Targeted exome sequencing reveals homozygous TREM2 R47C mutation presenting with behavioral variant frontotemporal dementia without bone involvement

Publication date: August 2018
Source:Neurobiology of Aging, Volume 68
Author(s): Adeline S.L. Ng, Yi Jayne Tan, Zhao Yi, Moses Tandiono, Elaine Chew, Jacqueline Dominguez, Mabel Macas, Ebonne Ng, Shahul Hameed, Simon Ting, Eng King Tan, Jia Nee Foo, Nagaendran Kandiah
To identify genes associated with frontotemporal dementia (FTD) in South-East Asia, targeted exome sequencing and C9orf72 genotyping was performed in 198 subjects (52 patients with FTD and 146 healthy controls) who were screened for mutations in 12 FTD-associated genes. We detected a homozygous TREM2 R47C mutation in a patient with behavioral variant FTD without bone cysts or bone-associated phenotype. Two novel nonsense GRN mutations in 3 FTD patients from the Philippines were detected, but no known pathogenic mutations in other FTD-associated genes were found. In 45 subjects screened for C9orf72 repeat expansions, no pathogenic expansion (≥30 repeats) was identified, but there was a higher proportion of intermediate length (≥10–29 repeats) alleles in patients compared with controls (8/90 alleles, 8.9% vs. 9/164 alleles, 5.5%). Overall, we detected a mutation rate of 7.7% (4/52 patients) in our cohort. Given recent findings of enrichment of rare TREM2 variants (including R47C) in Alzheimer's disease, it is notable that we detected a homozygous TREM2 R47C carrier presenting with an FTD rather than an Alzheimer's disease phenotype.



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