A conditional allele to dissect Porcn-dependent Wnt signaling in vivo

描述(由申请人提供)：研究人员可以通过生物化学或正向遗传学寻找人类生理学和病理学的分子基础，也可以以患者的形式为常见或罕见的先天性疾病寻求治疗。这两种方法经常会聚在一起，例如X连锁显性人类疾病局灶性真皮发育不良(FDH)。这种综合征最近被定位到PORCN基因，这是果蝇基因豪猪的唯一同源基因，需要分泌Wnt配体。尽管WNTS被认为调节发育和疾病的许多方面，但由于19个家族成员之间的冗余，哺乳动物配基功能的遗传研究变得复杂。为了建立一种基因工具来克服这种冗余，我们的实验室产生了小鼠PORCN的条件基因敲除等位基因，并证明它提供了FDH的动物模型。在我们最近发表的发现的基础上，我们建议在这里检查与FDH相关的两种新的和疾病相关的表型，异位脂肪沉积和不完全体壁关闭，我们的小鼠模型提供了独特的途径。我们的初步发现表明，这些表型具有共同的外胚层病因学，我们将从三个具体目标进行研究：(1)确定PORCN在产生外胚层表达的Wnt蛋白方面的需求；(2)表征PORCN介导的Wnt信号在抑制脂肪生成中的作用；(3)分析PORCN突变小鼠作为体壁关闭缺陷的模型。这些研究将坚定地确立PORCN突变体作为FDH模型和体内抑制Wnt信号的工具的实用性。他们还将为发育生物学中未被研究的与人类疾病有关的方面提供新的见解，并在我们的实验室建立一个新的以PORCN/WNT为重点的研究计划。

DESCRIPTION (provided by applicant): The molecular underpinnings of human physiology and pathology can be sought out by the researcher, via biochemistry or forward genetics, or they can present themselves in the form of a patient seeking treatment for a common or rare congenital disorder. These dual approaches frequently converge, as in the case of the X-linked dominant human disorder focal dermal hypoplasia (FDH). This syndrome was recently mapped to the PORCN gene, the unique homolog of a Drosophila gene, porcupine, required for secretion of Wnt ligands. Although Wnts are thought to regulate many aspects of development and disease, genetic studies of ligand function in mammals are complicated by redundancy among the 19 family members. To establish a genetic tool with which to overcome this redundancy, our lab generated a conditional knockout allele of mouse Porcn and demonstrated that it provides an animal model of FDH. Building on our recently published findings, we propose here to examine two novel and disease-relevant phenotypes associated with FDH, ectopic fat deposition and incomplete body wall closure, to which our mouse model provides unique access. Our preliminary findings indicate that these phenotypes share an ectodermal etiology, which we will investigate in three specific aims: (1) determine the requirement for Porcn in production of ectodermally-expressed Wnt proteins; (2) characterize the role of Porcn-mediated Wnt signals in suppressing adipogenesis; (3) analyze Porcn mutant mice as a model for body wall closure defects. These studies will firmly establish the utility of Porcn mutants as an FDH model and as a tool to inhibit Wnt signaling in vivo. They will also provide new insight into understudied aspects of developmental biology, with connections to human disease, and establish a new Porcn/Wnt-focused research program in our lab.