The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, The Ohio State University, Columbus, OH 43205, USA.
Hum Genet. 2009 Dec;126(6):833-41. doi: 10.1007/s00439-009-0733-7.
Proximal spinal muscular atrophy (SMA) is a neuromuscular disease caused by low levels of the survival motor neuron (SMN) protein. In humans there are two nearly identical SMN genes, SMN1 and SMN2. The SMN2 gene generates a truncated protein, due to a C to T nucleotide alteration in exon 7, which leads to inefficient RNA splicing of exon 7. This exclusion of SMN exon 7 is central to the onset of the SMA disease. Exon 7 splicing is regulated by a number of exonic and intronic splicing regulatory sequences and the trans-factors that bind them. Here, we identify conserved intronic sequences in the SMN genes. Five regions were examined due to conservation and their proximity to exons 6 through 8. Using mutagenesis two conserved elements located in intron 7 of the SMN genes that affect exon 7 splicing have been identified. Additional analysis of one of these regions showed decreased inclusion of exon 7 in SMN transcripts when deletions or mutations were introduced. Furthermore, multimerization of this conserved region was capable of restoring correct SMN splicing. Together these results describe a novel intronic splicing enhancer sequence located in the final intron of the SMN genes. This discovery provides insight into the splicing of the SMN genes using conserved intonic sequence as a tool to uncover regions of importance in pre-messenger RNA splicing. A better understanding of the way SMN premRNA is spliced can lead to the development of new therapies.
近端脊髓性肌萎缩症（SMA）是一种由运动神经元存活（SMN）蛋白水平降低引起的神经肌肉疾病。在人类中，有两个几乎相同的 SMN 基因，SMN1 和 SMN2。SMN2 基因由于第 7 外显子中的 C 到 T 核苷酸改变而产生截断蛋白，导致第 7 外显子的 RNA 剪接效率低下。这种第 7 外显子的排除是 SMA 疾病发病的核心。外显子 7 的剪接受许多外显子和内含子剪接调节序列以及结合它们的反式因子调节。在这里，我们鉴定了 SMN 基因中的保守内含子序列。由于保守性和与外显子 6 到 8 的接近性，检查了五个区域。通过诱变，在 SMN 基因的 7 号内含子中鉴定出两个影响外显子 7 剪接的保守元件。对其中一个区域的进一步分析表明，当引入缺失或突变时，SMN 转录物中外显子 7 的包含减少。此外，该保守区域的多聚化能够恢复正确的 SMN 剪接。这些结果共同描述了位于 SMN 基因最后一个内含子中的新的内含子剪接增强子序列。这一发现提供了使用保守内含子序列作为工具来揭示前信使 RNA 剪接中重要区域的 SMN 基因剪接的见解。更好地了解 SMN pre-mRNA 是如何剪接的，可以为新疗法的开发提供依据。
