In addition, netrin-G1 and CDKL5, known to bind NGL-1, have been implicated in various brain disorders—netrin-G1 with Rett syndrome, ASD, schizophrenia and bipolar disorder (Borg et al., 2005; Archer et al., 2006; Nectoux et al., 2007; Eastwood and Harrison, 2008; Ohtsuki et al., 2008; O’Roak et al., 2012), and CDKL5 with Rett syndrome, epilepsy, intellectual disability, and ASD (Posar et al., 2015; Zhou et al., 2017; Zhu and Xiong, 2019). This evidence concerns the gene LRRC4C and bipolar disorder.