Pellissier Lucie P, Lundvig Ditte M S, Tanimoto Naoyuki, Klooster Jan, Vos Rogier M, Richard Fabrice, Sothilingam Vithiyanjali, Garcia Garrido Marina, Le Bivic André, Seeliger Mathias W, Wijnholds Jan
Department of Neuromedical Genetics.
Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, Eberhard Karls University of Tübingen, Tübingen D-72076, Germany and.
Hum Mol Genet. 2014 Jul 15;23(14):3759-71. doi: 10.1093/hmg/ddu089. Epub 2014 Feb 23.
Mutations in the CRB1 gene lead to retinal dystrophies ranging from Leber congenital amaurosis (LCA) to early-onset retinitis pigmentosa (RP), due to developmental defects or loss of adhesion between photoreceptors and Müller glia cells, respectively. Whereas over 150 mutations have been found, no clear genotype-phenotype correlation has been established. Mouse Crb1 knockout retinas show a mild phenotype limited to the inferior quadrant, whereas Crb2 knockout retinas display a severe degeneration throughout the retina mimicking the phenotype observed in RP patients associated with CRB1 mutations. Crb1Crb2 double mutant retinas have severe developmental defects similar to the phenotype observed in LCA patients associated with CRB1 mutations. Therefore, CRB2 is a candidate modifying gene of human CRB1-related retinal dystrophy. In this study, we studied the cellular localization of CRB1 and CRB2 in human retina and tested the influence of the Crb2 gene allele on Crb1-retinal dystrophies in mice. We found that in contrast to mice, in the human retina CRB1 protein was expressed at the subapical region in photoreceptors and Müller glia cells, and CRB2 only in Müller glia cells. Genetic ablation of one allele of Crb2 in heterozygote Crb1(+/-) retinas induced a mild retinal phenotype, but in homozygote Crb1 knockout mice lead to an early and severe phenotype limited to the entire inferior retina. Our data provide mechanistic insight for CRB1-related LCA and RP.
CRB1基因突变会导致视网膜营养不良，范围从莱伯先天性黑蒙（LCA）到早发性视网膜色素变性（RP），分别是由于发育缺陷或光感受器与米勒胶质细胞之间的黏附丧失所致。虽然已经发现了150多种突变，但尚未建立明确的基因型-表型相关性。小鼠Crb1基因敲除视网膜表现出仅限于下象限的轻度表型，而Crb2基因敲除视网膜则在整个视网膜中呈现严重退化，类似于与CRB1突变相关的RP患者所观察到的表型。Crb1Crb2双突变视网膜具有严重的发育缺陷，类似于与CRB1突变相关的LCA患者所观察到的表型。因此，CRB2是人类CRB1相关视网膜营养不良的候选修饰基因。在本研究中，我们研究了CRB1和CRB2在人类视网膜中的细胞定位，并测试了Crb2基因等位基因对小鼠Crb1视网膜营养不良的影响。我们发现，与小鼠不同，在人类视网膜中，CRB1蛋白在光感受器和米勒胶质细胞的顶端下区域表达，而CRB2仅在米勒胶质细胞中表达。在杂合子Crb1(+/-)视网膜中对Crb2的一个等位基因进行基因敲除会诱导轻度视网膜表型，但在纯合子Crb1基因敲除小鼠中会导致仅限于整个下视网膜的早期严重表型。我们的数据为CRB1相关的LCA和RP提供了机制性见解。
