EXPRESSION PATTERNS OF NOVEL GENES DURING MOUSE PREIMPLANTATION EMBRYOGENESIS

Little is known about the repertoire of genes expressed following zygo tic gene activation, which occurs during the two-cell stage in the mou se. As an initial attempt to isolate novel genes, we used previously p repared two-cell and two-cell subtraction cDNA libraries (Rothstein et al., Genes Dev 6:1190-1201, 1992) to isolate a panel of seven cDNA cl ones. Three cDNAs had no match in the current DNA sequence data banks and three others revealed sequence homology to portions of sequences i n the data banks. One cDNA was 90% homologous to the ras-related gene Krev/rap 1A. The temporal patterns of expression of these genes during oocyte maturation and preimplantation development were analyzed by a reverse transcription-polymerase chain reaction (RT-PCR) assay develop ed to measure relative levels of mRNAs. Three distinct temporal patter ns of expression, designated Classes 1-3, were found. The two Class 1 genes displayed an actin-like pattern, with a gradual decline in expre ssion during oocyte maturation and through the two-cell stage, followe d by increases at the eight-cell and/or blastocyst stages. The four ge nes in Class 2 were expressed at relatively high levels during oocyte maturation and through the one-cell stage and then declined abruptly b etween the one- and two-cell stages; an increase then occurred at the eight-cell and/or blastocyst stages. The expression of the gene in Cla ss 3 declined during oocyte maturation; but then showed a transient in crease at the one-cell stage, with only a very slight increase in synt hesis at either the eight-cell or blastocyst stage. (C) 1994 Wiley-Lis s, Inc.