MicroRNA Mediating Networks in Granulosa Cells Associated with Ovarian Follicular Development

Multiomic meta-analysis suggests a correlation between steroid hormone-related genes and litter size in goats

Litter size is a key indicator of production performance in livestock. However, its genetic basis in goats remains poorly understood. In this work, a genome-wide selection sweep analysis (GWSA) on 100 published goat genomes with different litter rates was performed for the first time to identify candidate genes related to kidding rate. This analysis was combined with the public RNA-sequencing data of ovary tissues (follicular phase) from high- and low-yielding goats. A total of 2278 genes were identified by GWSA. Most of these genes were enriched in signaling pathways related to ovarian follicle development and hormone secretion. Moreover, 208 differentially expressed genes between groups were obtained from the ovaries of goats with different litter sizes. These genes were substantially enriched in the cholesterol and steroid synthesis signaling pathways. Meanwhile, the weighted gene co-expression network was used to perform modular analysis of differentially expressed genes. The results showed that seven modules were reconstructed, of which one module showed a very strong correlation with litter size (r = -0.51 and p-value <0.001). There were 51 genes in this module, and 39 hub genes were screened by Pearson's correlation coefficient between core genes > 0.4, correlation coefficient between module members > 0.80 and intra-module connectivity ≥5. Finally, based on the results of GWSA and hub gene Venn analysis, seven key genes (ACSS2, HECW2, KDR, LHCGR, NAMPT, PTGFR and TFPI) were found to be associated with steroid synthesis and follicle growth development. This work contributes to understanding of the genetic basis of goat litter size and provides theoretical support for goat molecular breeding.

Granulosa Cells-Related MicroRNAs in Ovarian Diseases: Mechanism, Facts and Perspectives

MicroRNAs (miRNAs) are a class of short single-stranded, noncoding RNAs that affect the translation of mRNAs by imperfectly binding to homologous 3'UTRs. Research on miRNAs in ovarian diseases is constantly expanding because miRNAs are powerful regulators of gene expression and cellular processes and are promising biomarkers. miRNA mimics, miRNA inhibitors and molecules targeting miRNAs (antimiRs) have shown promise as novel therapeutic agents in preclinical development. Granulosa cells (GCs) are supporting cells for developing oocytes in the ovary. GCs regulate female reproductive health by producing sex hormones and LH receptors. Increasing research has reported the relevance of miRNAs in GC pathophysiology. With in-depth studies of disease mechanisms, there are an increasing number of studies on the biomolecular pathways of miRNAs in gynecology and endocrinology. In the present review, we summarize the different functions of GC-related microRNAs in various ovarian disorders, such as polycystic ovary syndrome, premature ovarian insufficiency, premature ovarian failure and ovarian granulosa cell tumors.

gga-miR-449b-5p Regulates Steroid Hormone Synthesis in Laying Hen Ovarian Granulosa Cells by Targeting the IGF2BP3 Gene

MiRNAs have been found to be involved in the regulation of ovarian function as important post-transcriptional regulators, including regulators of follicular development, steroidogenesis, cell atresia, and even the development of ovarian cancer. In this study, we evaluated the regulatory role of gga-miR-449b-5p in follicular growth and steroid synthesis in ovarian granulosa cells (GCs) of laying hens through qRT-PCR, ELISAs, western blotting and dual-luciferase reporter assays, which have been described in our previous study. We demonstrated that gga-miR-449b-5p was widely expressed in granulosa and theca layers of the different-sized follicles, especially in the granulosa layer. The gga-miR-449b-5p had no significant effect on the proliferation of GCs, but could significantly regulate the expression of key steroidogenesis-related genes (StAR and CYP19A1) (p < 0.01) and the secretion of P4 and E2 (p < 0.01 and p < 0.05). Further research showed that gga-miR-449b-5p could target IGF2BP3 and downregulate the mRNA and protein expression of IGF2BP3 (p < 0.05). Therefore, this study suggests that gga-miR-449b-5p is a potent regulator of the synthesis of steroid hormones in GCs by targeting the expression of IGF2BP3 and may contribute to a better understanding of the role of functional miRNAs in laying hen ovarian development.

Plasma extracellular vesicle miRNAs as potential biomarkers of superstimulatory response in cattle

The ability to predict superstimulatory response would be a beneficial tool in assisted reproduction. Using small RNAseq technology, we profiled extracellular vesicle microRNA (EV-miRNA) abundance in the blood plasma of heifers exhibiting variable responses to superstimulation. Estrous synchronized crossbred beef heifers (n = 25) were superstimulated and blood samples were collected from each heifer on Day 7 of consecutive unstimulated (U) and superstimulated (S) cycles. A subset of high (H) and low (L) responders was selected depending on their response to superstimulation and EV-miRNA profiles were analysed at both time-points in each heifer. Approximately 200 known miRNAs were detected in each sample with 144 commonly detected in all samples. A total of 12 and 14 miRNAs were dysregulated in UH vs. UL and in SH vs. SL heifers, respectively. Interestingly, miR-206 and miR-6517 exhibited the same differential expression pattern in H compared to L heifers both before and after superstimulation. Pathway analysis indicated that circadian rhythm and signaling pathways were among the top pathways enriched with genes targeted by dysregulated miRNAs in H vs. L responding heifers. In conclusion, heifers with divergent ovarian responses exhibited differential expression of plasma EV-miRNAs which may be used as a potential biomarker to predict superstimulation response.

Supraphysiological Concentrations of Bisphenol A Alter the Expression of Extracellular Vesicle-Enriched miRNAs From Human Primary Granulosa Cells

Bisphenol A (BPA) is a widely used chemical that has been detected in follicular fluid and associated with adverse reproductive effects. Granulosa cells have an important role in follicular growth and oocyte maturation, however, little is known about the biological mechanisms of BPA toxicity on human granulosa cells. In this study, we exposed primary granulosa cells to different concentrations of BPA (0, 20, 200, 2000, and 20 000 ng/ml) and used quantitative polymerase chain reaction to measure the expression levels of miRNAs enriched in extracellular vesicles (EV-enriched miRNAs), and cellular levels of selected target genes of differentially expressed EV-enriched miRNAs. We found that exposure to 20 000 ng/ml BPA was associated with decreased levels of EV-miR-27b-3p (FC = 0.58, p = .04) and increased levels of its biologically relevant target genes FADD (FC = 1.22, p = .01), IGF1 (FC = 1.59, p = .06), and PPARG (FC = 1.73, p = .001) as compared with the control. In addition, we observed that under the same exposure conditions, the expression levels of miR-27b-3p in granulosa cells were also downregulated (FC = 0.65, p = .03) as compared with the control. Our findings suggest that both cellular and extracellular changes in gene expression may mediate BPA toxicity in granulosa cells.

MicroRNAs regulate granulosa cells apoptosis and follicular development - A review

Objective

MicroRNAs (miRNAs) are the most abundant small RNAs. Approximately 2,000 annotated miRNAs genes have been found to be differentially expressed in ovarian follicles during the follicular development (FD). Many miRNAs exert their regulatory effects on the apoptosis of follicular granulosa cells (FGCs) and FD. However, accurate roles and mechanism of miRNAs regulating apoptosis of FGCs remain undetermined.

Methods

In this review, we summarized the regulatory role of each miRNA or miRNA cluster on FGCs apoptosis and FD on the bases of 41 academic articles retrieved from PubMed and web of science and other databases.

Results

Total of 30 miRNAs and 4 miRNAs clusters in 41 articles were reviewed and summarized in the present article. Twenty nine documents indicated explicitly that 24 miRNAs and miRNAs clusters in 29 articles promoted or induced FGCs apoptosis through their distinctive target genes. The remaining 10 miRNAs and miRNAs of 12 articles inhibited FGCs apoptosis. MiRNAs exerted modulation actions by at least 77 signal pathways during FGCs apoptosis and FD.

Conclusion

We concluded that miRNAs or miRNAs clusters could modulate the apoptosis of GCs (including follicular GCs, mural GCs and cumulus cells) by targeting their specific genes. A great majority of miRNAs show a promoting role on apoptosis of FGCs in mammals. But the accurate mechanism of miRNAs and miRNA clusters has not been well understood. It is necessary to ascertain clearly the role and mechanism of each miRNA or miRNA cluster in the future. Understanding precise functions and mechanisms of miRNAs in FGCs apoptosis and FD will be beneficial in developing new diagnostic and treatment strategies for treating infertility and ovarian diseases in humans and animals.

MiR-26a promotes apoptosis of porcine granulosa cells by targeting the 3β-hydroxysteroid-Δ24-reductase gene

Objective

Apoptosis of ovarian granulosa cells (GCs) affects mammalian follicular development and fecundity. This study aimed to explore the regulatory relationship between microRNA-26a (miR-26a) and the 3β-hydroxysteroid-Δ24-reductase gene (DHCR24) gene in porcine follicular granular cells (pGCs), and to provide empirical data for the development of methods to improve the reproductive capacity of pigs.

Methods

The pGCs were transfected with miR-26a mimic, miR-26a inhibitor and DHCR24-siRNA in vitro. The cell apoptosis rate of pGCs was detected by the flow cytometry. The secretion levels of estradiol (E2) and progesterone (P) in pGCs were detected by enzyme-linked immunosorbent assay. Double luciferase validation system was used to detect the binding sites between miR-26a and DHCR24 3′-UTR region. Qualitative real-time polymerase chain reaction and Western blotting were used to verify the DHCR24 mRNA and protein expression in pGCs, respectively, after transfecting with miR-26a mimic and miR-26a inhibitor.

Results

Results showed that enhancement of miR-26a promoted apoptosis, and inhibited E2 and P secretion in pGCs. Meanwhile, inhibition of DHCR24 also upregulated the Caspase-3 expression, reduced the BCL-2 expression, promoted pGCs apoptosis, and inhibited E2 and P secretion in pGCs. There were the binding sites of miR-26a located within DHCR24 3′-UTR. Up-regulation of miR-26a inhibited DHCR24 mRNA and protein expression in pGCs.

Conclusion

This study demonstrates that miR-26a can promote cell apoptosis and inhibit E2 and P secretion by inhibiting the expression of DHCR24 in pGCs.

RNA-seq Transcriptome Analysis in Ovarian Tissue of Pelibuey Breed to Explore the Regulation of Prolificacy

The Pelibuey sheep (Ovis aries) is an indigenous breed distributed in the tropical regions of Mexico. The prolificacy of this sheep is on average from 1 to 1.5 lambs, being an important breeding characteristic that owners seek to increase with the purpose of economic improvements. New-generation RNA sequencing technology has been used to identify the genes that are expressed in the ovarian tissue of sheep that have two or more lambs per parturition, as well as to elucidate the metabolic pathways that are affected by the expression of these genes, with the purpose of better understanding the prolificacy in the sheep. In the present study, the transcriptional expression of multiparous and uniparous sheep was compared using RNA sequencing. Multiparous (M group) and uniparous (U group) sheep that had a genealogical record for three generations (M, n = 5 and U, n = 5) were selected. RNA was extracted from ovarian tissue and subsequently used to prepare the libraries that were sequenced using the Illumina NextSeq500 platform. A total of 31,575 genes were detected from the transcriptomic analysis of which 4908 were significantly expressed (p-value ≤ 0.001) in the ovary of sheep. Subsequently, a second filter was carried out to evaluate the false discovery rate (FDR) and select those genes with p-values ≤ 0.05 and values of expression ≥ 1 (log2), obtaining 354 differential expressed genes (DEG): 120 genes up-regulated and 234 genes down-regulated in the group M with respect to the group U. Through Gene Ontology (GO) and metabolic analysis, we obtained information on the function of differentially expressed genes, and its importance in the reproduction of multiparous sheep. This result suggest that genes identified in the present study participate in the development of the final stages of follicles.

Non-coding RNA regulation in reproduction: Their potential use as biomarkers

Non-coding RNAs (ncRNAs) are crucial regulatory elements in most biological processes and reproduction is also controlled by them. The different types of ncRNAs, as well as the high complexity of these regulatory pathways, present a complex scenario; however, recent studies have shed some light on these questions, discovering the regulatory function of specific ncRNAs on concrete reproductive biology processes. This mini review will focus on the role of ncRNAs in spermatogenesis and oogenesis, and their potential use as biomarkers for reproductive diseases or for reproduction success.

Emerging roles for nucleoporins in reproductive cellular physiology 1

Nucleoporins are a specialized subset of nuclear proteins that comprise the nuclear pore complex and regulate nucleocytoplasmic transport. Recent demonstrations of roles for individual nucleoporins in multiple paradigms of differentiation via mechanisms independent of nuclear trafficking represent conceptual advances in understanding the contributions of nucleoporins to cellular development. Among these, a functional role for nucleoporins in reproductive fitness and gametogenesis has been identified, supported by robust models and clinical studies that leverage the power of next generation sequencing technology to identify reproductive-disease-associated mutations in specific nucleoporins. Proper nucleoporin function manifests in different ways during oogenesis and spermatogenesis. However, nonhuman models of gametogenesis may not recapitulate human mechanisms, which may confound translational interpretation and relevance. To circumvent these limitations, identification of reproductive pathologies in patients, combined with next generation sequencing approaches and advanced in silico tools, offers a powerful approach to investigate the potential function of nucleoporins in human reproduction. Ultimately, elucidating the role of nucleoporins in reproductive biology will provide opportunities for predictive, diagnostic, and therapeutic strategies to address reproductive disorders.