C9orf72 and frontotemporal dementia: Although reduced levels of C9ORF72 protein cause motor neuron degeneration in Caenorhabditis elegans (Ciura et al., 2013) and zebrafish (Therrien et al., 2013), loss of C9ORF72 in mice did not elicit the ALS or FTD phenotype (Koppers et al., 2015).