Spinal muscular atrophy therapy using recombinant SMN proteins

描述(申请人提供)：脊髓性肌萎缩症(SMA)是一种运动神经元的神经退行性疾病，由存活运动神经元基因(SMN1)的缺失或突变引起。SMN1编码存活运动神经元(SMN)蛋白，该蛋白对小核核糖核蛋白颗粒的生物发生至关重要，而核糖核蛋白颗粒对前mRNA剪接是重要的，但参与SMA发病机制的剪接靶点尚不清楚。人类含有第二个部分功能的SMN2，与SMN1相比，它在外显子7上包含一个核苷酸差异，导致大多数SMN2转录本和截短的SMN蛋白中跳过外显子7。SMN2表达的功能全长SMN蛋白数量有限，但通常不能弥补SMN1蛋白的缺失。SMN蛋白的丢失会导致衰弱的肌肉无力、呼吸窘迫，在严重情况下还会导致死亡。SMA的发生率为每6000到10000名活产儿中就有一例，它是美国婴儿死亡的主要遗传原因。目前还没有治疗方法 或预防疾病，尽管一些方法已被广泛研究为潜在的治疗方法。这些方法包括基因治疗以传递SMN1基因，以及使用反义寡核苷酸或小分子剪接调节SMN1以增加全长SMN蛋白的表达。在这个项目中，我们提出了一种新的方法来补偿SMN的损失，使用连接到细胞穿透肽(CPP)的重组SMN蛋白。CPP是一种短小的(长度为10-30个氨基酸)和高正电荷的多肽，可以将其共价结合的分子货物(包括DNA、RNA、多肽和蛋白质)带入几乎所有类型的细胞。在这项建议中，我们将评估使用CPP-SMN结合物治疗SMA的可能性。

DESCRIPTION (provided by applicant): Spinal muscular atrophy (SMA) is a neurodegenerative disease of the motor neuron that is caused by deletion or mutation of the survival motor neuron gene (SMN1). SMN1 encodes the survival motor neuron (SMN) protein that is important for the biogenesis of small nuclear ribonucleoprotein particles that are important for pre-mRNA splicing, but the splicing target involved in SMA pathogenesis remains unclear. Humans contain a second and partially functional SMN2, which contains one nucleotide difference in exon 7 compared to SMN1, leading to the skipping of exon 7 in most SMN2 transcripts and truncated SMN proteins. Limited amount of functional full-length SMN protein is expressed from SMN2 but it typically cannot compensate for the loss of SMN1. The loss of SMN protein causes debilitating muscle weakness, respiratory distress, and death in severe cases. SMA occurs at a frequency of one in 6,000 to one in 10,000 live births and it is the leading genetic cause of infant mortality in the United States. There is currently no treatment or prevention of the disease, although a number of approaches have been extensively researched as potential therapeutics. These approaches include gene therapy to deliver the SMN1 gene, and splicing modulation of SMN2 using anti-sense oligo or small molecules to increase the expression of full-length SMN proteins. In this project, we propose a new approach to compensate for the loss of SMN using recombinant SMN protein conjugated to a cell penetrating peptide (CPP). CPP are short (10-30 amino acids in length) and highly positively charged peptides that can bring its covalently conjugated molecular cargos (including DNA, RNA, peptide, and protein) into almost all cell types. In this proposal, we will evaluate the possibility of using CPP-SMN conjugate for SMA therapy.