NRN1 and Alzheimer disease: Furthermore, alterations in mRNA levels of Cnr1, CDC42 and neuritin have been linked to the development of schizophrenia (Eggan et al., 2008; Hill et al., 2006; Chandler et al., 2010), and alterations in the level of Sorl1 mRNA have been linked to the development of Alzheimer’s disease (Kölsch et al., 2009).