Comparative proteomic and regulatory network analyses of the elongating pig conceptus

Embryo loss during peri-implantation can approach 20% in swine following artificial insemination or natural mating and coincides with rapid conceptus elongation. The objective of the present study was to establish a comprehensive profile of the abundant proteins of the pig conceptus at the time prior to implantation and identify stage-specific changes during elongation. The abundant proteins of a homogenous population of gestational day-11 ovoid (0.7-1 cm) and gestational day-12 filamentous (15-20 cm) porcine concepti were compared by extracting proteins from three independent conceptus pools and separating the proteins by 2-DE. Proteins in 305 spots were analyzed by MALDI-TOF or additionally by LC-MS/MS and 275 were positively identified representing 174 distinct proteins. The proteins could be classified into the following functional categories: cell proliferation/differentiation, cytoskeleton, metabolism, and stress response. Based on spot density, 35 proteins associated with cell proliferation, differentiation, apoptosis, and embryo/maternal signaling, were found to be differentially expressed between ovoid and filamentous concepti. A comparison of the protein expression profile with transcriptomic data from pig concepti of the same developmental stages identified similarities and dissimilarities between protein and mRNA expression profiles. This proteomic study helps to elucidate the biological mechanisms underlying the early embryonic development of the pig.