DMPK and motor neuron disorder: There are also examples showing how variants in the human mRNA export mediator GLE1 result in a severe fetal motor neuron disease (Nousiainen et al., 2008) and amyotrophic lateral sclerosis (ALS; Kaneb et al., 2015), and toxic CUG expansion in the 3′ untranslated region of the DM protein kinase mRNA can cause myotonic dystrophy type I by impairing RNA transport out of the nucleus (Brook et al., 1992).