Fig. 7. The genetic regulatory hierarchy that regulates DV pattern in the neuroectoderm (left) and the molecular pathway through which Dichaete, vnd and ind might regulate target gene expression (right). Left: Egfr stands atop the genetic pathway that regulates DV pattern in the neuroectoderm. Egfr activates ind in the intermediate column and Dichaete in the medial and intermediate columns, while maintaining vnd expression in the medial column. vnd is activated independently of Egfr and plays a supporting role in regulating Dichaete expression. Dichaete activity appears to converge with that of vnd in the medial column and that of ind in the intermediate column to regulate DV pattern and cell fate. Right: a model that proposes that physical interactions between Dichaete and Vnd, as well as Dichaete and Ind, mediate the ability of Dichaete to carry out distinct function in different columns. Other proteins (X/Y) are likely required in these processes.