Laboratory for Motor Neuron Disease, RIKEN Brain Science Institute, Wako, Saitama, Japan.
EMBO Mol Med. 2013 Feb;5(2):221-34. doi: 10.1002/emmm.201202303. Epub 2013 Jan 25.
Two motor neuron diseases, amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA), are caused by distinct genes involved in RNA metabolism, TDP-43 and FUS/TLS, and SMN, respectively. However, whether there is a shared defective mechanism in RNA metabolism common to these two diseases remains unclear. Here, we show that TDP-43 and FUS/TLS localize in nuclear Gems through an association with SMN, and that all three proteins function in spliceosome maintenance. We also show that in ALS, Gems are lost, U snRNA levels are up-regulated and spliceosomal U snRNPs abnormally and extensively accumulate in motor neuron nuclei, but not in the temporal lobe of FTLD with TDP-43 pathology. This aberrant accumulation of U snRNAs in ALS motor neurons is in direct contrast to SMA motor neurons, which show reduced amounts of U snRNAs, while both have defects in the spliceosome. These findings indicate that a profound loss of spliceosome integrity is a critical mechanism common to neurodegeneration in ALS and SMA, and may explain cell-type specific vulnerability of motor neurons.
两种运动神经元疾病，肌萎缩性侧索硬化症（ALS）和脊髓性肌萎缩症（SMA），分别由涉及 RNA 代谢的不同基因，即 TDP-43 和 FUS/TLS，以及 SMN 引起。然而，这两种疾病的 RNA 代谢是否存在共同的缺陷机制尚不清楚。在这里，我们表明 TDP-43 和 FUS/TLS 通过与 SMN 结合定位于核 Gems 中，并且这三种蛋白质都在剪接体维持中发挥作用。我们还表明，在 ALS 中，Gems 丢失，U snRNA 水平上调，剪接体 U snRNPs 异常且广泛地在运动神经元核中积累，但不在 FTLD 伴 TDP-43 病理的颞叶中积累。在 ALS 运动神经元中，U snRNAs 的这种异常积累与 SMA 运动神经元形成鲜明对比，后者显示 U snRNAs 减少，而两者的剪接体都有缺陷。这些发现表明，剪接体完整性的严重丧失是 ALS 和 SMA 神经退行性变的共同关键机制，并可能解释运动神经元的细胞类型特异性易感性。
