Figure 6. BDNF-induced localization of β-actin mRNA is significantly reduced in Zbp1-deficient mice. A, C, Neurons from Zbp1+/+ (A) and Zbp1−/− (C) embryos were starved for 3 h and then treated with a vehicle control for 15 min. Q-FISH for β-actin mRNA demonstrates only a small amount of staining in the growth cone (tubulin, left panel; β-actin mRNA, right panel). Images of β-actin mRNA are shown in false color for ease of visualization. A false-color intensity map is shown on the far right, with lowest intensities at the bottom of the bar and highest intensities on the top (low intensity pixels are black and blue, and intensities increase from there to yellow, red, and finally white). Scale bar, 5 μm. B, Neurons cultured from Zbp1+/+ embryos were starved for 3 h and then stimulated with BDNF for 15 min, which resulted in a visible increase in β-actin mRNA fluorescent signal in the growth cone (tubulin, left panel; β-actin mRNA, right panel). Scale bar, 5 μm. D, Neurons cultured from Zbp1−/− embryos were starved for 3 h and then stimulated with BDNF for 15 min, which resulted in only a modest increase in β-actin mRNA fluorescent signal in the growth cone (tubulin, left panel; β-actin mRNA, right panel). Scale bar, 5 μm. E, Using Q-FISH, there is no significant difference between Zbp1+/+ and Zbp1−/− neurons that are starved and vehicle treated in terms of the β-actin mRNA fluorescent signal in the growth cone. F, Quantification of β-actin mRNA FISH signal in neurons from Zbp1+/+ or Zbp1−/− embryos subjected to the above treatments. The fluorescent signal of growth cones treated with BDNF was normalized to vehicle-treated growth cones. Treatment of neurons from Zbp1+/+ embryos with BDNF results in significantly increased localization of β-actin mRNA fluorescent signal in the growth cone, as compared to those from Zbp1−/− embryos. *p ≤ 0.05, Mann–Whitney test.