miRNAs are categorized according to base sequences and their genomic loci. A microRNA ‘family' is a group of miRNAs that have an identical seed sequence, and a miRNA ‘cluster' is a group of miRNAs that reside in the same genomic locus. In previous studies, the miRNAs of miR-17 family and miR-17/92 cluster have been reported to show abnormal expression levels in schizophrenic brains.33 The miR-17 family (Figure 3c) includes miR-17 (in the current study, hsa-miR-17-3p showed FC=0.7 and P=0.0449; Supplementary Figures 3a and 3b), miR-20a/b, miR-93 and miR-106a/b.34, 35 The miR-17/92 cluster (Figure 3c) includes miR-17, miR-18a, miR-19a, miR-19b-1, miR-20a and miR-92a-1. Therefore, we set out to precisely quantify the expression levels of those eight miRNAs (miR-17, miR-18a, miR-19a, miR-19b-1, miR-20a, miR-92a-1 and miR-106a/b), all of which belong to the miR-17 family or the miR-17/92 cluster, using real-time quantitative RT-PCR with U6 snRNA as an internal control probe. All the eight miRNAs showed significant downregulation in patient-derived neurospheres (Figure 3d). Importantly, downregulation of miR-106b detected in patient neurospheres is also reported in schizophrenic brains36 and Df(16)A+/− mice.9 Complementing these results,
