{"gene":"TG_289910","gene_symbol":"HAD2A","run_date":"2026-09-08T17:00:02+00:00","timeline":{"discoveries":[{"year":2016,"finding":"HAD2a, identified by yeast two-hybrid screen with TgMORN1, physically interacts with MORN1, the major scaffolding protein of the basal complex, placing HAD2a in a MORN1-associated complex at the basal complex during its contraction.","method":"Yeast two-hybrid screen; co-localization by fluorescence microscopy","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid identification plus co-localization evidence; single lab, two orthogonal methods but no reciprocal Co-IP or pulldown reported in abstract","pmids":["26840427"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"finding":"HAD2a possesses demonstrable haloacid dehalogenase (HAD) phosphatase enzymatic activity, as confirmed by in vitro phosphatase assay.","method":"In vitro enzymatic assay","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic activity demonstrated, but single lab, single method, no mutagenesis details in abstract","pmids":["26840427"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"finding":"HAD2a localizes to nascent daughter buds and co-localizes with MORN1 at the basal complex during its contraction phase of endodyogeny.","method":"Fluorescence microscopy / subcellular localization","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional context, single lab","pmids":["26840427"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"finding":"Conditional knockout of HAD2a in Toxoplasma disrupts basal complex assembly, leading to incomplete cytokinesis, conjoined daughters, and severely impaired proliferation, establishing HAD2a as essential for daughter bud separation.","method":"Conditional knockout (genetic loss-of-function) with phenotypic readouts of basal complex assembly, cytokinesis, and parasite proliferation","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional KO with defined cellular phenotype (basal complex defect, incomplete cytokinesis, growth arrest) and mechanistic pathway placement, single lab but multiple orthogonal readouts","pmids":["26840427"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"finding":"The HAD2a ortholog in Plasmodium localizes to the basal complex toward the end of schizogony, indicating conservation of HAD2a basal complex function across apicomplexan budding mechanisms.","method":"Fluorescence microscopy / subcellular localization in Plasmodium","journal":"Cellular microbiology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single localization experiment in Plasmodium ortholog, no functional validation reported in abstract","pmids":["26840427"],"is_preprint":false,"attribution":[{"species":"Plasmodium","strain":""}]},{"year":2024,"finding":"Knockout of had2a in the type I RH strain disrupts daughter budding and in vitro replication, and attenuates virulence in mice, confirming HAD2a's essential role in parasite proliferation and establishing it as a virulence determinant.","method":"Gene knockout (CRISPR or homologous recombination), in vitro replication assay, mouse virulence model","journal":"Pathogens (Basel, Switzerland)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined proliferation and virulence phenotypes, corroborating prior work; single lab","pmids":["38392859"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]}],"current_model":"HAD2a is a HAD-family phosphatase with demonstrated in vitro enzymatic activity that physically associates with the basal complex scaffolding protein MORN1; it localizes to nascent daughter buds and the contracting basal complex during endodyogeny, and its loss disrupts basal complex assembly, causes incomplete cytokinesis and conjoined daughters, and ablates parasite proliferation and virulence, indicating that HAD2a-mediated phosphoregulation is essential for basal complex contraction and daughter bud separation in Toxoplasma gondii."},"narrative":{"mechanistic_narrative":"HAD2a is a haloacid dehalogenase (HAD)-family phosphatase in Toxoplasma gondii that provides phosphoregulatory control over basal complex contraction and daughter cell separation during endodyogeny [PMID:26840427]. It possesses demonstrable HAD phosphatase activity in vitro [PMID:26840427] and physically associates with MORN1, the major scaffolding protein of the basal complex, as identified by yeast two-hybrid screening [PMID:26840427]; consistent with this partnership it localizes to nascent daughter buds and co-localizes with MORN1 at the contracting basal complex [PMID:26840427]. Conditional loss of HAD2a disrupts basal complex assembly and causes incomplete cytokinesis with conjoined daughters and severely impaired proliferation, establishing it as essential for daughter bud separation [PMID:26840427]. Independent knockout in the type I RH strain confirms these budding and replication defects and shows HAD2a is required for virulence in mice [PMID:38392859]. Beyond this basal-complex role, the physiological substrates of HAD2a and the phosphosites governing basal complex contraction have not been characterized in the available corpus.","teleology":[{"year":2016,"claim":"Whether a phosphatase acts at the apicomplexan basal complex was unknown; identifying a MORN1 interactor placed HAD2a within the basal complex scaffold machinery.","evidence":"Yeast two-hybrid screen against TgMORN1 with co-localization by fluorescence microscopy in Toxoplasma gondii","pmids":["26840427"],"confidence":"Medium","gaps":["No reciprocal Co-IP or pulldown reported","Direct vs. bridged interaction with MORN1 not resolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"claim":"To establish HAD2a as an enzyme rather than a passive scaffold component, its catalytic activity was tested, confirming it is a functional HAD-family phosphatase.","evidence":"In vitro phosphatase assay","pmids":["26840427"],"confidence":"Medium","gaps":["No catalytic-dead mutant to link activity to phenotype","Physiological substrate unidentified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"claim":"Whether HAD2a acts at the site and time of basal complex contraction was addressed by localization, tying it spatially and temporally to endodyogeny.","evidence":"Fluorescence microscopy of subcellular localization during daughter budding in Toxoplasma gondii","pmids":["26840427"],"confidence":"Medium","gaps":["Recruitment mechanism to the basal complex unknown","Dependence of localization on MORN1 not tested"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"claim":"The functional requirement for HAD2a was tested by conditional knockout, establishing it as essential for basal complex assembly and daughter bud separation.","evidence":"Conditional knockout with phenotypic readouts of basal complex assembly, cytokinesis, and proliferation in Toxoplasma gondii","pmids":["26840427"],"confidence":"High","gaps":["Whether the phenotype depends on phosphatase activity not demonstrated","Direct substrates driving contraction not identified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"claim":"To test conservation of HAD2a function across apicomplexan budding, the Plasmodium ortholog was localized, showing basal complex targeting late in schizogony.","evidence":"Fluorescence microscopy of the HAD2a ortholog in Plasmodium","pmids":["26840427"],"confidence":"Low","gaps":["No functional validation in Plasmodium reported","Interaction with a MORN1 ortholog not tested"],"attribution":[{"species":"Plasmodium","strain":""}]},{"year":2024,"claim":"Whether HAD2a is required in a virulent strain and contributes to infection was tested, confirming its essentiality for replication and identifying it as a virulence determinant.","evidence":"Gene knockout, in vitro replication assay, and mouse virulence model in the type I RH strain","pmids":["38392859"],"confidence":"Medium","gaps":["Molecular basis of virulence attenuation beyond replication defect not defined","Single lab; substrate-level mechanism still open"],"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":null,"claim":"The physiological substrate(s) of HAD2a and the phosphorylation events it reverses to drive basal complex contraction remain unidentified, as does whether its catalytic activity is required for daughter bud separation.","evidence":"No substrate identification or catalytic-dead complementation in the available corpus","pmids":[],"confidence":"Low","gaps":["No phosphoproteomic substrate mapping","No catalytic-dead rescue experiment","Mechanism of MORN1-dependent recruitment unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["MORN1-associated basal complex"],"partners":["MORN1"],"other_free_text":["HAD-family phosphatase essential for basal complex contraction and daughter bud separation during endodyogeny in Toxoplasma gondii","Virulence determinant: RH-strain knockout attenuates virulence in mice","Ortholog localizes to the basal complex late in Plasmodium schizogony, indicating conserved apicomplexan budding function"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"26840427","id":"PMC_26840427","title":"A MORN1-associated HAD phosphatase in the basal complex is essential for Toxoplasma gondii daughter budding.","date":"2016","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/26840427","citation_count":24,"is_preprint":false},{"pmid":"38392859","id":"PMC_38392859","title":"Immunization with Live-Attenuated RHΔhad2a Strain Confers Partial Protective Immunity against Acute and Chronic Infection of Toxoplasma gondii in Mice.","date":"2024","source":"Pathogens (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/38392859","citation_count":2,"is_preprint":false},{"pmid":"42252477","id":"PMC_42252477","title":"Gene-edited live-attenuated vaccines against Toxoplasma gondii: recent advances and future frontiers.","date":"2026","source":"Parasites & vectors","url":"https://pubmed.ncbi.nlm.nih.gov/42252477","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3953,"output_tokens":1397,"usd":0.016407,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6511,"output_tokens":2442,"usd":0.046802,"stage2_stop_reason":"end_turn"},"total_usd":0.0,"stage1_batch_id":"msgbatch_01WgHz6kceqm573AGLyz57at","stage2_batch_id":"msgbatch_01LK4wDYj5zYquahv7gi9893","note":"batch pricing = 50% of standard","skipped":true},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"HAD2a, identified by yeast two-hybrid screen with TgMORN1, physically interacts with MORN1, the major scaffolding protein of the basal complex, placing HAD2a in a MORN1-associated complex at the basal complex during its contraction.\",\n      \"method\": \"Yeast two-hybrid screen; co-localization by fluorescence microscopy\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid identification plus co-localization evidence; single lab, two orthogonal methods but no reciprocal Co-IP or pulldown reported in abstract\",\n      \"pmids\": [\"26840427\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HAD2a possesses demonstrable haloacid dehalogenase (HAD) phosphatase enzymatic activity, as confirmed by in vitro phosphatase assay.\",\n      \"method\": \"In vitro enzymatic assay\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic activity demonstrated, but single lab, single method, no mutagenesis details in abstract\",\n      \"pmids\": [\"26840427\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HAD2a localizes to nascent daughter buds and co-localizes with MORN1 at the basal complex during its contraction phase of endodyogeny.\",\n      \"method\": \"Fluorescence microscopy / subcellular localization\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional context, single lab\",\n      \"pmids\": [\"26840427\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Conditional knockout of HAD2a in Toxoplasma disrupts basal complex assembly, leading to incomplete cytokinesis, conjoined daughters, and severely impaired proliferation, establishing HAD2a as essential for daughter bud separation.\",\n      \"method\": \"Conditional knockout (genetic loss-of-function) with phenotypic readouts of basal complex assembly, cytokinesis, and parasite proliferation\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with defined cellular phenotype (basal complex defect, incomplete cytokinesis, growth arrest) and mechanistic pathway placement, single lab but multiple orthogonal readouts\",\n      \"pmids\": [\"26840427\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The HAD2a ortholog in Plasmodium localizes to the basal complex toward the end of schizogony, indicating conservation of HAD2a basal complex function across apicomplexan budding mechanisms.\",\n      \"method\": \"Fluorescence microscopy / subcellular localization in Plasmodium\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single localization experiment in Plasmodium ortholog, no functional validation reported in abstract\",\n      \"pmids\": [\"26840427\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Knockout of had2a in the type I RH strain disrupts daughter budding and in vitro replication, and attenuates virulence in mice, confirming HAD2a's essential role in parasite proliferation and establishing it as a virulence determinant.\",\n      \"method\": \"Gene knockout (CRISPR or homologous recombination), in vitro replication assay, mouse virulence model\",\n      \"journal\": \"Pathogens (Basel, Switzerland)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined proliferation and virulence phenotypes, corroborating prior work; single lab\",\n      \"pmids\": [\"38392859\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    }\n  ],\n  \"current_model\": \"HAD2a is a HAD-family phosphatase with demonstrated in vitro enzymatic activity that physically associates with the basal complex scaffolding protein MORN1; it localizes to nascent daughter buds and the contracting basal complex during endodyogeny, and its loss disrupts basal complex assembly, causes incomplete cytokinesis and conjoined daughters, and ablates parasite proliferation and virulence, indicating that HAD2a-mediated phosphoregulation is essential for basal complex contraction and daughter bud separation in Toxoplasma gondii.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"HAD2a is a haloacid dehalogenase (HAD)-family phosphatase in Toxoplasma gondii that provides phosphoregulatory control over basal complex contraction and daughter cell separation during endodyogeny [#3]. It possesses demonstrable HAD phosphatase activity in vitro [#1] and physically associates with MORN1, the major scaffolding protein of the basal complex, as identified by yeast two-hybrid screening [#0]; consistent with this partnership it localizes to nascent daughter buds and co-localizes with MORN1 at the contracting basal complex [#2]. Conditional loss of HAD2a disrupts basal complex assembly and causes incomplete cytokinesis with conjoined daughters and severely impaired proliferation, establishing it as essential for daughter bud separation [#3]. Independent knockout in the type I RH strain confirms these budding and replication defects and shows HAD2a is required for virulence in mice [#5]. Beyond this basal-complex role, the physiological substrates of HAD2a and the phosphosites governing basal complex contraction have not been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Whether a phosphatase acts at the apicomplexan basal complex was unknown; identifying a MORN1 interactor placed HAD2a within the basal complex scaffold machinery.\",\n      \"evidence\": \"Yeast two-hybrid screen against TgMORN1 with co-localization by fluorescence microscopy in Toxoplasma gondii\",\n      \"pmids\": [\"26840427\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reciprocal Co-IP or pulldown reported\", \"Direct vs. bridged interaction with MORN1 not resolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"To establish HAD2a as an enzyme rather than a passive scaffold component, its catalytic activity was tested, confirming it is a functional HAD-family phosphatase.\",\n      \"evidence\": \"In vitro phosphatase assay\",\n      \"pmids\": [\"26840427\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No catalytic-dead mutant to link activity to phenotype\", \"Physiological substrate unidentified\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Whether HAD2a acts at the site and time of basal complex contraction was addressed by localization, tying it spatially and temporally to endodyogeny.\",\n      \"evidence\": \"Fluorescence microscopy of subcellular localization during daughter budding in Toxoplasma gondii\",\n      \"pmids\": [\"26840427\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Recruitment mechanism to the basal complex unknown\", \"Dependence of localization on MORN1 not tested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The functional requirement for HAD2a was tested by conditional knockout, establishing it as essential for basal complex assembly and daughter bud separation.\",\n      \"evidence\": \"Conditional knockout with phenotypic readouts of basal complex assembly, cytokinesis, and proliferation in Toxoplasma gondii\",\n      \"pmids\": [\"26840427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the phenotype depends on phosphatase activity not demonstrated\", \"Direct substrates driving contraction not identified\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"To test conservation of HAD2a function across apicomplexan budding, the Plasmodium ortholog was localized, showing basal complex targeting late in schizogony.\",\n      \"evidence\": \"Fluorescence microscopy of the HAD2a ortholog in Plasmodium\",\n      \"pmids\": [\"26840427\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No functional validation in Plasmodium reported\", \"Interaction with a MORN1 ortholog not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Whether HAD2a is required in a virulent strain and contributes to infection was tested, confirming its essentiality for replication and identifying it as a virulence determinant.\",\n      \"evidence\": \"Gene knockout, in vitro replication assay, and mouse virulence model in the type I RH strain\",\n      \"pmids\": [\"38392859\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of virulence attenuation beyond replication defect not defined\", \"Single lab; substrate-level mechanism still open\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The physiological substrate(s) of HAD2a and the phosphorylation events it reverses to drive basal complex contraction remain unidentified, as does whether its catalytic activity is required for daughter bud separation.\",\n      \"evidence\": \"No substrate identification or catalytic-dead complementation in the available corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No phosphoproteomic substrate mapping\", \"No catalytic-dead rescue experiment\", \"Mechanism of MORN1-dependent recruitment unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016791\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:1990905\", \"supporting_discovery_ids\": [0, 2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0000910\", \"supporting_discovery_ids\": [3, 5], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\n      \"MORN1-associated basal complex\"\n    ],\n    \"partners\": [\n      \"MORN1\"\n    ],\n    \"other_free_text\": [\n      \"HAD-family phosphatase essential for basal complex contraction and daughter bud separation during endodyogeny in Toxoplasma gondii\",\n      \"Virulence determinant: RH-strain knockout attenuates virulence in mice\",\n      \"Ortholog localizes to the basal complex late in Plasmodium schizogony, indicating conserved apicomplexan budding function\"\n    ]\n  },\n  \"strain_conflicts\": []\n}\n```","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_289910","name":"HAD2A","product":"haloacid dehalogenase-like hydrolase HAD2a","uniprot_acc":"S8F033","chromosome":"TGME49_chrIX","start_pos":3514572},{"strain":"GT1","gene_id":"TGGT1_289910","name":null,"product":"hypothetical protein","uniprot_acc":null,"chromosome":"TGGT1_chrIX","start_pos":3322620},{"strain":"RH88","gene_id":"TGRH88_014670","name":null,"product":"unspecified product","uniprot_acc":null,"chromosome":"CM023090","start_pos":3578439},{"strain":"VEG","gene_id":"TGVEG_289910","name":null,"product":"hypothetical protein","uniprot_acc":"B9PTL3","chromosome":"TGVEG_chrIX","start_pos":3549742}]}