Molecular Mechanisms of Pancreas Development in Xenopus

脊椎动物胰腺发育的分子调控是一个非常活跃的研究课题，这也是因为对这一过程的更好的理解可能会导致建立体外由前体细胞生成胰腺组织的实验方案，这将被用于胰腺功能障碍的细胞治疗。在过去的两年里，我们已经制定了用于肝脏和胰腺发育的分子分析以及在非洲爪哇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。我们还发现维甲酸(RA)作为一个关键信号，在非洲爪哇的早期内胚层模式朝向胰腺命运的过程中是必不可少的；此外，我们观察到过量的RA促进了内分泌胰腺细胞的形成，而牺牲了外分泌细胞。在这些研究的延伸中，我们现在打算识别参与原始内胚层模式形成的类风湿反应基因。此外，我们希望通过获得和丧失功能的方法来研究三种不同的转录调控因子，即P48/Ptf1a，ESR-10和ngnr1，在内分泌-外分泌胰腺分化的背景下的活性。我们还打算进一步推进我们的实验方案，通过使用相关的转录调控因子，从多能胚胎前体细胞中产生内分泌和外分泌胰腺细胞。最后，我们希望通过基于SAGE和微阵列的方法来确定纯化的、GFP标记的胰腺前体细胞的转录组，以便识别与早期胰腺发育有关的新的候选调控活动。

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.