Comparison of rod photoreceptor outer segment renewal in wild type and Tmem138-deficient mice using AAV-delivered Dendra2-tagged rhodopsin.

Visualization of photoreceptor outer segment (OS) renewal dynamics is essential for vision research but has proved difficult in mice due to the small size and dense packing of their photoreceptors. Lack of effective protein "trackers" and the time-consuming generation of transgenic reporter lines add to these challenges. In this study, we evaluated AAV-mediated delivery of photoconvertible Rhodopsin/Dendra2 and Peripherin2/Dendra2 fusion proteins as a means to track OS renewal in mouse photoreceptors. OS renewal was assessed by two approaches: (1) comparing the lengths of native (green) Dendra2 domains at two post-infection time points, and (2) using photoconversion of Dendra2 to distinguish newly synthesized discs from preexisting ones within the same cell. We validated this method in both wild type mice and a Tmem138-deficient ciliopathy mice, in which a reduced OS renewal rate was observed. Taken together, this method offers a rapid genetic tool for "real-time" evaluation of OS renewal dynamics in mice, overcoming the limitations posed by the compact and densely organized photoreceptor architecture.