{"gene":"TG_306620","gene_symbol":"AP2IX9","run_date":"2026-09-10T21:09:19","timeline":{"discoveries":[{"year":2013,"finding":"AP2IX-9 protein is localized exclusively to the early bradyzoite nucleus and is repressed in tachyzoites and in mature bradyzoites from 30-day infected animals, indicating stage-specific nuclear localization.","method":"Immunofluorescence / protein-level detection in stage-specific parasites","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct protein localization experiment with stage-specific expression profiling, single lab with multiple orthogonal methods (protein detection, conditional overexpression, gene disruption, reporter assay, ChIP)","pmids":["23572590"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"finding":"AP2IX-9 functions as a transcriptional repressor of bradyzoite development: conditional overexpression significantly reduced tissue cyst formation and conferred alkaline pH-resistant growth, while disruption of AP2IX-9 increased tissue cyst formation.","method":"Conditional overexpression (FKBP/Shield-1 system) and gene disruption with tissue cyst formation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal gain- and loss-of-function experiments with defined phenotypic readout in a single lab, confirmed by multiple orthogonal approaches","pmids":["23572590"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"finding":"AP2IX-9 specifically inhibits expression of bradyzoite mRNAs including BAG1 (bradyzoite antigen 1), acting as a direct transcriptional repressor.","method":"Gene expression profiling and mRNA quantification in AP2IX-9 overexpression and knockout parasites","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function transcriptomics combined with reporter and ChIP assays in single lab","pmids":["23572590"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"finding":"The AP2 domain of AP2IX-9 binds the DNA sequence motif CAGTGT, as established by protein binding microarray analysis, and this domain is capable of binding cis-regulatory elements in the BAG1 and bradyzoite-specific NTPase (B-NTPase) promoters.","method":"Protein binding microarray (PBM) for DNA motif identification","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical assay (PBM) identifying specific DNA binding motif, corroborated by in vivo reporter and ChIP experiments in same study","pmids":["23572590"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"finding":"AP2IX-9 directly represses the BAG1 promoter in vivo: it inhibits expression of a firefly luciferase reporter under BAG1 promoter control, and epitope-tagged AP2IX-9 can be immunoprecipitated with the BAG1 promoter in parasite chromatin (ChIP).","method":"Luciferase reporter assay and chromatin immunoprecipitation (ChIP)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vivo reporter assay plus ChIP demonstrating direct promoter occupancy, two orthogonal methods in single lab","pmids":["23572590"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2017,"finding":"AP2IX-9 and AP2IV-3 are expressed in two overlapping waves during bradyzoite development (AP2IX-9 earlier, AP2IV-3 later) and have opposing functions: AP2IX-9 is a repressor (its disruption enhances cyst formation) while AP2IV-3 is an activator (its deletion decreases cyst formation). Both regulate overlapping sets of bradyzoite genes including BAG1.","method":"Gene disruption and conditional overexpression with tissue cyst formation assays and gene expression profiling; BAG1 promoter-luciferase reporter and ChIP","journal":"mSphere","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal KO and OE experiments with defined phenotypes, confirmed by reporter and ChIP assays, extends prior PNAS findings with an independent lab study","pmids":["28251183"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2010,"finding":"AP2IX-9 mRNA exhibits a cyclical expression profile during the tachyzoite cell cycle, with peak expression in the S/M-subtranscriptome (associated with parasite maturation), and AP2IX-9 protein expression forms a sharp peak in the same timeframe as its mRNA, suggesting protein timing is mediated through AP2 domain-dependent mechanisms.","method":"Global cell cycle transcriptome profiling and protein expression timing analysis in dividing tachyzoites","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — genome-wide transcriptomic approach with protein expression correlation, single lab, no direct functional dissection of AP2IX-9 specifically","pmids":["20865045"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2017,"finding":"AP2IX-9 mRNA demonstrates the largest expression increase among 15 AP2-domain-encoding mRNAs during alkaline-induced bradyzoite differentiation.","method":"mRNA expression profiling during alkaline stress-induced differentiation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — transcriptomic screen across multiple AP2 factors, identifies AP2IX-9 as top hit but this is a comparative expression result supporting its regulatory role","pmids":["23572590"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"AP2IX-9 is an ApiAP2 transcription factor that localizes exclusively to the early bradyzoite nucleus, where it acts as a direct transcriptional repressor of bradyzoite development by binding a CAGTGT DNA motif and occupying promoters (including BAG1 and B-NTPase) to suppress bradyzoite gene expression; its opposing action to the activator AP2IV-3 positions AP2IX-9 as part of a competing transcriptional switch that controls commitment to tissue cyst formation in Toxoplasma gondii."},"narrative":{"mechanistic_narrative":"AP2IX-9 is an ApiAP2 transcription factor of Toxoplasma gondii that acts as a direct repressor of bradyzoite (tissue cyst) development, functioning as one arm of a transcriptional switch controlling commitment to the encysted stage [PMID:23572590, PMID:28251183]. Its expression is tightly stage-restricted: AP2IX-9 protein accumulates exclusively in the early bradyzoite nucleus and is repressed in tachyzoites and in mature bradyzoites [PMID:23572590], and its mRNA shows the largest induction among ApiAP2 genes during alkaline-stress differentiation [PMID:23572590]. Functionally, conditional overexpression suppresses tissue cyst formation and confers alkaline-pH-resistant growth, whereas gene disruption enhances cyst formation, establishing repressor activity [PMID:23572590]. AP2IX-9 achieves this by binding the CAGTGT DNA motif through its AP2 domain and occupying cis-regulatory elements of bradyzoite genes such as BAG1 and bradyzoite-specific NTPase, directly repressing their transcription as shown by promoter-luciferase reporter and ChIP occupancy of the BAG1 promoter [PMID:23572590]. AP2IX-9 acts in opposition to the later-expressed activator AP2IV-3 over an overlapping set of bradyzoite genes including BAG1, defining a competing early-repressor/late-activator system that gates cyst commitment [PMID:28251183].","teleology":[{"year":2010,"claim":"Before any function was assigned, it was unknown whether AP2IX-9 expression was developmentally timed; cell-cycle transcriptomics showed cyclical S/M-phase-peaked mRNA and matched protein timing, hinting at a regulated role tied to parasite maturation.","evidence":"Global cell-cycle transcriptome and protein timing analysis in dividing tachyzoites","pmids":["20865045"],"confidence":"Medium","gaps":["No functional dissection of AP2IX-9 in this study","Does not link expression timing to a downstream target or phenotype"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"claim":"It was unknown which factor controls bradyzoite gene repression; stage-specific detection placed AP2IX-9 exclusively in the early bradyzoite nucleus and repressed in tachyzoites and mature cysts, and its mRNA was the most induced ApiAP2 during alkaline differentiation, positioning it as a stage-transition regulator.","evidence":"Immunofluorescence/protein-level stage profiling and mRNA expression profiling during alkaline-induced differentiation","pmids":["23572590"],"confidence":"High","gaps":["Localization alone does not establish direction of regulation","Does not identify direct target genes"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"claim":"Whether AP2IX-9 promotes or suppresses cyst formation was resolved by reciprocal genetics: overexpression reduced cyst formation and gave alkaline-resistant growth while disruption increased cysts, establishing AP2IX-9 as a repressor of bradyzoite development.","evidence":"Conditional FKBP/Shield-1 overexpression and gene disruption with tissue cyst formation assays and transcriptomics","pmids":["23572590"],"confidence":"High","gaps":["Does not identify the direct DNA binding site or target promoters","Mechanism of transcriptional repression (co-repressor recruitment) unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"claim":"To show repression is direct rather than indirect, the DNA specificity and promoter occupancy were defined: the AP2 domain binds the CAGTGT motif and binds BAG1 and B-NTPase promoter elements, and AP2IX-9 represses a BAG1-promoter reporter and is ChIP-recovered at the BAG1 promoter.","evidence":"Protein binding microarray for motif identification, luciferase reporter assay, and chromatin immunoprecipitation","pmids":["23572590"],"confidence":"High","gaps":["Genome-wide occupancy map not defined","Does not identify repressive chromatin machinery recruited by AP2IX-9"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2017,"claim":"It was unclear how repression is balanced against activation of the same genes; AP2IX-9 (early) and AP2IV-3 (later) were shown to be expressed in overlapping waves with opposing activities on shared bradyzoite genes including BAG1, defining a competing repressor/activator switch controlling cyst commitment.","evidence":"Reciprocal gene disruption and overexpression with cyst assays, expression profiling, BAG1 promoter-luciferase reporter and ChIP","pmids":["28251183"],"confidence":"High","gaps":["Mechanism of competition/co-occupancy at shared promoters not resolved","Upstream signal driving the AP2IX-9 to AP2IV-3 handoff unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"How AP2IX-9 mechanistically represses transcription and how it is displaced or overridden by AP2IV-3 during commitment to encystation remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No co-repressor or chromatin-modifying partner identified","No structural basis for CAGTGT recognition","Genome-wide direct target set not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["AP2IV-3 (FUNCTIONALLY OPPOSING ACTIVATOR CO-REGULATING BAG1 AND OVERLAPPING BRADYZOITE GENES) [#5]"],"other_free_text":["Binds CAGTGT DNA motif via its AP2 domain [#3]","Occupies and represses the BAG1 and bradyzoite-specific NTPase (B-NTPase) promoters [#3, #4]","Overexpression confers alkaline-pH-resistant growth and reduces tissue cyst formation; disruption increases cyst formation [#1, #5]","mRNA is cell-cycle regulated, peaking in the S/M-subtranscriptome [#6]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"20865045","id":"PMC_20865045","title":"Coordinated progression through two subtranscriptomes underlies the tachyzoite cycle of Toxoplasma gondii.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20865045","citation_count":234,"is_preprint":false},{"pmid":"23572590","id":"PMC_23572590","title":"ApiAP2 transcription factor restricts development of the Toxoplasma tissue cyst.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23572590","citation_count":108,"is_preprint":false},{"pmid":"28251183","id":"PMC_28251183","title":"Opposing Transcriptional Mechanisms Regulate Toxoplasma Development.","date":"2017","source":"mSphere","url":"https://pubmed.ncbi.nlm.nih.gov/28251183","citation_count":68,"is_preprint":false},{"pmid":"29932347","id":"PMC_29932347","title":"The Epigenome, Cell Cycle, and Development in Toxoplasma.","date":"2018","source":"Annual review of microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/29932347","citation_count":51,"is_preprint":false},{"pmid":"20657661","id":"PMC_20657661","title":"The construction and use of log-odds substitution scores for multiple sequence alignment.","date":"2010","source":"PLoS computational biology","url":"https://pubmed.ncbi.nlm.nih.gov/20657661","citation_count":48,"is_preprint":false},{"pmid":"19146987","id":"PMC_19146987","title":"Repeated secondary loss of adaptin complex genes in the Apicomplexa.","date":"2008","source":"Parasitology international","url":"https://pubmed.ncbi.nlm.nih.gov/19146987","citation_count":36,"is_preprint":false},{"pmid":"22486860","id":"PMC_22486860","title":"Cactin is essential for G1 progression in Toxoplasma gondii.","date":"2012","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/22486860","citation_count":23,"is_preprint":false},{"pmid":"25393307","id":"PMC_25393307","title":"Distinct strains of Toxoplasma gondii feature divergent transcriptomes regardless of developmental stage.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25393307","citation_count":22,"is_preprint":false},{"pmid":"18983845","id":"PMC_18983845","title":"New eukaryotic systematics: a phylogenetic perspective of developmental gene expression in the Apicomplexa.","date":"2008","source":"International journal for parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/18983845","citation_count":12,"is_preprint":false},{"pmid":"39690155","id":"PMC_39690155","title":"Apicomplexan mitoribosome from highly fragmented rRNAs to a functional machine.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/39690155","citation_count":9,"is_preprint":false},{"pmid":"36178892","id":"PMC_36178892","title":"Genomic insights into host and parasite interactions during intracellular infection by Toxoplasma gondii.","date":"2022","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/36178892","citation_count":2,"is_preprint":false},{"pmid":"40934260","id":"PMC_40934260","title":"HIV-1 Tat favors the multiplication of Mycobacterium tuberculosis and Toxoplasma by inhibiting clathrin-mediated endocytosis and autophagy.","date":"2025","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/40934260","citation_count":0,"is_preprint":false},{"pmid":"42087241","id":"PMC_42087241","title":"Host-cell dependent epigenetic profiles associated with survival outcomes in T. gondii infection.","date":"2026","source":"Epigenetics & chromatin","url":"https://pubmed.ncbi.nlm.nih.gov/42087241","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":20705,"output_tokens":2058,"usd":0.046492,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7521,"output_tokens":2817,"usd":0.054015,"stage2_stop_reason":"end_turn"},"total_usd":0.100507,"stage1_batch_id":"msgbatch_01S6GjoYQm8LTPUsdhASdqag","stage2_batch_id":"msgbatch_01VX63RTMdBJqsG6gQMqoCjz","note":"batch pricing = 50% of standard","corrective_rerun":"2026-09-10 wrong-gene rerun (round-4 rules)","corrective_reason":"paper list: removed papers about other genes"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"AP2IX-9 protein is localized exclusively to the early bradyzoite nucleus and is repressed in tachyzoites and in mature bradyzoites from 30-day infected animals, indicating stage-specific nuclear localization.\",\n      \"method\": \"Immunofluorescence / protein-level detection in stage-specific parasites\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein localization experiment with stage-specific expression profiling, single lab with multiple orthogonal methods (protein detection, conditional overexpression, gene disruption, reporter assay, ChIP)\",\n      \"pmids\": [\"23572590\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AP2IX-9 functions as a transcriptional repressor of bradyzoite development: conditional overexpression significantly reduced tissue cyst formation and conferred alkaline pH-resistant growth, while disruption of AP2IX-9 increased tissue cyst formation.\",\n      \"method\": \"Conditional overexpression (FKBP/Shield-1 system) and gene disruption with tissue cyst formation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain- and loss-of-function experiments with defined phenotypic readout in a single lab, confirmed by multiple orthogonal approaches\",\n      \"pmids\": [\"23572590\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AP2IX-9 specifically inhibits expression of bradyzoite mRNAs including BAG1 (bradyzoite antigen 1), acting as a direct transcriptional repressor.\",\n      \"method\": \"Gene expression profiling and mRNA quantification in AP2IX-9 overexpression and knockout parasites\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function transcriptomics combined with reporter and ChIP assays in single lab\",\n      \"pmids\": [\"23572590\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The AP2 domain of AP2IX-9 binds the DNA sequence motif CAGTGT, as established by protein binding microarray analysis, and this domain is capable of binding cis-regulatory elements in the BAG1 and bradyzoite-specific NTPase (B-NTPase) promoters.\",\n      \"method\": \"Protein binding microarray (PBM) for DNA motif identification\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical assay (PBM) identifying specific DNA binding motif, corroborated by in vivo reporter and ChIP experiments in same study\",\n      \"pmids\": [\"23572590\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AP2IX-9 directly represses the BAG1 promoter in vivo: it inhibits expression of a firefly luciferase reporter under BAG1 promoter control, and epitope-tagged AP2IX-9 can be immunoprecipitated with the BAG1 promoter in parasite chromatin (ChIP).\",\n      \"method\": \"Luciferase reporter assay and chromatin immunoprecipitation (ChIP)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vivo reporter assay plus ChIP demonstrating direct promoter occupancy, two orthogonal methods in single lab\",\n      \"pmids\": [\"23572590\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"AP2IX-9 and AP2IV-3 are expressed in two overlapping waves during bradyzoite development (AP2IX-9 earlier, AP2IV-3 later) and have opposing functions: AP2IX-9 is a repressor (its disruption enhances cyst formation) while AP2IV-3 is an activator (its deletion decreases cyst formation). Both regulate overlapping sets of bradyzoite genes including BAG1.\",\n      \"method\": \"Gene disruption and conditional overexpression with tissue cyst formation assays and gene expression profiling; BAG1 promoter-luciferase reporter and ChIP\",\n      \"journal\": \"mSphere\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal KO and OE experiments with defined phenotypes, confirmed by reporter and ChIP assays, extends prior PNAS findings with an independent lab study\",\n      \"pmids\": [\"28251183\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"AP2IX-9 mRNA exhibits a cyclical expression profile during the tachyzoite cell cycle, with peak expression in the S/M-subtranscriptome (associated with parasite maturation), and AP2IX-9 protein expression forms a sharp peak in the same timeframe as its mRNA, suggesting protein timing is mediated through AP2 domain-dependent mechanisms.\",\n      \"method\": \"Global cell cycle transcriptome profiling and protein expression timing analysis in dividing tachyzoites\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — genome-wide transcriptomic approach with protein expression correlation, single lab, no direct functional dissection of AP2IX-9 specifically\",\n      \"pmids\": [\"20865045\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"AP2IX-9 mRNA demonstrates the largest expression increase among 15 AP2-domain-encoding mRNAs during alkaline-induced bradyzoite differentiation.\",\n      \"method\": \"mRNA expression profiling during alkaline stress-induced differentiation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — transcriptomic screen across multiple AP2 factors, identifies AP2IX-9 as top hit but this is a comparative expression result supporting its regulatory role\",\n      \"pmids\": [\"23572590\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"AP2IX-9 is an ApiAP2 transcription factor that localizes exclusively to the early bradyzoite nucleus, where it acts as a direct transcriptional repressor of bradyzoite development by binding a CAGTGT DNA motif and occupying promoters (including BAG1 and B-NTPase) to suppress bradyzoite gene expression; its opposing action to the activator AP2IV-3 positions AP2IX-9 as part of a competing transcriptional switch that controls commitment to tissue cyst formation in Toxoplasma gondii.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"AP2IX-9 is an ApiAP2 transcription factor of Toxoplasma gondii that acts as a direct repressor of bradyzoite (tissue cyst) development, functioning as one arm of a transcriptional switch controlling commitment to the encysted stage [#1, #5]. Its expression is tightly stage-restricted: AP2IX-9 protein accumulates exclusively in the early bradyzoite nucleus and is repressed in tachyzoites and in mature bradyzoites [#0], and its mRNA shows the largest induction among ApiAP2 genes during alkaline-stress differentiation [#7]. Functionally, conditional overexpression suppresses tissue cyst formation and confers alkaline-pH-resistant growth, whereas gene disruption enhances cyst formation, establishing repressor activity [#1]. AP2IX-9 achieves this by binding the CAGTGT DNA motif through its AP2 domain and occupying cis-regulatory elements of bradyzoite genes such as BAG1 and bradyzoite-specific NTPase, directly repressing their transcription as shown by promoter-luciferase reporter and ChIP occupancy of the BAG1 promoter [#2, #3, #4]. AP2IX-9 acts in opposition to the later-expressed activator AP2IV-3 over an overlapping set of bradyzoite genes including BAG1, defining a competing early-repressor/late-activator system that gates cyst commitment [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Before any function was assigned, it was unknown whether AP2IX-9 expression was developmentally timed; cell-cycle transcriptomics showed cyclical S/M-phase-peaked mRNA and matched protein timing, hinting at a regulated role tied to parasite maturation.\",\n      \"evidence\": \"Global cell-cycle transcriptome and protein timing analysis in dividing tachyzoites\",\n      \"pmids\": [\"20865045\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional dissection of AP2IX-9 in this study\", \"Does not link expression timing to a downstream target or phenotype\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"It was unknown which factor controls bradyzoite gene repression; stage-specific detection placed AP2IX-9 exclusively in the early bradyzoite nucleus and repressed in tachyzoites and mature cysts, and its mRNA was the most induced ApiAP2 during alkaline differentiation, positioning it as a stage-transition regulator.\",\n      \"evidence\": \"Immunofluorescence/protein-level stage profiling and mRNA expression profiling during alkaline-induced differentiation\",\n      \"pmids\": [\"23572590\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Localization alone does not establish direction of regulation\", \"Does not identify direct target genes\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Whether AP2IX-9 promotes or suppresses cyst formation was resolved by reciprocal genetics: overexpression reduced cyst formation and gave alkaline-resistant growth while disruption increased cysts, establishing AP2IX-9 as a repressor of bradyzoite development.\",\n      \"evidence\": \"Conditional FKBP/Shield-1 overexpression and gene disruption with tissue cyst formation assays and transcriptomics\",\n      \"pmids\": [\"23572590\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not identify the direct DNA binding site or target promoters\", \"Mechanism of transcriptional repression (co-repressor recruitment) unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"To show repression is direct rather than indirect, the DNA specificity and promoter occupancy were defined: the AP2 domain binds the CAGTGT motif and binds BAG1 and B-NTPase promoter elements, and AP2IX-9 represses a BAG1-promoter reporter and is ChIP-recovered at the BAG1 promoter.\",\n      \"evidence\": \"Protein binding microarray for motif identification, luciferase reporter assay, and chromatin immunoprecipitation\",\n      \"pmids\": [\"23572590\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genome-wide occupancy map not defined\", \"Does not identify repressive chromatin machinery recruited by AP2IX-9\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"It was unclear how repression is balanced against activation of the same genes; AP2IX-9 (early) and AP2IV-3 (later) were shown to be expressed in overlapping waves with opposing activities on shared bradyzoite genes including BAG1, defining a competing repressor/activator switch controlling cyst commitment.\",\n      \"evidence\": \"Reciprocal gene disruption and overexpression with cyst assays, expression profiling, BAG1 promoter-luciferase reporter and ChIP\",\n      \"pmids\": [\"28251183\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of competition/co-occupancy at shared promoters not resolved\", \"Upstream signal driving the AP2IX-9 to AP2IV-3 handoff unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How AP2IX-9 mechanistically represses transcription and how it is displaced or overridden by AP2IV-3 during commitment to encystation remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No co-repressor or chromatin-modifying partner identified\", \"No structural basis for CAGTGT recognition\", \"Genome-wide direct target set not defined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0001227\", \"supporting_discovery_ids\": [1, 2, 4, 5], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0043565\", \"supporting_discovery_ids\": [3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0000981\", \"supporting_discovery_ids\": [3, 4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006355\", \"supporting_discovery_ids\": [1, 2, 4, 5], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"AP2IV-3 (functionally opposing activator co-regulating BAG1 and overlapping bradyzoite genes) [#5]\"\n    ],\n    \"other_free_text\": [\n      \"Binds CAGTGT DNA motif via its AP2 domain [#3]\",\n      \"Occupies and represses the BAG1 and bradyzoite-specific NTPase (B-NTPase) promoters [#3, #4]\",\n      \"Overexpression confers alkaline-pH-resistant growth and reduces tissue cyst formation; disruption increases cyst formation [#1, #5]\",\n      \"mRNA is cell-cycle regulated, peaking in the S/M-subtranscriptome [#6]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_306620","name":"AP2IX9","product":"AP2 domain transcription factor AP2IX-9","uniprot_acc":"S8EYQ9","chromosome":"TGME49_chrIX","start_pos":6215618},{"strain":"GT1","gene_id":"TGGT1_306620","name":null,"product":"AP2 domain transcription factor AP2IX-9","uniprot_acc":null,"chromosome":"TGGT1_chrIX","start_pos":6000552},{"strain":"RH88","gene_id":"TGRH88_018070","name":null,"product":"AP2 domain transcription factor AP2IX-9","uniprot_acc":null,"chromosome":"CM023090","start_pos":6343011},{"strain":"VEG","gene_id":"TGVEG_306620","name":null,"product":"AP2 domain transcription factor AP2IX-9","uniprot_acc":"A0A125YT60","chromosome":"TGVEG_chrIX","start_pos":6259265}]}