Characterization of cytoplasmic Eyes absent function in Drosophila eye development. Charlene Hoi, Wenjun Xiong, Fangfang Jiang, Ilaria Rebay. University of Chicago, Chicago, IL.

   Eyes Absent (Eya) is a dual-function transcription factor (TF) and protein tyrosine phosphatase (PTP) that lies at the center of the retinal determination gene network which is essential for Drosophila eye development. Eyas two functions are spatially separated by the non-receptor tyrosine kinase, Abelson (Abl), which phosphorylates Eya to relocalize it from the nucleus, where it regulates eye specification at the level of transcription, to the cytoplasm, where it directs photoreceptor morphogenesis. Although both activities of Eya are necessary for eye development, understanding of Eyas contribution to retinal development have mostly centered on its role as a TF. To gain insight into cytoplasmic signaling pathways that Eya may be involved with, we performed a genetic screen of phosphotyrosine signaling networks based on Src Homology 2 (SH2) and Phosphotyrosine binding (PTB) domains and identified four Jak/Stat components: hopscotch (Jak), stat92E (Stat), socs36E and socs44A. Biochemical and genetic assays confirm that Eya interfaces with Jak/Stat signaling members, however further studies need to be done to fully understand the biological implications of these interactions and their mechanisms. Given Eya's unique dual-functionality and dynamic cellular localization, we suspect that it may be pivotal in integrating information from multiple signaling pathways during development. Unraveling Eya's relationship with the Jak/Stat pathway will hopefully increase our insight into Eyas broader role as a hub of signaling cross-talk during development.