Model of OPMD with constitutive PABPN1 expression

描述(申请人提供)：眼咽肌营养不良症(OPMD)是由编码核聚腺苷结合蛋白PABPN1的基因中短GCG重复序列的扩张引起的。GCG重复序列被翻译为一小段丙氨酸。野生型等位基因编码PABPN1 N端10个连续的丙氨酸残基。当这个聚丙氨酸束至少有12个，但不超过17个丙氨酸时，OPMD的结果是主要遗传的。有证据支持突变的PABPN1蛋白聚集导致肌肉退化的模型。突变的蛋白质在骨骼肌中形成核包涵体。 在许多蛋白质构象疾病中，如聚谷氨酰胺病，突变蛋白的聚集导致神经元变性，尽管突变蛋白在非神经组织中广泛表达。相比之下，OPMD是第一个蛋白质构象疾病的例子，涉及一种可能在所有哺乳动物细胞中表达的基因，似乎选择性地影响骨骼肌。然而，神经和肌肉退行性变对表型的各自贡献目前尚不确定，而OPMD仅是一种骨骼肌疾病的传统观点最近受到了挑战。需要动物模型来研究这种疾病的病理生理学和治疗。已经开发了几种转基因模型，但它们都有局限性，仍然需要一种模型来再现PABPN1的表型和自然表达模式。该建议的目的是建立和鉴定一种转基因小鼠模型，在该模型中，突变的PABPN1的表达受PABPN1基因的自然调控元件控制。我们已经开发了一种结构，其中抑制PABPN1表达的潜在自动调节机制被禁用，从而使PABPN1启动子的转录能够支持更高水平的蛋白质表达。这些修饰应该会增强突变等位基因的致病性。我们计划建立表达突变型或野生型PABPN1蛋白的转基因小鼠系，并对其表型进行初步分析。这些转基因小鼠品系将有助于研究这种肌肉退化的新机制，也可能为了解蛋白质构象疾病的一般病理生理学提供帮助。此外，有迹象表明，这种形式的肌营养不良特别适合于治疗干预。通过开发一种可用于临床前研究的小鼠模型，该项目的结果将为开发有效的治疗方法奠定基础。

DESCRIPTION (provided by applicant): Oculopharyngeal muscular dystrophy (OPMD) is caused by expansion of a short GCG repeat in the gene encoding the nuclear polyadenylate binding protein, PABPN1. The GCG repeat is translated as a short tract of alanines. The wild-type allele encodes 10 consecutive alanine residues at the N terminus of PABPN1. Dominantly-inherited OPMD results when this polyalanine tract has at least 12, but not more than 17 alanines. Evidence supports a model in which aggregation of the mutant PABPN1 protein leads to muscle degeneration. The mutant protein forms nuclear inclusions in skeletal muscle. In many protein conformation diseases, such as, polyglutamine diseases, aggregation of mutant protein leads to neuronal degeneration, even though the mutant proteins are widely expressed in non-neural tissues. By contrast, OPMD is the first example of a protein conformation disease, involving a gene that is probably expressed in all mammalian cells, that appears to selectively affect skeletal muscle. However, the respective contribution or neural versus muscle degeneration to the phenotype is presently uncertain, and the conventional view that OPMD is exclusively a disease of skeletal muscle has been recently challenged. Animal models are needed to study the pathophysiology and treatment of this disorder. Several transgenic models have been developed, but they have limitations, and there still is a need for a model that reproduces the phenotype and the natural pattern of PABPN1 expression. The aim of this proposal is to develop and characterize a transgenic mouse model in which the expression of mutant PABPN1 is controlled by the natural regulatory elements from the PABPN1 gene. We have developed a construct in which potential autoregulatory mechanisms for restraining PABPN1 expression are disabled, so that transcription from the PABPN1 promoter can support a higher level of protein expression. These modifications should enhance the pathogenicity of the mutant allele. We plan to develop lines of transgenic mice expressing the mutant or wild-type PABPN1 protein, and carry out an initial analysis of the phenotype. These lines of transgenic mice will be useful to study this novel mechanism for muscle degeneration, and they also may provide insight into the general pathophysiology of protein conformation diseases. Furthermore, there are indications that this form of muscular dystrophy is particularly amenable to therapeutic intervention. By developing a mouse model that is valid for preclinical studies, results from this project will lay the groundwork for developing effective treatments.