Carter Stephen P, Moran Ailís L, Matallanas David, McManus Gavin J, Blacque Oliver E, Kennedy Breandán N
UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland.
UCD Conway Institute, University College Dublin, Dublin, Ireland.
Front Cell Dev Biol. 2020 Mar 17;8:136. doi: 10.3389/fcell.2020.00136. eCollection 2020.
The photoreceptor outer segment is the canonical example of a modified and highly specialized cilium, with an expanded membrane surface area in the form of disks or lamellae for efficient light detection. Many ciliary proteins are essential for normal photoreceptor function and cilium dysfunction often results in retinal degeneration leading to impaired vision. Herein, we investigate the function and localization of the ciliary G-protein RAB28 in zebrafish cone photoreceptors. CRISPR-Cas9 generated mutant zebrafish display significantly reduced shed outer segment material/phagosomes in the RPE at 1 month post fertilization (mpf), but otherwise normal visual function up to 21 dpf and retinal structure up to 12 mpf. Cone photoreceptor-specific transgenic reporter lines show Rab28 localizes almost exclusively to outer segments, independently of GTP/GDP nucleotide binding. Co-immunoprecipitation analysis demonstrates tagged Rab28 interacts with components of the phototransduction cascade, including opsins, phosphodiesterase 6C and guanylate cyclase 2D. Our data shed light on RAB28 function in cones and provide a model for RAB28-associated cone-rod dystrophy.
光感受器外段是经过修饰的高度特化纤毛的典型例子，其具有以盘状或片层形式存在的扩大膜表面积，用于高效的光检测。许多纤毛蛋白对于正常光感受器功能至关重要，纤毛功能障碍通常会导致视网膜变性，进而导致视力受损。在此，我们研究了睫状G蛋白RAB28在斑马鱼视锥光感受器中的功能和定位。CRISPR-Cas9技术构建的突变斑马鱼在受精后1个月（mpf）时，视网膜色素上皮（RPE）中脱落的外段物质/吞噬体显著减少，但在21天胚胎期（dpf）之前视觉功能正常，在12 mpf之前视网膜结构正常。视锥光感受器特异性转基因报告系显示，Rab28几乎仅定位于外段，与GTP/GDP核苷酸结合无关。免疫共沉淀分析表明，标记的Rab28与光转导级联反应的组分相互作用，包括视蛋白、磷酸二酯酶6C和鸟苷酸环化酶2D。我们的数据揭示了RAB28在视锥细胞中的功能，并为RAB28相关的视锥-视杆营养不良提供了一个模型。
