Cone photoreceptors are responsible for the visual acuity and color vision of the human eye. Red/green cone opsin missense mutations N94K, W177R, P307L, R330Q, and G338E have been identified in subjects with congenital blue cone monochromacy or color-vision deficiency. Studies on disease mechanisms due to these cone opsin mutations have been previously carried out exclusively in vitro, and the reported impairments were not always consistent. Here we expressed these mutants via AAV specifically in vivo in M-opsin knockout mouse cones to investigate their subcellular localization, the pathogenic effects on cone structure, function, and cone viability. We show that these mutations alter the M-opsin structure, function, and localization. N94K and W177R mutants appeared to be misfolded since they localized exclusively in cone inner segments and endoplasmic reticulum. In contrast, P307L, R330Q, and G338E mutants were detected predominately in cone outer segments. Expression of R330Q and G338E, but not P307L opsins, also partially restored expression and correct localization of cone PDE6α’ and cone transducin γ and resulted in partial rescue of M-cone-mediated light responses. Expression of W177R and P307L mutants significantly reduced cone viability, whereas N94K, R330Q, and G338E were only modestly toxic. We propose that although the underlying biochemical and cellular defects caused by these mutants are distinct, they all seem to exhibit a dominant phenotype, resembling autosomal dominant retinitis pigmentosa associated with the majority of rhodopsin missense mutations. The understanding of the molecular mechanisms associated with these cone opsin mutants is fundamental to developing targeted therapies for cone dystrophy/dysfunction.

中文翻译：

---

红绿锥视蛋白错义突变引起X连锁视锥细胞营养不良的发病机制

视锥细胞负责人眼的视力和色觉。已在先天性蓝锥单色性或色觉缺陷的受试者中鉴定出红/绿视蛋白错义突变 N94K、W177R、P307L、R330Q 和 G338E。由于这些锥视蛋白突变导致的疾病机制的研究以前仅在体外进行，并且报告的损伤并不总是一致的。在这里，我们通过 AAV 在 M-视蛋白敲除小鼠视锥细胞中特异性地在体内表达这些突变体，以研究它们的亚细胞定位、对视锥细胞结构、功能和视锥细胞活力的致病作用。我们表明这些突变改变了 M-视蛋白的结构、功能和定位。N94K 和 W177R 突变体似乎是错误折叠的，因为它们仅定位于锥体内部段和内质网。相比之下，P307L、R330Q 和 G338E 突变体主要在锥体外段中检测到。R330Q 和 G338E 的表达，但不是 P307L 视蛋白，也部分恢复了锥体 PDE6α' 和锥体转导蛋白 γ 的表达和正确定位，并导致 M-锥体介导的光反应的部分拯救。W177R 和 P307L 突变体的表达显着降低了视锥细胞的活力，而 N94K、R330Q 和 G338E 仅具有适度的毒性。我们认为，尽管这些突变体引起的潜在生化和细胞缺陷是不同的，但它们似乎都表现出显性表型，类似于与大多数视紫红质错义突变相关的常染色体显性视网膜色素变性。