Development of a Porcine Model of Ataxia-Telangiectasia

描述（由申请人提供）：共济失调-毛细血管扩张症（A-T）是一种多系统性、复发性遗传性疾病，在全球范围内的发病率为1/40，000至1/100，000。其主要特征是早发性小脑共济失调和毛细血管扩张，疾病名称由此而来。此外，患者还表现出许多其他临床症状，包括对癌症（淋巴瘤、白血病、脑肿瘤）、免疫缺陷、胰岛素抵抗性糖尿病、染色体不稳定性、电离辐射敏感性、支气管肺结核病易感性和胸腺缺失或几乎完全缺失的易感性增加。目前A-T的治疗方法是针对症状的管理。物理和语言治疗可以改善患者的生活，可以给予球蛋白注射以支持免疫系统。然而，没有针对潜在缺陷的治疗。因此，A-T仍然是一种致命的疾病。A-T的改进疗法的开发目前受到缺乏动物模型的限制，该动物模型完全且准确地概括了这种疾病的多系统性质。多年来，通过靶向破坏小鼠Atm基因，已经开发了许多A-T小鼠模型，这些模型对于研究ATM功能和A-T疾病的某些方面非常有价值。然而，没有一个小鼠模型完全复制在人类疾病中观察到的复杂临床症状，更重要的是，没有一个小鼠模型发展出严重的神经系统表型，这是人类A-T疾病的标志。小鼠模型未能出现A-T的经典症状可能是两个物种之间生理学、解剖学和发育差异的结果。相比之下，猪可能是研究人类疾病的更好模型，因为它们的发育，解剖学和生理学与人类更密切相关。鉴于猪脑的发育和解剖结构与人类比小鼠更相似，猪ATM基因的突变可能导致许多与A-T患者相同的神经系统变化。因此，本提案的最终目标是通过破坏ATM基因来开发和商业化A-T的猪模型。我们打算通过结合基因靶向和体细胞核移植（SCNT）分两步实现这一目标。在这个提议中，ATM+/-胎儿成纤维细胞， 将用作体细胞核移植的核供体。将核移植胚胎转移至受体雌性进行妊娠。所得仔猪将具有一个靶向ATM基因。我们将培育杂合子以产生ATM-/-猪，并进行彻底的分子、生化和生理表征。最后，我们将建立长期的繁殖群。该项目旨在产生共济失调-毛细血管扩张的猪模型，这将为学术和行业研究人员提供一个机会，以更好地了解ATM功能障碍的后果，A-T疾病的发病机制，并提供一个改进的模型，以开发和测试新的治疗策略。

DESCRIPTION (provided by applicant): Ataxia-telangiectasia (A-T) is a multi-systemic, recessively inherited disorder that affects between 1 in 40,000 to 1 in 100,000 individuals worldwide. It is characterized primarily by early onset cerebellar ataxia and telangiectasia, from which the disease name is derived. In addition, patients also exhibit a number of other clinical symptoms including increased susceptibility to cancer (lymphomas, leukemia, brain tumors), immunodeficiency, insulin-resistant diabetes, chromosomal instability, sensitivity to ionizing radiation, susceptibility to bronchopulmonary disease, and the absence, or almost complete absence, of a thymus. Current treatments for A-T are directed toward the management of symptoms. Physical and speech therapy can improve the lives of patients, and ¿-globulin injections can be given to support the immune system. However, no treatment is directed at the underlying defect. Consequently, A-T remains a fatal disease. The development of improved therapies for A-T is currently limited by the lack of an animal model that fully, and accurately, recapitulates the multi-systemic nature of this disease. A number of mouse models of A-T have been developed over the years by the targeted disruption of the mouse Atm gene, and these models have proved invaluable for studying some aspects of ATM function and A-T disease. However, no single mouse model fully replicates the complex clinical symptoms observed in human disease, and more importantly, none of the murine models develop the severe neurological phenotype that is the hallmark of human A-T disease. The failure of mouse models to develop the classical symptoms of A-T is likely the result of physiological, anatomical, and developmental differences between the two species. In contrast, pigs may serve as a better model in which to study human disease given that their development, anatomy, and physiology are more closely related to that of humans. Given that the development and anatomy of the pig brain more closely resembles that of humans than mice, mutations in the porcine ATM gene may result in many of the same neurological changes that are observed in A-T patients. Therefore, the ultimate goal of this proposal is to develop and commercialize a porcine model of A-T by disrupting the ATM gene. We intend to accomplish this in two steps by combining gene-targeting and somatic cell nuclear transfer (SCNT). In this proposal, ATM+/- fetal fibroblasts that were developed in Phase I will be used as nuclear donors for somatic cell nuclear transfer. Nuclear transfer embryos will be transferred to recipient females for gestation. Resulting piglets will have one targeted ATM gene. We will breed heterozygotes to produce ATM-/- pigs and perform a thorough molecular, biochemical, and physiological characterization. Finally, we will establish long-term breeding herds. This project is intended to produce a porcine model of ataxia-telangiectasia that will provide academic and industry researchers with an opportunity to better understand the consequences of ATM dysfunction, the pathogenesis of A-T disease, and provide an improved model in which to develop and test new therapeutic strategies.