Int. J. Dev. Biol. 42: 43 - 52 (1998)
© UPV/EHU Press

Differential expression of nucleoside diphosphate kinases (NDPK/NM23) during Xenopus early development.

T Ouatas, M Sélo, Z Sadji, J Hourdry, H Denis and A Mazabraud

Centre de Génétique Moléculaire, CNRS, Gif-sur-Yvette, France.

ABSTRACT In Xenopus laevis, three nucleoside diphosphate kinase (NDPK) monomers have been described (NDPK X1, X2 and X3) (Ouatas et al., 1997). In eucaryotes, this kinase is known as a hetero- or homohexamer. Here, we examine the distribution of the enzyme and its different subunit mRNAs during oogenesis and early embryogenesis of Xenopus laevis, respectively by immunohistofluorescence and whole-mount in situ hybridization. These analyses show that NDPKs and their mRNAs are differentially distributed throughout the oocyte and early embryos with a high level of transcription in somites and brain. We emphasize two points. First, each mRNA displays a distinct subcellular localization in somites, suggesting a complex regulation of NDPK genes both at the transcriptional and translational level and a possible involvement of NDPK X2 homohexamers in the dorsal muscle differentiation. Second, in oocytes and early embryos, the proteins are mainly localized in the nucleus, suggesting a new mechanism for their nuclear import, since they do not possess any known nuclear import sequences.