XNF7 FUNCTIONS IN DORSAL-VENTRAL PATTERNING OF THE XENOPUS EMBRYO

Xenopus nuclear factor 7 (xnf7) is a maternally expressed nuclear prot ein that is retained in the cytoplasm from oocyte maturation until the midblastula transition (MBT). Mutations of the xnf7 phosphorylation s ites to glutamic acids (dnxnf7) resulted in the retention of the endog enous protein in the cytoplasm past the MET, indicating that cytoplasm ic retention is a phosphorylation dependent process. In addition, dnxn f7 acted as a dominant negative mutant by keeping the endogenous xnf7 protein in the cytoplasm past the MET. Overexpression of dnxnf7 in fut ure dorsal blastomeres resulted in a ventralized or posteriorized phen otype in which the embryos lacked anterior structures, while overexpre ssion in ventral blastomeres resulted in dorsalized embryos. dnxnf7 al so affected the expression of both dorsal and ventral mesodermal marke rs. These data suggest that xnf7 functions in dorsal/ventral patternin g and that the movement of the protein from the cytoplasm to the nucle us at the MBT is critical for the execution of a genetic program confe rring a dorsal or ventral identity to the mesoderm. (C) 1997 Academic Press.