Mouse models of genomic instability and birth defects

描述(申请人提供)：肾上腺皮质发育不良(ACD)是一种自发的常染色体隐性遗传小鼠突变，表现为多效性表型，包括胚胎和围产期死亡。ACD突变胚胎的胚胎缺陷包括后体轴截断、椎体分割缺陷、肾积水和肢体畸形，类似于在患有尾部退化综合征(CRS)和Vacterl(脊柱、肛门、心脏、气管食管瘘、肾脏和肢体畸形)的人类中观察到的常见畸形。此外，ACD突变胚胎表现出生长迟缓、广泛的细胞凋亡、血管构型缺陷和造血干细胞群体的异常。ACD基因编码一种新的端粒结合蛋白(也称为TPP1)，它在多蛋白复合体中发挥功能，维持端粒的完整性。与此功能一致的是，ACD突变小鼠有端粒功能障碍的证据，这表明基因组不稳定。虽然基因组不稳定和癌症之间的联系已经有了很好的记录，但人类基因组不稳定和出生缺陷之间的联系还没有被探索过。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Rothmund-Thomson综合征；然而，这些综合征导致出生缺陷的机制尚不清楚。该项目的总体目标是使用ACD小鼠作为模型系统，了解由基因组不稳定导致的出生缺陷的机制，包括CRS和Vacterl。ACD小鼠是这些研究的杰出模型，因为它展示了基因组不稳定和类似CRS和Vacterl的畸形的细胞证据。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。在目标1中，将探索ACD和P53家族成员之间的相互作用，这两个成员在维持基因组稳定方面具有众所周知的作用。这些研究将建立在本实验室先前工作的基础上，表明ACD表型的某些方面，特别是脊椎异常和肢体发育不良，是由于p53依赖的细胞凋亡所致。在目标2中，将通过在发育过程中对ACD基因进行可诱导的靶向敲除来检验正常的ACD功能在早期器官发生中至关重要的假设。目的3研究ACD在造血干细胞存活和维持中的作用。在目标4中，将使用转基因小鼠模型在体内检测ACD的区域特异性表型。利用ACD小鼠模型阐明人类常见出生缺陷的机制，如CRS和Vacterl，是识别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会导致治疗和预防这些出生缺陷。 公共卫生相关性：出生缺陷是美国婴儿死亡的主要原因，每年占婴儿死亡人数的五分之一。肾上腺皮质发育不良(ACD)小鼠是人类尾部退行性综合征和Vacterl(脊椎、肛门、心脏、气管食管瘘、肾脏和肢体畸形)相关的模型，ACD基因编码一种蛋白质，在端粒保护和基因组稳定中发挥作用。基因组不稳定作为出生缺陷的原因的作用还没有被探索；因此，这项提议的目标是使用ACD小鼠模型来帮助理解基因组不稳定和出生缺陷之间的联系。从这些研究中获得的信息将是识别导致人类出生缺陷的致病基因和环境因素的关键一步，并可能最终导致治疗和预防这些出生缺陷。

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.