Using TSUNAMI in a sensitized mouse to generate an intermediate SMA model

描述（由申请人提供）：近端脊髓性肌萎缩症（SMA）是一种神经退行性疾病，是婴儿死亡的主要遗传原因。存活运动神经元-1 （SMN1）基因的缺失或突变导致人类SMA疾病。人类基因组包含一个几乎相同的基因SMN2，它与SMN1在功能上是冗余的。然而，SMN2基因的表达由于外显子7的剪接突变而严重受损。SMA患者的疾病严重程度与SMN2拷贝数呈负相关，SMN蛋白水平最低导致SMA表型最严重。虽然严重形式的SMA是致命的，但中度和轻度形式的疾病会导致患者行动不便和呼吸问题。在严重的SMA小鼠模型中恢复SMN蛋白已显示出该疾病表型的部分拯救，然而在中度或轻度SMA模型中尚未有恢复神经缺陷的治疗性试验。因此，迫切需要开发一种中度SMA小鼠模型，并确定中度至轻度形式的疾病的治疗窗口期。在缺乏这些知识的情况下，适当的治疗仍将难以捉摸，SMA将继续成为导致残疾和死亡的主要原因。本申请的主要重点是利用小鼠模型研究SMA的治疗方法，其长期目标是测试候选疗法来纠正患者的神经退行性缺陷。为此，我们的实验室开发了一种新的轻度SMA小鼠模型（接近SMA IV型），其中小鼠基因Smn发生突变，产生低水平的Smn蛋白。此外，为了生成急需的中间SMA小鼠模型（类似于人类的III型），我们假设我们将能够通过使用最近发表的海啸技术（使用负ASOs来模拟疾病的靶向剪接）进一步降低当前轻度模型中SMN蛋白的水平。我们的目标是确定我们生成的中间模型的治疗窗口。

DESCRIPTION (provided by applicant): Proximal spinal muscular atrophy (SMA) is a neuro-degenerative disease that is a primary genetic cause of infant mortality. Deletion or mutation of the survival motor neuron-1 (SMN1) gene leads to the SMA disease in humans. The human genome harbors a nearly identical gene, SMN2, that is functionally redundant with SMN1. However, expression of the SMN2 gene is severely compromised as a result of a splicing mutation in exon 7. Disease severity in SMA patients is inversely correlated with the copy number of SMN2 with the lowest levels of SMN protein causing the most severe SMA phenotypes. While the severe forms of SMA are fatal, the intermediate and mild forms of the disease cause immobility and respiratory issues for patients. Restoration of SMN protein to severe SMA mouse models has shown partial rescue of the disease phenotype, however there has been no therapeutic testing for restoration of neurological defects in intermediate or mild models for SMA. Therefore, there is a critical need to develop an intermediate SMA mouse model and to determine the therapeutic window for the intermediate to mild forms of the disease. In the absence of such knowledge, adequate treatment will remain elusive and SMA will continue to be a leading cause of disability and death. The main focus of this application is to utilize mouse models to study the treatment of SMA, with the long-term goal of testing candidate therapies to correct the neuro-degenerative defect in patients. To this end, our lab has developed a new mild SMA mouse model (approximates SMA TYPE IV) with the mouse gene, Smn, mutated to produce low levels of the SMN protein. Furthermore, in order to generate the much needed intermediate SMA mouse model (similar to Type III in humans), we hypothesize that we will be able to further decrease the levels of SMN protein in our current mild model by using the recently published TSUNAMI technique (targeting splicing using negative ASOs to model illness). We aim to determine the therapeutic window for the intermediate model that we generate.