Analysis of premigratory neural crest development. (A, B) One-fourth of 16-h aln/+ intercross progeny display a marked reduction in the expression of snail-2 along the dorsal midline of the head and anterior trunk (B), compared to the remaining three-fourths (A). Expression of snail-2 in the developing trunk somites is similar in the two classes. (C–H) Expression of markers for premigratory neural crest in the trunk and tail of sibling WT (C, E, G) and aln mutant (D, F, H) 18-h embryos. Mutant embryos were identified by simultaneous staining for trp-2 expression, which is greatly reduced in the mutant retina. Mutant embryos display severely reduced expression of snail-2 (C, D), AP-2 (E, F), and fkd-6 (G, H) along the dorsal midline of the trunk and tail. (I, J) Dorsal views of the heads of 12-h aln/+ intercross progeny dissected from the yolk and mounted flat (anterior to the left). Expression of snail-2 in neural crest at the edges of the anterior neural keel is reduced in one-fourth of the embryos (J) compared to the remaining three-fourths (I). (K, L) Dorsal views of neural keels dissected from 20-h aln/+ intercross progeny doubly stained for trp-2 and snail-2 (anterior is to the left). Mutant embryos display dramatically reduced snail-2-expression. (M, N) Transverse sections through the nascent somite of 24-h aln/+ intercross progeny (dorsal to the top). Mutant embryos display reduced expression of snail-2 mRNA in the premigratory neural crest (arrowheads). Expression of snail-2 in the somites (s) appears normal in both expression pattern and level in mutants.
|