{"gene":"TG_310900","gene_symbol":"AP2XI2","run_date":"2026-09-10T21:09:19","timeline":{"discoveries":[{"year":2023,"finding":"AP2XI-2 and AP2XII-1 function as transcriptional repressors that silence merozoite-stage genes during tachyzoite development. In tachyzoites, AP2XI-2 and AP2XII-1 bind DNA as heterodimers at merozoite promoters and recruit the epigenetic repressors MORC and HDAC3, thereby restricting chromatin accessibility and suppressing transcription of merozoite-specific genes. Their conditional and simultaneous depletion leads to a full transcriptional transition from tachyzoites to merozoites (pre-gametes) in vitro.","method":"Conditional knockdown (simultaneous depletion), chromatin immunoprecipitation/CUT&Tag, co-immunoprecipitation, RNA-seq, immunofluorescence, ATAC-seq","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (conditional depletion, ChIP/CUT&Tag for heterodimer binding, chromatin accessibility assays, transcriptomics) in a single rigorous study, replicated across two independent publications (PMID:38093015 and PMID:36711883)","pmids":["38093015","36711883"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2024,"finding":"AP2XI-2 acts as a negative regulator suppressing merozoite-primed pre-sexual commitment during asexual development in type II Pru strain. Depletion of AP2XI-2 in Pru strain induces merogony and production of mature merozoites under alkaline conditions. Two additional AP2XI-2-interacting proteins were identified that are also involved in repressing merozoite programming.","method":"Conditional knockdown, immunoprecipitation/mass spectrometry to identify interacting proteins, transcriptomics, alkaline induction assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockdown with defined phenotypic readout, interactor identification by MS, multiple labs reporting consistent findings (PMID:38278808 and PMID:38093015)","pmids":["38278808"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"Pru"}]},{"year":2024,"finding":"AP2XII-1 specifically binds to a subset of ApiAP2 transcription factors including AP2XI-2, and there is considerable overlap in the downstream gene profiles regulated by AP2XII-1 and AP2XI-2, with AP2XII-1 acting upstream of AP2XI-2 in a hierarchical transcriptional regulatory network controlling merozoite-specific gene expression.","method":"Conditional knockout, immunoprecipitation, RNA-seq, CUT&Tag","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and transcriptomics in a single lab, two orthogonal methods","pmids":["38791568"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2010,"finding":"AP2XI-2 mRNA exhibits a cyclical expression profile during the tachyzoite cell cycle, with peak expression occurring in one of two transcriptional waves, placing it in the S/M-subtranscriptome. AP2XI-2 protein expression shows a sharp, successive peak consistent with its mRNA pattern, suggesting its transcriptional activity may be temporally regulated by AP2 domain-mediated promoter recognition.","method":"Genome-wide cell cycle transcriptomics, protein expression profiling by immunofluorescence/western blot across cell cycle stages","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 / Weak — expression profiling only, single study, no direct functional manipulation of AP2XI-2","pmids":["20865045"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2025,"finding":"Depletion of AP2XII-1 and AP2XI-2 reveals a hybrid zoite co-expressing bradyzoite and merozoite markers, suggesting a transitional developmental state. Their simultaneous knockdown reactivates the presexual program in vitro, demonstrating the two factors together maintain a binary tachyzoite fate and prevent presexual commitment.","method":"Conditional depletion, transcriptional profiling, marker analysis","journal":"Current opinion in microbiology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — review summarizing findings, no new primary experimental data presented in this abstract","pmids":["40886497"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2026,"finding":"AP2XI-2 depletion (together with AP2XII-1 depletion) enables merozoite formation in human fibroblasts in vitro, but progression to advanced sexual stages (beyond merozoites) appears to require additional cues present in the feline intestinal environment, as demonstrated by using merozoites derived from AP2XI-2/AP2XII-1-depleted parasites in a feline intestinal organoid system.","method":"Conditional depletion, feline intestinal organoid culture, ultrastructural analysis, transcriptional analysis","journal":"Communications biology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — AP2XI-2's role is used as a tool here rather than being directly investigated; single study with organoid system","pmids":["41691108"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"AP2XI-2 is a tachyzoite-expressed ApiAP2 transcription factor that functions as a heterodimeric repressor with AP2XII-1, binding to merozoite gene promoters to recruit MORC and HDAC3, thereby maintaining chromatin in a closed state and suppressing the merozoite/pre-sexual developmental program; its conditional depletion (especially combined with AP2XII-1 depletion) drives a full transcriptional and morphological transition from tachyzoites to merozoites in vitro."},"narrative":{"mechanistic_narrative":"AP2XI-2 is a tachyzoite-expressed ApiAP2 transcription factor that acts as a negative regulator of the merozoite/pre-sexual developmental program in Toxoplasma gondii, maintaining parasites in the asexual tachyzoite state [PMID:38093015, PMID:36711883, PMID:38278808]. In RH tachyzoites, AP2XI-2 partners with AP2XII-1 as a DNA-binding heterodimer at merozoite gene promoters and recruits the epigenetic repressors MORC and HDAC3, restricting chromatin accessibility and silencing merozoite-specific transcription [PMID:38093015, PMID:36711883]. AP2XII-1 binds AP2XI-2 and acts upstream of it within a hierarchical regulatory network, with substantial overlap in the genes the two factors control [PMID:38791568]. Conditional depletion of AP2XI-2 in the type II Pru strain induces merogony and mature merozoite production under alkaline conditions, and simultaneous depletion of AP2XI-2 and AP2XII-1 drives a full transcriptional and morphological transition from tachyzoites to merozoites in vitro [PMID:38093015, PMID:36711883, PMID:38278808]. Additional AP2XI-2-interacting proteins that also repress merozoite programming have been identified by mass spectrometry [PMID:38278808], but their individual mechanisms are not further characterized in the available corpus. Depletion of AP2XII-1 and AP2XI-2 reveals a hybrid zoite co-expressing bradyzoite and merozoite markers, suggesting a transitional developmental state, and their simultaneous knockdown reactivates the presexual program in vitro, demonstrating the two factors together maintain a binary tachyzoite fate and prevent presexual commitment [PMID:40886497]. AP2XI-2 depletion together with AP2XII-1 depletion enables merozoite formation in human fibroblasts in vitro, but progression to advanced sexual stages beyond merozoites appears to require additional cues present in the feline intestinal environment, as demonstrated by using merozoites derived from AP2XI-2/AP2XII-1-depleted parasites in a feline intestinal organoid system [PMID:41691108]. AP2XI-2 mRNA exhibits a cyclical expression profile during the tachyzoite cell cycle, with peak expression occurring in one of two transcriptional waves, placing it in the S/M-subtranscriptome, and AP2XI-2 protein expression shows a sharp, successive peak consistent with its mRNA pattern, suggesting its transcriptional activity may be temporally regulated by AP2 domain-mediated promoter recognition [PMID:20865045].","teleology":[{"year":2010,"claim":"Before its function was known, establishing when AP2XI-2 is expressed placed it temporally within the tachyzoite cell cycle, hinting at cell-cycle-coupled transcriptional activity.","evidence":"genome-wide cell-cycle transcriptomics and protein expression profiling in RH","pmids":["20865045"],"confidence":"Low","gaps":["expression profiling only, no functional manipulation","does not identify DNA targets or partners","no link to a developmental phenotype"],"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2023,"claim":"Defining AP2XI-2 as a DNA-binding heterodimeric repressor with AP2XII-1 that recruits MORC and HDAC3 established the direct mechanism by which merozoite genes are kept silenced in tachyzoites, and its simultaneous depletion converting tachyzoites to merozoites proved this repression gates developmental fate.","evidence":"conditional simultaneous knockdown, ChIP/CUT&Tag, Co-IP, RNA-seq, ATAC-seq and immunofluorescence in RH","pmids":["38093015","36711883"],"confidence":"High","gaps":["contribution of AP2XI-2 alone versus the heterodimer to promoter binding not fully resolved","DNA sequence motif recognized by AP2XI-2 not defined","in vitro tachyzoite system only"],"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2024,"claim":"Depleting AP2XI-2 in the type II Pru strain showed its repressive role generalizes beyond RH, and interactor mass spectrometry expanded the repressive complex beyond AP2XII-1/MORC/HDAC3.","evidence":"conditional knockdown with alkaline induction, IP/MS interactor identification and transcriptomics in Pru","pmids":["38278808"],"confidence":"High","gaps":["the two new interacting proteins not mechanistically characterized","whether alkaline stress acts through AP2XI-2 directly unclear"],"attribution":[{"species":"Toxoplasma gondii","strain":"Pru"}]},{"year":2024,"claim":"Mapping AP2XII-1 binding to AP2XI-2 and comparing their downstream targets ordered the network, placing AP2XII-1 hierarchically upstream of AP2XI-2 in controlling merozoite gene expression.","evidence":"conditional knockout, Co-IP, RNA-seq and CUT&Tag","pmids":["38791568"],"confidence":"Medium","gaps":["single-lab study","molecular basis of the hierarchy not defined","strain not specified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"claim":"Observing a hybrid bradyzoite/merozoite zoite after AP2XII-1/AP2XI-2 depletion reframed the factors as guardians of a binary tachyzoite fate that block presexual commitment.","evidence":"conditional depletion with transcriptional profiling and marker analysis (review synthesis)","pmids":["40886497"],"confidence":"Low","gaps":["review summary rather than new primary data","stability and identity of the hybrid state not resolved","AP2XI-2-specific contribution not isolated"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2026,"claim":"Using AP2XI-2/AP2XII-1-depleted merozoites in feline intestinal organoids delimited the reach of AP2XI-2 repression: its removal is sufficient for merozoite formation but not for advanced sexual stages, which need host-derived cues.","evidence":"conditional depletion, feline intestinal organoid culture, ultrastructural and transcriptional analysis","pmids":["41691108"],"confidence":"Low","gaps":["AP2XI-2 used as a tool rather than directly investigated","nature of the required feline intestinal cues unknown","single study with organoid system"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["AP2XI-2 / AP2XII-1 DNA-binding heterodimer","MORC-HDAC3 repressive complex (AP2XI-2 as component)"],"partners":["AP2XII-1","MORC","HDAC3","TWO ADDITIONAL AP2XI-2-INTERACTING MEROZOITE-REPRESSOR PROTEINS (PRU, IDENTITY NOT SPECIFIED)"],"other_free_text":["AP2XI-2 mRNA and protein peak in the S/M phase of the tachyzoite cell cycle [#4].","AP2XI-2 is detected as arginine-monomethylated in the T. gondii monomethylarginine proteome [#5].","Simultaneous AP2XI-2/AP2XII-1 depletion is sufficient for tachyzoite-to-merozoite conversion in vitro, but advanced sexual stages require feline intestinal cues [#7]."]},"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":"38093015","id":"PMC_38093015","title":"In vitro production of cat-restricted Toxoplasma pre-sexual stages.","date":"2023","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/38093015","citation_count":52,"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":"38278808","id":"PMC_38278808","title":"The transcription factor AP2XI-2 is a key negative regulator of Toxoplasma gondii merogony.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38278808","citation_count":39,"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":"38791568","id":"PMC_38791568","title":"AP2XII-1 and AP2XI-2 Suppress Schizogony Gene Expression in Toxoplasma gondii.","date":"2024","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38791568","citation_count":12,"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":"36711883","id":"PMC_36711883","title":"In vitro production of cat-restricted Toxoplasma pre-sexual stages by epigenetic reprogramming.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/36711883","citation_count":5,"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":"40886497","id":"PMC_40886497","title":"Decoding the epigenetic blueprint behind Toxoplasma (pre)sexual commitment and chronic persistence.","date":"2025","source":"Current opinion in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/40886497","citation_count":1,"is_preprint":false},{"pmid":"41691108","id":"PMC_41691108","title":"Long-term feeder cell-free cat intestinal organoid cultures to study Toxoplasma gondii's sexual development.","date":"2026","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/41691108","citation_count":0,"is_preprint":false},{"pmid":"39245231","id":"PMC_39245231","title":"Identification of subtelomeric cluster-genes associated to sexual stage in Toxoplasma gondii.","date":"2024","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/39245231","citation_count":0,"is_preprint":false},{"pmid":"41278634","id":"PMC_41278634","title":"Single-cell analysis of brain-derived Toxoplasma bradyzoites reveals a novel cell cycle regulated by AP2XI-6.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41278634","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":20968,"output_tokens":2287,"usd":0.048605,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7754,"output_tokens":3764,"usd":0.066435,"stage2_stop_reason":"end_turn"},"total_usd":0.122123,"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":"summary amended"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2023,\n      \"finding\": \"AP2XI-2 and AP2XII-1 function as transcriptional repressors that silence merozoite-stage genes during tachyzoite development. In tachyzoites, AP2XI-2 and AP2XII-1 bind DNA as heterodimers at merozoite promoters and recruit the epigenetic repressors MORC and HDAC3, thereby restricting chromatin accessibility and suppressing transcription of merozoite-specific genes. Their conditional and simultaneous depletion leads to a full transcriptional transition from tachyzoites to merozoites (pre-gametes) in vitro.\",\n      \"method\": \"Conditional knockdown (simultaneous depletion), chromatin immunoprecipitation/CUT&Tag, co-immunoprecipitation, RNA-seq, immunofluorescence, ATAC-seq\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (conditional depletion, ChIP/CUT&Tag for heterodimer binding, chromatin accessibility assays, transcriptomics) in a single rigorous study, replicated across two independent publications (PMID:38093015 and PMID:36711883)\",\n      \"pmids\": [\"38093015\", \"36711883\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"AP2XI-2 acts as a negative regulator suppressing merozoite-primed pre-sexual commitment during asexual development in type II Pru strain. Depletion of AP2XI-2 in Pru strain induces merogony and production of mature merozoites under alkaline conditions. Two additional AP2XI-2-interacting proteins were identified that are also involved in repressing merozoite programming.\",\n      \"method\": \"Conditional knockdown, immunoprecipitation/mass spectrometry to identify interacting proteins, transcriptomics, alkaline induction assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockdown with defined phenotypic readout, interactor identification by MS, multiple labs reporting consistent findings (PMID:38278808 and PMID:38093015)\",\n      \"pmids\": [\"38278808\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"AP2XII-1 specifically binds to a subset of ApiAP2 transcription factors including AP2XI-2, and there is considerable overlap in the downstream gene profiles regulated by AP2XII-1 and AP2XI-2, with AP2XII-1 acting upstream of AP2XI-2 in a hierarchical transcriptional regulatory network controlling merozoite-specific gene expression.\",\n      \"method\": \"Conditional knockout, immunoprecipitation, RNA-seq, CUT&Tag\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and transcriptomics in a single lab, two orthogonal methods\",\n      \"pmids\": [\"38791568\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"AP2XI-2 (referred to in the MORC study context) is part of the MORC complex. MORC, in complex with AP2 transcription factors including AP2XI-2, recruits HDAC3 to impede chromatin accessibility at sexual stage genes, acting as an upstream transcriptional repressor of sexual commitment.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, chromatin accessibility assays, conditional depletion (auxin-inducible degron)\",\n      \"journal\": \"Nature microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS and functional depletion in one study; AP2XI-2 is listed as a MORC complex component but the primary focus is MORC itself\",\n      \"pmids\": [\"32094587\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"AP2XI-2 mRNA exhibits a cyclical expression profile during the tachyzoite cell cycle, with peak expression occurring in one of two transcriptional waves, placing it in the S/M-subtranscriptome. AP2XI-2 protein expression shows a sharp, successive peak consistent with its mRNA pattern, suggesting its transcriptional activity may be temporally regulated by AP2 domain-mediated promoter recognition.\",\n      \"method\": \"Genome-wide cell cycle transcriptomics, protein expression profiling by immunofluorescence/western blot across cell cycle stages\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — expression profiling only, single study, no direct functional manipulation of AP2XI-2\",\n      \"pmids\": [\"20865045\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"AP2XI-2 protein is detected in the arginine monomethylome of T. gondii, identified by affinity purification with anti-monomethylarginine antibodies followed by mass spectrometry, suggesting that AP2XI-2 undergoes arginine monomethylation as a post-translational modification.\",\n      \"method\": \"Affinity purification with anti-MMA antibodies, mass spectrometry\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single proteomics screen, no functional follow-up on AP2XI-2 specifically\",\n      \"pmids\": [\"28143887\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Depletion of AP2XII-1 and AP2XI-2 reveals a hybrid zoite co-expressing bradyzoite and merozoite markers, suggesting a transitional developmental state. Their simultaneous knockdown reactivates the presexual program in vitro, demonstrating the two factors together maintain a binary tachyzoite fate and prevent presexual commitment.\",\n      \"method\": \"Conditional depletion, transcriptional profiling, marker analysis\",\n      \"journal\": \"Current opinion in microbiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — review summarizing findings, no new primary experimental data presented in this abstract\",\n      \"pmids\": [\"40886497\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"AP2XI-2 depletion (together with AP2XII-1 depletion) enables merozoite formation in human fibroblasts in vitro, but progression to advanced sexual stages (beyond merozoites) appears to require additional cues present in the feline intestinal environment, as demonstrated by using merozoites derived from AP2XI-2/AP2XII-1-depleted parasites in a feline intestinal organoid system.\",\n      \"method\": \"Conditional depletion, feline intestinal organoid culture, ultrastructural analysis, transcriptional analysis\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — AP2XI-2's role is used as a tool here rather than being directly investigated; single study with organoid system\",\n      \"pmids\": [\"41691108\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"AP2XI-2 is a tachyzoite-expressed ApiAP2 transcription factor that functions as a heterodimeric repressor with AP2XII-1, binding to merozoite gene promoters to recruit MORC and HDAC3, thereby maintaining chromatin in a closed state and suppressing the merozoite/pre-sexual developmental program; its conditional depletion (especially combined with AP2XII-1 depletion) drives a full transcriptional and morphological transition from tachyzoites to merozoites in vitro.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"AP2XI-2 is a tachyzoite-expressed ApiAP2 transcription factor that acts as a negative regulator of the merozoite/pre-sexual developmental program in Toxoplasma gondii, maintaining parasites in the asexual tachyzoite state [#0, #1]. In RH tachyzoites, AP2XI-2 partners with AP2XII-1 as a DNA-binding heterodimer at merozoite gene promoters and recruits the epigenetic repressors MORC and HDAC3, restricting chromatin accessibility and silencing merozoite-specific transcription [#0, #3]. AP2XII-1 binds AP2XI-2 and acts upstream of it within a hierarchical regulatory network, with substantial overlap in the genes the two factors control [#2]. Conditional depletion of AP2XI-2 in the type II Pru strain induces merogony and mature merozoite production under alkaline conditions, and simultaneous depletion of AP2XI-2 and AP2XII-1 drives a full transcriptional and morphological transition from tachyzoites to merozoites in vitro [#0, #1]. Additional AP2XI-2-interacting proteins that also repress merozoite programming have been identified by mass spectrometry [#1], but their individual mechanisms are not further characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Before its function was known, establishing when AP2XI-2 is expressed placed it temporally within the tachyzoite cell cycle, hinting at cell-cycle-coupled transcriptional activity.\",\n      \"evidence\": \"genome-wide cell-cycle transcriptomics and protein expression profiling in RH\",\n      \"pmids\": [\"20865045\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"expression profiling only, no functional manipulation\", \"does not identify DNA targets or partners\", \"no link to a developmental phenotype\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A proteomic screen detected AP2XI-2 as arginine-monomethylated, raising the possibility that its activity is tuned by post-translational modification.\",\n      \"evidence\": \"anti-monomethylarginine affinity purification and mass spectrometry\",\n      \"pmids\": [\"28143887\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"single proteomics screen with no functional follow-up\", \"modification site and responsible methyltransferase unknown\", \"functional consequence for AP2XI-2 activity untested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Linking AP2XI-2 to the MORC complex identified a physical route by which it could silence developmental genes, framing it as part of a chromatin-repressive machinery upstream of sexual commitment.\",\n      \"evidence\": \"Co-IP/MS, chromatin accessibility assays and auxin-inducible degron depletion in RH\",\n      \"pmids\": [\"32094587\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"AP2XI-2 characterized only as a listed MORC component, not the study focus\", \"AP2XI-2-specific DNA targets not defined here\", \"whether AP2XI-2 is required for MORC/HDAC3 recruitment not directly tested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defining AP2XI-2 as a DNA-binding heterodimeric repressor with AP2XII-1 that recruits MORC and HDAC3 established the direct mechanism by which merozoite genes are kept silenced in tachyzoites, and its simultaneous depletion converting tachyzoites to merozoites proved this repression gates developmental fate.\",\n      \"evidence\": \"conditional simultaneous knockdown, ChIP/CUT&Tag, Co-IP, RNA-seq, ATAC-seq and immunofluorescence in RH\",\n      \"pmids\": [\"38093015\", \"36711883\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"contribution of AP2XI-2 alone versus the heterodimer to promoter binding not fully resolved\", \"DNA sequence motif recognized by AP2XI-2 not defined\", \"in vitro tachyzoite system only\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Depleting AP2XI-2 in the type II Pru strain showed its repressive role generalizes beyond RH, and interactor mass spectrometry expanded the repressive complex beyond AP2XII-1/MORC/HDAC3.\",\n      \"evidence\": \"conditional knockdown with alkaline induction, IP/MS interactor identification and transcriptomics in Pru\",\n      \"pmids\": [\"38278808\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"the two new interacting proteins not mechanistically characterized\", \"whether alkaline stress acts through AP2XI-2 directly unclear\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Mapping AP2XII-1 binding to AP2XI-2 and comparing their downstream targets ordered the network, placing AP2XII-1 hierarchically upstream of AP2XI-2 in controlling merozoite gene expression.\",\n      \"evidence\": \"conditional knockout, Co-IP, RNA-seq and CUT&Tag\",\n      \"pmids\": [\"38791568\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"single-lab study\", \"molecular basis of the hierarchy not defined\", \"strain not specified\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Observing a hybrid bradyzoite/merozoite zoite after AP2XII-1/AP2XI-2 depletion reframed the factors as guardians of a binary tachyzoite fate that block presexual commitment.\",\n      \"evidence\": \"conditional depletion with transcriptional profiling and marker analysis (review synthesis)\",\n      \"pmids\": [\"40886497\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"review summary rather than new primary data\", \"stability and identity of the hybrid state not resolved\", \"AP2XI-2-specific contribution not isolated\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Using AP2XI-2/AP2XII-1-depleted merozoites in feline intestinal organoids delimited the reach of AP2XI-2 repression: its removal is sufficient for merozoite formation but not for advanced sexual stages, which need host-derived cues.\",\n      \"evidence\": \"conditional depletion, feline intestinal organoid culture, ultrastructural and transcriptional analysis\",\n      \"pmids\": [\"41691108\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"AP2XI-2 used as a tool rather than directly investigated\", \"nature of the required feline intestinal cues unknown\", \"single study with organoid system\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How AP2XI-2 selects its promoter targets and how its repressive activity is switched off during natural sexual commitment remain open.\",\n      \"evidence\": \"no discovery in the timeline defines the AP2XI-2 DNA recognition motif or the physiological trigger that relieves its repression\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"DNA-binding motif of AP2XI-2 not defined\", \"signal that de-represses the pathway in vivo unknown\", \"functional role of arginine monomethylation untested\"],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0001227\", \"supporting_discovery_ids\": [0, 1, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]},\n      {\"term_id\": \"GO:0003700\", \"supporting_discovery_ids\": [0, 4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]},\n      {\"term_id\": \"GO:0046982\", \"supporting_discovery_ids\": [0, 2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0045892\", \"supporting_discovery_ids\": [0, 1, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]},\n      {\"term_id\": \"GO:0006338\", \"supporting_discovery_ids\": [0, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]},\n      {\"term_id\": \"GO:0060218\", \"supporting_discovery_ids\": [0, 1, 6, 7], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]}\n    ],\n    \"complexes\": [\n      \"AP2XI-2 / AP2XII-1 DNA-binding heterodimer\",\n      \"MORC-HDAC3 repressive complex (AP2XI-2 as component)\"\n    ],\n    \"partners\": [\n      \"AP2XII-1\",\n      \"MORC\",\n      \"HDAC3\",\n      \"two additional AP2XI-2-interacting merozoite-repressor proteins (Pru, identity not specified)\"\n    ],\n    \"other_free_text\": [\n      \"AP2XI-2 mRNA and protein peak in the S/M phase of the tachyzoite cell cycle [#4].\",\n      \"AP2XI-2 is detected as arginine-monomethylated in the T. gondii monomethylarginine proteome [#5].\",\n      \"Simultaneous AP2XI-2/AP2XII-1 depletion is sufficient for tachyzoite-to-merozoite conversion in vitro, but advanced sexual stages require feline intestinal cues [#7].\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_310900","name":"AP2XI2","product":"AP2 domain transcription factor AP2XI-2","uniprot_acc":"A0A125YJB8","chromosome":"TGME49_chrXI","start_pos":1643720},{"strain":"GT1","gene_id":"TGGT1_310900","name":null,"product":"AP2 domain transcription factor AP2XI-2","uniprot_acc":null,"chromosome":"TGGT1_chrXI","start_pos":1609168},{"strain":"RH88","gene_id":"TGRH88_050410","name":null,"product":"AP2 domain transcription factor AP2XI-2","uniprot_acc":null,"chromosome":"CM023092","start_pos":1694803},{"strain":"VEG","gene_id":"TGVEG_310900","name":null,"product":"AP2 domain transcription factor AP2XI-2","uniprot_acc":"B6KAF6","chromosome":"TGVEG_chrXI","start_pos":1657784}]}