OPTN and frontotemporal dementia: The incidence of OPTN mutations in FTD is still under debate, as one study reported copy number variants in OPTN in 4.8% of FTD cases (Pottier et al., 2015) while another study, recruiting a larger cohort of 371 FTD cases, did not detect any mutations using whole exome sequencing (Rollinson et al., 2012).