Stage-Specific Proteome Signatures in Early Bovine Embryo Development

Development of early embryonic stages
before activation of the
embryonic genome depends on sufficiently stored products of the maternal
genome, adequate recruitment and degradation of mRNAs, as well as
activation, deactivation, and relocation of proteins. By application
of an isobaric tagging for relative and absolute quantification (iTRAQ)-based
approach, the proteomes of bovine embryos at the zygote and 2-cell
and 4-cell stage with MII oocytes as a reference were quantitatively
analyzed. Of 1072 quantified proteins, 87 differed significantly in
abundance between the four stages. The proteomes of 2-cell and 4-cell
embryos differed most from the reference MII oocyte, and a considerable
fraction of proteins continuously increased in abundance during the
stages analyzed, despite a strongly attenuated rate of translation
reported for this period. Bioinformatic analysis revealed particularly
interesting proteins involved in the p53 pathway, lipid metabolism,
and mitosis. Verification of iTRAQ results by targeted SRM (selected
reaction monitoring) analysis revealed excellent agreement for all
five proteins analyzed. By principal component analysis, SRM quantifications
comprising a panel of only five proteins were shown to discriminate
between all four developmental stages analyzed here. For future experiments,
an expanded SRM protein panel will provide the potential to detect
developmental disturbances with high sensitivity and enable first
insights into the underlying molecular pathways.