Wnt controls the medial–lateral subdivision of the <i>Drosophila</i> head

Abstract

In insects, the subdivision of the head into a lateral region, harbouring the compound eyes (CEs), and a dorsal (medial) region, where the ocelli localize, is conserved. This organization might have been already present in the insects' euarthropodan ancestors. In <i>Drosophila,</i> the Wnt-1 homologue <i>wingless (wg)</i> plays a major role in the genetic subdivision of the head. To analyse specifically the role of <i>wg</i> signalling in the development of the dorsal head, we attenuated this pathway specifically in this region by genetic means. We find that loss of <i>wg</i> signalling transforms the dorsal/medial head into lateral head structures, including the development of ectopic CEs<i>.</i> Our genetic analysis further suggests that <i>wg</i> signalling organizes the dorsal head medial-lateral axis by controlling, at least in part, the expression domains of the transcription factors Otd and Ey/Pax6.