Large-scale cDNA analysis reveals phased gene expression patterns during preimplantation mouse development

Little is known about gene action in the preimplantation events that initia te mammalian development. Based on cDNA collections made from each stage fr om egg to blastocyst, 25438 3'-ESTs were derived, and represent 9718 genes, half of them novel. Thus, a considerable fraction of mammalian genes is de dicated to embryonic expression. This study reveals profound changes in gen e expression that include the transient induction of transcripts at each st age. These results raise the possibility that development is driven by the action of a series of stage-specific expressed genes. The new genes, 798 of them placed on the mouse genetic map, provide entry points for analyses of human and mouse developmental disorders.