IDENTIFICATION OF GENES SHOWING ALTERED EXPRESSION IN PREIMPLANTATIONAND EARLY POSTIMPLANTATION PARTHENOGENETIC EMBRYOS

Uniparental embryos have been instrumental in studying imprinting beca use contributions from the parental genomes can be determined unambigu ously. In this study, we set out to identify imprinted genes showing d ifferential expression between parthenogenetic and fertilized embryos during preimplantation and early postimplantation stages of developmen t. We identified three genes-apolipoprotein E, pyruvate kinase-3, and protein phosphatase 1 gamma-that represent excellent candidates for im printed genes, based on the results of the differential screen, their function in differentiation and the cell cycle, and their location wit hin imprinted chromosomal regions. In addition,two novel genes express ed in trophoblast were identified, 1661 and RA81. These genes, togethe r with four known imprinted genes, H19, Igf2r, lgf2, and Snrpn, showed evidence of expression from both parental alleles in early stage embr yos, indicating a role for postfertilization processes in regulating i mprinted gene function. (C) 1995 Wiley-Liss, Inc.