Mouse models of genomic instability and birth defects

描述（由申请人提供）：肾上腺皮质发育不良（add）是一种自发的常染色体隐性小鼠突变，表现出多效表型，包括胚胎和围产期致死。add突变胚胎的胚胎学缺陷包括体后轴截短、椎体分割缺陷、肾积水和肢体异常，类似于尾回综合征（CRS）和VACTERL（椎体、肛门、心脏、气管-食管瘘、肾脏、肢体异常）相关的人类常见畸形。此外，add突变胚胎在造血干细胞群体中表现出生长迟缓、广泛的细胞凋亡、血管模式缺陷和异常。add基因编码一种新的端粒结合蛋白（也称为TPP1），该蛋白在多蛋白复合物中起作用，以维持端粒的完整性。与这种功能一致，add突变小鼠有端粒功能障碍的证据，表明基因组不稳定。虽然基因组不稳定性与癌症之间的关系已被充分记录，但基因组不稳定性与人类出生缺陷之间的关系尚未被探索。VACTERL和VACTERL样缺陷在其他以基因组不稳定为特征的遗传综合征中也有报道，包括Fanconi贫血和rothmond - thomson综合征；然而，导致这些综合征出生缺陷的机制尚不清楚。该项目的总体目标是了解基因组不稳定导致出生缺陷的机制，包括CRS和VACTERL，使用add小鼠作为模型系统。add小鼠是这些研究的杰出模型，因为它表现出类似CRS和VACTERL的基因组不稳定和畸形的细胞证据。这项工作很重要，因为导致人类CRS和VACTERL的潜在机制可能是相似的。在Aim 1中，我们将探讨Acd和p53家族成员之间的相互作用，它们在维持基因组稳定性中发挥着众所周知的作用。这些研究将建立在该实验室先前的工作基础上，表明acd表型的各个方面，特别是椎体异常和肢体发育不全，是由于p53依赖性的细胞凋亡。在Aim 2中，正常的Acd功能在早期器官发生过程中至关重要的假设将在发育过程中通过诱导靶向敲除Acd基因来验证。目的3将研究Acd在造血干细胞存活和维持中的作用。在aims 4中，将使用转基因小鼠模型在体内检查add的结构域特异性表型。使用add小鼠模型来阐明人类常见出生缺陷（如CRS和VACTERL）的机制，是确定人类致病遗传和环境因素的关键一步。从这些研究中获得的信息可能最终导致这些出生缺陷的治疗和预防。

DESCRIPTION (provided by applicant): Adrenocortical dysplasia (acd) is a spontaneous autosomal recessive mouse mutation that exhibits a pleiotropic phenotype that includes embryonic and perinatal lethality. The embryologic defects in acd mutant embryos consist of truncation of the posterior body axis, vertebral segmentation defects, hydronephrosis, and limb anomalies, resembling common malformations observed in humans with caudal regression syndrome (CRS) and VACTERL (vertebral, anal, cardiac, tracheo-esophageal fistula, renal, limb anomalies) association. In addition, acd mutant embryos exhibit growth retardation, widespread apoptosis, vascular patterning defects, and abnormalities in hematopoietic stem cell populations. The Acd gene encodes a novel telomeric binding protein (also known as TPP1) that functions in a multiprotein complex to maintain telomere integrity. Consistent with this function, acd mutant mice have evidence of telomere dysfunction, indicative of genomic instability. While the association between genomic instability and cancer is well documented, the association between genomic instability and birth defects in humans is unexplored. VACTERL and VACTERL-like defects have been reported in other genetic syndromes characterized by genomic instability, including Fanconi anemia and Rothmund-Thomson syndrome; however, the mechanisms that lead to birth defects in these syndromes are unknown. The overall goal of this project is to understand the mechanisms that lead to birth defects resulting from genomic instability, including CRS and VACTERL, using the acd mouse as a model system. The acd mouse is an outstanding model for these studies because it exhibits cellular evidence of genomic instability and malformations that resemble CRS and VACTERL. This work is important because the underlying mechanisms leading to CRS and VACTERL in humans are likely to be similar. In Aim 1, interactions between Acd and p53 family members, which have a well-known role in maintaining genomic stability, will be explored. These studies will build upon prior work in this laboratory showing that aspects of the acd phenotype, specifically the vertebral anomalies and limb hypoplasia, are due to p53-dependent apoptosis. In Aim 2, the hypothesis that normal Acd function is critical during early organogenesis will be tested using an inducible targeted knockout of the Acd gene during development. Aim 3 will investigate the role of Acd in hematopoietic stem cell survival and maintenance. In Aim 4, domain-specific phenotypes of Acd will be examined in vivo using transgenic mouse models. The use of the acd mouse model to elucidate the mechanisms underlying common birth defects in humans, such as CRS and VACTERL, is a critical step toward identification of causative genetic and environmental factors in humans. The information gained from these studies may ultimately lead to treatment and prevention of these birth defects. PUBLIC HEALTH RELEVANCE: Birth defects are the leading cause of infant mortality in the United States, accounting for 1 in 5 infant deaths annually. The adrenocortical dysplasia (acd) mouse is a model for caudal regression syndrome and VACTERL (vertebral, anal, cardiac, tracheo-esophageal fistula, renal, and limb anomalies) association in humans, and the Acd gene encodes a protein that has a role in telomere protection and genome stability. The role of genomic instability as a cause of birth defects is unexplored; therefore, the goal of this proposal is to use the acd mouse model to help understand the link between genomic instability and birth defects. The information gained from these studies will be a critical step toward identification of causative genetic and environmental factors that lead to birth defects in humans and may ultimately lead to treatment and prevention of these birth defects.