Analyses MAPT, GRN, and C9orf72 mutations in Chinese patients with frontotemporal dementia.

Frontotemporal dementia (FTD) is a clinically heterogeneous neurodegenerative disorder, including behavior behavioral variant FTD (bvFTD), semantic dementia, progressive nonfluent aphasia (PNFA), FTD-parkinsonism, and FTD-motor neuron disease. To date, there are at least 8 causative genes identified in patients with FTD. Among them, variants in the microtubule-associated protein tau (MAPT), GRN, and chromosome 9 open-reading frame 72 (C9orf72) genes are considered the major cause of FTD. To date, no comprehensive analyses of mutations in these 3 genes have been conducted in the Chinese population. In this study, we screened all exons of MAPT, and GRN, as well as GGGGCC repeats in C9orf72 in a cohort of 52 patients from mainland China, including 38 bvFTD, 7 PNFA, 2 semantic dementia, and 5 FTD-parkinsonism. As a result, 2 novel mutations in MAPT (p.D177V and p.P513A) were identified in a sporadic and familial patient with PNFA respectively, and one known mutation in MAPT (p.N279K) was detected in an FTD-parkinsonism family. In addition, one reported nonsense mutation (p.Q300Term) in GRN was found in a sporadic patient with bvFTD. Finally, no pathogenic GGGGCC repeats in C9orf72 were detected in any case. To our knowledge, this is the first cohort report screening for common causative mutations in patients with FTD in the Chinese population. Our findings indicate that variants of MAPT and GRN are a common cause of FTD in mainland China.