The v-ATPase is required for NB regrowth after asymmetric cell division. (a) Vha68-2 inhibition by RNAi caused a reduction in NB size. Images are magnifications of the red boxes in g. Larval brains were stained for the stem cell marker Mira. (b) Quantification of NB diameter upon knockdown of Vha68-2, Vha100-2, or VhaAC39-1. Each data point represents the average type I NB diameter per brain lobe. n (control) = 14, n(Vha68-2^RNAi) = 10, n (Vha100-2^RNAi) = 10, n (VhaAC39-1^RNAi) = 11. (c) Vha100-2 knockdown by RNAi resulted in a defect in NB regrowth after asymmetric cell division and in a prolonged NB cell cycle time. GMC cell cycle times were not altered. Single frames from time-lapse videos of cultured NBs expressing UAS-stingerGFP under the control of ase-GAL4. Asterisks label NBs. Time in hours:minutes. (d) Automated quantification of volume variation with each cell division of control or Vha100-2^RNAi NBs. n (control) = 5, n (Vha100-2^RNAi) = 5. Div, cell division. (e) Automated quantification of volume variation within the lifespan of GMCs originating either from control or from Vha100-2^RNAi NBs. n (control) = 5, n (Vha100-2^RNAi) = 5. (f) Quantification of cell cycle times of control or Vha100-2^RNAi NBs and their siblings. Each data point represents the duration of one cell cycle. n (NB control) = 19, n (NB Vha100-2^RNAi) = 23, n (GMC control) = 8, n (GMC Vha100-2^RNAi) = 12. (g) Vha68-2 depletion by RNAi caused a reduction in NB number. Larval brains were stained for Mira. CB, central brain. (h) Quantification of NB number per brain lobe upon knockdown of Vha68-2, Vha100-2, or VhaAC39-1. Each data point represents the number of type I NBs per brain lobe. n (control) = 8, n (Vha68-2^RNAi) = 8, n (Vha100-2^RNAi) = 10, n (VhaAC39-1^RNAi) = 6. Error bars represent mean ± SD. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; unpaired two-sided Student’s t test.