Molecular pathogenesis of ALS: approach from TDP-43 function.

TDP-43在肌萎缩侧索硬化症(ALS)发病机制中起重要作用，但TDP-43的核功能尚不完全清楚。TDP-43与包括盘状星体双子座(Gemini)在内的核星体有关。宝石有助于富含尿苷的小核RNA(U SnRNA)的生物发生，U SnRNA是剪接机械的一个组成部分。在脊髓性肌萎缩症和运动神经元病中，GEM的数量和U SnRNAs的亚群减少，提示U SnRNAs的改变也可能是ALS分子发病的基础。我们用免疫组织化学方法检测了ALS组织中GEM和U11/12型小核糖核蛋白(SnRNP)的数量，并用实时定量RT-PCR法检测了它们在ALS组织中的表达水平。ALS患者TDP-43缺失的HeLa细胞和脊髓运动神经元的GEM均降低。在TDP-43缺失的SH-SY5Y和U87 MG细胞中，几种U SnRNAs的水平降低。在ALS影响的组织中，U12SnRNA的水平降低，而在未受ALS影响的组织中，U12SnRNA的表达水平没有下降。这些发现表明，TDP-43功能的丧失减少了宝石的数量，继而是ALS影响的组织中U11/U12剪接体对前mRN复制的干扰。

Disappearance of TAR-DNA binding protein 43 kDa (TDP-43) from the nucleuscontributes to the pathogenesis of amyotrophic lateral sclerosis (ALS), but the nuclearfunction of TDP-43 is not yet fully understood. TDP-43 associates with nuclear bodiesincluding Gemini of coiled bodies (GEMs). GEMs contribute to the biogenesis ofuridine-rich small nuclear RNA (U snRNA), a component of splicing machinery. Thenumber of GEMs and a subset of U snRNAs decrease in spinal muscular atrophy, alower motor neuron disease, suggesting that alteration of U snRNAs may also underliethe molecular pathogenesis of ALS. We investigated the number of GEMs andU11/12-type small nuclear ribonucleoproteins (snRNP) by immunohistochemistry andthe level of U snRNAs using real-time quantitative RT-PCR in ALS tissues. GEMsdecreased in both TDP-43-depleted HeLa cells and spinal motor neurons in ALSpatients. Levels of several U snRNAs decreased in TDP-43-depleted SH-SY5Y andU87MG cells. The level of U12 snRNA was decreased in tissues affected by ALS butnot in tissues unaffected by ALS. These findings suggest that loss of TDP-43 functiondecreases the number of GEMs, which is followed by a disturbance of pre-mRNAsplicing by the U11/U12 spliceosome in tissues affected by ALS.