487C Poster - 06. Regulation of gene expression
Saturday April 09, 1:30 PM - 3:30 PM

Authors:
Hongsu Wang ¹; Raja Komal ²; Kelvin Yeung ²; Graeme Mardon ²; Jessica Treisman ¹

Affiliations:
1) Skirball Institute for Biomolecular Medicine and Department of Cell Biology, NYU School of Medicine; 2) Department of Pathology and Immunology and Department of Molecular and Human Genetics, Baylor College of Medicine

Keywords:
f. pattern formation; f. eye disc

Light-detecting photoreceptors and supportive cone cells differentiate from identical precursor cells in the eye disc during late larval and early pupal stages. Reiterative Epidermal Growth Factor Receptor (EGFR) signaling induces the specification of photoreceptors R1-7 and cone cells. Glass (Gl) is an eye-specific transcription factor that is necessary for the differentiation of all cell types in the retina. Gl is expressed in all cells posterior to the morphogenetic furrow, but only turns on photoreceptor-specific genes in cells that receive an EGFR signal. We hypothesized that the cell-intrinsic transcription factor Gl and the external EGFR signal synergistically induce accurate and robust differentiation. Misexpression of Gl in the wing disc leads to the activation of some eye-specific genes, but only coexpression of Gl with an activated form of the EGFR signaling component Ras (Ras^v12) could induce expression of the neuronal markers Elav and Futsch. We used RNA-Seq to identify genes that are synergistically induced by Gl and Ras^V12 in the wing disc and to determine which of them are dependent on the presence of the transcription factor Pointed (Pnt), which acts downstream of Ras. A large proportion of these Pnt-dependent synergistically induced genes are characteristic of neurons. We are using Targeted Dam ID with Gl and PntP1 to determine which of these genes are direct targets of Gl and/or EGFR signaling. Alternatively, transcription factors that are regulated by the combination of Gl and Ras^V12 could mediate their downstream effects, and we are testing several candidates. Single-cell RNA-Seq revealed that gl mutant eye discs lack both the distinctive differentiation trajectory profile of photoreceptors R2, 5, 3, and 4 present in wild type white prepupal eye discs (accuracy of differentiation) and any clusters representing R1, 6, or 7 (robustness of differentiation). Studying the synergy between Gl and EGFR signaling will help us understand how the cell intrinsic factor Gl cooperates with external signaling to induce accurate and robust differentiation of key retinal cell types.