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.

• Keywords
• Autophagy, Embryonic genome activation, Maternal to zygotic transition, Proteasome system, Ubiquitin, Ubiquitin ligase,
• MeSH
• Embryo, Nonmammalian metabolism   physiology   MeSH
• Embryo, Mammalian metabolism   physiology   MeSH
• Embryonic Development physiology   MeSH
• Genome physiology   MeSH
• Humans MeSH
• Oocytes metabolism   physiology   MeSH
• Proteins metabolism   MeSH
• Gene Expression Regulation, Developmental physiology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Proteins MeSH

The degradation of maternal proteins is one of the most important events during early development, and it is presumed to be essential for embryonic genome activation (EGA), but the precise mechanism is still not known. It is thought that a large proportion of the degradation of maternal proteins is mediated by the ubiquitin-proteolytic system. In this study we focused on the expression of the Skp1-Cullin1-F-box (SCF) complex, a modular RING-type E3 ubiquitin-ligase, during bovine preimplantation development. The complex consists of three invariable components--Cul1, Skp1, Rbx1 and F-box protein, which determines the substrate specificity. The protein level and mRNA expression of all three invariable members were determined. Cul1 and Skp1 mRNA synthesis was activated at early embryonic stages, at the 4c and early 8c stage, respectively, which suggests that these transcripts are necessary for preparing the embryo for EGA. CUL1 protein level increased from MII to the morula stage, with a significant difference between MII and L8c, and between MII and the morula. The CUL1 protein was localized primarily to nuclei and to a lesser extent to the cytoplasm, with a lower signal in the inner cell mass (ICM) compared to the trophectoderm (TE) at the blastocyst stage. The level of SKP1 protein significantly increased from MII oocytes to 4c embryos, but then significantly decreased again. The localization of the SKP1 protein was analysed throughout the cell and similarly to CUL1 at the blastocyst stage, the staining was less intensive in the ICM. There were no statistical differences in RBX1 protein level and localization. The active SCF-complex, which is determined by the interaction of Cul1 and Skp1, was found throughout the whole embryo during preimplantation development, but there was a difference at the blastocyst stage, which exhibits a much stronger signal in the TE than in the ICM. These results suggest that all these genes could play an important role during preimplantation development. This paper reveals comprehensive expression profile, the basic but important knowledge necessary for further studying.

• MeSH
• Blastocyst metabolism   ultrastructure   MeSH
• Embryonic Development genetics   MeSH
• F-Box Proteins genetics   metabolism   MeSH
• Fertilization in Vitro MeSH
• Transcription, Genetic MeSH
• Cullin Proteins genetics   metabolism   MeSH
• RNA, Messenger genetics   metabolism   MeSH
• Oocytes cytology   growth & development   metabolism   MeSH
• SKP Cullin F-Box Protein Ligases genetics   metabolism   MeSH
• S-Phase Kinase-Associated Proteins genetics   metabolism   MeSH
• Signal Transduction MeSH
• Cattle MeSH
• Spermatozoa cytology   metabolism   MeSH
• Substrate Specificity MeSH
• Gene Expression Regulation, Developmental MeSH
• Zinc Fingers genetics   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Cattle MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cullin 1 MeSH Browser
• F-Box Proteins MeSH
• Cullin Proteins MeSH
• RNA, Messenger MeSH
• SKP Cullin F-Box Protein Ligases MeSH
• S-Phase Kinase-Associated Proteins MeSH