Role of Fgfr2IIIb in epithelial mesenchymal signaling in intestinal development

候选人：我的职业目标是成为肠道发育研究和短肠综合征患者转化疗法开发的领导者。为了实现这一目标，我将在发育生物学，上皮-间质信号传导以及研究伦理学的基础科学方面接受强化培训。这将包括正式的课程作业，在实验室会议，部门和大学范围内的研讨会和国家会议上一对一的导师介绍。我将领导一个新生的研究小组，研究肠闭锁，为理解纵向肠道生长的机制奠定科学基础。我将开始为短肠综合征患者开展全面的临床项目，以建立一个补充我科学兴趣的临床组成部分。我将在奖励期的第三年之前提交R 01申请。最后，我将寻求在国家组织中担任领导职务，以加强这一领域的合作努力，并将注意力和资源直接用于开发这一问题的疗法和解决方案。所有这些步骤将有助于我成功地过渡到独立。 环境：威斯康星州大学是美国首屈一指的研究机构之一，校园内有800多名生物学家。外科部在联邦资助和外科医生科学家的职业发展方面享有全国最高的声誉。该部调动了大量资源，对尼科尔博士的职业发展作出了坚定的承诺，包括保证3年的工资、启动资金（30万美元）和每年9个月的受保护时间。此外，尼科尔博士将由两个首屈一指的发展生物学家和最成功的导师在这个校园（博士布什曼和法伦）以及其他优秀的教师指导。这些因素将为他提供一个最佳的研究环境，确保他成功地向独立过渡。 调研：这项研究的长期目标是了解肠闭锁的病因，并为再生疗法建立科学基础，以解决常伴随闭锁的短肠综合征的特征。肠闭锁是由于肠发育的节段性缺陷引起的。这会导致肠道连续性丧失和梗阻。FGF信号是肠道生长和发育的关键调节因子。我们的初步研究表明，结肠上皮中的Fgfr 2 IIIb的条件性突变在小鼠中产生相当于人类缺陷的节段性闭锁。闭锁的形成之前，上皮分化失败，随后间充质的径向和纵向生长中断。我们已经确定Foxf 1表达的缺失是该事件在将要发生闭锁的节段内的特异性生物标志物。Foxf 1是一个重要的间充质组织者和刺猬（Hh）信号通路的目标。我们推测，闭锁产生于上皮间充质信号在一个关键的发展时期，当这些信号直接径向和纵向生长的间充质的节段性中断。具体而言，我们假设上皮刺猬信号是这种间充质生长的关键调节剂，并且持续的Hh信号依赖于通过激活Fgfr 2 IIIb受体的上皮细胞自主分化。因此，预测上皮Fgfr 2 IIIb表达的丧失导致细胞自主分化失败、Hh信号传导的破坏、间充质生长失败和随后的闭锁形成。我们将在以下目标中检验这些预测： 具体目标1：检验Fgfr 2 IIIb突变破坏上皮分化导致中胚层生长、增殖和Foxf 1基因表达改变的假设。 具体目标二：检验以下假设：Fgfr 2 IIIb条件突变体中上皮分化的丧失是一种细胞自主事件，完全是由于Fgfr 2 IIIb表达的丧失。 具体目标3：检验以下假设：Fgfr 2 IIIb条件突变体中间充质生长减少是上皮Hedgehog信号转导丧失的直接结果。 我们将在小鼠中采用条件诱变策略来描述上皮和间充质之间的特定相互作用以及正常肠发育和闭锁形成中上皮细胞中Fgfr 2 IIIb受体的功能。这种方法将提供干净的，高分辨率的数据，并允许我们直接测试我们的假设在哺乳动物的遗传模型，密切概括在人类的发展。

Candidate: My career goals are to become a leader in the study of intestinal development and development of translational therapies for patients with short gut syndrome. To achieve this I will undergo intensive training in the basic sciences in developmental biology, epithelial-mesenchymal signaling as well as ethics in the conduct of research. This will include formal coursework, one-on-one mentorship presentations at lab meetings, department and University-wide seminars and national meetings. I will lead a nascent team of investigators in the study of intestinal atresia to develop a scientific foundation for understanding the mechanisms of longitudinal intestinal growth. I will begin a comprehensive clinical program for patients with short gut syndrome in order to establish a clinical component that will complement my scientific interests. I will submit an R01 application no later than year 3 of the award period. Finally, I will seek leadership positions in national organizations in order to enhance collaborative efforts in this area as well as direct attention and resources towards developing therapies and solutions for this problem. All of these steps will facilitate my successful transition to independence. Environment: The University of Wisconsin is one of the premier research institutions in the United States with over 800 biologists on campus. The Department of Surgery enjoys a reputation as one of the top in the country in terms of federal funding and career development of surgeon-scientists. The Department has mobilized its significant resources in making an iron clad commitment to Dr. Nichol's career development including guarantees for 3 years of salary, start-up funds ($300,000) and 9 months of protected time per year. In addition, Dr. Nichol will be mentored by two of the premier developmental biologists and most successful mentors on this campus (Drs. Bushman and Fallon) as well as other outstanding faculty. These components will provide him with an optimal research environment that will ensure that his transition to independence is successful. Research: The long term goal of this research is to understand the etiology of intestinal atresias and to establish the scientific foundation for regenerative therapies to address the features of short gut syndrome that often accompany atresia. Intestinal atresia arises from a segmental defect in intestinal development. This results in a loss of intestinal continuity and obstruction. FGF signaling is a critical regulator of intestinal growth and development. Our preliminary studies indicate that conditional mutation of Fgfr2IIIb in the colonic epithelium produces a segmental atresia in mice equivalent to the human defect. The formation of atresia is preceded by a failure in epithelial differentiation and a subsequent disruption in radial and longitudinal growth of the mesenchyme. We have identified loss of Foxf1 expression as a specific biomarker for this event within the segment that will undergo atresia. Foxf1 is a critical mesenchymal organizer and target of the hedgehog (Hh) signaling pathway. We hypothesize that atresias arise from a segmental disruption in epithelial-mesenchymal signaling during a critical developmental period when these signals direct both radial and longitudinal growth of the mesenchyme. Specifically, we postulate that epithelial hedgehog signaling is a critical regulator of this mesenchymal growth and that sustained Hh signaling is dependent upon cell autonomous differentiation of the epithelium by activation of the Fgfr2IIIb receptor. Accordingly, loss of epithelial Fgfr2IIIb expression is predicted to result in a failure in cell autonomous differentiation, disruption of Hh signaling, failed mesenchymal growth and subsequent atresia formation. We will test these predictions in following aims: Specific Aim 1: Test the hypothesis that Fgfr2IIIb mutation disrupts epithelial differentiation leading to alterations in growth, proliferation and Foxf1 gene expression in the mesoderm. Specific Aim 2: Test the hypothesis that loss of epithelial differentiation in the Fgfr2IIIb conditional mutants is a cell autonomous event due exclusively to a loss of Fgfr2IIIb expression. Specific Aim 3: Test the hypothesis that the reduced mesenchymal growth in the Fgfr2IIIb conditional mutant is a direct result of loss of epithelial Hedgehog signaling. We will employ a conditional mutagenesis strategy in mice to delineate specific interactions between epithelium and mesenchyme and the function of the Fgfr2IIIb receptor in epithelial cells in normal intestinal development and atresia formation. This approach will provide clean, high resolution data and permit us to directly test our hypotheses in a mammalian genetic model that closely recapitulates development in the human.