For the analysis of the miR-Ctrl and miR-34a overexpressing hNPCs, the cells were seeded on glass coverslips at a density of 100,000 cells per well and differentiated as neurons. To measure the arbour complexity of the cells in both conditions after 3 weeks of differentiation, the cells were transfected at 19 days for 30 min with Lipofectamine 2000 and a plasmid encoding a membrane bound form of EGFP (Addgene, Plasmid 14757). 48h after transfection, the cells were then fixed and immunostained for GFP to enhance the signal and allow the complete visualization of the neuronal morphology. A total of 40 transfected neurons per condition from 5 biological replicates were captured using a Zeiss Axio Observer microscope and a 20× objective. The Sholl analysis was performed by superimposing concentric equidistant (10 µm) circles around the neuronal soma using Adobe Illustrator CS and counting the number of intersecting branches along the circumference of each circle. In a separate experiment, the effect of inhibiting miR-34a on the arbour complexity of differentiating hNPCs transfected with either the anti-miR-34a sequence (GeneCopoeia, HmiR-AN0440-AM03-B) or a control
