{"gene":"ACTRT2","run_date":"2026-06-09T22:02:40","timeline":{"discoveries":[{"year":2002,"finding":"ACTRT2 (Arp-T2) is a novel actin-related protein that localizes specifically to the cytoskeletal calyx of the mammalian sperm head (perinuclear theca), is expressed specifically in the testis late in spermatid differentiation, and is a major acidic component of the calyx structure characterized by resistance to high ionic strength and detergents.","method":"Partial amino acid sequencing of calyx preparations from bull spermatozoa; immunoblotting and immunofluorescence microscopy with antibodies raised against human ACTRT2","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein identification by sequencing plus immunolocalization, single lab but two orthogonal methods","pmids":["12243744"],"is_preprint":false},{"year":2022,"finding":"ACTRT2 interacts with ACTRT1, ACTL7A, and ACTL9 to form a multimeric complex that localizes to the subacrosomal region of spermatids and is required for anchoring the developing acrosome to the nucleus; this complex mediates the acrosome-nucleus connection during spermiogenesis.","method":"Co-immunoprecipitation; genetic knockout of Actrt1 in mice; immunofluorescence; Western blotting","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP establishing complex membership, corroborated by in vivo knockout phenotype with defined acrosomal detachment readout","pmids":["35616329"],"is_preprint":false},{"year":2014,"finding":"ACTRT2 localizes to the post-acrosomal region and middle piece of human spermatozoa, and its expression is decreased in obesity-associated asthenozoospermia.","method":"Immunofluorescence, Western blot, and flow cytometry on human sperm samples","journal":"Andrology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct subcellular localization by immunofluorescence confirmed by two orthogonal quantification methods, single lab","pmids":["25293813"],"is_preprint":false},{"year":2025,"finding":"ACTRT2 deficiency in spermatogonia increases vulnerability to ferroptosis: loss of ACTRT2 leads to intracellular iron overload (upregulation of SLC11A2, IREB2, TFRC), mitochondrial damage, upregulation of pro-ferroptotic ACSL4 and ALOX15, and downregulation of anti-ferroptotic SLC7A11 and GPX4, resulting in increased cell death upon busulfan treatment.","method":"In vitro busulfan treatment of GC-1 spermatogonial cells with ACTRT2 knockdown; ACTRT2 knockout and heterozygous mouse models; Western blotting; ROS measurement; electron microscopy of mitochondria","journal":"Molecular human reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined molecular pathway by multiple markers in both in vitro and in vivo systems, single lab","pmids":["40811009"],"is_preprint":false},{"year":2026,"finding":"ACTRT2 physically interacts with ACTRT3 (ARPM1/ACTRT3) as part of a perinuclear theca protein complex in spermatids, as demonstrated by co-immunoprecipitation in the context of ACTRT3 characterization.","method":"Co-immunoprecipitation (co-IP) from mouse testis","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single Co-IP from one lab identifying ACTRT2 as interaction partner of ACTRT3, consistent with prior complex data","pmids":["41668650"],"is_preprint":false},{"year":2025,"finding":"ACTRT2 interacts with ACTRT1 and ACTL7A (and ARPM1/ACTRT3) as part of the perinuclear theca cytoskeletal complex, corroborating its role as a structural component linking acrosome to nucleus.","method":"Co-immunoprecipitation (co-IP) in the context of ARPM1/ACTRT3 knockout mouse characterization","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP from preprint, single lab, finding consistent with peer-reviewed data but not independently confirmed in this study","pmids":["bio_10.1101_2025.03.27.645694"],"is_preprint":true}],"current_model":"ACTRT2 is a testis-specific actin-related protein that is a structural component of the sperm perinuclear theca (calyx/subacrosomal region), where it forms a multimeric complex with ACTRT1, ACTL7A, ACTL9, and ACTRT3 to mediate anchorage of the developing acrosome to the sperm nucleus during spermiogenesis; additionally, in spermatogonia, ACTRT2 protects against ferroptosis by maintaining iron homeostasis and mitochondrial integrity."},"narrative":{"mechanistic_narrative":"ACTRT2 (Arp-T2) is a testis-specific actin-related protein that serves as a structural component of the sperm head perinuclear theca, the cytoskeletal calyx that resists high ionic strength and detergent extraction, where it is a major acidic constituent expressed late in spermatid differentiation [PMID:12243744]. Within the subacrosomal region of developing spermatids, ACTRT2 assembles into a multimeric perinuclear theca complex with ACTRT1, ACTL7A, ACTL9, and ACTRT3 that anchors the developing acrosome to the sperm nucleus during spermiogenesis; loss of complex integrity produces acrosomal detachment [PMID:35616329, PMID:41668650]. In human spermatozoa it localizes to the post-acrosomal region and middle piece, and its expression is reduced in obesity-associated asthenozoospermia [PMID:25293813]. Beyond its structural role, ACTRT2 protects spermatogonia against ferroptosis: its loss drives intracellular iron overload, mitochondrial damage, and a shift in ferroptosis regulators (upregulation of ACSL4 and ALOX15 with downregulation of SLC7A11 and GPX4) that sensitizes cells to busulfan-induced death [PMID:40811009].","teleology":[{"year":2002,"claim":"Established ACTRT2 as a previously unrecognized actin-related protein and a bona fide structural building block of the sperm head, answering where this protein resides and what physical structure it belongs to.","evidence":"Partial amino acid sequencing of bull sperm calyx preparations plus immunoblotting and immunofluorescence with anti-human ACTRT2 antibodies","pmids":["12243744"],"confidence":"Medium","gaps":["No interaction partners within the calyx identified","Molecular function beyond being an acidic structural component not defined","No loss-of-function phenotype tested"]},{"year":2014,"claim":"Mapped ACTRT2 in human spermatozoa and linked its abundance to sperm quality, connecting the structural protein to a clinical phenotype.","evidence":"Immunofluorescence, Western blot, and flow cytometry on human sperm samples including obesity-associated asthenozoospermia","pmids":["25293813"],"confidence":"Medium","gaps":["Correlative association, not causal link to motility defect","Mechanism connecting reduced ACTRT2 to asthenozoospermia unknown"]},{"year":2022,"claim":"Defined the molecular complex and function: ACTRT2 partners with ACTRT1, ACTL7A, and ACTL9 to physically anchor the acrosome to the nucleus, moving from a localized protein to a functional structural module.","evidence":"Reciprocal co-immunoprecipitation, Actrt1 knockout mice, immunofluorescence and Western blotting with acrosomal detachment readout","pmids":["35616329"],"confidence":"High","gaps":["Direct Actrt2 knockout phenotype on acrosome anchoring not shown in this study","Stoichiometry and architecture of the complex unresolved","Mechanism of acrosome-to-nucleus tethering at structural resolution unknown"]},{"year":2025,"claim":"Revealed a second, non-structural role: ACTRT2 protects spermatogonia from ferroptosis by maintaining iron and mitochondrial homeostasis, expanding its function beyond the perinuclear theca.","evidence":"ACTRT2 knockdown in GC-1 spermatogonial cells with busulfan treatment, knockout and heterozygous mouse models, Western blotting, ROS measurement, mitochondrial electron microscopy","pmids":["40811009"],"confidence":"Medium","gaps":["Direct molecular mechanism linking ACTRT2 to iron-regulatory and ferroptosis gene changes not established","Whether the structural ACTRT2 pool or a separate pool mediates this protection unknown","Single lab"]},{"year":2026,"claim":"Extended the perinuclear theca complex membership to include ACTRT3 (ARPM1), reinforcing ACTRT2 as a core node of the cytoskeletal complex.","evidence":"Co-immunoprecipitation from mouse testis in the context of ACTRT3 characterization","pmids":["41668650"],"confidence":"Medium","gaps":["Single Co-IP, directness of ACTRT2-ACTRT3 contact not resolved","Functional consequence of the ACTRT2-ACTRT3 interaction not tested"]},{"year":null,"claim":"How the perinuclear theca complex is biochemically organized and how ACTRT2 reconciles its structural anchoring role with its protective role against ferroptosis remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of the ACTRT2-containing complex","Direct ACTRT2 knockout spermiogenesis phenotype not yet linked to acrosome anchoring","Molecular link between ACTRT2 and iron/ferroptosis regulators not mechanistically defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,2]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[1]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3]}],"complexes":["perinuclear theca (sperm calyx) cytoskeletal complex"],"partners":["ACTRT1","ACTL7A","ACTL9","ACTRT3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8TDY3","full_name":"Actin-related protein T2","aliases":["Actin-related protein M2"],"length_aa":377,"mass_kda":41.7,"function":"","subcellular_location":"Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/Q8TDY3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ACTRT2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ACTRT2","total_profiled":1310},"omim":[{"mim_id":"608535","title":"ACTIN-RELATED PROTEIN T2; ACTRT2","url":"https://www.omim.org/entry/608535"},{"mim_id":"300768","title":"CYLICIN 1; CYLC1","url":"https://www.omim.org/entry/300768"},{"mim_id":"300487","title":"ACTIN-RELATED PROTEIN T1; ACTRT1","url":"https://www.omim.org/entry/300487"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"testis","ntpm":146.1}],"url":"https://www.proteinatlas.org/search/ACTRT2"},"hgnc":{"alias_symbol":["Arp-T2","ARPM2","FLJ25424"],"prev_symbol":[]},"alphafold":{"accession":"Q8TDY3","domains":[{"cath_id":"3.30.420.40","chopping":"5-142_342-376","consensus_level":"medium","plddt":92.7324,"start":5,"end":376},{"cath_id":"3.30.420.40","chopping":"148-185_272-338","consensus_level":"medium","plddt":96.7737,"start":148,"end":338},{"cath_id":"3.90.640.10","chopping":"187-264","consensus_level":"high","plddt":91.7319,"start":187,"end":264}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TDY3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TDY3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TDY3-F1-predicted_aligned_error_v6.png","plddt_mean":93.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ACTRT2","jax_strain_url":"https://www.jax.org/strain/search?query=ACTRT2"},"sequence":{"accession":"Q8TDY3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8TDY3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8TDY3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TDY3"}},"corpus_meta":[{"pmid":"12243744","id":"PMC_12243744","title":"Novel actin-related proteins Arp-T1 and Arp-T2 as components of the cytoskeletal calyx of the mammalian sperm head.","date":"2002","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/12243744","citation_count":60,"is_preprint":false},{"pmid":"25293813","id":"PMC_25293813","title":"Proteomic pattern changes associated with obesity-induced asthenozoospermia.","date":"2014","source":"Andrology","url":"https://pubmed.ncbi.nlm.nih.gov/25293813","citation_count":39,"is_preprint":false},{"pmid":"35616329","id":"PMC_35616329","title":"Loss of perinuclear theca ACTRT1 causes acrosome detachment and severe male subfertility in mice.","date":"2022","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/35616329","citation_count":29,"is_preprint":false},{"pmid":"32787870","id":"PMC_32787870","title":"Effect of transient scrotal hyperthermia on human sperm: an iTRAQ-based proteomic analysis.","date":"2020","source":"Reproductive biology and endocrinology : RB&E","url":"https://pubmed.ncbi.nlm.nih.gov/32787870","citation_count":23,"is_preprint":false},{"pmid":"38414365","id":"PMC_38414365","title":"Deletion of ACTRT1 is associated with male infertility as sperm acrosomal ultrastructural defects and fertilization failure in human.","date":"2024","source":"Human reproduction (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/38414365","citation_count":11,"is_preprint":false},{"pmid":"31122248","id":"PMC_31122248","title":"Exome-wide search and functional annotation of genes associated in patients with severe tick-borne encephalitis in a Russian population.","date":"2019","source":"BMC medical genomics","url":"https://pubmed.ncbi.nlm.nih.gov/31122248","citation_count":6,"is_preprint":false},{"pmid":"35751016","id":"PMC_35751016","title":"Ectopic expression of a combination of 5 genes detects high risk forms of T-cell acute lymphoblastic leukemia.","date":"2022","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/35751016","citation_count":5,"is_preprint":false},{"pmid":"40811009","id":"PMC_40811009","title":"ACTRT2 deficiency increases spermatogonia vulnerability to ferroptosis.","date":"2025","source":"Molecular human reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/40811009","citation_count":2,"is_preprint":false},{"pmid":"38179408","id":"PMC_38179408","title":"Whole genome sequencing reveals population diversity and variation in HIV-1 specific host genes.","date":"2023","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38179408","citation_count":2,"is_preprint":false},{"pmid":"41668650","id":"PMC_41668650","title":"Actin-related protein T3 is required for acrosome biogenesis and sperm function in mice.","date":"2026","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/41668650","citation_count":0,"is_preprint":false},{"pmid":"41610073","id":"PMC_41610073","title":"Methylation-specific, universal, and highly sensitive identification of ctDNA in prostate cancer by multiplex droplet digital PCR.","date":"2026","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/41610073","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.03.27.645694","title":"Actin-related protein M1 (ARPM1) required for acrosome biogenesis and sperm function in mice","date":"2025-04-01","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.27.645694","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8870,"output_tokens":1481,"usd":0.024413,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8181,"output_tokens":2272,"usd":0.048853,"stage2_stop_reason":"end_turn"},"total_usd":0.073266,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"ACTRT2 (Arp-T2) is a novel actin-related protein that localizes specifically to the cytoskeletal calyx of the mammalian sperm head (perinuclear theca), is expressed specifically in the testis late in spermatid differentiation, and is a major acidic component of the calyx structure characterized by resistance to high ionic strength and detergents.\",\n      \"method\": \"Partial amino acid sequencing of calyx preparations from bull spermatozoa; immunoblotting and immunofluorescence microscopy with antibodies raised against human ACTRT2\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein identification by sequencing plus immunolocalization, single lab but two orthogonal methods\",\n      \"pmids\": [\"12243744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ACTRT2 interacts with ACTRT1, ACTL7A, and ACTL9 to form a multimeric complex that localizes to the subacrosomal region of spermatids and is required for anchoring the developing acrosome to the nucleus; this complex mediates the acrosome-nucleus connection during spermiogenesis.\",\n      \"method\": \"Co-immunoprecipitation; genetic knockout of Actrt1 in mice; immunofluorescence; Western blotting\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP establishing complex membership, corroborated by in vivo knockout phenotype with defined acrosomal detachment readout\",\n      \"pmids\": [\"35616329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ACTRT2 localizes to the post-acrosomal region and middle piece of human spermatozoa, and its expression is decreased in obesity-associated asthenozoospermia.\",\n      \"method\": \"Immunofluorescence, Western blot, and flow cytometry on human sperm samples\",\n      \"journal\": \"Andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct subcellular localization by immunofluorescence confirmed by two orthogonal quantification methods, single lab\",\n      \"pmids\": [\"25293813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ACTRT2 deficiency in spermatogonia increases vulnerability to ferroptosis: loss of ACTRT2 leads to intracellular iron overload (upregulation of SLC11A2, IREB2, TFRC), mitochondrial damage, upregulation of pro-ferroptotic ACSL4 and ALOX15, and downregulation of anti-ferroptotic SLC7A11 and GPX4, resulting in increased cell death upon busulfan treatment.\",\n      \"method\": \"In vitro busulfan treatment of GC-1 spermatogonial cells with ACTRT2 knockdown; ACTRT2 knockout and heterozygous mouse models; Western blotting; ROS measurement; electron microscopy of mitochondria\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined molecular pathway by multiple markers in both in vitro and in vivo systems, single lab\",\n      \"pmids\": [\"40811009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"ACTRT2 physically interacts with ACTRT3 (ARPM1/ACTRT3) as part of a perinuclear theca protein complex in spermatids, as demonstrated by co-immunoprecipitation in the context of ACTRT3 characterization.\",\n      \"method\": \"Co-immunoprecipitation (co-IP) from mouse testis\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single Co-IP from one lab identifying ACTRT2 as interaction partner of ACTRT3, consistent with prior complex data\",\n      \"pmids\": [\"41668650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ACTRT2 interacts with ACTRT1 and ACTL7A (and ARPM1/ACTRT3) as part of the perinuclear theca cytoskeletal complex, corroborating its role as a structural component linking acrosome to nucleus.\",\n      \"method\": \"Co-immunoprecipitation (co-IP) in the context of ARPM1/ACTRT3 knockout mouse characterization\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP from preprint, single lab, finding consistent with peer-reviewed data but not independently confirmed in this study\",\n      \"pmids\": [\"bio_10.1101_2025.03.27.645694\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"ACTRT2 is a testis-specific actin-related protein that is a structural component of the sperm perinuclear theca (calyx/subacrosomal region), where it forms a multimeric complex with ACTRT1, ACTL7A, ACTL9, and ACTRT3 to mediate anchorage of the developing acrosome to the sperm nucleus during spermiogenesis; additionally, in spermatogonia, ACTRT2 protects against ferroptosis by maintaining iron homeostasis and mitochondrial integrity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ACTRT2 (Arp-T2) is a testis-specific actin-related protein that serves as a structural component of the sperm head perinuclear theca, the cytoskeletal calyx that resists high ionic strength and detergent extraction, where it is a major acidic constituent expressed late in spermatid differentiation [#0]. Within the subacrosomal region of developing spermatids, ACTRT2 assembles into a multimeric perinuclear theca complex with ACTRT1, ACTL7A, ACTL9, and ACTRT3 that anchors the developing acrosome to the sperm nucleus during spermiogenesis; loss of complex integrity produces acrosomal detachment [#1, #4]. In human spermatozoa it localizes to the post-acrosomal region and middle piece, and its expression is reduced in obesity-associated asthenozoospermia [#2]. Beyond its structural role, ACTRT2 protects spermatogonia against ferroptosis: its loss drives intracellular iron overload, mitochondrial damage, and a shift in ferroptosis regulators (upregulation of ACSL4 and ALOX15 with downregulation of SLC7A11 and GPX4) that sensitizes cells to busulfan-induced death [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established ACTRT2 as a previously unrecognized actin-related protein and a bona fide structural building block of the sperm head, answering where this protein resides and what physical structure it belongs to.\",\n      \"evidence\": \"Partial amino acid sequencing of bull sperm calyx preparations plus immunoblotting and immunofluorescence with anti-human ACTRT2 antibodies\",\n      \"pmids\": [\"12243744\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No interaction partners within the calyx identified\",\n        \"Molecular function beyond being an acidic structural component not defined\",\n        \"No loss-of-function phenotype tested\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Mapped ACTRT2 in human spermatozoa and linked its abundance to sperm quality, connecting the structural protein to a clinical phenotype.\",\n      \"evidence\": \"Immunofluorescence, Western blot, and flow cytometry on human sperm samples including obesity-associated asthenozoospermia\",\n      \"pmids\": [\"25293813\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Correlative association, not causal link to motility defect\",\n        \"Mechanism connecting reduced ACTRT2 to asthenozoospermia unknown\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined the molecular complex and function: ACTRT2 partners with ACTRT1, ACTL7A, and ACTL9 to physically anchor the acrosome to the nucleus, moving from a localized protein to a functional structural module.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, Actrt1 knockout mice, immunofluorescence and Western blotting with acrosomal detachment readout\",\n      \"pmids\": [\"35616329\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct Actrt2 knockout phenotype on acrosome anchoring not shown in this study\",\n        \"Stoichiometry and architecture of the complex unresolved\",\n        \"Mechanism of acrosome-to-nucleus tethering at structural resolution unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed a second, non-structural role: ACTRT2 protects spermatogonia from ferroptosis by maintaining iron and mitochondrial homeostasis, expanding its function beyond the perinuclear theca.\",\n      \"evidence\": \"ACTRT2 knockdown in GC-1 spermatogonial cells with busulfan treatment, knockout and heterozygous mouse models, Western blotting, ROS measurement, mitochondrial electron microscopy\",\n      \"pmids\": [\"40811009\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct molecular mechanism linking ACTRT2 to iron-regulatory and ferroptosis gene changes not established\",\n        \"Whether the structural ACTRT2 pool or a separate pool mediates this protection unknown\",\n        \"Single lab\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended the perinuclear theca complex membership to include ACTRT3 (ARPM1), reinforcing ACTRT2 as a core node of the cytoskeletal complex.\",\n      \"evidence\": \"Co-immunoprecipitation from mouse testis in the context of ACTRT3 characterization\",\n      \"pmids\": [\"41668650\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single Co-IP, directness of ACTRT2-ACTRT3 contact not resolved\",\n        \"Functional consequence of the ACTRT2-ACTRT3 interaction not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the perinuclear theca complex is biochemically organized and how ACTRT2 reconciles its structural anchoring role with its protective role against ferroptosis remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structure of the ACTRT2-containing complex\",\n        \"Direct ACTRT2 knockout spermiogenesis phenotype not yet linked to acrosome anchoring\",\n        \"Molecular link between ACTRT2 and iron/ferroptosis regulators not mechanistically defined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\n      \"perinuclear theca (sperm calyx) cytoskeletal complex\"\n    ],\n    \"partners\": [\n      \"ACTRT1\",\n      \"ACTL7A\",\n      \"ACTL9\",\n      \"ACTRT3\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":4,"faith_total":4,"faith_pct":100.0}}