Effects of RAC1 on Proliferation of Hen Ovarian Prehierarchical Follicle Granulosa Cells

Single-cell transcriptomic analysis reveals regulative mechanisms of follicular selection and atresia in chicken granulosa cells

Eggs are an important food source for people. Follicle selection and atresia are the two directions of pre-hierarchical follicles that affect egg production in chickens. Granulosa cells (GCs), the vital somatic cells in follicles, determine the fate of follicles. In this study, single-cell RNA sequencing was performed on the GC layers from five follicular stages (small white follicles, atretic small white follicles, small yellow follicles, atretic small yellow follicles, and F6) to map the cellular differentiation trajectories and explore the follicle fate-determining genes. The results showed that GCs were genetically heterogeneous and could be divided into four subtypes, and the presence of GCs-Ⅲ with a steroid-producing capacity in unselected small follicles is a novel finding that differs from conventional wisdom. In addition, degenerated GCs were annotated for the first time, and GC degeneration was found to be significantly related to lipid metabolism disorders. Many candidate switch genes had been marked out, among which the overexpression of transforming growth factor-beta 2 (TGFB2) and insulin like growth factor binding protein 5 (IGFBP5) could inhibit the proliferation and differentiation of GCs and induce their degeneration. This study provided new insights into the regulatory mechanisms of follicle selection and atresia, which have significant value for improving egg production and prolonging the laying period of laying hens.

The inhibition roles of RAB23 gene in granulosa cell proliferation and progesterone synthesis of hen ovarian prehierarchical follicles

1. The proliferation of granulosa cells is vital for the development and recruitment of hen ovarian prehierarchical follicles (PF). The RAB23 protein is a member of the Rab family, belonging to the GTPase family. This study studied the regulatory roles of the RAB23 gene in PF.2. The expression of RAB23 was significantly increased in granulosa cells (GC) during PF growth and was highest in GC at 6-8 mm diameter (p < 0.05). The RAB23 protein was mainly expressed in the GC, oocytes (OC) as well as somatic cells (SC) of the PF.3. The mRNA expression of FSHR, CCND1,CYP11A1, StAR and HSD3B1 was significantly increased in the siRNA RAB23 group (p < 0.05). Additionally, protein expression of FSHR, CCND1, CYP11A1, HSD3B1 was significantly increased (p < 0.05) after GC were transfected with RAB23-specific siRNA. Protein expression of StAR in the siRNA RAB23 group was numerically higher than that in the positive control (PC) and negative control (NC) groups. The GC proliferation rate and progesterone synthesis of the prehierarchical follicles in hen ovaries were markedly increased in vitro (p < 0.05).4.This study revealed that RAB23 might play an inhibitory role in GC proliferation and progesterone synthesis during the prehierarchical follicles development in vitro.

Integrated transcriptomic analysis on chicken ovary reveals CYP21A1 affects follicle granulosa cell development and steroid hormone synthesis

Egg production is an economically important trait in poultry breeding and production. Follicular development was regulated by several hormones released and genes expressed in the granulosa cells, impacting the egg production and fecundity of hens. However, the molecular functions of these candidate genes that modulate these processes remain largely unknown. In the present study, bioinformatics analyses were performed to identify the candidate genes related to egg production in the ovarian tissue of White Leghorns with high egg production and Beijing You chicken with low egg production during sexual maturity and peak laying periods. The ovarian granulosa cells were used to assess the function of CYP21A1 by transfecting with CYP21A1-specific small interfering RNAs (siRNAs) and overexpression plasmids. We identified 514 differentially expressed genes (|Log2(fold change) | >1, P <0.05) between the 2 chicken breeds in both laying periods. Among these genes, CYP21A1, which is involved in the steroid hormone biosynthesis pathway was consistently upregulated in White Leghorns. Weighted gene co-expression network analysis (WGCNA) further suggested that CYP21A1 was a hub gene, which could positively respond to treatment with follicle stimulation hormone (FSH), affecting egg production. The interference of CYP21A1 significantly inhibited cell proliferation and promoted cell apoptosis. Overexpression of CYP21A1 promotes cell proliferation and inhibits cell apoptosis. Furthermore, the interference with CYP21A1 significantly downregulated the expression of STAR, CYP11A1, HSD3B1, and FSHR and also decreased the synthesis of progesterone (P4) and estradiol (E2) in granulosa cells. Overexpression of CYP21A1 increased the synthesis of P4 and estradiol E2 and the expression of steroid hormone synthesis-related genes in granulosa cells. Our findings provide new evidence for the biological role of CYP21A1 on granulosa cell proliferation, apoptosis, and steroid hormone synthesis, which lays the theoretical basis for improving egg production.

NET1 is a critical regulator of spindle assembly and actin dynamics in mouse oocytes

BACKGROUND

Neuroepithelial transforming gene 1 (NET1) is a RhoA subfamily guanine nucleotide exchange factor that governs a wide array of biological processes. However, its roles in meiotic oocyte remain unclear. We herein demonstrated that the NET1-HACE1-RAC1 pathway mediates meiotic defects in the progression of oocyte maturation.

METHODS

NET1 was reduced using a specific small interfering RNA in mouse oocytes. Spindle assembly, chromosomal alignment, the actin cap, and chromosomal spreads were visualized by immunostaining and analyzed under confocal microscopy. We also applied mass spectroscopy, and western blot analysis for this investigation.

RESULTS

Our results revealed that NET1 was localized to the nucleus at the GV stage, and that after GVBD, NET1 was localized to the cytoplasm and predominantly distributed around the chromosomes, commensurate with meiotic progression. NET1 resided in the cytoplasm and significantly accumulated on the spindle at the MI and MII stages. Mouse oocytes depleted of Net1 exhibited aberrant first polar body extrusion and asymmetric division defects. We also determined that Net1 depletion resulted in reduced RAC1 protein expression in mouse oocytes, and that NET1 protected RAC1 from degradation by HACE1, and it was essential for actin dynamics and meiotic spindle formation. Importantly, exogenous RAC1 expression in Net1-depleted oocytes significantly rescued these defects.

CONCLUSIONS

Our results suggest that NET1 exhibits multiple roles in spindle stability and actin dynamics during mouse oocyte meiosis.

Characterization of ovarian follicles, serum steroid hormone concentration and steroidogenic gene expression profiles in the developing ovarian follicles in White King pigeons

Paired pigeons only lay 2 eggs in a laying period, which is closely related to ovarian follicle development, but this process is not well understood. In this study, 60 pairs of 12-mo-old White King pigeons were selected and serum and follicles were collected at 4 stages of laying interval (LI), including the first (LI1), the third (LI3), the fifth (LI5), and the seventh day (LI7). Morphological results showed that paired pigeons normally had 2 preovulatory follicles and the second-largest follicle (F2) developed from LI3 and had been selected in LI5. Prehierarchical follicles were coupled and hierarchical, which was in accordance with its clutch size. The P₄ concentration increased gradually from LI1 to LI5, reaching a maximum of 30.67 ng/mL in LI5 and decreasing to 27.83 ng/mL in LI7 (P < 0.05). The levels of T in LI1 and LI5 were higher than LI3 and LI7 (P < 0.05), although there was no significant difference in E₂ in LI (P > 0.05), but it stayed at high levels. In the TCs of the largest follicle (F1), HSD3B1 mRNA and HSD17B1 mRNA levels peaked in LI7. The expression pattern of CYP17A1 and CYP19A1 was similar, increasing from LI3 to LI5 and then decreasing. In the TCs of F2, the expressions of HSD3B1 and CYP17A1 had no significant difference between LI5 and LI7 (P > 0.05), while the expression pattern of HSD17B1 and CYP19A1 was the opposite. In TCs of SF1, HSD3B1 mRNA level peaked in LI3 while CYP19A1 mRNA levels peaked in LI7. The expression of CYP17A1 had a minor change (P > 0.05) and the expression pattern of HSD17B1 was similar to F1. It was concluded that the morphological characteristics of follicles during the LI for the first time, including the number and diameter of small follicles (SFs) and hierarchical follicles in pigeon and the concentrations of steroid hormones and expressions of steroidogenic genes in TCs of different follicles could explain the growth and selection of 2 preovulatory follicles. This study facilitates further research into the regulation of ovulation and egg production in pigeons.

Unveiling Key Biomarkers and Therapeutic Drugs in Polycystic Ovary Syndrome (PCOS) Through Pathway Enrichment Analysis and Hub Gene-miRNA Networks

Background

Polycystic ovary syndrome (PCOS) affects women of reproductive age globally with an incidence rate of 5% - 26%. Growing evidence reports important roles for microRNAs (miRNAs) in the pathophysiology of granulosa cells (GCs) in PCOS.

Objectives

The objectives of this study were to identify the top differentially expressed miRNAs (DE-miRNAs) and their corresponding targets in hub gene-miRNA networks, as well as identify novel DE-miRNAs by analyzing three distinct microarray datasets. Additionally, functional enrichment analysis was performed using bioinformatics approaches. Finally, interactions between the 5 top-ranked hub genes and drugs were investigated.

Methods

Using bioinformatics approaches, three GC profiles from the gene expression omnibus (GEO), namely gene expression omnibus series (GSE)-34526, GSE114419, and GSE137684, were analyzed. Targets of the top DE-miRNAs were predicted using the multiMiR R package, and only miRNAs with validated results were retrieved. Genes that were common between the "DE-miRNA prediction results" and the "existing tissue DE-mRNAs" were designated as differentially expressed genes (DEGs). Gene ontology (GO) and pathway enrichment analyses were implemented for DEGs. In order to identify hub genes and hub DE-miRNAs, the protein-protein interaction (PPI) network and miRNA-mRNA interaction network were constructed using Cytoscape software. The drug-gene interaction database (DGIdb) database was utilized to identify interactions between the top-ranked hub genes and drugs.

Results

Out of the top 20 DE-miRNAs that were retrieved from the GSE114419 and GSE34526 microarray datasets, only 13 of them had "validated results" through the multiMiR prediction method. Among the 13 DE-miRNAs investigated, only 5, namely hsa-miR-8085, hsa-miR-548w, hsa-miR-612, hsa-miR-1470, and hsa-miR-644a, demonstrated interactions with the 10 hub genes in the hub gene-miRNA networks in our study. Except for hsa-miR-612, the other 4 DE-miRNAs, including hsa-miR-8085, hsa-miR-548w, hsa-miR-1470, and hsa-miR-644a, are novel and had not been reported in PCOS pathogenesis before. Also, GO and pathway enrichment analyses identified "pathogenic E. coli infection" in the Kyoto encyclopedia of genes and genomes (KEGG) and "regulation of Rac1 activity" in FunRich as the top pathways. The drug-hub gene interaction network identified ACTB, JUN, PTEN, KRAS, and MAPK1 as potential targets to treat PCOS with therapeutic drugs.

Conclusions

The findings from this study might assist researchers in uncovering new biomarkers and potential therapeutic drug targets in PCOS treatment.

Grade follicles transcriptional profiling analysis in different laying stages in chicken

During follicular development, a series of key events such as follicular recruitment and selection are crucially governed by strict complex regulation. However, its molecular mechanisms remain obscure. To identify the dominant genes controlling chicken follicular development, the small white follicle (SWF), the small yellow follicle (SYF), and the large yellow follicle (LYF) in different laying stages (W22, W31, W51) were collected for RNA sequencing and bioinformatics analysis. There were 1866, 1211, and 1515 differentially expressed genes (DEGs) between SWF and SYF in W22, W31, and W51, respectively. 4021, 2295, and 2902 DEGs were respectively identified between SYF and LYF in W22, W31, and W51. 5618, 4016, and 4809 DEGs were respectively identified between SWF and LYF in W22, W31, and W51. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that extracellular matrix, extracellular region, extracellular region part, ECM-receptor interaction, collagen extracellular matrix, and collagen trimer were significantly enriched (P < 0.05). Protein–protein interaction analysis revealed that COL4A2, COL1A2, COL4A1, COL5A2, COL12A1, ELN, ALB, and MMP10 might be key candidate genes for follicular development in chicken. The current study identified dominant genes and pathways contributing to our understanding of chicken follicular development. 

Novel insights into the regulation of LATS2 kinase in prehierarchical follicle development via the Hippo pathway in hen ovary

The large tumor suppressor homolog 2 (LATS2), one of the central regulators of the Hippo/MST signaling pathway, plays an inhibitory role in ovarian function and different organ development and growth in mammals. However, the exact roles and molecular regulatory mechanisms of LATS2 in chicken granulosa cell (GC) proliferation, differentiation, and steroidogenesis required for ovarian follicle growth, development, and follicular selection remain poorly understood. This study demonstrated that the LATS2 protein was predominantly localized in the oocytes and undifferentiated GCs of various-sized prehierarchical follicles of the hen ovary. Expression levels of LATS2 mRNA were significantly higher in the smaller follicles (from 1 mm to 5.9 mm in diameter) and the GCs than in the larger follicles (6–6.9 mm in diameter up to F1). Moreover, we found that high levels of LATS2 suppressed the GC proliferation and the mRNA and protein expression of the genes serving as the biomarkers of follicle selection, GC differentiation, and steroidogenesis in the GCs, including FSHR, STAR, CYP11A1, ESR1, and ESR2. Interestingly, the LATS2 significantly downregulated SAV1 and YAP1 transcripts but upregulated the expression of STK3, STK4, TEAD1, and TEAD3 mRNA. Our study provided evidences that STK3/4-LATS2-YAP1 not only acts as a suppressor of cell proliferation and follicle selection but also LATS2 may serve as an enhancer in cell proliferation and follicle selection through the YAP1-LATS2 and the LATS2-STK3/4 feedback loops by promoting the expression of TEAD1/3 but inhibiting the expression of SAV1 transcripts in the prehierarchical follicle development of hen ovary. Taken together, the present study initially revealed the pivotal role and molecular mechanism of LATS2 in the regulation of hen prehierarchical follicle development by controlling GC proliferation, differentiation, steroidogenesis, and follicle selection via the Hippo/MST signaling pathway.

MERTK-Mediated LC3-Associated Phagocytosis (LAP) of Apoptotic Substrates in Blood-Separated Tissues: Retina, Testis, Ovarian Follicles

Timely and efficient elimination of apoptotic substrates, continuously produced during one’s lifespan, is a vital need for all tissues of the body. This task is achieved by cells endowed with phagocytic activity. In blood-separated tissues such as the retina, the testis and the ovaries, the resident cells of epithelial origin as retinal pigmented epithelial cells (RPE), testis Sertoli cells and ovarian granulosa cells (GC) provide phagocytic cleaning of apoptotic cells and cell membranes. Disruption of this process leads to functional ablation as blindness in the retina and compromised fertility in males and females. To ensure the efficient elimination of apoptotic substrates, RPE, Sertoli cells and GC combine various mechanisms allowing maintenance of tissue homeostasis and avoiding acute inflammation, tissue disorganization and functional ablation. In tight cooperation with other phagocytosis receptors, MERTK—a member of the TAM family of receptor tyrosine kinases (RTK)—plays a pivotal role in apoptotic substrate cleaning from the retina, the testis and the ovaries through unconventional autophagy-assisted phagocytosis process LAP (LC3-associated phagocytosis). In this review, we focus on the interplay between TAM RTKs, autophagy-related proteins, LAP, and Toll-like receptors (TLR), as well as the regulatory mechanisms allowing these components to sustain tissue homeostasis and prevent functional ablation of the retina, the testis and the ovaries.