Figure 4.

Effect of m44 or p48 transgene expression on the light-dependent degeneration of Arr–/– retinas. A, Transgene expression attenuated (m44) or prevented (p48) the photoreceptor cell death observed in Arr–/– mice under standard cyclic light conditions. Left, Light micrographs of retinal sections from 1-year-old Arr–/–, m44^Arr–/–, and p48^Arr–/– mice reared under standard 12 h dark/light cycles. Right, Outer nuclear layer thickness at four different regions of the retina (see A, B, C, D regions in retinal section inset) was determined in 1-year-old Arr–/–, m44^Arr–/–, and p48^Arr–/– mice. Two mice were analyzed per phenotype, and error bars represent the range of measurements. B, Protective effect of p48, but not m44, to damage induced by a bright light regimen. Dark-reared mice from the indicated genotypes were exposed to constant 2000 lux white fluorescent light for 72 h. The eyes were then processed immediately for morphological analysis. Top, Representative light micrographs. Bottom, Measurements of the outer nuclear layer thickness taken at four different regions (A, B, C, D, inset) of central retinal sections. Error bars indicate SD for wild type (n = 4), Arr–/– (n = 4), and m44^Arr–/– (n = 4) and the range of measurements for p48^Arr–/– (n = 2). os, Outer segment; is, inner segment; onl, outer nuclear layer; inl, inner nuclear layer.