Abstract
The Pumilio gene was first identified in Drosophila
melanogaster, where is required for posterior patterning of the
embryo, embryonic development and cellular differentiation.
Studies carried out in different species suggested that Pumilio is involved in the regulation of stem cell development and maintenance, but the biological roles of Pumilio proteins in Vertebrates are still unclear. Pumilio homologues are involved in repression mechanisms of traslation. This function is made possible by the presence of a specific RNA-binding domain, known as Pumilio homology domain (PUM-HD), composed of eight consecutive Puf repeats located near the C-terminal end of the protein.
In the present study, I have investigated the expression of a
Pumilio homolog gene, XPum2, during Xenopus embryonic
development, with special interest to germ line. Through in silico analysis, I have selected two clones: XPum1 (BC080379), homolog to genes of the subfamily Pumilio1, and XPum2 (CA790091), IMAGE clone that showed a significant homology with the genes of subfamily
Pumilio2; the two clones were used to generate RNA probes used for in situ hybridization experiments.
Whole-mount in situ hybridizations, showed that XPum2 was asimmetrically located throughout the animal hemisphere in oocytes and during early embryogenesis of Xenopus. This skewed transcript distribution may contribute to specify the animal-vegetal axis, the first cell polarity signal to be determined during the oogenesis. XPum2 expression is observed in the animal blastomeres in 2, 4, 8 cell embryos and in morula stages. At the early blastula stages, zygotic
XPum2 was expressed in cells of the marginal zone and the blastocoel
roof. These preliminary results suggested that XPum2 was a maternal transmission gene, because the zygotic transcription started at the mid-blastula transition (stage 10). At later developmental stages Xpum2 expression was detected in ectodermal- and mesodermal-derived structures such as eye, branchial arches, otic vesicle, and notochord.
The gene epression analysis during oogenesis revealed the presence both of Xpum1 and Xpum2 transcripts in pre-vitellogenic primary oocytes of pre-metamorphic developmental stages and adults.
