{"gene":"TG_287510","gene_symbol":"AAH1","run_date":"2026-09-08T14:08:30","timeline":{"discoveries":[{"year":2014,"finding":"AAH1 is essential for parasite growth in nondopaminergic cells, suggesting a role beyond dopamine biosynthesis in host cells.","method":"Knockout and complementation genetics with in vitro and in vivo growth assays","journal":"Infection and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean KO with defined growth phenotype, single lab, single study","pmids":["25547791"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2014,"finding":"AAH1 encodes an aromatic amino acid hydroxylase capable of producing L-DOPA; expression levels in tachyzoites and bradyzoites were negligible, and AAH enzyme activity did not cause global or regional alterations of dopamine in the host brain.","method":"Knockout and complementation genetics; dopamine measurement in vitro and in vivo; qRT-PCR expression analysis","journal":"Infection and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout with biochemical readout (dopamine levels) and expression profiling, single lab","pmids":["25547791"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2017,"finding":"AAH1 (along with AAH2) encodes a protein that produces L-DOPA; ablation of AAH genes reduced infection in the cat, lowered oocyst yields, and decreased sporulation rates, indicating a predominant role for AAH1 in the sexual reproductive cycle within the feline definitive host, potentially linked to oocyst wall formation via dityrosine crosslinks.","method":"Genetic knockout; cat infection experiments measuring oocyst yield and sporulation rates","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined in vivo phenotype in definitive host, single lab but multiple phenotypic readouts","pmids":["28288194"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2023,"finding":"AAH1 expression is transcriptionally repressed by the AP2XII-2 transcription factor, which recruits epigenetic silencing machinery (HDAC3 and MORC) to the AAH1 promoter, placing AAH1 downstream of the AP2XII-2 regulatory pathway controlling sexual stage gene expression.","method":"CUT&Tag chromatin profiling; genetic knockdown/complementation of AP2XII-2; co-association with HDAC3 and MORC","journal":"mSphere","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CUT&Tag with functional genetic validation in single lab, two orthogonal methods (chromatin profiling + KD phenotype)","pmids":["36786611"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"AAH1 encodes an aromatic amino acid hydroxylase that produces L-DOPA and is essential for parasite growth in nondopaminergic cells and for the sexual reproductive cycle in the feline definitive host (contributing to oocyst production and sporulation), while its expression is transcriptionally repressed in non-sexual stages by the AP2XII-2 transcription factor acting through HDAC3 and MORC epigenetic silencing machinery."},"narrative":{"mechanistic_narrative":"AAH1 encodes an aromatic amino acid hydroxylase that produces L-DOPA and supports the Toxoplasma gondii life cycle across both host contexts [PMID:25547791, PMID:28288194]. In the intermediate host, AAH1 is essential for parasite growth in nondopaminergic cells, a requirement that is independent of any effect on host dopamine, since its enzyme activity does not alter global or regional brain dopamine and its expression is negligible in tachyzoites and bradyzoites [PMID:25547791]. Its predominant physiological role lies in the sexual reproductive cycle within the feline definitive host: ablation of AAH genes reduces cat infection, oocyst yield, and sporulation, consistent with a contribution to oocyst wall formation via dityrosine crosslinks [PMID:28288194]. AAH1 transcription is silenced outside the sexual stages by the AP2XII-2 transcription factor, which recruits HDAC3 and MORC epigenetic machinery to the AAH1 promoter [PMID:36786611]. The catalytic mechanism, substrate specificity, and structural basis of AAH1 hydroxylase activity have not been characterized in the available corpus.","teleology":[{"year":2014,"claim":"Establishing whether AAH1 functions merely in host dopamine manipulation or has an intrinsic parasite role, knockout genetics showed AAH1 is required for growth even in cells that lack dopamine, defining a function beyond neuromodulation.","evidence":"Knockout and complementation genetics with in vitro and in vivo growth assays in Toxoplasma gondii","pmids":["25547791"],"confidence":"Medium","gaps":["The specific growth-relevant metabolite or pathway downstream of AAH1 in nondopaminergic cells was not identified","Single lab, single study"],"attribution":[]},{"year":2014,"claim":"To define the biochemical activity and physiological relevance of AAH1, enzyme and dopamine assays confirmed L-DOPA production but showed negligible tachyzoite/bradyzoite expression and no impact on host brain dopamine, decoupling AAH1 from the behavioral-manipulation hypothesis.","evidence":"Knockout/complementation genetics, dopamine measurement in vitro and in vivo, and qRT-PCR expression profiling","pmids":["25547791"],"confidence":"Medium","gaps":["The stage in which AAH1 is expressed at functionally relevant levels was not resolved here","Substrate specificity and catalytic mechanism not characterized"],"attribution":[]},{"year":2017,"claim":"Cat infection experiments located AAH1's predominant role in the sexual cycle, showing that AAH ablation lowers oocyst yield and sporulation and linking L-DOPA production to oocyst wall biogenesis.","evidence":"Genetic knockout with cat infection experiments measuring oocyst yield and sporulation rates in Toxoplasma gondii","pmids":["28288194"],"confidence":"Medium","gaps":["The dityrosine-crosslink contribution to oocyst wall formation was inferred rather than directly demonstrated","Relative contributions of AAH1 versus AAH2 not separately resolved"],"attribution":[]},{"year":2023,"claim":"To explain the stage-restricted expression of AAH1, chromatin profiling and genetic manipulation placed AAH1 under AP2XII-2 transcriptional repression via recruitment of HDAC3 and MORC, defining the epigenetic circuit that confines AAH1 to sexual stages.","evidence":"CUT&Tag chromatin profiling with AP2XII-2 knockdown/complementation and co-association analysis with HDAC3 and MORC in Toxoplasma gondii","pmids":["36786611"],"confidence":"Medium","gaps":["Direct binding of AP2XII-2 to the AAH1 promoter versus indirect regulation not fully separated","The activating signal that relieves repression during sexual commitment is unknown"],"attribution":[]},{"year":null,"claim":"The catalytic mechanism, structural basis, and cofactor requirements of AAH1 hydroxylase activity, and the direct molecular link between L-DOPA production and oocyst wall dityrosine crosslinking, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of AAH1","No direct biochemical demonstration of dityrosine crosslink formation from AAH1-derived L-DOPA","Growth-essential mechanism in nondopaminergic cells not defined"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["AP2XII-2 (UPSTREAM TRANSCRIPTIONAL REPRESSOR)","HDAC3 (EPIGENETIC SILENCING VIA AP2XII-2)","MORC (EPIGENETIC SILENCING VIA AP2XII-2)","AAH2 (CO-ACTING AROMATIC AMINO ACID HYDROXYLASE)"],"other_free_text":["AAH1 produces L-DOPA and is essential for parasite growth in nondopaminergic cells, indicating a role independent of host dopamine modulation [#0, #1].","AAH1 activity does not alter global or regional host brain dopamine, and expression is negligible in tachyzoites and bradyzoites [#1].","AAH1 contributes predominantly to the sexual reproductive cycle in the feline definitive host, affecting oocyst yield and sporulation, potentially via dityrosine crosslinks in the oocyst wall [#2].","AAH1 is transcriptionally repressed outside sexual stages by AP2XII-2 recruiting HDAC3 and MORC to its promoter [#3]."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"25547791","id":"PMC_25547791","title":"Reassessment of the role of aromatic amino acid hydroxylases and the effect of infection by Toxoplasma gondii on host dopamine.","date":"2014","source":"Infection and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/25547791","citation_count":63,"is_preprint":false},{"pmid":"28288194","id":"PMC_28288194","title":"The aromatic amino acid hydroxylase genes AAH1 and AAH2 in Toxoplasma gondii contribute to transmission in the cat.","date":"2017","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/28288194","citation_count":38,"is_preprint":false},{"pmid":"36786611","id":"PMC_36786611","title":"Toxoplasma gondii AP2XII-2 Contributes to Transcriptional Repression for Sexual Commitment.","date":"2023","source":"mSphere","url":"https://pubmed.ncbi.nlm.nih.gov/36786611","citation_count":32,"is_preprint":false},{"pmid":"29555339","id":"PMC_29555339","title":"AAH2 gene is not required for dopamine-dependent neurochemical and behavioral abnormalities produced by Toxoplasma infection in mouse.","date":"2018","source":"Behavioural brain research","url":"https://pubmed.ncbi.nlm.nih.gov/29555339","citation_count":23,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4160,"output_tokens":1006,"usd":0.013785,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5949,"output_tokens":2308,"usd":0.043722,"stage2_stop_reason":"end_turn"},"total_usd":0.057507,"stage1_batch_id":"msgbatch_015xmQKDRqnTh9anE4m7LiD6","stage2_batch_id":"msgbatch_01JLpkFTVhoQBNgqHCKFrVVU","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"AAH1 is essential for parasite growth in nondopaminergic cells, suggesting a role beyond dopamine biosynthesis in host cells.\",\n      \"method\": \"Knockout and complementation genetics with in vitro and in vivo growth assays\",\n      \"journal\": \"Infection and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean KO with defined growth phenotype, single lab, single study\",\n      \"pmids\": [\"25547791\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"AAH1 encodes an aromatic amino acid hydroxylase capable of producing L-DOPA; expression levels in tachyzoites and bradyzoites were negligible, and AAH enzyme activity did not cause global or regional alterations of dopamine in the host brain.\",\n      \"method\": \"Knockout and complementation genetics; dopamine measurement in vitro and in vivo; qRT-PCR expression analysis\",\n      \"journal\": \"Infection and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout with biochemical readout (dopamine levels) and expression profiling, single lab\",\n      \"pmids\": [\"25547791\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"AAH1 (along with AAH2) encodes a protein that produces L-DOPA; ablation of AAH genes reduced infection in the cat, lowered oocyst yields, and decreased sporulation rates, indicating a predominant role for AAH1 in the sexual reproductive cycle within the feline definitive host, potentially linked to oocyst wall formation via dityrosine crosslinks.\",\n      \"method\": \"Genetic knockout; cat infection experiments measuring oocyst yield and sporulation rates\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined in vivo phenotype in definitive host, single lab but multiple phenotypic readouts\",\n      \"pmids\": [\"28288194\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"AAH1 expression is transcriptionally repressed by the AP2XII-2 transcription factor, which recruits epigenetic silencing machinery (HDAC3 and MORC) to the AAH1 promoter, placing AAH1 downstream of the AP2XII-2 regulatory pathway controlling sexual stage gene expression.\",\n      \"method\": \"CUT&Tag chromatin profiling; genetic knockdown/complementation of AP2XII-2; co-association with HDAC3 and MORC\",\n      \"journal\": \"mSphere\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CUT&Tag with functional genetic validation in single lab, two orthogonal methods (chromatin profiling + KD phenotype)\",\n      \"pmids\": [\"36786611\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"AAH1 encodes an aromatic amino acid hydroxylase that produces L-DOPA and is essential for parasite growth in nondopaminergic cells and for the sexual reproductive cycle in the feline definitive host (contributing to oocyst production and sporulation), while its expression is transcriptionally repressed in non-sexual stages by the AP2XII-2 transcription factor acting through HDAC3 and MORC epigenetic silencing machinery.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"AAH1 encodes an aromatic amino acid hydroxylase that produces L-DOPA and supports the Toxoplasma gondii life cycle across both host contexts [#1, #2]. In the intermediate host, AAH1 is essential for parasite growth in nondopaminergic cells, a requirement that is independent of any effect on host dopamine, since its enzyme activity does not alter global or regional brain dopamine and its expression is negligible in tachyzoites and bradyzoites [#0, #1]. Its predominant physiological role lies in the sexual reproductive cycle within the feline definitive host: ablation of AAH genes reduces cat infection, oocyst yield, and sporulation, consistent with a contribution to oocyst wall formation via dityrosine crosslinks [#2]. AAH1 transcription is silenced outside the sexual stages by the AP2XII-2 transcription factor, which recruits HDAC3 and MORC epigenetic machinery to the AAH1 promoter [#3]. The catalytic mechanism, substrate specificity, and structural basis of AAH1 hydroxylase activity have not been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Establishing whether AAH1 functions merely in host dopamine manipulation or has an intrinsic parasite role, knockout genetics showed AAH1 is required for growth even in cells that lack dopamine, defining a function beyond neuromodulation.\",\n      \"evidence\": \"Knockout and complementation genetics with in vitro and in vivo growth assays in Toxoplasma gondii\",\n      \"pmids\": [\"25547791\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The specific growth-relevant metabolite or pathway downstream of AAH1 in nondopaminergic cells was not identified\", \"Single lab, single study\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"To define the biochemical activity and physiological relevance of AAH1, enzyme and dopamine assays confirmed L-DOPA production but showed negligible tachyzoite/bradyzoite expression and no impact on host brain dopamine, decoupling AAH1 from the behavioral-manipulation hypothesis.\",\n      \"evidence\": \"Knockout/complementation genetics, dopamine measurement in vitro and in vivo, and qRT-PCR expression profiling\",\n      \"pmids\": [\"25547791\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The stage in which AAH1 is expressed at functionally relevant levels was not resolved here\", \"Substrate specificity and catalytic mechanism not characterized\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Cat infection experiments located AAH1's predominant role in the sexual cycle, showing that AAH ablation lowers oocyst yield and sporulation and linking L-DOPA production to oocyst wall biogenesis.\",\n      \"evidence\": \"Genetic knockout with cat infection experiments measuring oocyst yield and sporulation rates in Toxoplasma gondii\",\n      \"pmids\": [\"28288194\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The dityrosine-crosslink contribution to oocyst wall formation was inferred rather than directly demonstrated\", \"Relative contributions of AAH1 versus AAH2 not separately resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"To explain the stage-restricted expression of AAH1, chromatin profiling and genetic manipulation placed AAH1 under AP2XII-2 transcriptional repression via recruitment of HDAC3 and MORC, defining the epigenetic circuit that confines AAH1 to sexual stages.\",\n      \"evidence\": \"CUT&Tag chromatin profiling with AP2XII-2 knockdown/complementation and co-association analysis with HDAC3 and MORC in Toxoplasma gondii\",\n      \"pmids\": [\"36786611\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding of AP2XII-2 to the AAH1 promoter versus indirect regulation not fully separated\", \"The activating signal that relieves repression during sexual commitment is unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The catalytic mechanism, structural basis, and cofactor requirements of AAH1 hydroxylase activity, and the direct molecular link between L-DOPA production and oocyst wall dityrosine crosslinking, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of AAH1\", \"No direct biochemical demonstration of dityrosine crosslink formation from AAH1-derived L-DOPA\", \"Growth-essential mechanism in nondopaminergic cells not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004497\", \"supporting_discovery_ids\": [1, 2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006571\", \"supporting_discovery_ids\": [1, 2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0019953\", \"supporting_discovery_ids\": [2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"AP2XII-2 (upstream transcriptional repressor)\", \"HDAC3 (epigenetic silencing via AP2XII-2)\", \"MORC (epigenetic silencing via AP2XII-2)\", \"AAH2 (co-acting aromatic amino acid hydroxylase)\"],\n    \"other_free_text\": [\n      \"AAH1 produces L-DOPA and is essential for parasite growth in nondopaminergic cells, indicating a role independent of host dopamine modulation [#0, #1].\",\n      \"AAH1 activity does not alter global or regional host brain dopamine, and expression is negligible in tachyzoites and bradyzoites [#1].\",\n      \"AAH1 contributes predominantly to the sexual reproductive cycle in the feline definitive host, affecting oocyst yield and sporulation, potentially via dityrosine crosslinks in the oocyst wall [#2].\",\n      \"AAH1 is transcriptionally repressed outside sexual stages by AP2XII-2 recruiting HDAC3 and MORC to its promoter [#3].\"\n    ]\n  },\n  \"strain_conflicts\": []\n}\n```","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_287510","name":"AAH1","product":"aromatic amino acid hydrolase AAH1","uniprot_acc":"S8G872","chromosome":"KE139705","start_pos":807}]}