Comparison of protein analysis between embryonic and extraembryonic tissues during the 11th day of gestation of the mouse

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Abstract
At day 11 of gestation, embryos and their extraembryonic tissues were isolated from the uterus of Him OF1/SPF mice and incubated in Dulbecco's modified Eagle's medium (DMEM) containing L‐[35S]methionine. After 4 h of incubation, the embryos were dissected to obtain the heart, liver, limb buds, and brain. The latter was fragmented into the telencephalon, mesencephalon, and myelencephalon. These organs and the extraembryonic tissues such as chorion, yolk sac, and placenta were processed for two‐dimensional (2‐D) gel electrophoresis. About 1000 proteins with relative molecular weights (Mr) varying from 10 000 to 200 000 and isoelectric points ranging from 4 to 10 could be detected on these gels. The protein patterns of the various organs and tissues were analyzed for organ‐ and cell lineage‐specific protein spots. We detected subtle differences in the protein patterns of the three cerebral areas when compared to each other. In addition, we found protein spots characteristic for the entire brain. We also found several heart‐specific protein spots. Distinct protein synthesis was also detected in liver and limb buds. Several groups of protein spots seem to be differentially regulated in these organs. Substantial differences between the patterns of embryonic and extraembryonic tissues were observed. In addition, several clusters of protein spots of well‐defined molecular weight could be detected only in extraembryonic tissues. We propose that organ‐ and tissue‐specific differences in protein synthesis are linked to some of the morphogenetic and functional processes during mammalian embryogenesis. Identification of particular proteins will serve as a basis to search for the corresponding genes.