The expression of Steroidogenic Factor-1 and its role in bovine steroidogenic ovarian cells during the estrus cycle and first trimester of pregnancy

MiR-214-3p promotes proliferation and inhibits estradiol synthesis in porcine granulosa cells

Background

Granulosa cells (GCs) proliferation and estradiol synthesis significantly affect follicular development. The miR-214-3p expression in the ovarian tissues of high-yielding sows is higher than that in low-yielding sows, indicating that miR-214-3p may be involved in sow fertility. However, the functions and mechanisms of miR-214-3p on GCs are unclear. This study focuses on miR-214-3p in terms of the effects on GCs proliferation and estradiol synthesis.

Results

Our findings revealed that miR-214-3p promotes proliferation and inhibits estradiol synthesis in porcine GCs. MiR-214-3p can increase the percentage of S-phase cells, the number of EdU labeled positive cells, and cell viability. However, E₂ concentration was reduced after miR-214-3p agomir treatment. We also found that miR-214-3p up-regulates the expression of cell cycle genes including cell cycle protein B (Cyclin B), cell cycle protein D (Cyclin D), cell cycle protein E (Cyclin E), and cyclin-dependent kinase 4 (CDK4) at the transcription and translation levels, but down-regulates the mRNA and protein levels of cytochrome P450 family 11 subfamily A member 1 (CYP11A1), cytochrome P450 family 19 subfamily A member 1 (CYP19A1), and steroidogenic acute regulatory protein (StAR) (i.e., the key enzymes in estradiol synthesis). On-line prediction, bioinformatics analysis, a luciferase reporter assay, RT-qPCR, and Western blot results showed that the target genes of miR-214-3p in proliferation and estradiol synthesis are Mfn2 and NR5A1, respectively.

Conclusions

Our findings suggest that miR-214-3p plays an important role in the functional regulation of porcine GCs and therefore may be a target gene for regulating follicular development.

Nuclear receptor Ftz-f1 promotes follicle maturation and ovulation partly via bHLH/PAS transcription factor Sim

The NR5A-family nuclear receptors are highly conserved and function within the somatic follicle cells of the ovary to regulate folliculogenesis and ovulation in mammals; however, their roles in Drosophila ovaries are largely unknown. Here, we discover that Ftz-f1, one of the NR5A nuclear receptors in Drosophila, is transiently induced in follicle cells in late stages of oogenesis via ecdysteroid signaling. Genetic disruption of Ftz-f1 expression prevents follicle cell differentiation into the final maturation stage, which leads to anovulation. In addition, we demonstrate that the bHLH/PAS transcription factor Single-minded (Sim) acts as a direct target of Ftz-f1 to promote follicle cell differentiation/maturation and that Ftz-f1’s role in regulating Sim expression and follicle cell differentiation can be replaced by its mouse homolog steroidogenic factor 1 (mSF-1). Our work provides new insight into the regulation of follicle maturation in Drosophila and the conserved role of NR5A nuclear receptors in regulating folliculogenesis and ovulation.

When animals reproduce, females release eggs from their ovaries which then get fertilized by sperm from males. Each egg needs to properly mature within a collection of cells known as follicle cells before it can be let go. As the egg matures, so do the follicle cells surrounding it, until both are primed and ready to discharge the egg from the ovary. Mammals rely on a protein called SF-1 to mature their follicle cells, but it is unclear how this process works.

Most animals – from humans to fruit flies – release their eggs in a very similar way, using many of the same proteins and genes. For example, the gene for SF-1 in mammals is similar to a gene in fruit flies which codes for another protein called Ftz-f1. Since it is more straightforward to study ovaries in fruit flies than in humans and other mammals, investigating this protein could shed light on how follicle cells mature. However, it remained unclear whether Ftz-f1 plays a similar role to its mammalian counterpart.

Here, Knapp et al. show that Ftz-f1 is present in the follicle cells of fruit flies and is required for them to properly mature. Ftz-f1 controlled this process by regulating the activity of another protein called Sim. Further experiments found that the gene that codes for the SF-1 protein in mice was able to compensate for the loss of Ftz-f1 and drive follicle cells to mature.

Studying how ovaries release eggs is an essential part of understanding female fertility. This work highlights the similarities between these processes in mammals and fruit flies and may help us understand how ovaries work in humans and other mammals. In the future, the findings of Knapp et al. may lead to new therapies for infertility in females and other disorders that affect ovaries.

The Orphan Nuclear Receptors Steroidogenic Factor-1 and Liver Receptor Homolog-1: Structure, Regulation, and Essential Roles in Mammalian Reproduction

Nuclear receptors are intracellular proteins that act as transcription factors. Proteins with classic nuclear receptor domain structure lacking identified signaling ligands are designated orphan nuclear receptors. Two of these, steroidogenic factor-1 (NR5A1, also known as SF-1) and liver receptor homolog-1 (NR5A2, also known as LRH-1), bind to the same DNA sequences, with different and nonoverlapping effects on targets. Endogenous regulation of both is achieved predominantly by cofactor interactions. SF-1 is expressed primarily in steroidogenic tissues, LRH-1 in tissues of endodermal origin and the gonads. Both receptors modulate cholesterol homeostasis, steroidogenesis, tissue-specific cell proliferation, and stem cell pluripotency. LRH-1 is essential for development beyond gastrulation and SF-1 for genesis of the adrenal, sexual differentiation, and Leydig cell function. Ovary-specific depletion of SF-1 disrupts follicle development, while LRH-1 depletion prevents ovulation, cumulus expansion, and luteinization. Uterine depletion of LRH-1 compromises decidualization and pregnancy. In humans, SF-1 is present in endometriotic tissue, where it regulates estrogen synthesis. SF-1 is underexpressed in ovarian cancer cells and overexpressed in Leydig cell tumors. In breast cancer cells, proliferation, migration and invasion, and chemotherapy resistance are regulated by LRH-1. In conclusion, the NR5A orphan nuclear receptors are nonredundant factors that are crucial regulators of a panoply of biological processes, across multiple reproductive tissues.

Do chlorinated insecticides (aldrin and DDT) or products of their transformations (dieldrin and DDE) impair signal transfer from regulators (oxytocin and relaxin) of bovine myometrium motility in vitro?

Aldrin, dieldrin, and DDT are chlorinated insecticides that are unintentionally widespread in the environment. It was previously shown that all of the aforementioned compounds increased secretion of ovarian oxytocin (OT), which is a potent uterotonic agent. However, only DDT and its metabolite (DDE) promoted, while aldrin and dieldrin inhibited basal and OT-stimulated myometrial contractions in cows. Therefore, the aim of this study was to determine the effect of these treatments on the reception and further transmission of the OT-signal for myometrial contractions and on the levels of contractile-associated integral proteins (caveolin; CAV) and gap junction proteins (GAPs). Moreover, their effect on reception of signal for the relaxation of myometrium was also studied. Myometrial strips or cells from non-pregnant (8-12 days of oestrous cycle) or late pregnant (5-8 months) cows were incubated with the studied compounds at environmentally relevant dose (10 ng/ml), which was chosen according to the previous studies. DDT and DDE increased the CAV protein level, while dieldrin decreased the GAPs level. None of the studied compounds affected mRNA expression of the OT receptor and expression of the second messengers (DAG, IP3, PKC, MLCK). Oppositely, DDE and dieldrin decreased mRNA expression of the relaxin (RLX) receptor. Changes in the amount of contractile-associated integral proteins may be involved in the molecular mechanism underlying the adverse effects of the studied insecticides on myometrial motility. Admittedly, none of the studied compounds impaired the reception or further intracellular transmission of the OT signal to promote contractions during the oestrous cycle, while they showed potential to impair the transmission the signal between cells as well as to diminish the effects of one of the primary inhibitor (RLX) of myometrial contractions during gestation.

Sexually Dimorphic Expression of Foxl2 and Ftz-F1 in Chinese Giant Salamander Andrias Davidianus

Foxl2 and FTZ-F1 play a crucial role in the regulation of gonad development in fish and mammals, but studies of their function in amphibians are scarce. We isolated the full length of Foxl2 (adFoxl2) and Ftz-F1 (adFtz-f1) cDNA from the Chinese giant salamander Andrias davidianus and quantified its expression in various tissues and developing gonads. The adFoxl2 gene encodes 301aa including a conserved forkhead box, and the adFtz-f1 gene encodes 467aa containing an Ftz-F1 box. The amino acid sequences showed high homology with other amphibians. adFoxl2 expression was high in ovary, whereas adFtz-f1 was higher in testis, moderate in pituitary, ovary, and kidney; and low in the remaining tested tissues. Expression of adFoxl2 gradually increased from 1Y to 5Y in ovary, whereas adFtz-f1 expression gradually decreased in testis. In addition, adFoxl2 and adFtz-f1 were detected in granulosa cell in ovary and in spermatocytes in testis. The adFoxl2 transcription was inhibited in brain and ovary after treatment with methyltestosterone and with letrozole, whereas adFtz-f1 expression was upregulated. High-temperature suppressed the expression of adFxl2 in ovary and enhanced the transcription of adFtz-f1. These results suggest that adFoxl2 functioned in ovary differentiation, whereas adFtz-f1 played a role in testis development, which lays a foundation for study of the sex differentiation mechanism in A. davidianus.

Comparative transcriptome analysis reveals early pregnancy-specific genes expressed in peripheral blood of pregnant sows

Early and accurate diagnosis of pregnancy is important for effective management of an economical pig farm. Besides the currently available methods used in early diagnosis of sows, circulating nucleic acids in peripheral blood may contain some early pregnancy-specific molecular markers. For the first time, microarray analysis of peripheral blood from pregnant sows versus non-pregnant sows identified 127 up-regulated and 56 down-regulated genes at day 14 post-insemination. Gene Ontology annotation grouped the total differently expressed genes into 3 significantly enriched terms, cell surface receptor linked signal transduction, G-protein coupled receptor protein signaling pathway and regulation of vesicle-mediated transport. Signaling pathway analysis revealed the only one significantly changed pathway was arachidonic acid metabolism. Of the differently expressed genes, nine (including LPAR3, RXFP4, GALP, CBR1, CBR2, GPX6, USP18, LHB and NR5A1) were found to exert function related to early pregnancy processes. This study provides a clue that differentially abundant RNAs in maternal peripheral blood can help to identify the molecular markers of early pregnancy in pigs.