NPTN and Hearing impairment: The mutants audio-1 (I122N), pitch (C315S), and Y219X, generated by N-ethyl-N-nitrosaurea (ENU) mutagenesis, and two insertional EUCOMM mutants (insertional mutant Nptn intron 3 and Nptntm1b(EUCOMM)Hmgu with deletion of Ig3 and transmembrane encoding Nptn exons 5 and 6) are associated with progressive hearing impairment or deafness (Zeng et al. 2016; Carrott et al. 2016).