Poly(A) binding protein II in Xenopus laevis is expressed in developing brain and pancreas

We have isolated Xenopus homolog of poly(A) binding protein II (XPABPII) and examined its expression during early embryogenesis and embryonic gut development. XpabpII encodes a nuclear protein of 296 amino acids that contains an alpha-helical coiled-coil domain and a ribonucleoprotein-type RNA binding domain. XpabpII is expressed both maternally and zygotically. In gastrula and neurula embryos, XpabpII is expressed mainly in ectoderm, neural and epidermal. From tailbud through to tadpole stages, the neural tissue specific expression of XpabpII gradually becomes confined to the specific vesicle regions of developing brain, being detected in the eye, olfactory pit, telencephalon and mesencephalon, but being excluded from the diencephalon region. Intriguingly, XpabpII transcripts are observed in differentiating gut endoderm. XpabpII first becomes visible in the anterior part of a stage 35 embryonic gut in which prospective liver, stomach and pancreas are located. During further development, uniform expression in anterior gut gradually becomes restricted to the pancreas rudiment. At the seventh day of development, when the gut has formed a complex coiled structure in which each organ contains clearly differentiated cell type, XpabpII is detectable exclusively in the pancreas. Taken together, we suggest that XpabpII plays a specific role in the polyadenylation process of genes involved in brain and pancreas development.