A Phylogenomic Investigation into the Origin of Metazoa
Bibliographic record
Abstract
The evolution of multicellular animals (Metazoa) from their unicellular ancestors was a key transition that was accompanied by the emergence and diversification of gene families associated with multicellularity. To clarify the timing and order of specific events in this transition, we conducted expressed sequence tag surveys on 4 putative protistan relatives of Metazoa including the choanoflagellate Monosiga ovata, the ichthyosporeans Sphaeroforma arctica and Amoebidium parasiticum, and the amoeba Capsaspora owczarzaki, and 2 members of Amoebozoa, Acanthamoeba castellanii and Mastigamoeba balamuthi. We find that homologs of genes involved in metazoan multicellularity exist in several of these unicellular organisms, including 1 encoding a membrane-associated guanylate kinase with an inverted arrangement of protein-protein interaction domains (MAGI) in Capsaspora. In Metazoa, MAGI regulates tight junctions involved in cell-cell communication. By phylogenomic analyses of genes encoded in nuclear and mitochondrial genomes, we show that the choanoflagellates are the closest relatives of the Metazoa, followed by the Capsaspora and Ichthyosporea lineages, although the branching order between the latter 2 groups remains unclear. Understanding the function of "metazoan-specific" proteins we have identified in these protists will clarify the evolutionary steps that led to the emergence of the Metazoa.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".