The CASK-neurexin interaction was traditionally suggested to be mediated by the binding of a few residues at the end of neurexin’s cytoplasmic tail to CASK’s PDZ domain (LaConte et al., 2016; LaConte et al., 2018), and missense variants located on the PDZ domain may be linked to developmental disorders with/without microcephaly (Seto et al., 2017). Here, CASK is linked to microcephaly.