Quantification of the immunofluorescent staining results of neuronal markers Tuj1 (A), Map2 (B) or Tbr2 (C) positive cells 7–8 days after RA treatment of NE-4C cells (Blank), or NE-4C cells transiently transfected with vector (Vector), wildtype CYP26B1 (WT), or different CYP26B1 variants. The percentage of immunopositive cells relative to all cells (Hoechst labeled) in a field of view were scored and then compared to cells transfected with WT CYP26B1. ***: P < 0.0001; **: P < 0.01; Student’s t-test. D) Typical images of the immunofluorescent staining used for calculations in A–C. For each genotype and neuronal marker, three to four replicates were performed.