{"gene":"TG_263220","gene_symbol":"ROP21","run_date":"2026-09-08T14:08:29","timeline":{"discoveries":[{"year":2016,"finding":"ROP21 localizes to the parasitophorous vacuole and cyst matrix, and is not secreted from microneme, rhoptry, or dense granule organelles, but rather is located in small vesicles consistent with a constitutive secretory pathway.","method":"CRISPR/Cas9-engineered C-terminal epitope tagging with localization imaging","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization experiment with epitope-tagged protein in a single lab study","pmids":["27450947"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"Pru"}]},{"year":2016,"finding":"Combined deletion of ROP21 and ROP17 (∆rop21/∆rop17 double knockout) led to a ~50% reduction in tissue cyst burden in vivo, while single ∆rop21 knockout showed normal in vitro growth and bradyzoite differentiation, indicating ROP21 contributes redundantly to cyst burden during chronic infection.","method":"CRISPR/Cas9 gene deletion, in vitro growth assays, in vivo mouse infection cyst quantification","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean KO with defined in vivo phenotypic readout, single lab","pmids":["27450947"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"Pru"}]},{"year":2016,"finding":"Deletion of PVM-associated ROP21 did not abrogate antitumor immunity activated by uracil auxotrophic T. gondii mutants, indicating ROP21 is dispensable for the parasite-driven antitumor immune response.","method":"Targeted gene deletion in Δku80 vaccine strain followed by in vivo antitumor efficacy assay","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean KO with defined immunological phenotype, single lab; finding is negative/dispensability result","pmids":["27447180"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"finding":"ROP21 protein catalyzes the phosphorylation of protein substrates, indicating it functions as an active kinase.","method":"Stated as a property of the protein in the context of vaccine design (no detailed in vitro kinase assay described in abstract)","journal":"Microbial pathogenesis","confidence":"Low","confidence_rationale":"Tier 4 / Weak — asserted without experimental kinase assay detail in the abstract; bioinformatic/annotation-level claim","pmids":["39855488"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"T. gondii ROP21 is a rhoptry-derived pseudokinase/kinase that localizes to the parasitophorous vacuole membrane and cyst matrix via a constitutive vesicular pathway rather than classical secretory organelles; it redundantly contributes (together with ROP17) to tissue cyst burden during chronic infection in vivo, but is dispensable for parasite growth in vitro, bradyzoite differentiation, and parasite-driven antitumor immunity."},"narrative":{"mechanistic_narrative":"ROP21 is a Toxoplasma gondii rhoptry-family protein that localizes to the parasitophorous vacuole and the cyst matrix, reaching these compartments not through classical microneme, rhoptry, or dense granule secretion but via small vesicles consistent with a constitutive secretory pathway [PMID:27450947]. Functionally, ROP21 acts redundantly with ROP17: single deletion leaves in vitro growth and bradyzoite differentiation intact, whereas combined ∆rop21/∆rop17 loss reduces tissue cyst burden by roughly half during chronic infection, implicating ROP21 in the establishment or maintenance of cysts in vivo [PMID:27450947]. ROP21 is dispensable for the antitumor immunity elicited by uracil-auxotrophic T. gondii vaccine strains [PMID:27447180]. Beyond its localization and redundant contribution to cyst burden, no detailed enzymatic mechanism or substrate has been characterized in the available corpus.","teleology":[{"year":2016,"claim":"Establishing where ROP21 goes and how it gets there addressed whether it is a canonical secreted effector; it instead traffics via a non-classical vesicular route to the vacuole and cyst matrix, distinguishing it from typical rhoptry/dense-granule effectors.","evidence":"CRISPR/Cas9 C-terminal epitope tagging and localization imaging in T. gondii Pru","pmids":["27450947"],"confidence":"Medium","gaps":["Trafficking machinery routing ROP21 through the constitutive pathway is unidentified","No molecular partner at the PVM or cyst matrix defined","Single-lab localization in one strain"],"attribution":[{"species":"Toxoplasma gondii","strain":"Pru"}]},{"year":2016,"claim":"Genetic deletion tested whether ROP21 is required for parasite fitness; it is dispensable in vitro and for differentiation but contributes redundantly with ROP17 to in vivo cyst burden, defining a chronic-infection role.","evidence":"CRISPR/Cas9 single and double (∆rop21/∆rop17) knockouts with in vitro growth/differentiation assays and in vivo mouse cyst quantification in T. gondii Pru","pmids":["27450947"],"confidence":"Medium","gaps":["The molecular basis of the redundancy with ROP17 is unknown","Whether ROP21 acts on host or parasite targets during cyst formation is undetermined","Single-lab in vivo readout"],"attribution":[{"species":"Toxoplasma gondii","strain":"Pru"}]},{"year":2016,"claim":"Deletion in a vaccine-strain background tested whether ROP21 is needed for parasite-driven immunotherapy; it is not, showing the antitumor immune response does not depend on this PVM protein.","evidence":"Targeted deletion in Δku80 uracil-auxotroph vaccine strain with in vivo antitumor efficacy assay","pmids":["27447180"],"confidence":"Medium","gaps":["Does not address a role in natural infection immunity","Negative/dispensability result gives no positive function","Strain background not specified beyond Δku80 vaccine strain"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"claim":"The question of ROP21's biochemical activity was addressed by asserting it phosphorylates protein substrates, positioning it as an active kinase rather than a pseudokinase.","evidence":"Property stated in a vaccine-design context without a described in vitro kinase assay","pmids":["39855488"],"confidence":"Low","gaps":["No in vitro kinase assay or substrate identified in the source","Annotation-level claim not backed by direct enzymology","Cannot distinguish active kinase from pseudokinase experimentally"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The direct substrate(s), the trafficking machinery for its constitutive secretion, and the molecular basis of its redundancy with ROP17 remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No validated phosphorylation substrate","No identified receptor/machinery for vesicular delivery to the PVM and cyst matrix","Mechanism of the cyst-burden phenotype uncharacterized"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["ROP17 (FUNCTIONAL REDUNDANCY FOR CYST BURDEN IN VIVO)"],"other_free_text":["Traffics via a constitutive secretory/vesicular pathway rather than microneme, rhoptry, or dense granule secretion [#0]","Dispensable for in vitro growth and bradyzoite differentiation [#1]","Dispensable for antitumor immunity elicited by uracil-auxotroph vaccine strains [#2]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"27447180","id":"PMC_27447180","title":"Secretion of Rhoptry and Dense Granule Effector Proteins by Nonreplicating Toxoplasma gondii Uracil Auxotrophs Controls the Development of Antitumor Immunity.","date":"2016","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27447180","citation_count":47,"is_preprint":false},{"pmid":"29867820","id":"PMC_29867820","title":"Immune Protection of Rhoptry Protein 21 (ROP21) of Toxoplasma gondii as a DNA Vaccine Against Toxoplasmosis.","date":"2018","source":"Frontiers in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/29867820","citation_count":40,"is_preprint":false},{"pmid":"27450947","id":"PMC_27450947","title":"Secreted protein kinases regulate cyst burden during chronic toxoplasmosis.","date":"2016","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/27450947","citation_count":25,"is_preprint":false},{"pmid":"37519638","id":"PMC_37519638","title":"Bioinformatics-based prediction and screening of immunogenic epitopes of Toxoplasma gondii rhoptry proteins 7, 21 and 22 as candidate vaccine target.","date":"2023","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/37519638","citation_count":9,"is_preprint":false},{"pmid":"39855488","id":"PMC_39855488","title":"Immunogenicity of an in-silico designed multi-epitope DNA vaccine encoding ROP21 and ROP29 of Toxoplasma gondii against both acute and chronic toxoplasmosis in BALB/c mice.","date":"2025","source":"Microbial pathogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/39855488","citation_count":8,"is_preprint":false},{"pmid":"38844693","id":"PMC_38844693","title":"Rapid genotyping of Toxoplasma gondii isolates via Nanopore-based multi-locus sequencing.","date":"2024","source":"AMB Express","url":"https://pubmed.ncbi.nlm.nih.gov/38844693","citation_count":5,"is_preprint":false},{"pmid":"26672223","id":"PMC_26672223","title":"[Cloning and Bioinformatics Analysis of Toxoplasma gondii ROP21 Gene].","date":"2015","source":"Zhongguo ji sheng chong xue yu ji sheng chong bing za zhi = Chinese journal of parasitology & parasitic diseases","url":"https://pubmed.ncbi.nlm.nih.gov/26672223","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6027,"output_tokens":997,"usd":0.016518,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5900,"output_tokens":2184,"usd":0.04205,"stage2_stop_reason":"end_turn"},"total_usd":0.058568,"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\": 2016,\n      \"finding\": \"ROP21 localizes to the parasitophorous vacuole and cyst matrix, and is not secreted from microneme, rhoptry, or dense granule organelles, but rather is located in small vesicles consistent with a constitutive secretory pathway.\",\n      \"method\": \"CRISPR/Cas9-engineered C-terminal epitope tagging with localization imaging\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization experiment with epitope-tagged protein in a single lab study\",\n      \"pmids\": [\"27450947\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Combined deletion of ROP21 and ROP17 (∆rop21/∆rop17 double knockout) led to a ~50% reduction in tissue cyst burden in vivo, while single ∆rop21 knockout showed normal in vitro growth and bradyzoite differentiation, indicating ROP21 contributes redundantly to cyst burden during chronic infection.\",\n      \"method\": \"CRISPR/Cas9 gene deletion, in vitro growth assays, in vivo mouse infection cyst quantification\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean KO with defined in vivo phenotypic readout, single lab\",\n      \"pmids\": [\"27450947\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Deletion of PVM-associated ROP21 did not abrogate antitumor immunity activated by uracil auxotrophic T. gondii mutants, indicating ROP21 is dispensable for the parasite-driven antitumor immune response.\",\n      \"method\": \"Targeted gene deletion in Δku80 vaccine strain followed by in vivo antitumor efficacy assay\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean KO with defined immunological phenotype, single lab; finding is negative/dispensability result\",\n      \"pmids\": [\"27447180\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ROP21 protein catalyzes the phosphorylation of protein substrates, indicating it functions as an active kinase.\",\n      \"method\": \"Stated as a property of the protein in the context of vaccine design (no detailed in vitro kinase assay described in abstract)\",\n      \"journal\": \"Microbial pathogenesis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — asserted without experimental kinase assay detail in the abstract; bioinformatic/annotation-level claim\",\n      \"pmids\": [\"39855488\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"T. gondii ROP21 is a rhoptry-derived pseudokinase/kinase that localizes to the parasitophorous vacuole membrane and cyst matrix via a constitutive vesicular pathway rather than classical secretory organelles; it redundantly contributes (together with ROP17) to tissue cyst burden during chronic infection in vivo, but is dispensable for parasite growth in vitro, bradyzoite differentiation, and parasite-driven antitumor immunity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ROP21 is a Toxoplasma gondii rhoptry-family protein that localizes to the parasitophorous vacuole and the cyst matrix, reaching these compartments not through classical microneme, rhoptry, or dense granule secretion but via small vesicles consistent with a constitutive secretory pathway [#0]. Functionally, ROP21 acts redundantly with ROP17: single deletion leaves in vitro growth and bradyzoite differentiation intact, whereas combined \\u2206rop21/\\u2206rop17 loss reduces tissue cyst burden by roughly half during chronic infection, implicating ROP21 in the establishment or maintenance of cysts in vivo [#1]. ROP21 is dispensable for the antitumor immunity elicited by uracil-auxotrophic T. gondii vaccine strains [#2]. Beyond its localization and redundant contribution to cyst burden, no detailed enzymatic mechanism or substrate has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Establishing where ROP21 goes and how it gets there addressed whether it is a canonical secreted effector; it instead traffics via a non-classical vesicular route to the vacuole and cyst matrix, distinguishing it from typical rhoptry/dense-granule effectors.\",\n      \"evidence\": \"CRISPR/Cas9 C-terminal epitope tagging and localization imaging in T. gondii Pru\",\n      \"pmids\": [\"27450947\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking machinery routing ROP21 through the constitutive pathway is unidentified\", \"No molecular partner at the PVM or cyst matrix defined\", \"Single-lab localization in one strain\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Genetic deletion tested whether ROP21 is required for parasite fitness; it is dispensable in vitro and for differentiation but contributes redundantly with ROP17 to in vivo cyst burden, defining a chronic-infection role.\",\n      \"evidence\": \"CRISPR/Cas9 single and double (\\u2206rop21/\\u2206rop17) knockouts with in vitro growth/differentiation assays and in vivo mouse cyst quantification in T. gondii Pru\",\n      \"pmids\": [\"27450947\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The molecular basis of the redundancy with ROP17 is unknown\", \"Whether ROP21 acts on host or parasite targets during cyst formation is undetermined\", \"Single-lab in vivo readout\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Deletion in a vaccine-strain background tested whether ROP21 is needed for parasite-driven immunotherapy; it is not, showing the antitumor immune response does not depend on this PVM protein.\",\n      \"evidence\": \"Targeted deletion in \\u0394ku80 uracil-auxotroph vaccine strain with in vivo antitumor efficacy assay\",\n      \"pmids\": [\"27447180\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address a role in natural infection immunity\", \"Negative/dispensability result gives no positive function\", \"Strain background not specified beyond \\u0394ku80 vaccine strain\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The question of ROP21's biochemical activity was addressed by asserting it phosphorylates protein substrates, positioning it as an active kinase rather than a pseudokinase.\",\n      \"evidence\": \"Property stated in a vaccine-design context without a described in vitro kinase assay\",\n      \"pmids\": [\"39855488\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No in vitro kinase assay or substrate identified in the source\", \"Annotation-level claim not backed by direct enzymology\", \"Cannot distinguish active kinase from pseudokinase experimentally\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct substrate(s), the trafficking machinery for its constitutive secretion, and the molecular basis of its redundancy with ROP17 remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No validated phosphorylation substrate\", \"No identified receptor/machinery for vesicular delivery to the PVM and cyst matrix\", \"Mechanism of the cyst-burden phenotype uncharacterized\"],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004672\", \"supporting_discovery_ids\": [3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020005\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]},\n      {\"term_id\": \"GO:0016192\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0051701\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Pru\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ROP17 (functional redundancy for cyst burden in vivo)\"],\n    \"other_free_text\": [\n      \"Traffics via a constitutive secretory/vesicular pathway rather than microneme, rhoptry, or dense granule secretion [#0]\",\n      \"Dispensable for in vitro growth and bradyzoite differentiation [#1]\",\n      \"Dispensable for antitumor immunity elicited by uracil-auxotroph vaccine strains [#2]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_263220","name":"ROP21","product":"rhoptry kinase family protein ROP21","uniprot_acc":"S8F4V1","chromosome":"TGME49_chrVIIb","start_pos":698964},{"strain":"GT1","gene_id":"TGGT1_263220","name":null,"product":"rhoptry kinase family protein ROP21","uniprot_acc":null,"chromosome":"TGGT1_chrVIIb","start_pos":673016},{"strain":"RH88","gene_id":"TGRH88_067800","name":null,"product":"rhoptry kinase family protein ROP21","uniprot_acc":null,"chromosome":"CM023089","start_pos":712261},{"strain":"VEG","gene_id":"TGVEG_263220","name":null,"product":"rhoptry kinase family protein ROP21","uniprot_acc":"V4YUJ7","chromosome":"TGVEG_chrVIIb","start_pos":704069}]}