Abstract
Purpose :
Very-long-chain polyunsaturated fatty acids (VLC-PUFAs) play an important role in maintaining vision and ocular health. They make up less than 2% of the total fatty acids in the eye, and their depletion is associated with diseases such as age-related macular degeneration, diabetic retinopathy, and Stargardt 3 disease. The gene ELOVL4 encodes an elongase responsible for the VLC-PUFA biosynthesis in mammals, while Elovl4b, one of its gene homologs in zebrafish, encodes the fish VLC-PUFA elongase. We hypothesized that Elovl4b ablation would lead to the loss of ocular VLC-PUFAs, retinal deformities, and lipid dysregulation in zebrafish.
Methods :
Elovl4b mutant zebrafish were generated using CRISPR Cas9 and crossed with wild-type fish to produce heterozygotes and then homozygous mutant fish. Elovl4b ablation was confirmed through DNA sequencing and RT-PCR analyses, and lipids were analyzed via GC-MS and LC-MS/MS. Histology was performed on zebrafish retinal sections, and neutral lipid accumulation was assessed by Oil Red O staining.
Results :
We previously found that Elovl4b-ablation leads to a loss in ocular C30-C36 VLC-PUFAs and visual-motor deficiencies. Here, we present lipidomic analyses of zebrafish ocular tissue showing Elovl4b mutant zebrafish with elevated levels of acylcarnitines, cholesteryl esters, and oxidized triglycerides compared to wild-type age-matched controls. We also observed thinner retinal layers and more diffuse lipid droplets in mutant retinal sections compared to age-matched wild-type controls.
Conclusions :
Acylcarnitines function in the transportation of fatty acids to the mitochondria for β-oxidation, and increased plasma acylcarnitines can indicate metabolism disorders. Moreover, elevated levels of cholesteryl esters are thought to be associated with dysfunctional cholesterol metabolism. Future directions may be to assess cholesterol and lipofuscin accumulation in the ocular tissue and perform VLC-PUFA feeding studies to evaluate the rescue to a normal phenotype.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.