225. Characterisation of a diverse secretome generated by the mouse preimplantation embryo

Abstract

This study investigated the suitability of surface-enhanced laser desorption and ionisation time-of-flight (SELDI-TOF) and electro-spray ionisation (ESI) mass spectrometry for the analysis of the proteins released by the mouse preimplantation embryo in vitro. SELDI-TOF analysis with CM10 or IMAC30 (but not Q10) chips detected a protein peak at m/z 8570 released by both C57BL6 and hybrid embryos. No other peaks unique to the embryo were identified with this method. ESI mass spectrometry of tryptic digests of embryo conditioned media identified a total of 20 proteins released during development from the zygote to blastocysts stage. Four proteins were expressed in at least 7 out of 8 cultures tested, one of these (lactate dehydrogenase B) was in all cultures. A further five proteins were in at least half of the cultures and 11 more putative proteins were detected in at least one culture. The pattern of protein secretion was not obviously different for C57BL6 or hyrid embryos. The expression of two of these proteins is essential for preimplantation embryo development (NLR family, pyrin domain containing 5 protein and peptidyl arginine deiminase, type VI). A further four proteins detected have roles in redox regulation of cells, and three others are capable of inducing post-translational modification of proteins. This study shows the feasibility of ESI mass spectrometry and the limitations of SELD-TOF mass spectrometry for identifying the proteins scereted by the preimplantation embryo in vitro. This analysis identifies a range of targets that now require detailed functional analysis to assess whether their release by the embryo is an important property of the early embryo, or an artefact of in vitro culture.