Miro1 regulates mitochondrial homeostasis and meiotic resumption of mouse oocyte

Editing the growth differentiation factor 9 gene affects porcine oocytes in vitro maturation by inactivating the maturation promoting factor

Growth differentiation factor 9 (GDF9), an oocyte-secreted factor, plays a vital role in porcine oocyte development. However, its function during oocyte in vitro maturation (IVM) remains unclear. In this study, we achieved GDF9 editing in approximately 59 % of cultured oocytes by cytoplasmic injection of a pre-assembled crRNA-tracrRNA-Cas9 ribonucleoprotein complex into porcine oocytes at the germinal vesicle (GV) stage. GDF9 editing caused significant damage to porcine oocytes during IVM. Additionally, GDF9 editing impaired mitochondrial function, increased reactive oxygen species (ROS) accumulation, and decreased glutathione (GSH) levels. The impaired IVM of GDF9-edited porcine oocytes was primarily driven by active cAMP-PKA signaling, which inhibited MOS expression, leading to the activation of the WEE1B/MYT1 kinase and inactivation of CDC25B phosphatase. This cascade resulted in the inactivation of CDK1, thereby preventing the activation of maturation-promoting factor (MPF) and inhibiting first polar body (PB1) extrusion. Our findings enhance the understanding of GDF9's regulatory role in porcine oocyte IVM and provide a theoretical foundation for improving porcine reproductive performance.

miRNA-125a regulates porcine oocyte maturation in vitro by targeting ADAR

Follicular fluid extracellular vesicles are beneficial for in vitro oocyte maturation and development; however, their effect on the expression profiles of oocyte microRNAs (miRNAs) and the roles of related miRNAs are unknown. In this study, we aimed to investigate miRNA expression in mature oocytes cultured in follicular fluid extracellular vesicles and the effect of miRNA-125a (miR-125a) on oocyte maturation. The expression profiles of the miRNAs were determined by microRNA sequencing, followed by target gene prediction analysis. We transfected miR-125a mimics and an miR-125a inhibitor to evaluate the effect of modulated miRNA-125a on cumulus expansion, oocyte maturation rate, changes in cytoplasmic maturation-related indicators, and changes in the expression of oocyte maturation-related, cumulus expansion-related, and predicted target genes. We found that miR-125a overexpression decreased the levels of cumulus expansion-related, oocyte maturation-related, and predicted target genes, adenosine deaminase RNA specific (ADAR), and lipid droplet number, and it increased the percentage of oocytes with abnormal cortical granule distribution. Inhibiting miR-125a increased the expression levels of oocyte maturation-related and target genes, number of lipid droplets, and endoplasmic reticulum function, and it decreased lipid droplet size. Mitochondrial membrane potential and reactive oxygen species levels were not significantly different between groups. In conclusion, our results suggest that extracellular vesicles may improve oocyte quality by modulating ADAR through regulating miR-125a.

In Vivo-Matured Oocyte Resists Post-Ovulatory Aging through the Hub Genes DDX18 and DNAJC7 in Pigs

Assisted reproduction technology (ART) procedures are often impacted by post-ovulatory aging (POA), which can lead to reduced fertilization rates and impaired embryo development. This study used RNA sequencing analysis and experimental validation to study the similarities and differences between in vivo- and vitro-matured porcine oocytes before and after POA. Differentially expressed genes (DEGs) between fresh in vivo-matured oocyte (F_vivo) and aged in vivo-matured oocyte (A_vivo) and DEGs between fresh in vitro-matured oocyte (F_vitro) and aged in vitro-matured oocyte (A_vitro) were intersected to explore the co-effects of POA. It was found that "organelles", especially "mitochondria", were significantly enriched Gene Ontology (GO) terms. The expression of genes related to the "electron transport chain" and "cell redox homeostasis" pathways related to mitochondrial function significantly showed low expression patterns in both A_vivo and A_vitro groups. Weighted correlation network analysis was carried out to explore gene expression modules specific to A_vivo. Trait-module association analysis showed that the red modules were most associated with in vivo aging. There are 959 genes in the red module, mainly enriched in "RNA binding", "mRNA metabolic process", etc., as well as in GO terms, and "spliceosome" and "nucleotide excision repair" pathways. DNAJC7, IK, and DDX18 were at the hub of the gene regulatory network. Subsequently, the functions of DDX18 and DNAJC7 were verified by knocking down their expression at the germinal vesicle (GV) and Metaphase II (MII) stages, respectively. Knockdown at the GV stage caused cell cycle disorders and increase the rate of abnormal spindle. Knockdown at the MII stage resulted in the inefficiency of the antioxidant melatonin, increasing the level of intracellular oxidative stress, and in mitochondrial dysfunction. In summary, POA affects the organelle function of oocytes. A_vivo oocytes have some unique gene expression patterns. These genes may be potential anti-aging targets. This study provides a better understanding of the detailed mechanism of POA and potential strategies for improving the success rates of assisted reproductive technologies in pigs and other mammalian species.

Implication of Rac1 GTPase in molecular and cellular mitochondrial functions

Rac1 is a member of the Rho GTPase family which plays major roles in cell mobility, polarity and migration, as a fundamental regulator of actin cytoskeleton. Signal transduction by Rac1 occurs through interaction with multiple effector proteins, and its activity is regulated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). The small protein is mainly anchored to the inner side of the plasma membrane but it can be found in endocellular compartments, notably endosomes and cell nuclei. The protein localizes also into mitochondria where it contributes to the regulation of mitochondrial dynamics, including both mitobiogenesis and mitophagy, in addition to signaling processes via different protein partners, such as the proapoptotic protein Bcl-2 and chaperone sigma-1 receptor (σ-1R). The mitochondrial form of Rac1 (mtRac1) has been understudied thus far, but it is as essential as the nuclear or plasma membrane forms, via its implication in regulation of oxidative stress and DNA damages. Rac1 is subject to diverse post-translational modifications, notably to a geranylgeranylation which contributes importantly to its mitochondrial import and its anchorage to mitochondrial membranes. In addition, Rac1 contributes to the mitochondrial translocation of other proteins, such as p53. The mitochondrial localization and functions of Rac1 are discussed here, notably in the context of human diseases such as cancers. Inhibitors of Rac1 have been identified (NSC-23766, EHT-1864) and some are being developed for the treatment of cancer (MBQ-167) or central nervous system diseases (JK-50561). Their effects on mtRac1 warrant further investigations. An overview of mtRac1 is provided here.

NAMPT regulates mitochondria function and lipid metabolism during porcine oocyte maturation

Oocyte maturation defect can lead to maternal reproduction disorder. NAMPT is a rate-limiting enzyme in mammalian NAD+ biosynthesis pathway, which can regulate a variety of cellular metabolic processes including glucose metabolism and DNA damage repair. However, the function of NAMPT in porcine oocytes remains unknown. In this study, we showed that NAMPT involved into multiple cellular events during oocyte maturation. NAMPT expressed during all stages of porcine oocyte meiosis, and inhibition of NAMPT activity caused the cumulus expansion and polar body extrusion defects. Mitochondrial dysfunction was observed in NAMPT-deficient porcine oocytes, which showed decreased membrane potential, ATP and mitochondrial DNA content, increased oxidative stress level and apoptosis. We also found that NAMPT was essential for spindle organization and chromosome arrangement based on Ac-tubulin. Moreover, lack of NAMPT activity caused the increase of lipid droplet and affected the imbalance of lipogenesis and lipolysis. In conclusion, our study indicated that lack of NAMPT activity affected porcine oocyte maturation through its effects on mitochondria function, spindle assembly and lipid metabolism.

Melatonin improves the quality of rotenone-exposed mouse oocytes through association with histone modifications

Rotenone, an insecticide that inhibits mitochondrial complex I and generates oxidative stress, is responsible for neurological disorders and affects the female reproductive system. However, the underlying mechanism is not fully understood. Melatonin, a potential free-radical scavenger, has been shown to protect the reproductive system from oxidative damage. In this study, we investigated the impact of rotenone on mouse oocyte quality and evaluated the protective effect of melatonin on oocytes exposed to rotenone. Our results showed that rotenone impaired mouse oocyte maturation and early embryo cleavage. However, melatonin prevented these negative effects by ameliorating rotenone-induced mitochondrial dysfunction and dynamic imbalance, intracellular Ca²⁺ homeostasis damage, ER stress, early apoptosis, meiotic spindle formation disruption, and aneuploidy in oocytes. Additionally, RNA sequencing analysis showed that rotenone exposure changed the expression of multiple genes involved in histone methylation and acetylation modifications that result in mouse meiotic defects. However, melatonin partially rescued these defects. These findings suggest that melatonin has protective effects against rotenone-induced mouse oocyte defects.