Department of Molecular Neurobiology and Neuropathology, National Institute of Neurology, La Rabta, Tunis, Tunisia. wieme
Int J Neurosci. 2011 Feb;121(2):107-11. doi: 10.3109/00207454.2010.529209. Epub 2010 Nov 3.
Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by degeneration of the anterior horn cells of the spinal cord. The survival motor neuron (SMN) gene has been identified as an SMA-determining gene. SMN exists as two copies in 5q13, and deletions in exons 7 and 8 of the telomeric copy (SMN(T)) occur in 95% of patients, regardless of disease severity. In a minority of patients, exon 7 but not exon 8 of SMN(T) appears deleted. We now report a patient with typical features of SMA type II who carried homozygous deletions of SMN(T) exon 7 and centromeric SMN (SMN(C)) exon 8 but retained SMN(T) exon 8 and SMN(C) exon 7. Sequence analysis demonstrated that SMN(C) exon 7 was adjacent to SMN(T) exon 8 on both SMN copies, indicating a double conversion. We confirm that sequence conversion is a common event in SMA and is associated with the milder form of the disease. The severity, however, can be modified in either positive or negative direction by other factors.
脊髓性肌萎缩症（SMA）是一种常染色体隐性疾病，其特征是脊髓前角运动神经元退化。运动神经元存活（SMN）基因已被确定为 SMA 决定基因。SMN 在 5q13 上存在两个拷贝，95%的患者存在端粒拷贝（SMN(T)) 的 7 号和 8 号外显子缺失，无论疾病严重程度如何。在少数患者中，SMN(T) 的 7 号外显子但不是 8 号外显子缺失。我们现在报告了一名具有 SMA Ⅱ型典型特征的患者，其 SMN(T) 外显子 7 和着丝粒 SMN（SMN(C)) 外显子 8 纯合缺失，但保留了 SMN(T) 外显子 8 和 SMN(C) 外显子 7。序列分析表明，SMN(C) 外显子 7 在两个 SMN 拷贝上都紧邻 SMN(T) 外显子 8，表明发生了双重转换。我们证实序列转换是 SMA 的常见事件，与疾病的较轻形式有关。然而，其他因素可以正向或负向改变疾病的严重程度。
