Fig. 1. Altered pattern of cranial NCC migration 20 hours after unilateral r3 removal. (A-C) Whole-mount HNK-1 immunostaining of NCCs showing the operated (A) and unoperated (B) sides of the same embryo. (C) Dorsal view. (D-F) Sox10 in situ hybridisation to show migrating NCCs on the operated (D) and unoperated (E) sides of the same embryo. (F) A transverse section through the embryo at the level of r3 that corresponds to the broken line in D,E. On the operated side, in addition to the normal pattern of NCC migration (r2 crest migrates into ba1; r4 crest migrates into ba2), a stream of NCCs (arrow in A,C,D,F) migrates aberrantly through the mesenchyme adjacent to the removed r3 (r3*). This ectopic NCC stream is more clearly defined by Sox10 mRNA expression than by HNK1 immunoreactivity. In addition, HNK1⁺ cells are detected within the space previously occupied by r3 (arrowhead in A). ba1 and ba2, branchial arches 1 and 2; OV, otic vesicle.