DPP4 and psychiatric disorder: Many of our identified differentially expressed genes at the transcript- and exon-level, such as Cyclic Nucleotide Gated Channel Subunit Beta 1 (CNGB1), Cystatin B (CSTB) and Dipeptidyl peptidase 4 (DPP4), have been previously linked to psychiatric disorders in various studies, including exome sequencing and GWAS of schizophrenia [3, 48–50].