Rac1 is dispensable for oocyte maturation and female fertility in vivo

Genetic Abnormalities of Oocyte Maturation: Mechanisms and Clinical Implications

Genetic anomalies in oocyte maturation present significant fertility and embryonic development challenges. This review explores the intricate mechanisms of nuclear and cytoplasmic maturation, emphasizing the genetic and molecular factors contributing to oocyte quality and competence. Chromosomal mutations, errors in segregation, genetic mutations in signaling pathways and meiosis-related genes, and epigenetic alterations are discussed as critical contributors to oocyte maturation defects. The role of mitochondrial defects, maternal mRNA dysregulation, and critical proteins such as NLRP14 and BMP6 are highlighted. Understanding these genetic factors is crucial for improving diagnostic approaches and therapeutic interventions in reproductive medicine, particularly for couples encountering recurrent in vitro fertilization failures. This review will explore how specific genetic mutations impact fertility treatments and reproductive success by examining the intricate oocyte maturation process. We will focus on genetic abnormalities that may disrupt the oocyte maturation pathway, discussing the underlying mechanisms involved and considering their potential clinical implications for enhancing fertility outcomes.

Integration of GWAS and transcriptomic analyses reveal candidate genes for duck gonadal development during puberty onset

BACKGROUND

Puberty onset signifies the beginning of sexual maturation and reproductive phase in poultry indeed, and plays an essential role in genetics and breeding. Studying gonadal development is one of the important approaches to exploring the genetic mechanism of puberty onset.

RESULT

In our study, the phenotype data of the testes and ovaries of the 120-day-old Nonghua duck showed a large coefficient of variation, indicating that their gonads were in different developmental states. The CNV-based GWAS results for 358 Nonghua ducks showed two deleted-type CNVRs were associated with testicular weight (TW) and testicular percentage (TP), namely CNVR492 (Chr2: 59473501-59478500 bp) and CNVR494 (Chr2: 59514001-59517000 bp). Additionally, two both-type CNVRs were associated with ovarian weight (OW) and ovarian percentage (OP), namely CNVR557 (Chr2: 99951001-99956500 bp) and CNVR891 (Chr7: 39115001-39122500 bp). RNA-seq analysis showed 6228 and 1070 differentially expressed genes (DEGs) related to the TW and OW. These DEGs were mainly enriched in the MAPK signaling pathway, cytokine-cytokine receptor interaction, and focal adhesion, which were reported to affect gonadal development. Further, by joint analysis of CNV-based GWAS and RNA-seq data, 3 genes, including LOC106019197, CDH19 (LOC101793040), and TYW5 were identified as potential candidate genes for TW and OW. LOC106019197 and CDH19 were down-regulated in the heavier-testes group (> 5 g), while TYW5 was also down-regulated in the heavier-ovaries group (> 3 g). The qRT-PCR revealed that LOC106019197 and CDH19 exhibited higher expression levels in the wild/CN0 and CN0/CN0 genotypes compared to the wild/wild genotype. TYW5 showed the highest expression level in the wild/CN0 genotype and the lowest in the CN2/CN2 genotype. In addition, the expression levels of LOC106019197 and CDH19 were significantly higher at 0w than at 8w and 24w.

CONCLUSION

Our results revealed that LOC106019197 and CDH19 may act as inhibitors of duck testicular development. TYW5 may play a role in delaying ovarian development. These findings provide new insights into the mechanism of puberty onset in ducks.

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.

The paralogs' enigma of germ-cell specific genes dispensable for fertility: the case of 19 oogenesin genes†

Gene knockout experiments have shown that many genes are dispensable for a given biological function. In this review, we make an assessment of male and female germ cell-specific genes dispensable for the function of reproduction in mice, the inactivation of which does not affect fertility. In particular, we describe the deletion of a 1 Mb block containing nineteen paralogous genes of the oogenesin/Pramel family specifically expressed in female and/or male germ cells, which has no consequences in both sexes. We discuss this notion of dispensability and the experiments that need to be carried out to definitively conclude that a gene is dispensable for a function.

The effects of H22 tumor on the quality of oocytes and the development of early embryos from host mice: A single-cell RNA sequencing approach

The association between cancer and female reproduction remains largely unknown. Here we investigated the quality of oocytes and the developmental potential of zygotes using H22 tumor-bearing mice model. The results showed that the number of oocytes was decreased in tumor-bearing mice compared with the control mice, and accompanied scattered chromosomes was observed. Further study revealed an abnormal epigenetic reprogramming occurred in the zygotes from the H22 tumor-bearing mice, as exemplified by the aberrant 5hmC/5mC modifications in the pronuclei. Finally, single-cell RNA sequencing was performed on the oocytes collected from the H22 tumor-bearing mice. Our data showed that 45 of the 202 differentially expressed genes in tumor-bearing group were closely associated with oocyte quality. Protein interaction analysis indicated that the potential interaction among these 45 genes. Collectively, our study uncovered that the quality of oocytes and early embryonic development were affected by H22 tumor bearing via the altered expression patterns of genes related with reproduction, providing new insights into the reproductive capability of female cancer patients.

"Biomechanical Signaling in Oocytes and Parthenogenetic Cells"

Oocyte-specific competence remains one of the major targets of current research in the field of reproduction. Several mechanisms are involved in meiotic maturation and the molecular signature of an oocyte is considered to reflect its quality and to predict its subsequent developmental and functional capabilities. In the present minireview, we focus on the possible role of mechanotransduction and mechanosensor signaling pathways, namely the Hippo and the RhoGTPase, in the maturing oocyte. Due to the limited access to female gametes, we propose the use of cells isolated from parthenogenetic embryos as a promising model to characterize and dissect the oocyte distinctive molecular signatures, given their exclusive maternal origin. The brief overview here reported suggests a role of the mechanosensing related pathways in oocyte quality and developmental competence and supports the use of uniparental cells as a useful tool for oocyte molecular signature characterization.