Survival motor neuron SMN1 and SMN2 gene promoters: identical sequences and differential expression in neurons and non-neuronal cells
Survival motor neuron SMN1 and SMN2 gene promoters: identical sequences and differential expression in neurons and non-neuronal cells
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DOI：
10.1038/sj.ejhg.5201217
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发表时间：
2004-09-01
影响因子：
5.2
通讯作者：
Simonneau, M
中科院分区：
文献类型：
--
作者：
Boda, B;Mas, C;Simonneau, M
脊髓性肌萎缩症(SMA)是一种隐性疾病，涉及脊髓运动神经元的丢失。运动神经元1基因(SMN1)的纯合子缺失是SMA的主要原因，但疾病的严重程度主要取决于SMN2基因的拷贝数。SMN蛋白水平在正常脊髓中很高，而在SMA患者的脊髓中则低得多，这表明这种普遍表达的基因具有神经元特异性调控。我们从SMN1或SMN2缺失的个体中提取基因组DNA，并对这些缺失的5‘上游区域的4.6kb进行了测序。我们发现，这些上游区域，其中一个是端粒，另一个是着丝粒，是相同的。我们研究了SMN启动子驱动β-半乳糖苷酶基因表达的三种转基因对小鼠胚胎脊髓和成纤维细胞SMN表达的早期调控。4.6kb的构建使报告基因在神经元中的表达水平比在成纤维细胞中高5倍，这是由于一般增强子和非神经元细胞沉默的共同作用。在神经元和成纤维细胞中观察到的差异表达表明SMN基因在发育过程中发挥着神经元特有的作用。了解SMN启动子活性的调控机制可能为治疗SMA提供新的途径。
Spinal muscular atrophy (SMA) is a recessive disorder involving the loss of motor neurons from the spinal cord. Homozygous absence of the survival of motor neuron 1 gene (SMN1) is the main cause of SMA, but disease severity depends primarily on the number of SMN2 gene copies. SMN protein levels are high in normal spinal cord and much lower in the spinal cord of SMA patients, suggesting neuron-specific regulation for this ubiquitously expressed gene. We isolated genomic DNA from individuals with SMN1 or SMN2 deletions and sequenced 4.6 kb of the 5' upstream regions of the these. We found that these upstream regions, one of which is telomeric and the other centromeric, were identical. We investigated the early regulation of SMN expression by transiently transfecting mouse embryonic spinal cord and fibroblast primary cultures with three transgenes containing 1.8, 3.2 and 4.6, respectively, of the SMN promoter driving beta-galactosidase gene expression. The 4.6 kb construct gave reporter gene expression levels five times higher in neurons than in fibroblasts, due to the combined effects of a general enhancer and a non-neuronal cell silencer. The differential expression observed in neurons and fibroblasts suggests that the SMN genes play a neuron-specific role during development. An understanding of the mechanisms regulating SMN promoter activity may provide new avenues for the treatment of SMA.