Current Progress in Deciphering Importance of VLC-PUFA in the Retina

Stargardt-like macular dystrophy-3 (STGD3) is a juvenile-onset disease caused by mutations in ELOVL4 (elongation of very long fatty acids-4). This gene product catalyzes the elongation of long chain saturated and polyunsaturated fatty acids (LC-FAs and LC-PUFAs) into very long chain FAs and PUFAs (VLC-FAs and VLC-PUFAs). These mutations cause a frame shift in the ELOVL4 transcript, introducing a premature stop codon that results in the translation of a truncated protein that has lost a C-terminus endoplasmic reticulum (ER) retention/retrieval signal. The truncated protein is not targeted to the ER, the site of very long-chain PUFA (VLC-PUFA; 28-40 carbons) synthesis. Expression of the ELOVL4 gene is limited mainly to the brain, testis, skin, and photoreceptor cells of the retina. While the skin and brain contain very long chain saturated fatty acids (VLC-FAs), the other tissues expressing ELOVL4 contain VLC-PUFAs, with sperm and the retina having the highest levels. This review focuses on the current information available concerning the role of VLC-PUFAs in the retina.