov/25734885","citation_count":112,"is_preprint":false},{"pmid":"36069445","id":"PMC_36069445","title":"Separate To Operate: the Centriole-Free Inner Core of the Centrosome Regulates the Assembly of the Intranuclear Spindle in Toxoplasma gondii.","date":"2022","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/36069445","citation_count":17,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3843,"output_tokens":1154,"usd":0.01442,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6117,"output_tokens":2245,"usd":0.043355,"stage2_stop_reason":"end_turn"},"total_usd":0.057775,"stage1_batch_id":"msgbatch_015xmQKDRqnTh9anE4m7LiD6","stage2_batch_id":"msgbatch_01JLpkFTVhoQBNgqHCKFrVVU","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2015,\n      \"finding\": \"CEP250L1 (a distant ortholog of the CEP250/C-Nap protein family) localizes to the inner core of the bipartite Toxoplasma gondii centrosome, which is closely aligned with the unique spindle pole (centrocone) and is spatially distinct from the outer core. The inner core and outer core duplicate sequentially (outer first, inner second) during S phase, ensuring each daughter inherits one copy of each core type.\",\n      \"method\": \"Fluorescence microscopy (localization), genetic analysis of temperature-sensitive mutants establishing spatial and functional separation of inner vs. outer centrosome cores\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment plus genetic epistasis in ts mutants, single lab, two orthogonal methods\",\n      \"pmids\": [\"25734885\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Conditional degradation of TgCEP250L1 causes lethality in T. gondii, with severe nuclear segregation defects: daughter cells form but nuclei fail to segregate, accumulating at the residual body. The centriole-containing outer/middle centrosome disconnects from the nucleus in the absence of TgCEP250L1.\",\n      \"method\": \"Conditional protein degradation (auxin-inducible degron or similar), fluorescence microscopy of nuclear segregation and centrosome positioning\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional loss-of-function with defined lethal phenotype and specific nuclear segregation defect, multiple orthogonal readouts (viability, nuclear accumulation, centrosome disconnection), single lab\",\n      \"pmids\": [\"36069445\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In the absence of TgCEP250L1, the microtubule-binding protein TgEB1 fails to localize at the mitotic spindle, and the intranuclear mitotic spindle does not assemble (or is unstable), directly linking TgCEP250L1 inner-core function to mitotic spindle nucleation or stabilization.\",\n      \"method\": \"Conditional protein degradation of TgCEP250L1 combined with localization analysis of TgEB1 by fluorescence microscopy and ultrastructure expansion microscopy\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with specific downstream marker (TgEB1) mislocalization and ultrastructure expansion microscopy, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"36069445\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TgCEP250L1's localization within the centrosome changes relative to other markers during the cell cycle, specifically encompassing the transition to mitotic spindle formation, indicating it undergoes dynamic repositioning as division progresses.\",\n      \"method\": \"Ultrastructure expansion microscopy (U-ExM) combined with multi-marker co-localization across cell cycle stages\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with high-resolution expansion microscopy, single lab, single method for this specific finding\",\n      \"pmids\": [\"36069445\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"TgCEP250L1 is an essential component of the inner core of the bipartite Toxoplasma gondii centrosome that, by remaining proximal to the nucleus and tethering the centrosome to it, is required for assembly or stabilization of the intranuclear mitotic spindle (evidenced by TgEB1 mislocalization upon its loss) and thereby for nuclear segregation during endodyogeny, while being dispensable for daughter cell budding per se.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TgCEP250L1 is an essential structural component of the bipartite Toxoplasma gondii centrosome that couples centrosome function to nuclear segregation during endodyogeny [#0, #1]. A distant ortholog of the CEP250/C-Nap protein family, it localizes to the inner core of the centrosome, which is closely aligned with the spindle pole (centrocone) and duplicates sequentially after the outer core during S phase [#0]. Conditional degradation of TgCEP250L1 is lethal: daughter cells still form but nuclei fail to segregate and accumulate at the residual body, while the centriole-containing outer/middle centrosome disconnects from the nucleus [#1]. Loss of TgCEP250L1 abolishes proper localization of the microtubule-binding protein TgEB1 and prevents assembly or stabilization of the intranuclear mitotic spindle, linking its inner-core function directly to spindle nucleation [#2]. TgCEP250L1 repositions within the centrosome across the cell cycle, coincident with the transition to mitotic spindle formation [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Establishing that the T. gondii centrosome is bipartite required identifying markers of its distinct cores; TgCEP250L1 defined the inner core aligned with the spindle pole, showing the two cores are spatially and functionally separable and duplicate sequentially.\",\n      \"evidence\": \"Fluorescence microscopy localization plus genetic epistasis in temperature-sensitive mutants\",\n      \"pmids\": [\"25734885\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of inner-core loss not tested\", \"Molecular partners of TgCEP250L1 within the inner core not identified\", \"Mechanism of sequential core duplication unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Whether the inner core is functionally essential was unknown; conditional degradation showed TgCEP250L1 loss is lethal and specifically blocks nuclear segregation while daughter buds still form, establishing it as a nuclear-centrosome tether rather than a budding factor.\",\n      \"evidence\": \"Conditional protein degradation with fluorescence microscopy of nuclear segregation and centrosome positioning in T. gondii\",\n      \"pmids\": [\"36069445\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular tether to the nuclear envelope not identified\", \"How TgCEP250L1 maintains outer-core to nucleus connection mechanistically unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The downstream consequence of inner-core loss for the spindle was untested; TgEB1 mislocalization and failed intranuclear spindle assembly upon TgCEP250L1 depletion tied inner-core function to mitotic spindle nucleation or stabilization.\",\n      \"evidence\": \"Conditional degradation plus TgEB1 localization by fluorescence and ultrastructure expansion microscopy\",\n      \"pmids\": [\"36069445\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TgCEP250L1 acts in spindle nucleation versus stabilization not distinguished\", \"No direct biochemical link between TgCEP250L1 and TgEB1 or spindle microtubules\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Whether TgCEP250L1 is a static or dynamic centrosome component was open; U-ExM showed its position shifts relative to other markers coincident with spindle formation, indicating cell-cycle-regulated repositioning.\",\n      \"evidence\": \"Ultrastructure expansion microscopy with multi-marker co-localization across cell cycle stages\",\n      \"pmids\": [\"36069445\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signals driving repositioning unknown\", \"Post-translational regulation of TgCEP250L1 not characterized\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct molecular partners and biochemical mechanism by which TgCEP250L1 tethers the centrosome to the nucleus and enables spindle assembly remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No identified binding partners at the nuclear envelope\", \"No structural model of the inner core\", \"Mechanism connecting TgCEP250L1 loss to TgEB1 mislocalization not established\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [\n      {\"term_id\": \"GO:0005813\", \"supporting_discovery_ids\": [0, 1, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0000922\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0007059\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0007052\", \"supporting_discovery_ids\": [2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\"Inner core of the bipartite Toxoplasma gondii centrosome\"],\n    \"partners\": [\"TgEB1 (localization dependent on TgCEP250L1, not a demonstrated direct interaction)\"],\n    \"other_free_text\": [\n      \"Distant ortholog of the CEP250/C-Nap protein family [#0]\",\n      \"Essential gene: conditional degradation is lethal in T. gondii [#1]\",\n      \"Required for nuclear segregation but dispensable for daughter cell budding during endodyogeny [#1]\",\n      \"Inner core duplicates after the outer core during S phase [#0]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_290620","name":"CEP250L1","product":"centrosomal protein CEP250L1","uniprot_acc":"S8F3G6","chromosome":"TGME49_chrIX","start_pos":3769378},{"strain":"GT1","gene_id":"TGGT1_290620","name":null,"product":"hypothetical protein","uniprot_acc":null,"chromosome":"TGGT1_chrIX","start_pos":3578363},{"strain":"RH88","gene_id":"TGRH88_015070","name":null,"product":"unspecified product","uniprot_acc":null,"chromosome":"CM023090","start_pos":3834327},{"strain":"VEG","gene_id":"TGVEG_290620","name":null,"product":"hypothetical protein","uniprot_acc":"V4Z0V9","chromosome":"TGVEG_chrIX","start_pos":3805198}]}