GRM1 and aceruloplasminemia: Disruption of genes in the mGluR1 to IP3R cascade results in cerebellar ataxia indication that this signaling pathway is pivotal for normal PN function and motor coordination (Aiba et al., 1994; Conquet et al., 1994; Matsumoto et al., 1996; Offermanns et al., 1997; Kano et al., 1998; Ichise et al., 2000; Hartmann et al., 2004; Nakao et al., 2007; Hartmann et al., 2008; Becker et al., 2009; Sekerková et al., 2013).