The long-term objectives of this work are to elucidate the mechanisms whereby cells integrate instructions from multiple signaling pathways and respond in a context-appropriate manner. Reflecting the key role that precisely orchestrated signaling plays in all biological processes, uncontrolled or dysregulated activity of these pathways leads to tumorigenesis and/or developmental defects in humans. Our approach is to exploit the genetically tractable Drosophila system to uncover novel strategies whereby conserved signal transduction cascades converge on nuclear transcription factor networks to direct cell proliferation, fate specification, differentiation, morphogenesis and survival during retinal development. Because developmental signaling mechanisms have been highly conserved in evolution, knowledge of the molecular circuitries used in Drosophila will fundamentally advance our understanding of how cell fates are designated and maintained, and why misregulation results in cancer and disease in mammals. The goal of this proposal is to explore a novel mechanism of signal integration suggested by our ongoing study of transcriptional regulatory networks that orchestrate retinal specification and development. Specifically Eyes absent (Eya), through its unusual dual functionality as transcription factor and protein tyrosine phosphatase (PTP), has the potential both to respond to upstream signaling inputs by directing downstream patterns of gene expression and to influence the activity of these same pathways through its phosphatase function. Although impaired Eya PTP function has been implicated in human disease, including ocular defects, the normal biological function of Eya's PTP activity, and its relationship to Eya-mediated transcriptional regulation, remains poorly understood. This proposal describes a multi-faceted approach combining genetic, biochemical, and cell biological assays to address the hypothesis that proper coordination and regulation of Eya's two essential functions, one as a nuclear transcription factor and one as a component of phosphotyrosine signaling networks, is critical for retinal development. Successful completion of the proposed research plan will provide insight into the cellular and developmental contexts in which Eya's PTP function is required and should uncover novel mechanisms of cross-talk between Eya, the retinal determination gene network and other signaling modules critical for eye development.
The specific aims are to elucidate the phosphotyrosine signaling pathways in which Eyes absent (Eya) participates by exploring genetic and biochemical interactions with the Abelson (Abl) and Src64 tyrosine kinases, to investigate the contribution of new binding partners identified in an in vitro expression screen with respect to Eyes absent's two functions as transcription factor and phosphatase, and to test the hypothesis that spatial partitioning of Eyes absent function between nucleus and cytoplasm contributes to proper retinal development. Because the proteins and pathways we are studying have conserved functions in mammals, the new signaling strategies revealed by our work will advance understanding of human development and disease.

Public Health Relevance

Inappropriate regulation of gene function underlies a broad spectrum of human developmental abnormalities and diseases, including cancer. The goal of this research is to reveal the cellular mechanisms that regulate critical decisions during normal development of the eye, as an essential first step toward understanding the diseases and defects that arise when these key controls are lost and eventually toward developing effective therapeutic interventions.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Biology and Diseases of the Posterior Eye Study Section (BDPE)
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Neuhold, Lisa
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University of Chicago
Internal Medicine/Medicine
Schools of Medicine
United States
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Davis, Trevor L; Rebay, Ilaria (2017) Antagonistic regulation of the second mitotic wave by Eyes absent-Sine oculis and Combgap coordinates proliferation and specification in the Drosophila retina. Development 144:2640-2651
Davis, Trevor L; Rebay, Ilaria (2017) Master regulators in development: Views from the Drosophila retinal determination and mammalian pluripotency gene networks. Dev Biol 421:93-107
Hoi, Charlene S L; Xiong, Wenjun; Rebay, Ilaria (2016) Retinal Axon Guidance Requires Integration of Eya and the Jak/Stat Pathway into Phosphotyrosine-Based Signaling Circuitries in Drosophila. Genetics 203:1283-95
Rebay, Ilaria (2016) Multiple Functions of the Eya Phosphotyrosine Phosphatase. Mol Cell Biol 36:668-77
Zhou, Qingxiang; Zhang, Tianyi; Jemc, Jennifer C et al. (2014) Onset of atonal expression in Drosophila retinal progenitors involves redundant and synergistic contributions of Ey/Pax6 and So binding sites within two distant enhancers. Dev Biol 386:152-64
Xiong, Wenjun; Morillo, Santiago A; Rebay, Ilaria (2013) The Abelson tyrosine kinase regulates Notch endocytosis and signaling to maintain neuronal cell fate in Drosophila photoreceptors. Development 140:176-84
Morillo, Santiago A; Braid, Lorena R; Verheyen, Esther M et al. (2012) Nemo phosphorylates Eyes absent and enhances output from the Eya-Sine oculis transcriptional complex during Drosophila retinal determination. Dev Biol 365:267-76
Xiong, Wenjun; Rebay, Ilaria (2011) Abelson tyrosine kinase is required for Drosophila photoreceptor morphogenesis and retinal epithelial patterning. Dev Dyn 240:1745-55
Xiong, Wenjun; Dabbouseh, Noura M; Rebay, Ilaria (2009) Interactions with the Abelson tyrosine kinase reveal compartmentalization of eyes absent function between nucleus and cytoplasm. Dev Cell 16:271-9
Jemc, Jennifer; Rebay, Ilaria (2007) Identification of transcriptional targets of the dual-function transcription factor/phosphatase eyes absent. Dev Biol 310:416-29

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