Amphioxus: Beginning of Vertebrate and End of Invertebrate Type GnRH Receptor Lineage
Bibliographic record
Abstract
In vertebrates, activation of the GnRH receptor is necessary to initiate the reproductive cascade. However, little is known about the characteristics of GnRH receptors before the vertebrates evolved. Recently genome sequencing was completed for amphioxus, Branchiostoma floridae. To understand the GnRH receptors (GnRHR) from this most basal chordate, which is also classified as an invertebrate, we cloned and characterized four GnRHR cDNAs encoded in the amphioxus genome. We found that incubation of GnRH1 (mammalian GnRH) and GnRH2 (chicken GnRH II) with COS7 cells heterologously expressing the amphioxus GnRHRs caused potent intracellular inositol phosphate turnover in two of the receptors. One of the two receptors displayed a clear preference for GnRH1 over GnRH2, a characteristic not previously seen outside the type I mammalian GnRHRs. Phylogenetic analysis grouped the four receptors into two paralogous pairs, with one pair grouping basally with the vertebrate GnRH receptors and the other grouping with the octopus GnRHR-like sequence and the related receptor for insect adipokinetic hormone. Pharmacological studies showed that octopus GnRH-like peptide and adipokinetic hormone induced potent inositol phosphate turnover in one of these other two amphioxus receptors. These data demonstrate the functional conservation of two distinct types of GnRH receptors at the base of chordates. We propose that one receptor type led to vertebrate GnRHRs, whereas the other type, related to the mollusk GnRHR-like receptor, was lost in the vertebrate lineage. This is the first report to suggest that distinct invertebrate and vertebrate GnRHRs are present simultaneously in a basal chordate, amphioxus.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 0.000 |
| 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) | 0.002 | 0.001 |
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".