Purchase this article with an account.
Lea D. Marchette, R. Brush, R.E. Anderson; Reduced Levels Of VLC-PUFAs Lead To Structural And Functional Changes In Rod But Not Cone Photoreceptors. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4654.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Stargardt macular dystrophy (STGD3) is a juvenile-onset disease caused by mutations in ELOVL4 (elongation of very long fatty acids-4). This protein catalyzes the first step in the conversion of long chain polyunsaturated fatty acids (LC-PUFAs) into very long chain PUFAs (≥C28; VLC-PUFAs). We have developed a new conditional Elovl4 knock out (KO) mouse model. The retinal structure and function in the mice have been analyzed to determine the role of VLC-PUFAs in photoreceptor cells.
Mice expressing Cre-recombinase were mated with floxed-Elovl4 mice to produce offspring with the following genotypes: Cre+/Elovl4flox/flox (KO), Cre-/Elovl4flox/flox (WT), Cre+/Elovl4flox/wt (HET) and Cre+/Elovl4wt/wt (Cre). Retinal protein was analyzed by Western Blotting. Expression levels of mRNA were assessed by qRT-PCR and normalized to Rpl19. Fatty acid species were determined by GC-MS. Electroretinography (ERG) was performed on dark- and light-adapted mice. Rod-only ERG response was determined by fitting the raw data to a model developed based on the biochemistry of phototransduction. Outer nuclear layer (ONL) thickness was measured as an indicator of photoreceptor cell loss. Ultrastructure was evaluated with Transmission Electron Microscopy (TEM).
Retinal Elovl4 protein and mRNA expression in Het and KO mice were significantly reduced compared to WT retinas. GC-MS verified the loss of VLC-PUFAs in the KO mouse retinas. Rod ERG response for KO mice was reduced as early as 4 months of age compared to WT. Cone ERG responses were not different between WT and KO mice. Calculations also show a-wave max is also decreased in the VLC-PUFA deficient mice. ONL thickness was decreased in KO mice compared to WT mice. Preliminary results indicate a decrease in outer segment ultrastructure in the KO mice.
We have successfully ablated Elovl4 expression in the retina without disrupting its expression in other tissues. Reduction in retinal VLC-PUFAs reduces rod response to light stimuli at 4 months of age and later, which is coincidental with photoreceptor cell loss and outer segment morphological changes. Conversely, reduction of VLC-PUFAs in cones had no functional consequences.
This PDF is available to Subscribers Only