The Dact1 mouse as a model for OEIS

描述（由申请人提供）：OEIS复合体是人类胎儿和婴儿畸形的一种关联，主要影响膀胱、远端消化道和脊椎骨骼。它和一种更广泛的被称为“下中胚层缺陷序列”的畸形，构成了一种相对常见的死产、围产期死亡和可通过手术纠正的出生缺陷的零星原因。目前对这种畸形的遗传或发育病因了解甚少。该应用程序将使用细胞质信号调节剂Dact1中的靶向突变作为OEIS和相关畸形的动物模型。Dact1突变动物在出生前不久或出生后不久死于脐下腹壁、远端泌尿生殖系统、肛门和尾椎的综合缺陷。Dact1在胚胎早期在中胚层组织中表达。我假设Dact1蛋白在WntSa和WntSa细胞间信号传导的下游发挥作用，影响中胚层发育，并继发影响膀胱、生殖器和肛门形成所必需的内胚层。这一假设为OEIS和下中胚层缺陷序列提供了一个单一的遗传模型。我们将通过使用在我的实验室创建的组成型和中胚层特异性Dact1突变小鼠系，结合其他改变和监测Wnt信号的小鼠系来验证这一假设。具体目的是：(1)确定Dact1在wnt5a依赖的信号传导和中胚层增殖、迁移和存活中的作用；(2)确定Dact1在wntsa依赖的信号传导和中胚层分化中的作用；(3)使用Dact1突变体作为中胚层和后肠衍生物缺陷的模型。该研究设计利用了实验室小鼠的大量遗传、分子和胚胎实验资源。它将探讨Dact1基因对中胚层和内胚层发育的贡献，所涉及的信号通路，以及Dact1功能的破坏如何导致新生儿复杂的尾端畸形。这项研究对公共卫生很重要，因为它创造、建立并使用了一种新的动物模型来调查人类一系列复杂出生缺陷的起源。我们对Dact1小鼠的研究将有助于揭示出生缺陷的遗传、分子和细胞基础，这些缺陷在美国导致死产、婴儿死亡和新生儿手术。

DESCRIPTION (provided by applicant): The OEIS complex is an association of malformations in human fetuses and babies primarily affecting the bladder, distal digestive tract, and vertebral skeleton. It and a broader spectrum of malformations called the 'lower mesodermal defects sequence," comprise a relatively common sporadic cause of stillbirth, perinatal lethality, and surgically-correctable birth defects. Very little is currently understood about the genetic or developmental etiology of this collection of malformations. This application will use a targeted mutation in the cytoplasmic signaling modulator Dact1 as an animal model for OEIS and related malformations. Dact1 mutant animals die shortly before or after birth from combined defects in the infraumbilical abdominal wall, the distal urogenital system, the anus, and the caudal vertebral column. Dact1 is expressed at early embryonic stages in mesodermal tissues. I hypothesize that the Dact1 protein functions downstream of both WntSa and WntSa intercellular signaling to influence mesoderm development, and that this secondarily affects the endoderm necessary for formation of the bladder, genitalia, and anus. This hypothesis provides a single hit genetic model for OEIS and the lower mesodermal defects sequence. We will test this hypothesis by making use of constitutive and mesoderm-specific Dact1 mutant mouse lines created in my laboratory, in combination with other mouse lines that alter and monitor Wnt signaling. The specific aims are: (1) To determine the role of Dact1 in Wnt5a-dependent signaling and mesoderm proliferation, migration and survival, (2) To determine the role of Dact1 in WntSa-dependent signaling and mesoderm differentiation, and (3) To use Dact1 mutants as a model for defects in mesodermal plus hindgut derivatives. The research design draws on the tremendous genetic, molecular, and embryonic experimental resources available in the laboratory mouse. It will probe contributions of the Dact1 gene to mesoderm and endoderm development, the signaling pathways involved, and how disruptions in Dact1 function lead to complex caudal malformations in neonates. This research is important to public health because it creates, establishes, and uses a new animal model to investigate the origins of a series of complex birth defects in humans. Our studies of the Dact1 mouse will help uncover the genetic, molecular, and cellular basis for birth defects that contribute significantly to still-births, infant deaths, and neonatal surgeries in the United States.