Fig. 5. Npn2 is cell autonomously required for neural crest cells to avoid Sema3f in vitro. Neural tubes from 14 to 24 somite mouse embryos were cultured on Thermanox coverslips coated with fibronectin and spotted with AP-Sema-3F conditioned medium conjugated with anti-placental alkaline phosphatase. Neural crest cells normally avoid immobilized Sema3f (A), while neural crest cells lacking the Npn2 receptor migrate equally well on fibronectin and Sema3f substrates (B,C; n=5 spots in three separate experiments). Neural crest cells were labeled with anti-p75, while spots (outlined in white) were visualized using anti-mouse IgG-Alexa 488.