Overexpression of Musashi1 blocks neural differentiation. NSPCs (panels A-D) and SH-SY5Y cells (panels E-H) were transfected with a plasmid encoding the eGFP moity alone (A and E), wild-type Musashi1 (B and F) or Musashi1 encoding a non-phosphorylatable S337A mutation (C and F) fused to a C-terminal eGFP epitope tag and incubated at low cell density under differentiation conditions for 4 days (NSPCs) or 7 days (SH-SY5Y) and scored for initiation of differentiation phenotype (hypertrophic cells with neurites > 2 soma lengths). Representative photos shown. Some variations in the intensity and subcellular distribution of Musashi1 or Musashi1 S337A were noted in transfected cells within the same experiment. Over the course of three experiments, a total of 70 NSPC cells (A) or 136 SHSY5Y cells (E) transfected with eGFP alone were counted. (D and H) represent histograms showing quantitation of the differentiation data (mean of three experiments with SEM) at 14 days (D) or 7 days (H). ****,p < 0.0001 for (D); **,p < 0.01 for (H)) as assessed by one-way ANOVA.