PREPL and brain disorder: It is of interest to note that the PREPL-C2ORF34 gene pair has several features in common with some other human bidirectional gene pairs such as the Parkinson's disease-related PACRG-PARK2 gene pair at 6q25.2–27, and the brain-disease related PDCD10-SERPINI1 gene pair at 3q26 [44,45].