TipA is a Dictyostelium discoideum protein required for the sorting of the initial prestalk and prespore cell types and for formation of the organizing tip during multicellular development. It is preferentially expressed in prestalk PstO cells after cell-type sorting and acts cell-autonomously at an early developmental stage. Cells lacking TipA fail to sort prestalk cells to the top of the aggregate, do not form a proper tip or migrating slug, express the prestalk-specific gene ecmA at reduced levels, and produce very few spores. The protein is a novel ~83 kDa polypeptide containing a predicted PP2C-like (PPM-type) protein phosphatase domain and a coiled-coil region, but its molecular activity has not been experimentally established. Through its role in tip formation and prestalk cell sorting, TipA is essential for the transition from mound to slug and for subsequent culmination into a fruiting body (sorocarp).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0030587 sorocarp development | HMP PMID:17659086 High-throughput analysis of spatio-temporal dynamics in Dict... | ACCEPT | Summary: A high-throughput time-lapse phenotyping screen of insertional mutants placed tipA among a cluster of mutants defective at the slug and culmination stages of development, consistent with a requirement for tipA in sorocarp (fruiting body) development. This broad process term correctly captures the developmental role of the gene, even though the underlying molecular activity is unknown. Reason: tipA disruption produces a developmental phenotype affecting slug and culmination stages, so involvement in sorocarp development is well supported. The term is general but appropriate as the umbrella developmental process, and this HMP annotation is consistent with the independent IMP evidence from the tipA knockout. Supporting Evidence: PMID:17659086 Particularly noticeable are five mutants disrupted in tagB/C, mutations in tipA, tipB, tipC, and tipD PMID:17659086 Another major mutant cluster contains clones showing defective behavior at the slug and culmination stage, but wild-type behavior during aggregation |
| GO:0005737 cytoplasm | IDA PMID:9169048 Sorting of the initial cell types in Dictyostelium is depend... | UNDECIDED | Summary: Direct-assay (IDA) cytoplasmic localization annotated by dictyBase from the 1997 tipA characterization paper. The cached publication is abstract-only (full text not available), and the abstract does not describe subcellular localization, so the supporting evidence cannot be verified here. Cytoplasmic localization is plausible for this ~83 kDa PP2C-like protein, but the evidence is not verifiable from available material. Reason: The only cited reference is abstract-only in the cache and the abstract does not address subcellular localization. Per policy this experimental curator annotation is not overruled; it is marked UNDECIDED because the supporting evidence cannot be independently verified. |
| GO:0031154 culmination involved in sorocarp development | IMP PMID:9169048 Sorting of the initial cell types in Dictyostelium is depend... | ACCEPT | Summary: Loss of tipA by REMI mutagenesis blocks normal development - mutant cells fail to sort prestalk cells to the top of the aggregate, fail to form slugs, and produce very few spores - placing TipA upstream of the events leading to culmination and fruiting body formation. This IMP annotation from the tipA knockout is well supported by the mutant phenotype. Reason: The developmental arrest of tipA mutants (failure of prestalk sorting, tip formation and slug/fruiting-body formation) supports an acts_upstream_of_or_within relationship to culmination within sorocarp development. This is an experimental IMP annotation supported by the described phenotype and is retained as a core developmental role of the gene. Supporting Evidence: PMID:9169048 This mutant fails to form slugs and appears to have a defect in sorting of prestalk cells. PMID:9169048 The tipA gene appears to play an essential role in the sorting of the initial cell types. |
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