Abstract
Light regulates the mammalian vertebrate visual system to affect a wide array of visual behaviors. Light is detected by the canonical rods and cone photoreceptors, but also by a novel, third class of photoreceptor, termed intrinsically photosensitive retinal ganglion cells (ipRGCs). ipRGCs express the photopigment melanopsin (gene: Opn4) and are a diverse population, consisting of six types (M1-M6), which differ in morphology, electrophysiological properties, central brain projections, and their influences on visual behavior. However, the extent to which these ipRGC subtypes differ in their gene expression and how each individual subtype contributes to visual behavior is unknown. To address this gap in knowledge, the Schmidt Lab has developed an Opn4FlpO mouse line, which can genetically isolate individual ipRGC subtypes. My project involves validating and characterizing the Opn4FlpO mouse line using both single and double-reporters, while also analyzing retinal cell expression patterns. To validate the line, mammalian vertebrate (mouse) retinas were dissected and immunohistochemistry was performed, allowing for various ipRGCs to be labeled, imaged, and counted. One major conclusion of my preliminary data suggests that the Opn4FlpO line exclusively labels ipRGCs across various reporter lines. Interestingly, not all reporter-labeled cells can be co-labeled with Opn4, however, and a neurofilament staining was employed for elucidation of these results. This work helps contribute to a major goal of visual neuroscience, which is to understand how each of the 40 types of retinal ganglion cells influences visual behavior and determine any commonalities in their gene expression.