Abrupt Onset of Mutations in a Developmentally Regulated Gene during Terminal Differentiation of Post-Mitotic Photoreceptor Neurons in Mice
Figure 5
Spontaneous gene correction events in retinas of mutant mouse lines ID2-hRho-GFP/+ and Q344X-hRho-GFP/+.
A. Schematic diagram of the structure of the ID2-hRho-GFP and Q344X-hRho-GFP genes and the mechanism leading to hRho-GFP expression. Exons are represented as black rectangles. In the ID2-hRho-GFP gene, the duplicated exon 2 is marked by horizontal arrows and shown in white. B. Projection of a stack of confocal images of a retinal wholemount, showing the GFP positive photoreceptors. The images of clusters of rod cells all came from ID2-hRho-GFP mice. The first image shows an extended supercluster of rod cells that was observed in a single mouse; the adjacent image shows an area of this retina at higher magnification. The next images show a variety of clusters arranged by decreasing number of rods per cluster The two images on the right are from Q344X-hRho-GFP retinas; they show individual rod photoreceptors that are overexposed to make the inner segments and nuclei visible. Scale bars are shown; the 20-μm scale bar applies to all the images without explicit scale bars. C. Age-dependent appearance of single green rods and clusters in ID2-hRho-GFP heterozygous mice. Retinas from several mice were examined at the indicated times and the values were averaged (age in weeks∶number of mice; 4∶2; 17∶6; 20∶3; 24∶2; 36∶4; 38∶4; 52∶6). Error bars indicate standard deviations. D. Age-dependent appearance of single green rods in Q344X-hRho-GFP heterozygous mice. Retinas were examined from several mice at the indicated times and the values were averaged (age in weeks∶number of mice; 2∶12; 4∶22; 10∶3; 11∶4; 15∶5; 18∶16; 35∶4; 65∶4; 70∶7). Error bars indicate standard deviations.