122 EXTENSIVE ALTERATIONS IN THE QUANTITATIVE PROTEOME PROFILE DURING EARLY EMBRYONIC DEVELOPMENT

Abstract

Early embryonic development is morphologically well characterised, but there is limited knowledge available about the underlying molecular processes. Several studies have addressed early bovine embryonic development on the transcriptome level, but to our best knowledge, no comprehensive approach on the proteome level has been performed so far, although early embryos contain a huge number of proteins originating from the oocyte protein pool. Due to strong similarities in estric cycle (non-seasonal polyestric), kinetics of early embryo development, and singleton pregnancy, the bovine system reflects crucial parameters of the human reproductive system. Being interested in the dynamics of protein expression profiles during early embryogenesis, we here present a differential proteomic analysis comparing morulae and blastocysts. Protein lysates of embryos were analysed using the ultrasensitive 2D DIGE saturation approach, which facilitates quantitative 2D gel analysis from total protein amounts of <0.5 μg. Six biologically independent replicates of morulae and blastocysts, containing 25 embryos each, were prepared and analysed. Quantitative evaluation of spot signals was performed using DeCyder 6.5 software. Applying the FDR correction feature and a P-value of <0.01, 60 differentially abundant protein spots differing in their abundance ratios between morulae and blastocysts up to a factor of 12 were detected. Spots already identified by LC-MS/MS represent proteins involved in metabolic processes and cell redox homeostasis. Among several oxidoreductases decreasing during ongoing development, 3 isoforms of Peroxiredoxin-2 have been detected, which were not described previously. To characterize which proteins in early embryonic stages are contributed by the maternal part of the embryo, we generated a comprehensive qualitative proteomic dataset of bovine oocytes using a nano-LC-MS/MS approach on an Orbitrap XL mass spectrometer. From 900 oocytes, 1221 proteins were identified. For 1045 proteins, existence on the protein level was experimentally proved for the first time in the bovine system.