Hofstetter Katrina S, Haas Paula M, Kuntz Jonathon P, Zheng Yi, Fuhrmann Sabine
Dept. of Ophthalmology and Visual Sciences, Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN.
Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH.
bioRxiv. 2024 Oct 22:2024.10.20.619331. doi: 10.1101/2024.10.20.619331.
Congenital ocular malformations originate from defective morphogenesis during early eye development and cause 25% of childhood blindness. Formation of the eye is a multi-step, dynamic process; it involves evagination of the optic vesicle, followed by distal and ventral invagination, leading to the formation of a two-layered optic cup with a transient optic fissure. These tissue folding events require extensive changes in cell shape and tissue growth mediated by cytoskeleton mechanics and intercellular adhesion. We hypothesized that the Rho GTPase Cdc42 may be an essential, convergent effector downstream of key regulatory factors required for ocular morphogenesis. CDC42 controls actin remodeling, apicobasal polarity, and junction assembly. Here we identify a novel essential function for Cdc42 during eye morphogenesis in mouse; in mutant eyes expansion of the ventral optic cup is arrested, resulting in microphthalmia and a wide coloboma. Our analyses show that Cdc42 is required for expression of the polarity effector proteins PRKCZ and PARD6, intercellular junction protein tight junction protein 1, β-catenin, actin cytoskeleton F-actin, and contractile protein phospho myosin light chain 2. Expression of RPE fate determinants OTX2 and MITF, and formation of the RPE layer are severely affected in the temporal domain of the proximal optic cup. EdU incorporation is significantly downregulated. In addition, mitotic retinal progenitor cells mis-localized deeper, basal regions, likely contributing to decreased proliferation. We propose that morphogenesis of the ventral optic cup requires Cdc42 function for coordinated optic cup expansion and establishment of subretinal space, tissue tension, and differentiation of the ventral RPE layer.
先天性眼部畸形源于早期眼睛发育过程中的形态发生缺陷，是导致儿童失明的原因之一，占比达25%。眼睛的形成是一个多步骤的动态过程，包括视泡的外翻，随后是远端和腹侧内陷，最终形成带有暂时性视裂的双层视杯。这些组织折叠事件需要通过细胞骨架力学和细胞间粘附介导的细胞形状和组织生长的广泛变化。我们假设Rho GTP酶Cdc42可能是眼部形态发生所需关键调节因子下游的一个重要的汇聚效应器。Cdc42控制肌动蛋白重塑、顶基极性和连接组装。在这里，我们确定了Cdc42在小鼠眼睛形态发生过程中的一种新的重要功能；在突变眼中，腹侧视杯的扩张受阻，导致小眼症和宽视裂。我们的分析表明，Cdc42是极性效应蛋白PRKCZ和PARD6、细胞间连接蛋白紧密连接蛋白1、β-连环蛋白、肌动蛋白细胞骨架F-肌动蛋白和收缩蛋白磷酸化肌球蛋白轻链2表达所必需的。视网膜色素上皮（RPE）命运决定因子OTX2和MITF的表达以及RPE层的形成在近端视杯的颞侧区域受到严重影响。EdU掺入显著下调。此外，有丝分裂的视网膜祖细胞错误定位到更深的基底区域，这可能导致增殖减少。我们认为，腹侧视杯的形态发生需要Cdc42的功能来协调视杯扩张以及建立视网膜下间隙、组织张力和腹侧RPE层的分化。
