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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 gutendoderm. 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 anteriorgut 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.
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11677061
???displayArticle.link???Mech Dev
Fig. 4. In situ hybridization for XpabpII on whole embryos and guts. (A) A section of early gastrula stage embryo showing XpabpII expression in prospective neuroectoderm. An arrow indicates dorsal blastopore lip. (B) A cross-section of a neurula stage embryo. XpabpII mRNA is strongly expressed in the neural tissue. Inset is the enlarged view of the square part. Two arrowheads indicate neural tube. (C) The lateral view of an early tailbud stage embryo sectioned sagittally. XpabpII is detectable in brain, spinal cord and eye. (D) The dorsolateral view of the head region at stage 28. XpabpII is expressed in whole brain and eye (ey). (E) The dorsolateral view of the head region of a stage 35/36 embryo. XpabpII transcripts are uniformly expressed in the most part of the developing brain vesicles including telencephalon (tel), diencephalon (di) and mesencephalon (me). (F) The head region of a stage 39 embryo viewed dorsolaterally. XpabpII is localized to specific brain region, being strongly expressed in olfactory pit (op), eye (ey), telencephalon (tel), mesencephalon (me) and rhombencephalon (rh) but absent from diencephalon (di). (G) Stage 37 embryonic gut to show XpabpII expression restricted to the anteriorgut including liver (li), stomach (st), dorsal (dp) and ventral (vp) pancreatic rudiments. Anterior is to the left. (H) Left view of XpabpII expression in the stage 41 gut in which the pancreatic buds have fused. (I) The ventral view of stage 42 gut. The posterior expression boundary of XpabpII corresponds to the transitional zone/intestine boundary (an arrowhead). (J) The ventral view of stage 44 gut. XpabpII is expressed at a high level in the pancreas (p), but the expression in liver and stomach is much reduced. (K) The pancreatic expression of XpabpII in stage 46/47 gut. Strong signal is only observed in the pancreas, but not in other organs. Inset shows opposite side of pancreas. The positive signals are absent from liver (li), gall bladder (gb) and stomach (st). (L) In situ hybridization in stage 45 gut using sense probe against XpabpII. No positive signal is visible. ey, eye; op, olfactory pit; dp, dorsal pancreatic bud; vp, ventral pancreatic bud; p, pancreas; li, liver; st, stomach; gb, gall bladder; int, intestine; si, small intestine; co, colon; pd, proctodeum. Scale bar: (A–C, G–L), 500 μm; (D–F), 250 μm.
