E13.5 lumbar DRG from wild-type (A, B, and C), TauEWS-Pea3/+ Isl1Cre/+ (D, E, and F), or Bax−/− (G, H, and I) embryos cultured for 48 h without neurotrophic support (A, D, and G) or in the presence of NGF (B, E, and H) or NT-3 (C, F, and I) were stained for expression of neurofilament to visualize axonal extensions.