Phylogenetic Comparisons Implicate Sex Hormone-Binding Globulin in “Masculinization” of the Female Spotted Hyena (Crocuta crocuta)
Bibliographic record
Abstract
Exposures to sex steroids during fetal development are thought to contribute to the unique urogenital anatomy and social dominance of the female spotted hyena: overt phenotypes not shared by other hyenids (i.e. striped hyena, brown hyena, and aardwolf). Because both androgens and estrogens influence development of genitalia and behavior, and because plasma SHBG regulates their access to tissues, we compared the Shbg gene sequences, structures, and steroid-binding properties in the four extant hyenids. We found the hyenid Shbg genes (>95% identical) and mature protein sequences (98% identical) are highly conserved. As in other mammals, the hyenid SHBG all bind 5α-dihydrotestosterone with high affinity (K(d) = 0.62-1.47 nm), but they also bind estrone and dehydroepiandrosterone with similarly high affinity, and this unusual property was attributed to specific amino acids within their SHBG steroid-binding sites. Phylogenetic comparisons also indicated that the spotted hyena SHBG precursor uniquely lacks two leucine residues and has a L15W substitution within its secretion signal polypeptide, the reduced size and hydrophobicity of which markedly decreases the production of SHBG and may therefore explain why serum SHBG concentrations in male and female spotted hyenas are approximately five times lower than in other hyenids. This is important because low plasma SHBG concentrations in spotted hyenas will increase exposure to biologically active androgens and estrogen as well as to their precursors (dehydroepiandrosterone and estrone), which may contribute to the masculinized external genitalia of female spotted hyenas and to female social dominance over males.
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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 | 0.000 |
| 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) | 0.001 | 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".