PDF(Pubmed)
Abstract：
Vision under dim light relies on primary cilia elaborated by rod photoreceptors in the retina. This specialized sensory structure, called the rod outer segment (ROS), comprises hundreds of stacked, membranous discs containing the light-sensitive protein rhodopsin, and the incorporation of new discs into the ROS is essential for maintaining the rod\'s health and function. ROS renewal appears to be primarily regulated by extrinsic factors (light); however, results vary depending on different model organisms. We generated two independent transgenic mouse lines where rhodopsin\'s fate is tracked by a fluorescently labeled rhodopsin fusion protein (Rho-Timer) and show that rhodopsin incorporation into nascent ROS discs appears to be regulated by both external lighting cues and autonomous retinal clocks. Live-cell imaging of the ROS isolated from mice exposed to six unique lighting conditions demonstrates that ROS formation occurs in a periodic manner in cyclic light, constant darkness, and artificial light/dark cycles. This alternating bright/weak banding of Rho-Timer along the length of the ROS relates to inhomogeneities in rhodopsin density and potential points of structural weakness. In addition, we reveal that prolonged dim ambient light exposure impacts not only the rhodopsin content of new discs but also that of older discs, suggesting a dynamic interchange of material between new and old discs. Furthermore, we show that rhodopsin incorporation into the ROS is greatly altered in two autosomal recessive retinitis pigmentosa mouse models, potentially contributing to the pathogenesis. Our findings provide insights into how extrinsic (light) and intrinsic (retinal clocks and genetic mutation) factors dynamically regulate mammalian ROS renewal.
摘要：
昏暗光线下的视力依赖于视网膜中棒光感受器产生的初级纤毛。这种特殊的感官结构，称为棒外段(ROS)，包括数百个堆叠的，含有光敏蛋白视紫红质的膜盘，和新的光盘结合到ROS是必不可少的，以保持棒的健康和功能。ROS的更新似乎主要受外在因素(光)调节；然而，结果因不同的模式生物而异。我们产生了两个独立的转基因小鼠系，其中视紫红质的命运由荧光标记的视紫红质融合蛋白（Rho-Timer）追踪，并表明视紫红质掺入新生的ROS盘似乎受外部照明提示和自主视网膜时钟的调节。从暴露于六种独特光照条件的小鼠中分离出的ROS的活细胞成像表明，在循环光中以周期性方式发生ROS形成。不断的黑暗，和人造光/暗周期。Rho-Timer沿ROS长度的这种交替的亮/弱条带与视紫红质密度的不均匀性和结构弱点的潜在点有关。此外,我们发现，长时间昏暗的环境光暴露不仅影响新光盘的视紫红质含量，而且影响旧光盘的含量，建议在新光盘和旧光盘之间动态交换材料。此外，我们表明，在两个常染色体隐性遗传性视网膜色素变性小鼠模型中，可能有助于发病机制。我们的发现提供了有关外在（光）和内在（视网膜时钟和基因突变）因素如何动态调节哺乳动物ROS更新的见解。
