Fig. 7. Possible roles of Sema3A in migration and arrest of sympathetic neuron precursors. (A) In the wild-type embryo, Sema3A (blue) production in the dermamyotome (dm), forelimb (fl) and paraxial mesenchymal tissue forms a concentration gradient. Sympathetic neuron precursors (red spots), which have migrated through the ventral migratory pathway (a green arrow), are arrested at the bottom of the Sema3A gradient, the lateral part of the dorsal aorta (da). (B,C) Sympathetic neuron precursors in the neuropilin 1-deficient embryo (B) and the Sema3A-deficient embryo (C) do not stop at the lateral part of the dorsal aorta but migrate further along the permissive route. nt, neural tube; n, notochord.
