A XENOPUS DAZ-LIKE GENE ENCODES AN RNA COMPONENT OF GERM PLASM AND ISA FUNCTIONAL HOMOLOG OF DROSOPHILA BOULE

We have identified a localized RNA component of Xenopus germ plasm, Th is RNA, Xdazl (Xenopus DAZ-like), encodes a protein homologous to huma n DAZ (Deleted in Azoospermia), vertebrate DAZL and Drosophila Boule p roteins, Human males deficient in DAZ have few or no sperm and boule m utant flies exhibit complete azoospermia and male sterility, Xdazl RNA was detected in the mitochondrial cloud and vegetal cortex of oocytes . In early embryos, the RNA was localized exclusively in the germ plas m, Consistent with other organisms, Xdazl RNA was also expressed in th e spermatogonia and spermatocytes of frog testis, Proteins in the DAZ- family contain a conserved RNP domain implying an RNA-binding function , We have shown that Xdazl can function in vitro as an RNA-binding pro tein, To determine if the function of Xdazl in spermatogenesis was con served, we introduced the Xdazl cDNA into boule flies, This resulted i n rescue of the boule meiotic entry phenotype, including formation of spindles, phosphorylation of histone H3 and completion of meiotic cell division. Overall, these results suggest that Xdazl may be important for primordial germ cell specification in the early embryo and may pla y a role analogous to Boule in promoting meiotic cell division.