PTPRN2 and hearing loss disorder: Expression levels for the gene indeed matter, given the reports that the detection of CNVs and RNA-seq data connect PTPRN2 with neurodevelopmental disorders (Mosca et al., 2016) including autism (Filosi et al., 2020), attention deficit hyperactivity disorder (Lionel et al., 2011) and syndromes involving hearing impairments (Abu-Amero et al., 2013).