Control of the oocyte-to-embryo transition by the ubiquitin-proteolytic system in mouse and C. elegans. Verlhac MH et al. In metazoans the oocyte-to-embryo transition occurs in the absence of mRNA transcription and relies entirely on maternally provided mRNA and proteins. We review here recent findings illustrating the importance of degradation of key proteins allowing essential cell cycle transitions as well as important remodelling of the oocyte to produce a totipotent zygote. By following the chronological order of events, we update recent discoveries on the instrumental role of the cullin-RING and APC/C ubiquitin-ligases in promoting meiosis resumption and the oocyte-to-embryo transition.
General function
Cell cycle regulation
Comment
Cellular localization
Comment
Ovarian function
Oocyte maturation, Early embryo development
Comment
Proteomic based identification of oocyte maturation related proteins in mouse GV oocytes. Cao S et al. (2020) Oocyte proteins play an important role in oocyte maturation, fertilization and embryonic development. However, the protein composition of mouse germinal vesicle (GV) oocytes is still unclear. Using one-dimensional Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (1D SDS-PAGE) and Reverse-phase liquid chromatography tandem mass spectrometry (RP-LC-MS/MS), we constructed a protein profile of mouse GV oocytes. First, our proteomics profile identified 1405 different proteins from 11,000 mouse GV oocytes lacking zona pellucida. Second, with detailed bioinformatics analysis, a group of proteins that play an essential role in oocyte maturation was screened. In addition, the expression and localization of suppressor of G2 allele of skp1(SUGT1, also called SGT1), heterogeneous nuclear ribonucleoprotein K (Hnrpk), Seruin, Cullin1(Clu1) and nuclear distribution protein C (Nudc) in mouse ovaries and early embryos were also captured and investigated in this study. Moreover, the protein profile was submitted to the Proteomics Identifications Database (PRIDE) and is available via ProteomeXchange with the identifier PXD014314. Our research provides valuable resources for the study of oocyte proteins and oocyte maturation and helps to clarify the mechanisms of oocyte maturation.//////////////////
MAPK signaling couples SCF-mediated degradation of translational regulators to oocyte meiotic progression. Kisielnicka E et al. (2018) RNA-binding proteins (RBPs) are important regulators of gene expression programs, especially during gametogenesis. How the abundance of particular RBPs is restricted to defined stages of meiosis remains largely elusive. Here, we report a molecular pathway that subjects two nonrelated but broadly evolutionarily conserved translational regulators (CPB-3/CPEB and GLD-1/STAR) to proteosomal degradation inCaenorhabditis elegansgerm cells at the transition from pachytene to diplotene of meiotic prophase. Both RBPs are recognized by the same ubiquitin ligase complex, containing the molecular scaffold Cullin-1 and the tumor suppressor SEL-10/FBXW7 as its substrate recognition subunit. Destabilization of either RBP through this Skp, Cullin, F-box-containing complex (SCF) ubiquitin ligase appears to loosen its negative control over established target mRNAs, and presumably depends on a prior phosphorylation of CPB-3 and GLD-1 by MAPK (MPK-1), whose activity increases in mid- to late pachytene to promote meiotic progression and oocyte differentiation. Thus, we propose that the orchestrated degradation of RBPs via MAPK-signaling cascades during germ cell development may act to synchronize meiotic with sexual differentiation gene expression changes.//////////////////
In mammals, this is a family of genes.
Transcriptomic analysis of in vivo and in vitro produced bovine embryos revealed a developmental change in cullin 1 expression during maternal-to-embryonic transition. Kepkova KV et al. Pre-implantation embryos derived by in vitro fertilization differ in their developmental potential from embryos obtained in vivo. In order to characterize changes in gene expression profiles caused by in vitro culture environment, we employed microarray constructed from bovine oocyte and preimplantation embryo-specific cDNAs (BlueChip, Universit Laval, Qubec). The analysis revealed changes in the level of 134 transcripts between in vitro derived (cultured in COOK BVC/BVB media) and in vivo derived 4-cell stage embryos and 97 transcripts were differentially expressed between 8-cell stage in vitro and in vivo embryos. The expression profiles of 7 selected transcripts (BUB3, CUL1, FBL, NOLC1, PCAF, GABPA and CNOT4) were studied in detail. We have identified a switch from Cullin 1-like transcript variant 1 to Cullin 1 transcript variant 3 (UniGene IDs BT.36789 and BT.6490, respectively) expressions around the time of bovine major gene activation (8-cell stage). New fibrillarin protein was detected by immunofluorescence already in early 8-cell stage and this detection correlated with increased level of fibrillarin mRNA. The qRT-PCR analysis revealed significant differences in the level of BUB3, NOLC1, PCAF, GABPA and CNOT4 gene transcripts between in vivo derived (IVD) and in vitro produced (IVP) embryos in late 8-cell stage. The combination of these genes represents a suitable tool for addressing questions concerning normal IVD embryo development and can be potentially useful as a marker of embryo quality in future attempts to optimize in vitro culture conditions.
Expression regulated by
Comment
Ovarian localization
Oocyte
Comment
Genes Preferentially Expressed in Bovine Oocytes Revealed by Subtractive and Suppressive Hybridization Pennetier S, et al .
In order to isolate bovine oocyte marker genes, we performed suppressive subtraction hybridization between oocytes and somatic tissues (i.e. intestine, lung, muscle and cumulus cells). The subtracted library was characterized by sequencing 185 random clone inserts, representing 146 non redundant genes. After blast analysis within Genbank, 64% could be identified, while 21% were homologous to unannotated EST or genomic sequences, and 15% were novel. Out of 768 clone inserts submitted to differential screening by macroarray hybridization, 83% displayed a fourfold overexpression in the oocyte. The 40 most preferential non redundant EST were submitted to Genbank analysis. Several well-known oocyte-specific genes were represented, including growth differentiation factor 9, bone morphogenetic protein 15 or the zona pellucida glycoprotein genes. Other EST were not identified. We investigated the expression profile of several candidates in the oocyte and a panel of gonadic and somatic tissues by RT-PCR. B-cell translocation gene 4, cullin 1, MCF.2 transforming sequence, a locus similar to snail soma ferritin and 3 unidentified genes were indeed preferentially expressed in the oocyte, even though most were also highly expressed in testis. . Expression profiles of BTG4, CUL1, MCF2, and EST 5B4, 6D3, 8D7, 8B9 and 7F3 were analysed in oocyte and preimplantation embryos by RT-PCR. All were strongly detected in immature, in vitro matured oocytes and zygotes. The transcripts were degraded throughout preimplantation development and were not compensated for by embryonic transcription after the morula stage. These profiles suggest a role in gametogenesis, fertilization or early embryonic development.