Molecular Mechanisms of Pancreas Development in Xenopus

脊椎动物胰腺发育的分子调节是一个热门研究活动的主题，也是因为更好地理解这一过程可能会导致定义体外前体细胞生成胰腺组织的实验方案，这可用于胰腺功能障碍的细胞治疗。在过去的两年中，我们制定了用于肝脏和胰腺发育的分子分析以及在非洲爪蟾多能胚胎前体细胞中诱导胰腺（和肝脏）基因表达的工具和方案。我们还发现视黄酸 (RA) 可以作为关键信号，对于爪蟾的早期内胚层模式向胰腺命运而言是必需的。此外，我们观察到过量的 RA 会促进内分泌胰腺细胞的形成，但会损害外分泌细胞。在这些研究的扩展中，我们现在打算鉴定参与原始内胚层图案化的 RA 反应基因。此外，我们希望通过在转基因青蛙中使用功能获得和丧失的方法，研究三种不同转录调节因子（即 p48/Ptf1a、ESR-10 和 ngnr1）在内分泌与外分泌胰腺分化的背景下的活性。我们还打算通过采用相关的转录调节因子，进一步推进我们的实验方案，从多能胚胎前体细胞生成内分泌和外分泌胰腺细胞。最后，我们希望通过 SAGE 和基于微阵列的方法定义纯化的 GFP 标记的胰腺前体细胞的转录组，以便识别参与早期胰腺发育的新候选调控活性。

Molecular regulation of pancreas development in vertebrates is a topic of intense research activities, also because a better understanding of this process may lead to the definition of experimental protocols for the generation of pancreatic tissue from precursor cells in vitro, which could be employed in cell therapy of pancreas malfunction. During the past two years, we have worked out tools and protocols for the molecular analysis of liver and pancreas development, as well as for the induction of pancreas (and liver) gene expression in pluripotent embryonic precursor cells in Xenopus. We have also found retinoic acid (RA) to act as a key signal that is essentially reequired for the early endodermal patterning towards a pancreatic fate in Xenopus; furthermore, we observed that excessive RA promotes the formation of endocrine pancreatic cells at the expense of exocrine cells. In extension of these studies, we now intend to identify the RA-responcive genes that are involved in the patterning of the primitive endoderm. Furthermore, we wish to study the activity of three different transcription regulators, namely p48/Ptf1a, ESR-10 and ngnr1, in the context of endocrine-versus-exocrine pancreatic differentiation by use of gain- and loss-of-function approaches in transgenic frogs. We also intend to further advance our experimental protocol for the generation of endocrine and exocrine pancreatic cells from pluripotent embryonic precursor cells by employing relevant transcription regulators. Finally, we wish to define the transcriptome of purified, GFP-tagged pancreatic precursor cells by SAGE and microarray based approaches in order to identify novel candidate regulatory activities that are involved in early pancreas development.