Comparative proteomic analysis of hen egg white proteins during early phase of embryonic development by combinatorial peptide ligand library and matrix-assisted laser desorption ionization-time of flight.

Little is known regarding the diversification of relative low-abundance proteins in hen egg white that underlie the process of chicken embryonic development. The purpose of this study was to identify changes that may be involved in the development of chick embryos. Comparative proteomic analysis was conducive to revealing the potential biological function of low-abundance proteins and embryonic development demand. In addition, those proteins that are increased in abundance seem to have advantages to be targeted as new biomarkers for animal disease or animal production. However, the huge disparity in abundance in chicken egg white and poor performance of affinity depletion methods were specific challenges. This study applied combinatorial peptide ligand library for expanding the deep proteomics. Two-dimensional gel electrophoresis (2-DE) was performed with the hen embryo egg white, which was obtained from embryos at d 0 and 7. The protein spots showing significant increases were selected for identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry/mass spectrometry (2 mass analyzers for tandem mass spectrometry). Many precursors were identified as strongly increased after 7 d of incubation. They were ovoinhibitor precursor, clusterin precursor, apolipoprotein D precursor, and extracellular fatty acid-binding protein precursor. Moreover, clusterin precursor were observed concentrated in 2 regions: one is the range of molecular weight increase and the other is the range of high pH. In addition, ovalbumin and ovotransferrin were observed in high pH area in a 2-DE map. These findings will give insight into the changes in fertilized egg white proteins during hatching and provide a better understanding of the biochemical changes in the egg development process.