Bowes C, van Veen T, Farber D B
Jules Stein Eye Institute, UCLA School of Medicine 90024.
Exp Eye Res. 1988 Sep;47(3):369-90. doi: 10.1016/0014-4835(88)90049-8.
Retinal degeneration in rd mice is manifested during the most rapid period of postnatal photoreceptor differentiation and is hypothesized to be caused by a lesion in cGMP metabolism. We have studied the sequence of developmental expression of three proteins involved in the cGMP cascade and the mRNAs from which they are translated, in rd and control mouse retinas. Slot blot analysis of retinal RNAs indicates that the mRNAs coding for opsin, the alpha, beta and gamma subunits of G-protein and 48-kDa protein each has the same time for onset of expression in normal and diseased retinas. G beta and 48-kDa protein mRNAs are already detectable at birth, opsin mRNA appears by postnatal day 5 (P5), G gamma mRNA at P6 and G alpha mRNA by P8. The levels of all these mRNAs decrease in the diseased retinas after P11-P12, correlating with the reduction in photoreceptor cell number that characterizes the rd disease. Immunocytochemistry indicates that the 48-kDa protein is present at birth, G gamma and opsin are detectable at P4 and G alpha at P7. After P7, opsin and G-protein immunoreactivity are localized throughout the photoreceptor cell in the rd retinas but they are found only in the outer segment in control retinas. The 48-kDa protein immunoreactivity, which is observed in the whole photoreceptor layer both in rd and control retinas throughout development, is the only one of all immunoreactivities analysed that remains at 2 months of age in the rd retina and is probably localized in cones. However, at 6 months of age, 48-kDa protein immunoreactive cells are no longer present in the rd retina. We have also investigated whether there is a daily rhythm for the levels of mRNA present at different times during the light/dark periods in developing rd/rd and rd/+ retinas and in adult normal (+/+) retinas. We find that the levels of each mRNA analysed appear to cycle in the +/+ adult retina, with the greatest amount of opsin and the three subunits of G-protein mRNAs occurring just before light onset and the greatest amount of 48-kDa protein mRNA occurring just before lights off. Cycling in the developing diseased or control retinas (P0-P12) is not observed and may be masked by the pronounced cell growth that occurs during this period.
rd小鼠的视网膜退化在出生后光感受器分化最迅速的时期表现出来，据推测是由cGMP代谢损伤引起的。我们研究了rd和对照小鼠视网膜中参与cGMP级联反应的三种蛋白质及其翻译mRNA的发育表达序列。视网膜RNA的狭缝印迹分析表明，编码视蛋白、G蛋白的α、β和γ亚基以及48 kDa蛋白的mRNA在正常和患病视网膜中的表达起始时间相同。Gβ和48 kDa蛋白的mRNA在出生时即可检测到，视蛋白mRNA在出生后第5天（P5）出现，Gγ mRNA在P6出现，Gα mRNA在P8出现。在P11 - P12之后，患病视网膜中所有这些mRNA的水平均下降，这与rd疾病特征性的光感受器细胞数量减少相关。免疫细胞化学表明，48 kDa蛋白在出生时就存在，Gγ和视蛋白在P4时可检测到，Gα在P7时可检测到。P7之后，视蛋白和G蛋白免疫反应性在rd视网膜的整个光感受器细胞中定位，但在对照视网膜中仅在外段发现。在整个发育过程中，rd和对照视网膜的整个光感受器层均观察到48 kDa蛋白免疫反应性，这是所有分析的免疫反应性中唯一在rd视网膜2月龄时仍存在的，可能定位于视锥细胞。然而，在6月龄时，rd视网膜中不再存在48 kDa蛋白免疫反应性细胞。我们还研究了发育中的rd/rd和rd/+视网膜以及成年正常（+/+）视网膜在明/暗周期不同时间的mRNA水平是否存在日节律。我们发现，在+/+成年视网膜中，所分析的每种mRNA的水平似乎都呈周期性变化，视蛋白和G蛋白三个亚基的mRNA量在光照开始前最大，48 kDa蛋白mRNA量在光照关闭前最大。在发育中的患病或对照视网膜（P0 - P12）中未观察到周期性变化，这可能被此期间发生的明显细胞生长所掩盖。
