Abstract
Purpose :
Photoreceptors are sensory neurons that capture light within their outer segment, a narrow cylindrical organelle stacked with disc-shaped membranes housing the visual pigment. Photoreceptors are the most abundant neurons in the retina and are tightly packed to maximize the capture of incoming light. As a result, it is challenging to visualize an individual cell within a crowded photoreceptor population. To address this limitation, we developed a rod-specific mouse model that expresses tamoxifen-inducible cre recombinase under the control of the Nrl promoter. Measuring rates of ongoing disc synthesis in mouse models of retinal degeneration would clearly define the disease pathogenesis of a particular mutation. To that end, I have developed a new mouse model to monitor disc renewal in rods and present our initial findings.
Methods :
To characterize the Nrl:CreERT2 mouse, we crossed it to a mouse model containing a lox-stop-lox farnesylated GFP (GFPf) reporter. We induced GFPf expression with tamoxifen and collected eyes at various timepoints post-injection and analyzed GFPf expression in retinal sections. We have now crossed the inducible Nrl:CreERT2 mouse to our newly developed reporter mouse expressing a photoconvertible, outer segment-targeted, transmembrane fluorophore (TM-mEosCT). We induced TM-mEosCT reporter expression with tamoxifen and collected eyes at various timepoints post-injection and analyzed expression in retinal sections.
Results :
We characterized the Nrl:CreERT2 mouse model using a farnyslated GFP (GFPf) reporter mouse and found mosaic rod expression throughout the retina and the number of GFPf-expressing rods stabilized within three days post tamoxifen injection. We also show expression of our newly developed TM-mEosCT in rod photoreceptors is confined solely to the outer segment compartment, unlike GFPf, and we found the reporter accumulates in newly forming membrane discs that can be tracked over time.
Conclusions :
Mosaic cre expression in rod photoreceptors provided by the Nrl:CreERT2 mouse results in single cell resolution that can be utilized for a wide variety of applications. Here, we combined its utility with a newly developed reporter mouse model to investigate outer segment turnover over time.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.