Characterizing a Conditional Transgenic Mouse Model of FSHD

描述（由申请人提供）：面肩肱骨肌营养不良症（FSHD）是一种常染色体显性肌肉疾病，由复杂的遗传和分子机制引起。最近的发现提高了我们对FSHD遗传原因的理解，使我们能够集中精力研究FSHD中异常表达的DUX4。在FSHD中敲除DUX4蛋白是一个急迫的研究领域，因为它与疾病治疗直接相关。合适的DUX4模型将为此类研究提供关键工具。由于DUX4在异位表达时具有细胞毒性，因此产生适合研究FSHD的动物模型非常具有挑战性。为了克服这一障碍，我们建立了一个四环素抑制（tet-off） DUX4转基因小鼠模型。在该小鼠模型中，DUX4的表达受口服强力霉素的控制。当小鼠从饮水中口服强力霉素时，DUX4转基因基因被抑制。利用该系统，当小鼠与mCK-tTA小鼠系杂交时，DUX4可在所需时间诱导表达，且表达仅限于骨骼肌。在本应用的目的1中，我们将表征tet抑制肌肉特异性DUX4转基因小鼠（TRE-DUX4/mCK-tTA）的表型，并确定表达时间和小鼠年龄对表型的影响。在目的2中，我们将确定响应DUX4表达而产生的表型是否可逆。本应用程序的主要目的是表征小鼠模型，并确定DUX4模型是否在生理、组织病理学和分子水平上概括了人类疾病。如果DUX4模型被证明是研究FSHD机制、测试治疗手段或两者兼而有之的合适模型，它将对FSHD研究领域产生重大影响。

DESCRIPTION (provided by applicant): Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant muscle disorder caused by complex genetic and molecular mechanisms. Recent discoveries improved our understanding of the genetic cause of FSHD and allowed us to focus our efforts on the aberrantly expressed DUX4 in FSHD. Knocking down the DUX4 protein in FSHD is an acute area of research since it is directly relevant to disease treatment. A suitable DUX4 model will provide a critical tool for such studies. Generating a suitable animal model for studying FSHD has been extremely challenging due to the cytotoxic nature of the DUX4 when it is ectopically expressed. To overcome this obstacle, we generated a tetracycline-repressible (tet-off) DUX4 transgenic mouse model. In this mouse model, the expression of DUX4 is controlled by oral doxycycline. The DUX4 transgene is suppressed when the mice receive oral doxycycline from their drinking water. Using this system, the expression of DUX4 can be induced at a desired time and the expression is restricted to skeletal muscles when the mouse is cross-bred with a mCK-tTA mouse line. In aim 1 of this application, we will characterize the phenotypes of the tet- repressible muscle-specific DUX4 transgenic mice (TRE-DUX4/mCK-tTA) and determine the effects of the duration of expression and the age of mice on the phenotypes. In aim 2, we will determine whether the phenotypes developed in response to the DUX4 expression is reversible. The main goal of this application is to characterize the mouse model and to determine whether the DUX4 model recapitulates the human disease at the physiological, histopathological and molecular level. If proven to be a suitable model for investigating FSHD mechanisms, testing therapeutic means or both, this DUX4 model will have a high impact to the field of FSHD research.