Effects of ubiquitin C-terminal hydrolase L1 deficiency on mouse ova

Transcriptome and Proteome Analysis Revealed Key Pathways Regulating Final Stage of Oocyte Maturation of the Turkey (Meleagris gallopavo)

In birds, the zona pellucida (ZP) matrix that surrounds the ovulated oocyte—called the inner perivitelline layer—is involved in sperm–zona interaction and successful fertilization. To identify the important genes and proteins connected with the final step of egg development, next-generation sequencing and two-dimensional electrophoresis, combined with mass spectrometry, were used for the analysis of mature oocytes at the F1 developmental stage. A total of 8161 genes and 228 proteins were annotated. Six subfamilies of genes, with codes ZP, ZP1–4, ZPD, and ZPAX, were identified, with the dominant expression of ZPD. The main expression site for ZP1 was the liver; however, granulosa cells may also participate in local ZP1 secretion. A ubiquitination system was identified in mature oocytes, where ZP1 was found to be the main ubiquitinated protein. Analysis of transcripts classified in estrogen receptor (ESR) signaling indicated the presence of ESR1 and ESR2, as well as a set of estrogen-dependent genes involved in both genomic and nongenomic mechanisms for the regulation of gene expression by estrogen. Oxidative phosphorylation was found to be a possible source of adenosine triphosphate, and the nuclear factor erythroid 2-related factor 2 signaling pathway could be involved in the response against oxidative stress. Oocyte–granulosa cell communication by tight, adherens, and gap junctions seems to be essential for the final step of oocyte maturation.

Ovarian Transcriptomic Analysis Reveals Differential Expression Genes Associated with Cell Death Process after Selection for Ovulation Rate in Rabbits

Simple Summary

Transcriptomic analysis showed nineteen potential biomarkers in ovarian tissue from females belonged to a rabbit line selected for ovulation rate for 10 generations and the control line. These females differed not only in ovulation rate but also in prenatal survival since similar litter size were observed.

Abstract

Litter size is an essential trait in rabbit meat production but with low heritability. A selection experiment for ovulation rate has been performed for 10 generations to improve litter size in rabbits. The selected line increased two ova more than the control line but nevertheless a negative correlation was observed with prenatal survival. A transcriptomic study was performed, using microarrays, in ovarian tissue from females belonging to the selected line and the control line. Our results showed 1357 differential expressed genes and nineteen potential biomarkers associated with prenatal mortality, which could explain differences between litter size in rabbits. Cell death was the most relevant process.

The neglected part of early embryonic development: maternal protein degradation

The degradation of maternally provided molecules is a very important process during early embryogenesis. However, the vast majority of studies deals with mRNA degradation and protein degradation is only a very little explored process yet. The aim of this article was to summarize current knowledge about the protein degradation during embryogenesis of mammals. In addition to resuming of known data concerning mammalian embryogenesis, we tried to fill the gaps in knowledge by comparison with facts known about protein degradation in early embryos of non-mammalian species. Maternal protein degradation seems to be driven by very strict rules in terms of specificity and timing. The degradation of some maternal proteins is certainly necessary for the normal course of embryonic genome activation (EGA) and several concrete proteins that need to be degraded before major EGA have been already found. Nevertheless, the most important period seems to take place even before preimplantation development-during oocyte maturation. The defects arisen during this period seems to be later irreparable.

HASPIN kinase mediates histone deacetylation to regulate oocyte meiotic maturation in pigs

HASPIN kinase-catalyzed phosphorylation of histone H3 on threonine 3 (H3T3p) directs the activity and localization of chromosomal passenger complex (CPC) and spindle assembly checkpoint (SAC) to regulate chromosome condensation and segregation in both mitosis and meiosis. However, the function of HASPIN kinase in the meiotic maturation of porcine oocytes is not yet known. Here, we found that HASPIN mRNA is constantly expressed in porcine oocyte maturation and subsequent early embryo development. H3T3p is highly enriched on chromosomes at germinal vesicle breakdown (GVBD) stage and thereafter maintains a low level in progression through metaphase I (MI) to metaphase II (MII). Correspondingly, H3T3p was completely abolished in oocytes treated with an inhibitor of HASPIN kinase. Functionally, inhibition of HASPIN activity led to a significant reduction in the rate of oocyte meiotic maturation and the limited cumulus expansion. Additionally, HASPIN inhibition caused both spindle disorganization and chromosome misalignment in oocytes at MI and MII stage. Importantly, HASPIN inhibition severely prevented deacetylation of several highly conserved lysine (K) residues of histone H3 and H4 including H3K9, H3K14, H4K5, H4K8, H4K12 and H4K16 on the metaphase chromosomes during oocyte meiotic maturation. Taken together, these results demonstrate that HASPIN kinase regulates porcine oocyte meiotic maturation via modulating histone deacetylation.

Post-translational regulation of the maternal-to-zygotic transition

The maternal-to-zygotic transition (MZT) is essential for the developmental control handed from maternal products to newly synthesized zygotic genome in the earliest stages of embryogenesis, including maternal component (mRNAs and proteins) degradation and zygotic genome activation (ZGA). Various protein post-translational modifications have been identified during the MZT, such as phosphorylation, methylation and ubiquitination. Precise post-translational regulation mechanisms are essential for the timely transition of early embryonic development. In this review, we summarize recent progress regarding the molecular mechanisms underlying post-translational regulation of maternal component degradation and ZGA during the MZT and discuss some important issues in the field.

Protein deubiquitination during oocyte maturation influences sperm function during fertilisation, antipolyspermy defense and embryo development

Ubiquitination is a covalent post-translational modification of proteins by the chaperone protein ubiquitin. Upon docking to the 26S proteasome, ubiquitin is released from the substrate protein by deubiquitinating enzymes (DUBs). We hypothesised that specific inhibitors of two closely related oocyte DUBs, namely inhibitors of the ubiquitin C-terminal hydrolases (UCH) UCHL1 (L1 inhibitor) and UCHL3 (L3 inhibitor), would alter porcine oocyte maturation and influence sperm function and embryo development. Aberrant cortical granule (CG) migration and meiotic spindle defects were observed in oocytes matured with the L1 or L3 inhibitor. Embryo development was delayed or blocked in oocytes matured with the general DUB inhibitor PR-619. Aggresomes, the cellular stress-inducible aggregates of ubiquitinated proteins, formed in oocytes matured with L1 inhibitor or PR-619, a likely consequence of impaired protein turnover. Proteomic analysis identified the major vault protein (MVP) as the most prominent protein accumulated in oocytes matured with PR-619, suggesting that the inhibition of deubiquitination altered the turnover of MVP. The mitophagy/autophagy of sperm-contributed mitochondria inside the fertilised oocytes was hindered by DUB inhibitors. It is concluded that DUB inhibitors alter porcine oocyte maturation, fertilisation and preimplantation embryo development. By regulating the turnover of oocyte proteins and mono-ubiquitin regeneration, the DUBs may promote the acquisition of developmental competence during oocyte maturation.

Ubiquitin C-terminal hydrolase l1 is expressed in mouse pituitary gonadotropes in vivo and gonadotrope cell lines in vitro

The ubiquitin-proteasome system (UPS) plays a fundamental role in regulating various biological activities. Ubiquitin C-terminal hydrolase L1 (UCH-L1) is a deubiquitinating enzyme, belonging to the UPS. To date, it has been reported that UCH-L1 is highly and restrictedly expressed in neural and reproductive tissues and plays significant roles in these organs. Although the expression of UCH-L1 in the anterior pituitary gland has been reported, the detailed localization and the role of UCH-L1 remain obscure. In the present study, we detected UCH-L1 protein exclusively in hormone-producing cells, but not non-hormone producing folliculostellate cells in the anterior pituitary lobe. In addition, the cytoplasmic expression of UCH-L1 varied and was limited to gonadotropes and mammotropes. To investigate the role of UCH-L1 in anterior pituitary cells, we performed a comparative analysis using genetically UCH-L1-deficient gad mice. Significant decreases in the numbers of gonadotropes and mammotropes were observed in gad mice, suggesting a close involvement of UCH-L1 in these cells. Moreover, we also determined the expression of UCH-L1 in cultured gonadotropes. Taken together, this is the first report to definitely demonstrate the presence of UCH-L1 in mouse anterior pituitary gland, and our results might provide a novel insight for better understanding the role of UCH-L1 in the hypothalamic-pituitary-gonadal axis and in the reproduction.

Deubiquitinating enzymes in oocyte maturation, fertilization and preimplantation embryo development

Post-translational modifications of cellular proteins by ubiquitin and ubiquitin-like protein modifiers are important regulatory events involved in diverse aspects of gamete and embryo physiology including oocyte maturation, fertilization and development of embryos to term. Deubiquitinating enzymes (DUBs) regulate proteolysis by reversing ubiquitination, which targets proteins to the 26S proteasome. The ubiquitin C-terminal hydrolases (UCHs) comprise are DUBs that play a role in the removal of multi-ubiquitin chains. We review here the roles of UCHs in oocytes maturation, fertilization and development in mouse, bovine, porcine and rhesus monkeys. Oocyte UCHs contributes to fertilization and embryogenesis by regulating the physiology of the oocyte and blastomere cortex as well as oocyte spindle. Lack of UCHs in embryos reduces fertilization, while mutant embryos fail to undergo compaction and blastocyst formation. In addition to advancing our understanding of reproductive process, research on the role of deubiquitinating enzymes will allow us to better understand and treat human infertility, and to optimize reproductive performance in agriculturally important livestock species.

Winter hibernation and UCHL1-p34cdc2 association in toad oocyte maturation competence

Currently, it is believed that toad oocyte maturation is dependent on the physiological conditions of winter hibernation. Previous antibody-blocking experiments have demonstrated that toad ubiquitin carboxyl-terminal hydrolase L1 (tUCHL1) is necessary for germinal vesicle breakdown during toad oocyte maturation. In this paper, we first supply evidence that tUCHL1 is highly evolutionarily conserved. Then, we exclude protein availability and ubiquitin carboxyl-terminal hydrolase enzyme activity as factors in the response of oocytes to winter hibernation. In the context of MPF (maturation promoting factor) controlling oocyte maturation and to further understand the role of UCHL1 in oocyte maturation, we performed adsorption and co-immunoprecipitation experiments using toad oocyte protein extracts and determined that tUCHL1 is associated with MPF in toad oocytes. Recombinant tUCHL1 absorbed p34(cdc2), a component of MPF, in obviously larger quantities from mature oocytes than from immature oocytes, and p13(suc1) was isolated from tUCHL1 with a dependence on the ATP regeneration system, suggesting that still other functions may be involved in their association that require phosphorylation. In oocytes from hibernation-interrupted toads, the p34(cdc2) protein level was significantly lower than in oocytes from toads in artificial hibernation, providing an explanation for the different quantities isolated by recombinant tUCHL1 pull-down and, more importantly, identifying a mechanism involved in the toad oocyte's dependence on a low environmental temperature during winter hibernation. Therefore, in toads, tUCHL1 binds p34(cdc2) and plays a role in oocyte maturation. However, neither tUCHL1 nor cyclin B1 respond to low temperatures to facilitate oocyte maturation competence during winter hibernation.