P23H opsin knock-in mice reveal a novel step in retinal rod disc morphogenesis
P23H opsin knock-in mice reveal a novel step in retinal rod disc morphogenesis
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DOI：
10.1093/hmg/ddt561
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发表时间：
2014-04-01
影响因子：
3.5
通讯作者：
Palczewski, Krzysztof
中科院分区：
文献类型：
--
作者：
Sakami, Sanae;Kolesnikov, Alexander V.;Palczewski, Krzysztof
视网膜视杆光感受器细胞具有位于其外节（ROS）中的双膜盘，所述双膜盘从连接纤毛（CC）向近侧连续形成，并由视网膜色素上皮向远侧吞噬。这些视杆细胞的主要成分是光敏视色素视紫红质（Rho），它由一种与11-顺式-视网膜连接的视蛋白组成。视杆细胞视蛋白P23 H突变是常染色体显性视网膜色素变性（adRP）致盲的最常见原因。具有这种突变（Rho（P23 H/+））的adRP小鼠模型显示低水平的P23 H视蛋白、椎间盘的部分错位和进行性视网膜变性。然而，突变P23 H视蛋白对异常盘形成的影响尚不清楚，并且这种突变色素是否可以介导光转导仍然是未知的。利用视网膜电图记录，我们证明P23 H突变体Rho可以触发光转导，但RhOP 23 H/P23 H视杆细胞对光的敏感性比Rho（+/+）视杆细胞低17000倍，并产生异常快的光反应。通过分析纯合子RhOP 23 H/P23 H基因敲入小鼠，我们表明，P23 H视蛋白被运送到睫状突起，在那里它形成矢状伸长盘。出生后第14天（PND）Rho（P23 H/+）小鼠视网膜的透射电子显微镜显示在视网膜变性发作之前紊乱的矢状面定向盘。令人惊讶的是，我们还在PND 14 Rho（+/-）和Rho（+/+）小鼠中观察到较小的未成熟矢状面取向的椎间盘，这在老年动物中没有观察到。这些发现为P23 H突变型视蛋白的发病机制提供了基本的见解，并揭示了正常ROS椎间盘扩张中一种新的早期矢状排列椎间盘形成步骤。
Retinal rod photoreceptor cells have double membrane discs located in their outer segments (ROS) that are continuously formed proximally from connecting cilia (CC) and phagocytized distally by the retinal pigmented epithelium. The major component of these rod discs, the light-sensitive visual pigment rhodopsin (Rho), consists of an opsin protein linked to 11-cis-retinal. The P23H mutation of rod opsin (P23H opsin) is the most common cause of human blinding autosomal dominant retinitis pigmentosa (adRP). A mouse model of adRP with this mutation (Rho(P23H/+)) shows low levels of P23H opsin protein, partial misalignment of discs and progressive retinal degeneration. However, the impact of mutant P23H opsin on the formation of abnormal discs is unclear and it is still unknown whether this mutant pigment can mediate phototransduction. Using transretinal ERG recordings, we demonstrate that P23H mutant Rho can trigger phototransduction but RhOP23H/P23H rods are similar to 17 000-fold less sensitive to light than Rho(+/+) rods and produce abnormally fast photo-responses. By analyzing homozygous RhOP23H/P23H knock-in mice, we show that P23H opsin is transported to ciliary protrusions where it forms sagittally elongated discs. Transmission electron microscopy of postnatal day (PND) 14 Rho(P23H/+) mouse retina revealed disordered sagittally oriented discs before the onset of retinal degeneration. Surprisingly, we also observed smaller, immature sagittally oriented discs in PND14 Rho(+/-) and Rho(+/+) mice that were not seen in older animals. These findings provide fundamental insights into the pathogenesis of the P23H mutant opsin and reveal a novel early sagittally aligned disc formation step in normal ROS disc expansion.