Signaling mechanisms regulating the dual function transcription factor/protein phosphatase eyes absent during Drosophila eye development.

Saved in:
Bibliographic Details
Author / Creator:Morillo Salazar, Santiago Alejandro.
Imprint:2012.
Description:185 p.
Language:English
Format: E-Resource Dissertations
Local Note:School code: 0330.
URL for this record:http://pi.lib.uchicago.edu/1001/cat/bib/9370067
Hidden Bibliographic Details
Other authors / contributors:University of Chicago.
ISBN:9781267439888
Notes:Advisor: Ilaria Rebay.
Thesis (Ph.D.)--The University of Chicago, Division of the Biological Sciences, and The Pritzker School of Medicine, Department of Molecular Genetics and Cell Biology, 2012.
Dissertation Abstracts International, Volume: 73-11(E), Section: B.
Summary:The development of adult structures in multicellular organisms requires coordinated cell proliferation, differentiation, morphogenesis and cell fate maintenance, which are often controlled by multiple signaling pathways. Thus studying how downstream effectors such as transcription factors are regulated is crucial to understanding the mechanisms by which complex signaling inputs are coordinated to produce specific developmental decisions. The Drosophila eye provides a valuable experimental model to study these regulatory interactions because many of the molecular mechanisms that are involved in its development from an unpatterned epithelium into a complex structure with specific cell types have been conserved in evolution. In this thesis, I have focused on two molecular mechanisms involved in retinal determination through regulation of Eyes absent (Eya), a multifunctional protein that is essential during Drosophila eye development. I describe regulatory interactions between Eya and Nemo, a conserved proline-directed serine/threonine kinase, and between Eya and the Drosophila homologs of the c-Src tyrosine kinase. In addition, I describe a novel role for the Abelson kinase (Abl) in photoreceptor cell fate maintenance by studying its loss-of-function phenotypes in the Drosophila eye.
Eya is a member of a network of transcription factors referred to as the retinal determination (RD) network, which are required for eye development in Drosophila and in vertebrates. While the requirements for RD network components in the developing retina have been previously described, the mechanisms that coordinate their function are poorly understood. Eya has established functions as both a protein tyrosine phosphatase and a transcriptional coactivator, where it forms a bipartite complex with another RD factor, Sine oculis (So). In this study, I describe a regulatory interaction between Eya and the Nemo kinase. Nemo promotes Eya activity during retinal specification in ectopic eye assays and potentiates induction of the Eya-So transcriptional targets dachshund and lozenge. Mechanistically, Nemo directly phosphorylates Eya at two consensus MAPK phosphorylation sites, which are required for Nemo activation of Eya in vivo. My results present a novel mechanism of regulation of Eya’s function as a transcriptional activator during eye specification and provide a basis to explore the role of Nemo in eye development.
Previous work had identified genetic interactions between Eya and Src64 during eye development. I describe studies designed to explore the mechanism underlying this interaction and the contexts where Src64 regulates Eya function. Src64 antagonizes Eya activity in ectopic eye assays but not in genetic rescue experiments, suggesting that Eya-Src64 interactions are context-dependent. Src42, a second Drosophila homolog of Src, appears to be functionally redundant with Src64 with respect to Eya regulation. Src64 and Src42 directly phosphorylate the N-terminal region of Eya in vitro, and coexpression of Eya and Src64, but not Eya and Src42, causes Eya aggregation at the nuclear periphery in cultured cells. The specific developmental context for Eya-Src kinase interactions remains unclear; therefore additional work will be required to describe the consequences of this regulatory interaction.
In addition, I have contributed to a study examining the functions of the Abl kinase in patterning the Drosophila retina. Abl was previously identified as a regulator of Eya during photoreceptor morphogenesis, and here we show that Abl is also required for cell fate maintenance. Loss of Abl results in loss of neuronal markers in photoreceptor cells during late pupal stages and this correlates with upregulation of Notch signaling. Our results reveal developmental plasticity in photoreceptor cells and suggest a novel mechanism for terminal cell fate maintenance.