Purchase this article with an account.
Lea D. Marchette, Richard Brush, Michael Chan, Robert E. Anderson; Knocking Out Elovl4 Mouse Photoreceptors. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6672.
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 aids in converting long chain polyunsaturated fatty acids (LC-PUFAs) into very long chain PUFAs (VLC-PUFAs). Since Elvol4 is expressed in retina, skin, brain, and spinal cord, we have developed a new conditional knock out (cKO) mouse model that has Elovl4 deleted in photoreceptor cells.
Mice expressing Cre-recombinase driven by Chx10 promoter were mated with mice homozygous for floxed-Elovl4. Mice were backcrossed to produce offspring with the following genotypes: Cre+/Elovl4flox/flox (cKO), Cre-/Elovl4flox/flox (cWT), Cre+/Elovl4flox/wt (cHET) and Cre+/Elovl4wt/wt (Cre). Retina, brain and skin were harvested for protein analysis by Western blotting (WB). Expression levels of mRNA were assessed by reverse transcriptase polymerase chain reaction (RT-PCR) and normalized to Rpl19. Electroretinography (ERG) was performed on dark-adapted 8-12 week old mice. Rod a-wave was determined using xenon light intensity at 2000 cd.s/m2. Cone activity was determined after 5 minutes of photobleaching followed by light pulse of 2000 cd.s/m2. Optokinetics were measured by the mouse’s ability to track a sine-wave grating on a rotating drum at various spatial frequencies. This optomotor test was performed under light (70 cd m-2) and dark (3.5X10-5 cd m-2) conditions to assess visual acuity.
Retinal Elovl4 protein expression in cHET and cKO mice was reduced by 51 and 100% respectively, compared to cWT, whereas protein expression in brain and skin was comparable among each group. Retinal Elovl4 mRNA levels were decreased by 57% in cHET mice compared to cWT mice. Rod ERG a-wave for cWT, Cre, cHET, and cKO mice was 308µV, 242µV, 277µV, and 132µV respectively. Statistical analysis indicate a significant decrease (57%) in cKO compared to cWT a-wave amplitudes (2 tailed t-test, p=.002). Cone ERG a-wave responses were not different between the 4 groups of mice. Optomotor tests indicate a 66% and 78% reduction in light and dark visual acuity, respectively, for cKO mice compared to cWT mice.
We have successfully ablated Elovl4 expression in the retina without disrupting its expression in other tissues. Our preliminary optokinetic and ERG results suggest that loss of ELOVL4 (and thus reduction in VLC-PUFA) affects visual acuity and retinal function.
This PDF is available to Subscribers Only