Mutations in CHMP2B are not a cause of frontotemporal lobar degeneration in Finnish patients

Frontotemporal lobar degeneration (FTLD) is a genetically complex disorder. The majority of mutations linked to FTLD families are found in the microtubule-associated protein tau (MAPT) and progranulin (PGRN) genes. Mutations in the chromatin-modifying protein 2B gene (CHMP2B) have been identified in a few families. However, CHMP2B has been showed to be a rare cause of FTLD. Our aim was to determine the frequency of CHMP2B mutations in a clinical series of patients with FTLD in Northern Finland.

We examined 72 (36 men) Finnish patients with FTLD. The mean age at onset was 58.9 (range 43–80). Symptoms of motor neuron disease (FTLDMND) were present in 12 patients (17%). Positive family history was detected in 28% of the patients. Mutations in MAPT and PGRN were excluded from these patients. All exons and exon–intron boundaries of the CHMP2B gene were sequenced.

No pathogenic CHMP2B mutations were found. A rare polymorphism in the non-coding region of exon 1 (rs36098294) and three other previously reported polymorphisms were detected.

Our results confirm that mutations in CHMP2B are not a common cause of FTLD. MAPT and PGRN mutations are also rare in Finnish population, suggesting that other, still unknown genetic factors may play a role in the pathogenesis of FTLD in Finnish population.