REORGANIZATION OF MEMBRANE CONTACTS PRIOR TO APOPTOSIS IN THE DROSOPHILA RETINA - THE ROLE OF THE IRREC-RST PROTEIN

The final step of pattern formation in the developing retina of Drosop hila is the elimination of excess cells between ommatidia and the diff erentiation of the remaining cells into secondary and tertiary pigment cells, Temporally and spatially highly regulated expression of the ir regular chiasmC-roughest protein, an adhesion molecule of the inmunogl obulin superfamily known to be involved in axonal pathfinding, is esse ntial for correct sorting of cell-cell contacts in the pupal retina wi thout which the ensuing wave of apoptosis does not occur. Irregular ch iasmC-roughest accumulates strongly at the borders between primary pig ment and interommatidial cells. Mutant and misexpression analysis show that this accumulation of the irregular chiasmC-roughest protein is n ecessary for aligning interommatidial cells in a single row. This reor ganisation is a prerequisite for the identification of death candidate s. Irregular chiasmC-roughest function in retinal development demonstr ates the importance of specific cell contacts for assignment of the ap optotic fate.