DIFFERENCES IN CONE TYPE PROPORTIONS AND DISTRIBUTION BETWEEN PIGMENTED AND ALBINO STRAINS OF ADULT MICE

Abstract

 

Purpose

 

To analyze the population of L, S and dual cones and their topographic distribution in two strains of adult mice and to design a method of retinal sampling for accurate quantification of the cone populations.

 

Methods

 

In whole mounted retinas from C57/BL6 pigmented and Swiss albino mice the two opsins were immunodetected with two different fluorophores to analyze the number and distribution of L- and S-opsin cones or only with one fluorophore to analyze the number and distribution of the whole cone population (number of retinas per analysis =10 pigmented and 8 albino). Cones were automatically quantified and their topography shown with isodensity maps. Finally, based on the densities of each cone population, we determined the sampling areas needed for accurate non-automatic quantification of the total cone population.

 

Results

 

Automated quantification and data processing resulted in total numbers of 62,984 or 6,360 genuine L-cones, 47,445 or 35,619 genuine S-cones and 72,171 or 111,063 dual cones in pigmented or albino mice, respectively. In pigmented mice one third of the cone population are genuine L-cones, one third genuine S-cones and the remaining one third are dual. In albino mice, one third are genuine S-cones, 4% are genuine L-cones, and 80% of the cones are dual. L-opsin+cones were found in both strains across the retina and their density peaked in the central retina. S-opsin+cones were localized in the inferior retina in pigmented mice, but distributed across the retina, with highest densities in the inferior retina in albino mice. We distinguished retinal areas with different cone densities that should be sampled for non-automatic quantification of the total cone population.

 

Conclusions

 

The proportion of genuine L-, genuine S- and dual cones differs in both strains. Although the distribution of L-opsin+cones is similar in both strains, the distribution of S-opsin+cones differs between them. Our sampling method permits the accurate quantification of the whole cone population. These data can provide the basis for studying degeneration of cone populations and their prevention in pathologic conditions.

 

Keywords: 615 neuroprotection • 648 photoreceptors • 688 retina