Protein synthesis in murine organs during postimplantation development detected by two-dimensional gel electrophoresis

Two-dimensional electrophoresis of protein from cultured postimplantation rat embryos for developmental toxicity studies

A simple method for two-dimensional electrophoresis (2-DE) of rat embryonic protein was described. Rat embryos cultured for 24h from day 10.5 of gestation were used as protein samples. Protein samples were lysed in rehydration buffer and separated by isoelectric focusing with immobilized pH gradient for the first dimension and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the second dimension. The use of the DeStreak Reagent as an antioxidant in the lysis buffer and electrode pads in the isoelectric focusing greatly improved the 2-DE pattern. When an embryo was used as a protein sample, about 800 protein spots were detected by silver staining in a 2-DE gel of the standard format. Eighty-one protein spots were identified by mass spectrometry for a primary 2-DE map. The same method could be applied to yolk sac membranes from the cultured embryos. The present method was considered to be suitable for a concomitant 2-DE analysis in in vitro developmental toxicity studies.

Protein identification in DNA databases by peptide mass fingerprinting

Proteins can be identified using a set of peptide fragment weights produced by a specific digestion to search a protein database in which sequences have been replaced by fragment weights calculated for various cleavage methods. We present a method using multidimensional searches that greatly increases the confidence level for identification, allowing DNA sequence databases to be examined. This method provides a link between 2-dimensional gel electrophoresis protein databases and genome sequencing projects. Moreover, the increased confidence level allows unknown proteins to be matched to expressed sequence tags, potentially eliminating the need to obtain sequence information for cloning. Database searching from a mass profile is offered as a free service by an automatic server at the ETH, Zürich. For information, send an electronic message to the address cbrg/inf.ethz.ch with the line: help mass search, or help all.

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

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 (M(r) 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.