Fig. 6. Proneural genes are expressed within the larger domains of Iro expression in both Drosophila imaginal disc and Xenopus embryos. (A) Expression of caup and sc in late third instar wing discs and a drawing showing the overlap between both patterns of expression. ara and ac expressions are indistinguishable from those of caup and sc, respectively. Proneural clusters whose presence is known to depend on Iro-C are shown in brown. Other proneural clusters are denoted in red. al, allula; DC, dorsocentral cluster; L3, L3 proneural cluster; NP, notopleural clusters; WM, wing margin. (B) Overlapping patterns of expression of Xiro1 and Xash-3 in the neural plate of the Xenopus embryos at the neurula stage. Xiro2 is co-expressed with Xiro1. Xiro3 is expressed in a similar pattern although in slightly narrower bands. In addition, both Xiro1 and Xiro2 are expressed in the prospective placode region (pc), whereas Xiro3 is expressed in lateral mesoderm. Other Xenopus proneural genes such as Xnrgr-1 are expressed in domains that partially overlap with those of Xiro genes. (Data taken from Gómez-Skarmeta et al., 1996; Gómez-Skarmeta et al., 1998; Bellefroid et al., 1998.