PDF(Pubmed)
Abstract：
Congenital stationary night blindness (CSNB) is an inherited retinal disease that causes a profound loss of rod sensitivity without severe retinal degeneration. One well-studied rhodopsin point mutant, G90D-Rho, is thought to cause CSNB because of its constitutive activity in darkness causing rod desensitization. However, the nature of this constitutive activity and its precise molecular source have not been resolved for almost 30 y. In this study, we made a knock-in (KI) mouse line with a very low expression of G90D-Rho (equal in amount to ~0.1% of normal rhodopsin, WT-Rho, in WT rods), with the remaining WT-Rho replaced by REY-Rho, a mutant with a very low efficiency of activating transducin due to a charge reversal of the highly conserved ERY motif to REY. We observed two kinds of constitutive noise: one being spontaneous isomerization (R*) of G90D-Rho at a molecular rate (R* s-1) 175-fold higher than WT-Rho and the other being G90D-Rho-generated dark continuous noise comprising low-amplitude unitary events occurring at a very high molecular rate equivalent in effect to ~40,000-fold of R* s-1 from WT-Rho. Neither noise type originated from G90D-Opsin because exogenous 11-cis-retinal had no effect. Extrapolating the above observations at low (0.1%) expression of G90D-Rho to normal disease exhibited by a KI mouse model with RhoG90D/WTand RhoG90D/G90D genotypes predicts the disease condition very well quantitatively. Overall, the continuous noise from G90D-Rho therefore predominates, constituting the major equivalent background light causing rod desensitization in CSNB.
摘要：
先天性固定夜盲症（CSNB）是一种遗传性视网膜疾病，可导致视杆敏感性的严重丧失，而不会导致严重的视网膜变性。一个研究良好的视紫红质点突变体,G90D-Rho,被认为是导致CSNB的原因，因为其在黑暗中的组成活性会导致杆脱敏。然而,这种结构活性的性质及其精确的分子来源近30年没有得到解决。在这项研究中，我们制作了一个敲入（KI）小鼠系，G90D-Rho表达非常低（相当于正常视紫红质的〜0.1％，WT-Rho,在WT棒中)，剩下的WT-Rho被REY-Rho取代，由于高度保守的ERY基序向REY的电荷逆转，激活转导素的效率非常低的突变体。我们观察到两种本构噪声：一种是G90D-Rho的自发异构化（R*s-1），其分子速率（R*s-1）比WT-Rho高175倍，另一种是G90D-Rho产生的暗连续噪声，包括以非常高的分子速率发生的低振幅单位事件，相当于WT-Rho的R*s-1的约40,000倍。两种噪声类型均不起源于G90D-Opsin，因为外源性11-顺式视网膜没有影响。将G90D-Rho的低(0.1%)表达的上述观察结果外推至具有RhoG90D/WTandRhoG90D/G90D基因型的KI小鼠模型所表现出的正常疾病,非常好地定量地预测了疾病状况。总的来说,因此，来自G90D-Rho的连续噪声占主导地位，构成CSNB中引起棒脱敏的主要等效背景光。
