[Generation and characterization of Cyp4v3 gene knockout mice].

Objective: Bietti crystalline dystrophy (BCD) is a rare degenerative eye disease caused by mutations in the CYP4V2 gene, and Cyp4v3 is the murine ortholog to CYP4V2 . To better understand the molecular pathogenesis of this disease and to explore the potential treatment we have established a Cyp4v3 knock-out mouse model.
Methods: Cyp4v3 ^-/- mice were generated by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 in embryonic stem cells of C57BL/6J mice. Ocular morphologic characteristics were evaluated via fundus imaging, histologic analysis of rods and cones via immunofluorescence, and phalloidin stain to observe retinal pigment epithelium (RPE) in whole-mounts, electroretinogram (ERG) was also conducted to examine the retinal function.
Results: The characteristic features of BCD recurred in the Cyp4v3 ^-/- mice, including retinal crystalline deposits, atrophy and degeneration of RPE cells, and ERG amplitude decline of dark and light adapted a- and b- wave; however, the immunofluorescence stain of rod and cone cells did not show obvious differences when compared with the wild type (WT) mice. In the early stage of the disease, no crystal-like deposits were found in the fundus, ERG detection of the retinal function did not find a significant decline, and the morphological structure and quantity of the neural retina and RPE did not change significantly. Crystalline deposits occurred and converged when the Cyp4v3 ^-/- mice at the end of 6 months, and the deposits disappeared when the Cyp4v3 ^-/- mice at the end of 12 months. The ERG amplitude started to decline when the Cyp4v3 ^-/- mice at the end of 6 months and deteriorated at the end of 12 months. The RPE cells of the 12-month old Cyp4v3 ^-/- mice showed irregular shape by phalloidin staining of F-actin. The Cyp4v3 ^-/- mice behaved normally and were viable and fertile when maintained under specific pathogen-free (SPF) housing conditions.
Conclusion: Just like BCD patients, the disease progress of Cyp4v3 ^-/- mouse is correlated with the age, which provides a good model for pathogenesis and gene therapy study in the future. The atrophy and degeneration of RPE take the lead in progressing of the disease, but the mechanism is not clear yet.