Deletions/duplications in GRN and MAPT genes is not common in frontotemporal dementia

Abstract Background Frontotemporal dementia (FTD) is an umbrella term for several syndromes with behavioural and/or language symptoms. Mutations in GRN and MAPT genes are the most frequent genetic cause of FTD in different populations. Our previous data indicate that the frequency of mutations in GRN gene is up to 12.5% in familial FTD cases in Russian cohort of patients. Mutations in MAPT gene were absent in the same cohort. According to the literature, not only point mutation in these genes, but also deletions/duplications can be the genetic cause of FTD. Method We analyzed DNA from 50 patients with clinical diagnosis of behavioural variant of FTD, bvFTD (N = 33) and primary progressive aphasia, PPA (N = 17), picture 1. There were 26 familial and 24 sporadic FTD cases. Exon rearrangements were analyzed by MLPA method (SALSA MLPA P275‐C3, MRC‐Holland, Netherlands) using standard protocol. PCR products were separated by size with capillary electrophoresis using genetic analyzer Nanofor 5 (Syntol, Russia). The analysis of result was performed with GeneMarker V3.0.1. Result We did not find any deletion or duplication of exons in the GRN and MAPT genes. The results may indicate that this type of mutation is not common in Russian patients with FTD. Conclusion In 2017‐2021, we identified several point mutations in GRN in Russian patients with FTD; here we show that exon rearrangements in GRN and MAPT genes are not frequent in Russia. According to the literature, only 1.5% of individuals with GRN‐associated forms have deletion or duplication in GRN gene. The data about exon rearrangements in MAPT gene are absent. However, in the case of typical clinical phenotype of GRN‐ or MAPT‐associated form of FTD, MLPA analysis can be recommended.