A new visualization approach for identifying mutations that affect differentiation and organization of the Drosophila ommatidia

The Drosophila eye is widely used as a model system to study neuronal diffe rentiation, survival and axon projection. Photoreceptor differentiation sta rts with the specification of a founder cell R8, which sequentially recruit s other photoreceptor neurons to the ommatidium. The eight photoreceptors t hat compose each ommatidium exist in two chiral forms organized along two a xes of symmetry and this pattern represents a paradigm to study tissue pola rity. We have developed a method of fluoroscopy to visualize the different types of photoreceptors and the organization of the ommatidia in living ani mals. This allowed us to perform an Fl genetic screen to isolate mutants af fecting photoreceptor differentiation, survival or planar polarity. We illu strate the power of this detection system using known genetic backgrounds a nd new mutations that affect ommatidial differentiation, morphology or chir ality.