JNK is antagonized to ensure the correct number of interommatidial cells pattern the Drosophila retina

Apoptosis is crucial during the morphogenesis of most organs and tissues, and is utilized for tissues to achieve their proper size, shape and patterning. Many signaling pathways contribute to the precise regulation of apoptosis. Here we show that Jun N-terminal Kinase (JNK) activity contributes to the coordinated removal of interommatidial cells via apoptosis in the Drosophila pupal retina. This is consistent with previous findings that JNK activity promotes apoptosis in other epithelia. However, we found that JNK activity is repressed by Cindr (the CIN85 and CD2AP ortholog) in order to promote cell survival. Reducing the amount of Cindr resulted in ectopic cell death. Increased expression of the Drosophila JNK basket in the setting of reduced cindr expression was found to result in even more severe apoptosis, whilst ectopic death was found to be reduced if retinas were heterozygous for basket. Hence Cindr is required to properly restrict JNK-mediated apoptosis in the pupal eye, resulting in the correct number of interommatidial cells. A lack of precise control over developmental apoptosis can lead to improper tissue morphogenesis.