The Drosophila Jak kinase hopscotch is required for multiple developmentalprocesses in the eye

Jak kinases are critical signaling components in hematopoiesis. While a lar ge number of studies have been conducted on the roles of Jak kinases in the hematopoietic cells, much less is known about the requirements for these t yrosine kinases in other tissues. We have used loss of function mutations i n the Drosophila Jak kinase Hopscotch (Hop) to determine the role of Hop in eye development. We find that Hop is required for cell proliferation/survi val in the eye imaginal disc, for the differentiation of photoreceptor cell s, and for the establishment of the equator and of ommatidial polarity. The se results indicate that hop activity is required for multiple developmenta l processes in the eye, both cell-autonomously and nonautonomously. (C) 199 9 Academic Press.