Rutherford Nicola J, Zhang Yong-Jie, Baker Matt, Gass Jennifer M, Finch Nicole A, Xu Ya-Fei, Stewart Heather, Kelley Brendan J, Kuntz Karen, Crook Richard J P, Sreedharan Jemeen, Vance Caroline, Sorenson Eric, Lippa Carol, Bigio Eileen H, Geschwind Daniel H, Knopman David S, Mitsumoto Hiroshi, Petersen Ronald C, Cashman Neil R, Hutton Mike, Shaw Christopher E, Boylan Kevin B, Boeve Bradley, Graff-Radford Neill R, Wszolek Zbigniew K, Caselli Richard J, Dickson Dennis W, Mackenzie Ian R, Petrucelli Leonard, Rademakers Rosa
Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America.
PLoS Genet. 2008 Sep 19;4(9):e1000193. doi: 10.1371/journal.pgen.1000193.
The TAR DNA-binding protein 43 (TDP-43) has been identified as the major disease protein in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin inclusions (FTLD-U), defining a novel class of neurodegenerative conditions: the TDP-43 proteinopathies. The first pathogenic mutations in the gene encoding TDP-43 (TARDBP) were recently reported in familial and sporadic ALS patients, supporting a direct role for TDP-43 in neurodegeneration. In this study, we report the identification and functional analyses of two novel and one known mutation in TARDBP that we identified as a result of extensive mutation analyses in a cohort of 296 patients with variable neurodegenerative diseases associated with TDP-43 histopathology. Three different heterozygous missense mutations in exon 6 of TARDBP (p.M337V, p.N345K, and p.I383V) were identified in the analysis of 92 familial ALS patients (3.3%), while no mutations were detected in 24 patients with sporadic ALS or 180 patients with other TDP-43-positive neurodegenerative diseases. The presence of p.M337V, p.N345K, and p.I383V was excluded in 825 controls and 652 additional sporadic ALS patients. All three mutations affect highly conserved amino acid residues in the C-terminal part of TDP-43 known to be involved in protein-protein interactions. Biochemical analysis of TDP-43 in ALS patient cell lines revealed a substantial increase in caspase cleaved fragments, including the approximately 25 kDa fragment, compared to control cell lines. Our findings support TARDBP mutations as a cause of ALS. Based on the specific C-terminal location of the mutations and the accumulation of a smaller C-terminal fragment, we speculate that TARDBP mutations may cause a toxic gain of function through novel protein interactions or intracellular accumulation of TDP-43 fragments leading to apoptosis.
TAR DNA结合蛋白43（TDP - 43）已被确定为肌萎缩侧索硬化症（ALS）和伴有泛素包涵体的额颞叶痴呆（FTLD - U）中的主要疾病蛋白，从而定义了一类新型神经退行性疾病：TDP - 43蛋白病。最近在家族性和散发性ALS患者中报道了编码TDP - 43（TARDBP）基因的首批致病突变，支持了TDP - 43在神经退行性变中的直接作用。在本研究中，我们报告了在296例伴有TDP - 43组织病理学的不同神经退行性疾病患者队列中进行广泛突变分析后鉴定出的TARDBP中的两个新突变和一个已知突变及其功能分析。在对92例家族性ALS患者（3.3%）的分析中，在TARDBP外显子6中鉴定出三种不同的杂合错义突变（p.M337V、p.N345K和p.I383V），而在24例散发性ALS患者或180例其他TDP - 43阳性神经退行性疾病患者中未检测到突变。在825名对照和652名额外的散发性ALS患者中排除了p.M337V、p.N345K和p.I383V的存在。所有这三种突变均影响TDP - 43 C末端部分中已知参与蛋白质 - 蛋白质相互作用的高度保守氨基酸残基。与对照细胞系相比，ALS患者细胞系中TDP - 43的生化分析显示半胱天冬酶切割片段大幅增加，包括约25 kDa片段。我们的研究结果支持TARDBP突变是ALS的一个病因。基于突变的特定C末端位置以及较小C末端片段的积累，我们推测TARDBP突变可能通过新的蛋白质相互作用或TDP - 43片段的细胞内积累导致细胞凋亡，从而引起毒性功能获得。
