The goals of the proposed study are 1) to identify genes that contribute to cell differentiation and formation of the body plan during embryogenesis of the zebrafish, Brachydanio rerio, and 2) to characterize when and where in the embryo cell or region specific gene expression originates. To examine gene function during development, Dr. Grunwald will generate transgenic zebrafish that harbor promoter-less lacZ reporter genes integrated at random locations in the genome. Expression of the reporter gene will necessarily be derived from endogenous transcriptional promoters. Patterns of gene expression that signal early embryonic differentiation events will be recognized by virtue of the expression of the lacZ transgene. Developmental mutation that arise from disruption of host genes and that disturb the normal structure of the one day embryo will be recognized using simple anatomical and behavioral screens. The developmental mutations and their associated phenotypes will be characterized in detail. Mutations of interest will be molecularly isolated and analyzed. To characterize in detail the ontogeny of the earliest tissues that arise during zebrafish embryogenesis, Dr. Grunwald will examine the expression of well defined tissue specific genes. Analysis of the expression of Vg1 will contribute to an understanding of the maternal contribution to development in animals with pluripotent blastomeres. Establishing when and where tissue specific gene expression originates will help clarify the relation between cell movements at gastrulation and the induction of tissue differentiation, and will be a critical first step toward developing experimentally testable hypotheses regarding the forces that promote tissue differentiation in the zebrafish embryo.
