The timing of maternal protein degradation during mammalian preimplantation development is species-specific.

In brief: Proper degradation of maternally inherited proteins is a prerequisite for successful embryonic development. This study shows the species-specificity of this process. Abstract: The mechanism of targeting maternal proteins for degradation during preimplantation development is an unexplored process. Only a few proteins that need to be degraded for the proper course of the maternal-to-zygotic transition have been described in mice, and a few more in non-mammalian species. However, it is not well known whether the need for degradation is conserved across species or if it is driven in a species-specific way. Therefore, we selected six proteins that need to be degraded for the proper course of the maternal-to-zygotic transition in mice or Xenopus, and thoroughly characterized their expression at both the mRNA and protein level during bovine embryogenesis. Further, we analysed the protein expression in mice and pigs and compared it to bovine embryos. Thus, we provide a unique interspecies comparison of three mammalian representatives. We found that the degree of conservation between species is low and does not depend on the evolutionary relatedness of the species. This paper suggests that protein degradation during preimplantation development is controlled by a combination of species-specific factors from the embryo and the sequences of protein homologues.