# Genetic manipulation of rod-cone differences in mouse retina

## TL;DR

This study shows that altering specific proteins in mouse rod photoreceptors can make their light responses more similar to cone photoreceptors.

## Contribution

The paper demonstrates that modifying transducin and GTPase-activating proteins can reduce rod-cone sensitivity differences.

## Key findings

- TrUx;GapOx rods achieved sensitivity within a factor of 2 of WT cones after adjusting for outer-segment dimensions.
- Altered proteins did not affect photoreceptor adaptation, as rods still showed increment saturation.
- The results confirm that a few transduction protein changes can mimic some cone response features in rods.

## Abstract

Though rod and cone photoreceptors use similar phototransduction mechanisms, previous model calculations have indicated that the most important differences in their light responses are likely to be differences in amplification of the G-protein cascade, different decay rates of phosphodiesterase (PDE) and pigment phosphorylation, and different rates of turnover of cGMP in darkness. To test this hypothesis, we constructed TrUx;GapOx rods by crossing mice with decreased transduction gain from decreased transducin expression, with mice displaying an increased rate of PDE decay from increased expression of GTPase-activating proteins (GAPs). These two manipulations brought the sensitivity of TrUx;GapOx rods to within a factor of 2 of WT cone sensitivity, after correcting for outer-segment dimensions. These alterations did not, however, change photoreceptor adaptation: rods continued to show increment saturation though at a higher background intensity. These experiments confirm model calculations that rod responses can mimic some (though not all) of the features of cone responses after only a few changes in the properties of transduction proteins.