Comment: Double mutants of frontotemporal dementia genes--Simple co-occurrence?

In this international collaborative study searching for genetic modifiers in familial frontotemporal dementia (FTD), van Blitterswijk et al.1 detected C9ORF72 repeat expansions in 1.8% of 217 North American and Italian families harboring progranulin ( GRN ) or microtubule-associated protein tau ( MAPT ) gene mutations. Since the GRN/MAPT mutations harbored by the families were different, it does not seem a mutation-specific effect. All double...