Photoreceptor patterning in flies and mosquitoes

Project Summary: During development, sensory neurons differentiate into subtypes with distinct morphologies, gene expression, and functions. In the retina, the diversity of photoreceptor subtypes is critical for vision and the ability to interact with the environment. This proposal aims to advance our knowledge of cell fate specification by examining how photoreceptors are patterned during development in flies and mosquitoes. In the fly eye, stereotypical and stochastic patterns are overlaid during development. The stereotypical structure of the eye results from a wave of morphogenesis, driven by Hedgehog (Hh) signaling, which promotes expression of Decapentaplegic (Dpp). Overlaid on the regular morphology of the eye, two R7 photoreceptor subtypes are stochastically patterned, controlled by stochastic ON/OFF expression of the transcription factor, Spineless (Ss). My preliminary studies show that Hh signaling coordinates stereotyped and stochastic patterning in the fly eye, requiring activity of the receptor Patched (Ptc), but not Cubitus Interruptus (Ci), the canonical transcriptional effector. I hypothesize that Hh functions through an unidentified transcriptional factor to promote (1) dpp transcription and stereotypical morphological patterning and (2) ss transcription and stochastic R7 subtype patterning. To test this hypothesis in Aim 1, I will analyze the transcriptional and chromatin dynamics of dpp and ss regulation. I will generate a single-nucleus multiomics dataset to identify putative transcription factors mediating Hh signaling and examine their functions in the eye. This aim will address how signaling mechanisms that drive stereotypical patterning are co-opted to produce stochastic patterns during development. Mosquitoes are a disease vector that pose an increasing risk to human health and welfare. In mosquitoes, vision is critical for host-seeking, mating, and foraging behaviors, yet the mechanisms that establish patterning of the mosquito eye are not known. In contrast to the fly eye, R7 subtypes are found in stereotypical stripe patterns in the dorsal and ventral regions of the mosquito retina. I hypothesize that the gene network giving rise to stereotypical PR subtype specification is vital for mosquito survival behaviors. To test this hypothesis in Aim 2, I will generate a single-nucleus multiomics atlas of retinal development in An. gambiae, identify factors with cell-type-specific expression and roles in fly eye development, and validate their expression using IHC and RNA FISH. I will determine roles for Drosophila R7 patterning genes in An. gambiae. Finally, I will determine the functional roles of R7 subtype specification in behavior using host-seeking assays. In my lab, I will dissect the regulatory networks involved in mosquito retinal development, focusing on patterning and cell fate specification. Using the atlas, I will define the roles of ~30 key regulators previously characterized in flies, and compare their functions across species, including Ae. aegypti. I will also identify and test novel regulators of mosquito eye development. These studies will provide the first mechanistic dissection of eye development in mosquitoes, generate insights into evolution of the underlying mechanisms, and establish my independent research program.