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来寻找人类生理学和病理学的分子基础，或者他们可以以寻求治疗常见或罕见先天性疾病的患者的形式出现。这两种途径经常汇合，如x连锁显性人类疾病局灶性真皮发育不全（FDH）。这种综合征最近被定位到PORCN基因，这是果蝇基因豪猪的独特同源基因，是分泌Wnt配体所必需的。尽管wnt被认为调控发育和疾病的许多方面，但哺乳动物中配体功能的遗传研究因19个家族成员的冗余而变得复杂。为了建立一种克服这种冗余的遗传工具，我们的实验室产生了小鼠Porcn的条件敲除等位基因，并证明它提供了FDH的动物模型。基于我们最近发表的研究结果，我们建议研究与FDH相关的两种新的疾病相关表型，异位脂肪沉积和不完全的体壁关闭，我们的小鼠模型提供了独特的途径。我们的初步研究结果表明，这些表型具有外胚层病因学，我们将研究三个具体目标：(1)确定外胚层表达的Wnt蛋白生产中对Porcn的需求；(2)描述porcn介导的Wnt信号在抑制脂肪形成中的作用；(3)以Porcn突变小鼠作为体壁闭合缺陷模型进行分析。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未被充分研究的方面提供新的见解，与人类疾病的联系，并在我们的实验室建立一个新的Porcn/ wnt研究项目。

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. PUBLIC HEALTH RELEVANCE: Focal dermal hypoplasia (FDH) is a rare disease that affects the Wnt signaling pathway, which itself is very commonly dysregulated in additional congenital and acquired diseases. FDH is caused by mutations in the PORCN gene, for which we have generated a novel mouse genetic model. This proposal focuses on aspects of FDH that are also relevant to other diseases, and highlights the usefulness of mouse PORCN mutants to model disorders of Wnt signaling in humans.