Fig. 2. Npn2 is required to pattern segmental trunk neural crest migration. Trunk neural crest normally migrates in streams (A) restricted to the anterior-half sclerotome (B,C). In the absence of Npn2, segmental migration is lost (D) and neural crest cells migrate throughout both anterior- and posterior-half sclerotomes (E,F). Neural crest was visualized at E9.5 by in situ hybridization for Sox10. In A,D, anterior is towards the left, dorsal is upwards. (B,C,E,F) Longitudinal sections; B and E are sections through the embryos shown in A and D at the levels indicated. a, anterior; p, posterior; dm, dermomyotome; sc, sclerotome; nt, neural tube. Scale bars: 0.1 mm.