Dr Jose Casal-Jimenez

Epidermal cells of Drosophila are decorated with cuticular hairs. These hairs are always oriented in a particular direction; in the wing all the hairs are pointing distally, an example of what is known as planar polarity. How is this orientation achieved? One possibility is that each cell respondes to a global polarity signal as do Dictyostelium amoeba that are polarised and attracted by a source of cAMP. There is, however, evidence that a global polarity signal cannot be the only cause of polarisation: There are a number of fly genes that when mutated produce an abnormal, disturbed polarity. When a group of cells mutant for one of these genes is made in a otherwise normal fly, wild type cells adjacent to the mutant ones also show a disturbed polarity, even pointing their hairs in the direction opposite to normal. Thus, cells not only may respond to a global polarity system but they are also able to coordinate their polarity with with that of their neighbours. We are trying to understand how this global signalling and the local coordination occur, with the aim of understanding the logical relationship between the different components of planar polarity.