Figure 7.

Model for non-cell-autonomous and activity-dependent regulation of DRG position and identity. A, At 2–3 dpf, RB (red) and DRG (green) peripheral processes overlap in the skin. Electrical stimulation in RB cells increases release of BDNF, which promotes maintenance of DRG neurons. Between 2 and 7 dpf, RB cells undergo cell death, while the number of DRG neurons increases and DRG peripheral processes elaborate. B, When RB activity is reduced genetically, pharmacologically, or environmentally, BDNF release decreases and RB cells survive to later stages. The absence of BDNF triggers migration of differentiated DRG neurons between 2 and 4 dpf. At later stages (7 dpf), migratory DRG neurons adopt sympathetic neuron characteristics.