Pattern of Ovarian Gene Expression and Estrous Cyclicity in Mouse Lacking Nr5a2 in Granulosa Cells of Antral Follicles.
Bibliographic record
Abstract
The orphan nuclear receptor Nr5a2, also known as liver receptor homolog-1, has been shown to regulate several reproductive events in mice, including ovulation, luteinization and female fertility. Depletion of Nr5a2 specifically in granulosa cells of antral follicles using transgenic mice caused the formation of a non-functional luteal-like structure, low progesterone synthesis, irregular mating frequency, anovulation and infertility. Our objectives were to establish whether the above-mentioned female mice present normal estrous cyclicity, and to determine the basis of the failure in progesterone levels by gene expression analysis of the ovaries. We generated granulosa-specific knockout mice by crossing Nr5a2-floxed and cytochrome P450 aromatase (Cyp19) Cre mice (cKO, genotype: Nr5a2f/f; tgCyp19Cre/+). A group of cKO adult females (n=5) and the not-knockout littermates (CON; n=5) were evaluated daily by vaginal cytology to determine the phase of the estrous cycle. The cKO females presented normal cycles with a length of 4 to 5 days, in accordance to the pattern showed by the control group. Females were then housed with reproductively proven males, examined for copulatory plugs and euthanized 5.5 days post-coitum. Estradiol measurement in follicular fluid and in serum showed that there is no difference of levels between cKO and CON females. It was shown in a published study that excising Nr5a2 in granulosa cells of small follicles results in an abnormal prolonged estrus phase, due to reduced levels of nitric oxide synthase Nos3 mRNA, leading to increased intrafollicular estradiol levels. There was no difference in Nos3 mRNA abundance between the cKO and CON mice. By comparing cKO and CON levels we show that progesterone synthesis is affected by the lack of Nr5a2 through the downregulation of the steroidogenic acute regulatory protein, StAR (p<0.01), and scavenger receptor B 1, Scarb1 (p<0.01), but not of the cytochrome P450 side-chain cleavage, Cyp11a1 or Cyp19a1. This indicates that Nr5a2 is important for the regulation of the cholesterol transport genes, but not for the genes involved in cholesterol transformation during steroidogenesis in our conditional knockout mouse model. Moreover, the vascular endothelial growth factor A, Vegfa, an angiogenesis gene, showed a downregulation (p<0.05) in ovaries lacking Nr5a2 in granulosa cells of antral follicles, while Vegfb was not affected. The matrix metalloproteinase 2, Mmp2, a gene related to tissue remodeling, is upregulated (p<0.05) in cKO ovaries when compared to CON ovaries. In conclusion, the absence of Nr5a2 in antral follicles, does not impair normal estrous cyclicity nor reduce intrafollicular and serum levels of estradiol. We conclude that the transport of cholesterol into the cells and into the mitochondria appears to be the limiting factor for the functionality of the luteal-like structures found in the cKO ovaries. Further, Nr5a2 regulates different categories of genes, including steroidogenic, angiogenic and remodeling genes. Supported by CIHR Operating Grant OGP 11018. KB is supported by FQRNT PBEEE.
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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) | 0.002 | 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".