Number and Distribution of Mouse Retinal Cone Photoreceptors: Differences between an Albino (Swiss) and a Pigmented (C57/BL6) Strain

Abstract

We purpose here to analyze and compare the population and topography of cone photoreceptors in two mouse strains using automated routines, and to design a method of retinal sampling for their accurate manual quantification. In whole-mounted retinas from pigmented C57/BL6 and albino Swiss mice, the longwave-sensitive (L) and the shortwave-sensitive (S) opsins were immunodetected to analyze the population of each cone type. In another group of retinas both opsins were detected with the same fluorophore to quantify all cones. In a third set of retinas, L-opsin and Brn3a were immunodetected to determine whether L-opsin+cones and retinal ganglion cells (RGCs) have a parallel distribution. Cones and RGCs were automatically quantified and their topography illustrated with isodensity maps. Our results show that pigmented mice have a significantly higher number of total cones (all-cones) and of L-opsin+cones than albinos which, in turn, have a higher population of S-opsin+cones. In pigmented animals 40% of cones are dual (cones that express both opsins), 34% genuine-L (cones that only express the L-opsin), and 26% genuine-S (cones that only express the S-opsin). In albinos, 23% of cones are genuine-S and the proportion of dual cones increases to 76% at the expense of genuine-L cones. In both strains, L-opsin+cones are denser in the central than peripheral retina, and all-cones density increases dorso-ventrally. In pigmented animals S-opsin+cones are scarce in the dorsal retina and very numerous in the ventral retina, being densest in its nasal aspect. In albinos, S-opsin+cones are abundant in the dorsal retina, although their highest densities are also ventral. Based on the densities of each cone population, we propose a sampling method to manually quantify and infer their total population. In conclusion, these data provide the basis to study cone degeneration and its prevention in pathologic conditions.

Activated mTORC1 promotes long-term cone survival in retinitis pigmentosa mice

“…and the percentage of colocalization of red and green signals was the highest upon loss of TSC1 (52.7%). The actual cone count in WT retinae was in agreement with published data (59) and revealed that at P21, 95.2% of cones were still present in the rd1 Tsc1 cKO retinae when compared with those in WT retinae, meaning that 52.7% of colocalization (red to green signal) corresponds to 95.2% of cones. These numbers were used to calibrate all colocalization data representing cone survival.…”

Transretinal ERG in Studying Mouse Rod Phototransduction: Comparison With Local ERG Across the Rod Outer Segments

“…The photoreceptor ERG signal is a superposition of extracellular potential changes caused by both rods and cones. In the mouse retina the cone density is less than 1/30 of the rod density 29 and the light sensitivity of rods exceeds that of cones by 1000-fold. 13 Therefore, in dark-adapted retinas the ERG signal is expected to originate mainly from rods.…”

Evidence for multifactorial processes underlying phenotypic variation in bat visual opsins

“…For each species, IHC was performed on at least three retinas from at least three field-collected individuals, and three retinas from two individuals for museum-sampled species (for details see Table S1). Given the consistency of the detection of these antibodies across all bats and other mammals (Müller et al, 2009;Müller et al, 2007;Ortín-Martínez et al, 2014), and the number of replicates and individuals examined, we interpreted no labeling to indicate a true loss of the respective cone type.…”

“…Although variation in the complement 276 13 of photoreceptors across vertebrates is usually explained by disruptions to the protein-coding 277 sequence [e.g., (Mundy et al, 2016;Zhao, Rossiter, et al, 2009) Our results further allow us to hypothesize the developmental processes contributing to variation 282 in visual perception among bat taxa. Unlike species of Mus (Ortín-Martínez et al, 2014), in which 283 many cones express more than one photoreceptor, almost all cones in the bats we analyzed 284 expressed a single opsin type (OPN1SW or OPN1LW). Given this constraint, if S-opsin cones 285…”

“…For each species, IHC was performed on replicates from at least three 419 individual retinas. We considered no labeling to indicate a true loss of the cone type following 420 references (Müller et al, 2009;Müller et al, 2007;Ortín-Martínez et al, 2014). Labelled retinas 421…”