Opsin Expression in Disparate Cell Types of Hydra vulgaris

Abstract

Opsins serve as the first step in the phototransduction cascade which translates light into an electrochemical signal. Opsins are not just found in photoreceptor cells, they have also been found expressed in non-neuronal cell types such as progenitor cells in Hydra, muscle cells and nematocysts in jellyfish, and in the photoresponse of sea anemone muscle cells that were exposed to synaptic inhibitors. Expression of light sensing proteins such as opsins in non-neuronal and especially in progenitor cells could be an indication of cells using light as a signal in cell fate decisions. In order to further explore this idea we sought out single cell RNA sequencing datasets to pinpoint and visualize the expression of various opsin genes across cell types in Hydra. We identified 29 opsin genes expressed in serveral cell types in Hydra, and found that some opsins were expressed before cell differentiation. More analysis is needed to link this opsin expression with photosensitivity. A promising next step in this project is to implement WGCNA or Weighted Gene Co-expression Network Analysis, which is used to analyze the extent and degree of co-expression between specified genes. This can be used to further investigate the co-expression of opsin and the phototransduction genes that would be required for photosensitivity.