C9orf72 and frontotemporal dementia: More recently, overexpansion of G4C2 hexanucleotide repeats in the noncoding region of C9ORF72 has been found in patients with ALS and frontotemporal lobar degeneration (FTLD; DeJesus-Hernandez et al., 2011; Renton et al., 2011; Gijselinck et al., 2012) and has been shown to play a critical role in ALS pathogenesis (Rohrer et al., 2015; Jiang et al., 2016; Lee et al., 2016; Lin et al., 2016; Taylor et al., 2016).