Characterization of a Xenopus Homeobox Gene

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Both genetic and molecular analyses of Drosophila have clearly demonstrated that homeobox containing genes are intimately involved in the establishment of the body plan. Using molecular probes from Drosophila the vertebrate homeobox containing gene counterparts were isolated. However, there is no clear evidence demonstrating that the homeobox containing genes play a similar role in vertebrates. This proposal is focused on analyzing the function of a maternally expressed homeobox containing gene, X1Hox 2, in the frog Xenopus laevis. Dr. Etkin's preliminary data show that the X1Hox 2 mRNA is localized in the animal hemisphere in full grown oocytes and that destruction of the maternal mRNA by injection of antisense oligodeoxynucleotides results in a specific defect in the neural tube. Dr. Etkin hypothesis is that this gene plays a fundamental role in the regulatory gene hierarchy in early Xenopus development. He will test this hypothesis by accomplishing the following specific aims: 1) define the spatial and temporal pattern of expression of the X1Hox 2 gene using in situ hybridization, RNase protection assays, and immunostaining of the protein in tissue sections and whole mounts 2) analysis of how this gene is regulated during development by examining the role of cell cell interactions and autoregulation on its expression, as well as characterizing the putative target genes that the X1Hox 2 gene product may activate at the gastrula stage and 3) determine the function of the X1Hox 2 gene using several approaches including a novel combination of antisense oligodeoxynucleotide injection, maturation, and fertilization of oocytes in vitro. %%% The analysis of this gene and its product will be important in the formulation of basic principles of how homeobox containing genes function in the establishment of the vertebrate body plan.