C9orf72 and frontotemporal dementia: Eventually, a genetic linkage to a locus on chromosome 9p was found in many families with FTD and motor neuron disease (Morita et al., 2006; Vance et al., 2006; Luty et al., 2008; Le Ber et al., 2009; Boxer et al., 2011); only recently in 2011, two separate groups identified the defect as being an expanded hexanucleotide repeat in a non-coding region of the chromosome 9 open reading frame 72 (C9orf72) gene (DeJesus-Hernandez et al., 2011; Renton et al., 2011).