Fig. 6. The Wnt pathway and polarity. (A,B) Comparison of embryonic clones that are Pka– as well as being otherwise wild type (A) or homozygous for Df(2L)RF (B). This deficiency removes wg as well as Wnts 4, 6 and 10. Both types of clones make a4 cuticle with some a5 bristles (white arrowheads) (Lawrence et al., 1999a). The polarity of hairs at the back of the clones as well as wild-type hairs behind are reversed to a similar extent in both clones (red arrows). Pka– clones carrying the deficiency survive less often than Pka– controls. (C) A clone of sgg– cells, marked with yellow in the anterior region of the A compartment. Note the cluster of five yellow bristles and that the polarity is reversed behind them. The abdomen carries ptc.lacZ and, as in this case, these clones are usually associated with some sporadic up-regulation of ptc, suggesting that the Hh pathway is ectopically activated, inducing a source of X. (D) A clone of sgg– cells marked with yellow and stubby chaete (stc), situated far anterior in the A compartment (stc causes tufts of hairs to form). The a1 cuticle in this region is apparently transformed to make a3 cuticle with hairs and bristles. Some hairs behind the clone have reversed polarity. (E) A clone of sgg– cells marked with stc in the mid-region of the P compartment. The clone is transformed, making hairs characteristic of p3 cuticle. (F) A clone of cells that are mutant for arm in the tergites. The clone is transformed to form large pleural hairs and cuticle. It tends to sort out, forming a rounded shape (Lawrence et al., 1999b) and the polarity of the front of the clone, and of some wild-type cells anterior to the clone, is reversed.
