Genetical analysis ofvisual system disorganizer (vid), a new gene involved in normal development of eye and optic lobe of the brain inDrosophila melanogaster

A neuroanatomical screening of a collection of P-element mutagenized flies has been carried out with the aim of finding new mutants affecting the optic lobe of the adult brain inDrosophila melanogaster. We have identified a new gene that is involved in the development of the adult axon array in the optic ganglia and in the ommatidia assembly. We have named this locusvisual system disorganizer (vid). Reversional mutagenesis demonstrated that thevid mutant was the result of a P-element insertion in theDrosophila genome and allowed us to generate independent alleles, some of which resulted in semilethality, like thevid original mutant, while the others were completely lethal. A genetic somatic mosaic analysis indicated that thevid gene is required in the eye for its normal development by inductive effects. This analysis also suggests an inductive effect of thevid gene on the distal portion of the optic lobe, particularly the lamina and the first optic chiasma. Moreover, the absence of mutant phenotype in the proximal region of the optic ganglia, including the medulla, the second optic chiasma, and the lobula complex underlying mosaic eyes, is suggestive of an autonomously acting mechanism of thevid gene in the optic lobe. The complete or partial lethality generated by different mutations at thevid locus suggests that this gene's role may not be limited to the visual system, but may also affect a vital function duringDrosophila development.