To further investigate the functional consequence of altering miR-34a expression throughout early neurodevelopment, we next assessed the expression of putative miR-34a targets upon differentiation of iPSC-derived NPCs (hNPCs). Among the six putative miR-34a targets, mRNA levels of four (ANK3, CACNB3, ODZ4 and KLC2) were gradually increased until four weeks of differentiation, and then partially downregulated by eight weeks, whereas CACNA1C mRNA expression gradually increased during the eight weeks of differentiation (Figures 2B, 2C and Figure S3). DDN was not expressed in either hNPCs or differentiated neurons preventing its further analysis (data not shown). Since we observed an increase of miR-34a expression in BD patient-derived cellular models, we expected that expression of bona fide miR-34a targets would be decreased. Indeed, miR-34a validated targets were significantly downregulated in iPSC-derived neurons from BD individuals (Figures 2B-E).
