SMN deficiency in severe models of spinal muscular atrophy causes widespread intron retention and DNA damage
SMN deficiency in severe models of spinal muscular atrophy causes widespread intron retention and DNA damage
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DOI：
10.1073/pnas.1613181114
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发表时间：
2017-03-21
影响因子：
11.1
通讯作者：
Staropoli, John F.
中科院分区：
文献类型：
--
作者：
Jangi, Mohini;Fleet, Christina;Staropoli, John F.
脊髓性肌萎缩症（SMA）是一种常染色体隐性遗传的神经肌肉疾病，是婴儿死亡的主要单基因原因。运动神经元1（SMN 1）基因存活的纯合缺失导致下运动神经元的选择性变性和随后的近端骨骼肌萎缩。SMN 1蛋白产物运动神经元存活（SMN）广泛表达，是核心剪接机制组装中的关键因素。SMN广泛功能的破坏导致神经退行性变的分子机制尚不清楚。我们使用基于反义寡核苷酸（阿索）的SMA诱导型小鼠模型来研究与神经变性相关的SMN特异性转录组变化。我们发现广泛的内含子保留的证据，特别是较小的U12内含子，在脊髓中的小鼠SMA诱导后30天，然后由治疗阿索拯救。内含子保留伴随着p53通路和DNA损伤反应的强烈诱导，表现为脊髓和脑神经元中的γ-H2 A.X阳性。在人SH-SY 5 Y神经母细胞瘤细胞和人诱导多能干细胞衍生的运动神经元中也观察到广泛的内含子保留和DNA损伤反应的标记物与SMN耗竭。我们还发现，保留的内含子，高GC含量，作为底物的转录R-环的形成。我们认为SMA中内含子去除的缺陷部分地通过RNA：DNA杂交结构的形成促进DNA损伤，导致运动神经元死亡。
Spinal muscular atrophy (SMA), an autosomal recessive neuromuscular disease, is the leading monogenic cause of infant mortality. Homozygous loss of the gene survival of motor neuron 1 (SMN1) causes the selective degeneration of lower motor neurons and subsequent atrophy of proximal skeletal muscles. The SMN1 protein product, survival of motor neuron (SMN), is ubiquitously expressed and is a key factor in the assembly of the core splicing machinery. The molecular mechanisms by which disruption of the broad functions of SMN leads to neurodegeneration remain unclear. We used an antisense oligonucleotide (ASO)-based inducible mouse model of SMA to investigate the SMN-specific transcriptome changes associated with neurodegeneration. We found evidence of widespread intron retention, particularly of minor U12 introns, in the spinal cord of mice 30 d after SMA induction, which was then rescued by a therapeutic ASO. Intron retention was concomitant with a strong induction of the p53 pathway and DNA damage response, manifesting as gamma-H2A.X positivity in neurons of the spinal cord and brain. Widespread intron retention and markers of the DNA damage response were also observed with SMN depletion in human SH-SY5Y neuroblastoma cells and human induced pluripotent stem cell-derived motor neurons. We also found that retained introns, high in GC content, served as substrates for the formation of transcriptional R-loops. We propose that defects in intron removal in SMA promote DNA damage in part through the formation of RNA: DNA hybrid structures, leading to motor neuron death.