Objective To observe the effects of Crumbs (Crb) proteins on different types of zebrafish photoreceptors. Methods The retinal cell population dynamics of adult wild-type zebrafish and Tg (RH2-2:Crb2b-sf-EX/RH2-2:GFP)pt108b transgenic zebrafish (called pt108b zebrafish for short) were evaluated by monitoring the densities of three categories of retinal photoreceptors (rod cells, UV cone cells and RGB cone cells) in different retinal regions, which were visualized by Feulgen nuclear staining histology technique. Results The wild-type zebrafish retinal photoreceptor cell densities are generally higher in the central region than the peripheral regions. Compared with wild-type zebrafish, pt108b zebrafish had much less RGB cone cells at the top of outer nuclear layer, and no RGB cone cells at the central and intermediate regions of retina. While pt108b zebrafish had normal density of UV cone cells at the top of rods and the bottom of outer limiting membrane, they had much higher density of rods. Conclusions Crb proteins may affect the zebrafish retinal cell densities of different photoreceptor types.
Retinal diseases are severely limited in terms of effective treatment strategies due to their extremely complex pathogenesis. Given the limitations of traditional mammalian experimental animals in replicating certain characteristics of eye diseases, the zebrafish model, with its advantages such as fully transparent embryos facilitating in vivo tracking, extremely early development of visual functions, highly conserved retinal cell composition compared to humans, and the ability to regenerate neurons completely after damage, has risen to become a core tool for visual system research. Through modern technologies such as gene editing, RNA knockdown, and chemical induction, researchers have successfully constructed a zebrafish model system that highly mimics various genetic and non-genetic retinal disorders in humans. In non-genetic disorders, this model effectively replicates microvascular abnormal proliferation and electrophysiological changes caused by high sugar or low oxygen stress, and has been successfully applied to the efficacy evaluation of natural products and nanodelivery systems. In the exploration of genetic disorders, for complex diseases such as photoreceptor degeneration, nutritional disorders of cone and rod cells, early severe vision loss, defect in signal transduction-induced night blindness, and multi-system ciliary abnormalities syndrome, the zebrafish model precisely reproduces the corresponding clinical phenotypes. More importantly, it plays a decisive role in elucidating the functions of new pathogenic genes, clarifying the disorder of the light conduction pathway, revealing the multi-gene collaborative pathogenic network, and discovering new candidate pathogenic sites. Additionally, in the in vivo safety testing of nonsense mutation read-through drugs and functional rescue verification, the zebrafish model also demonstrates high clinical translational potential. The zebrafish model, by closely linking genetic variations with in vivo pathological phenotypes, has overcome the limitations of in vitro research. It not only provides an ideal platform for in-depth analysis of the pathogenesis of blinding diseases, exploration of molecular switches for neural regeneration, and provides a solid foundation for accelerating high-throughput screening of targeted drugs and promoting individualized precision medicine, but also has extremely broad application prospects in the future.
