The first evidence comes from the observation that deficiency or mutations in proteins involved in circRNA biogenesis are linked to the pathogenesis of neurodegenerative diseases: for instance deficiency of QKI may contribute to the development of inherited ataxia while mutations of the FUS gene as well as the deregulation of ADAR2 expression are linked to the pathogenesis of ALS (Chénard and Richard, 2008; Kwiatkowski et al., 2009; Vance et al., 2009; Hideyama et al., 2012; Aizawa et al., 2016). The gene discussed is FUS; the disease is amyotrophic lateral sclerosis.