SMN2 Silent Mutation Knock-in: New SMA Mouse Model-Better Therapies

描述（由申请方提供）：近端脊髓性肌萎缩症（SMA）是一种常染色体隐性遗传神经退行性疾病，是美国婴儿死亡的主要遗传原因。运动神经元1基因（SMN 1）的缺失或突变导致运动神经元1基因产物的缺失。SMN1蛋白是运动神经元存活所必需的。人类基因组含有一个几乎相同的基因SMN2，它与SMN1在功能上是冗余的，可能会挽救疾病表型。然而，由于SMN2 RNA产物的无效加工，SMN2基因的表达水平大大降低。具体而言，SMN2在位于外显子7中的单个核苷酸处与SMN1基因不同。这种改变的核苷酸导致剪接机制对外显子7的识别减少，最终导致外显子的跳跃和非功能性蛋白质产物的产生。因此，纠正SMN2剪接表型是SMA患者在正确的时间和地点恢复SMN活性的有力治疗选择。然而，没有动物模型可以准确地测试这种治疗选择。本提案的主要目标是生成在小鼠Smn基因中含有人SMN2外显子7点突变的SMA小鼠模型。我们假设该小鼠模型将更精确地重现与SMN2基因剪接相关的人SMA状况。此外，该模型对于解决旨在纠正SMN 2剪接的潜在疗法以及评估SMN替代疗法的时机和剂量是必要的。我们将使用新的和改进的SMA模型来解决此类治疗的适当给药时间。该提案的主要重点是生成脊髓性肌萎缩症（SMA）的小鼠模型，SMA是一种毁灭性的神经退行性疾病，是美国婴儿死亡的主要遗传原因。为了建立这种疾病的模型，我们计划建立一种小鼠模型，该模型具有运动神经元（SMN）存活基因的改变，该基因已知会导致人类SMA疾病。该小鼠将用于回答与SMN基因替代疗法的治疗可能性有关的许多问题，长期目标是测试候选疗法以纠正患者的神经退行性缺陷。

DESCRIPTION (provided by applicant): Proximal spinal muscular atrophy (SMA) is an autosomal recessive neuro-degenerative disease that is the primary genetic cause of infant mortality in the United States. Absence of the survival of motor neuron-1 gene (SMN1) gene product as a result of deletion or mutation leads to the disease. The SMN1 protein is necessary for motor neuron survival. The human genome harbors a nearly identical gene, SMN2, that is functionally redundant with SMN1 and could potentially rescue the disease phenotype. The SMN2 gene, however, is expressed at greatly reduced levels due to ineffective processing of the SMN2 RNA product. Specifically, the SMN2 varies from the SMN1 gene at a single nucleotide positioned in exon 7. This altered nucleotide leads to decreased recognition of exon 7 by the splicing machinery and results, ultimately, in skipping of the exon and the generation of a non-functional protein product. Correction of the SMN2 splicing phenotype is therefore a powerful therapeutic option to reinstate SMN activity in the correct time and place in SMA patients. However, no animal models exist to accurately test this therapeutic option. The primary goal of this proposal is to generate a SMA mouse model that contains the human SMN2 exon 7 point mutation in the mouse Smn gene. We hypothesize that this mouse model will more precisely recapitulate the human SMA condition relative to splicing of the SMN2 gene. Furthermore this model is necessary to address potential therapies aimed at correcting SMN2 splicing, and to evaluate the timing and dosage of SMN replacement therapies. We will use the new and improved SMA model to address the proper timing for the administration of such therapies. The main focus of this proposal is to generate mouse models for Spinal Muscular Atrophy (SMA), a devastating neuro-degenerative disease that is a primary genetic cause of infant mortality in the United States. In order to model the disease, we plan to generate a mouse model that has an alteration in the survival of motor neuron (SMN) gene that is known to lead to the SMA disease in humans. This mouse will be utilized to answer many questions pertaining the therapeutic possibilities of SMN gene replacement therapies with the long-term goal of testing candidate therapies to correct the neuro- degenerative defect in patients.