Abstract
Purpose: :
Very-low-density-lipoprotein receptor (VLDLR) and Apolipoprotein E Receptor 2 (ApoER2) are two receptors that bind Reelin, a protein which has been shown to have a vital role in neuronal development and adult synaptic plasticity. Absence of Reelin in Reeler mice leads to attenuated rod b-wave responses (Rice et al, Neuron, 9/2001) and loss of VLDLR results in choroidal neovascularization. ApoER2 is spliced in a diurnal fashion at exon19. The exon19 encoded insert plays a vital role in cell protection during normal aging and synaptic plasticity, but also facilitates cell death after injuries (Beffert et al, Neuron, 8/2005).To investigate the role of the ApoER2 exon19 splicing variant in retinal degeneration, electrophysiological testing was performed on knock-in mice that constitutively express ApoER2 with (+) or without (Δ) exon19.
Methods: :
Ten month old ApoER2+exon19 (n=11), ApoER2Δexon19 (n=11), ApoER2+exon19/ VLDLR-/- (n=11) and ApoER2Δexon19/ VLDLR-/- (n=10) mutant mice, were tested and compared to age-matched wildtypes (WT, n=11).Full-field electroretinograms (ERG) were recorded on an Espion ERG system with Ganzfeld Dome, following standard ISCEV protocol adjusted for mice.
Results: :
ApoER2+exon19/ VLDLR-/- mutants displayed the greatest reduction in amplitude in all responses (p<0.001). ApoER2+exon19 mice had attenuated rod responses and OPs (p<0.002).ApoER2Δexon19/ VLDLR-/- mutants showed smaller reductions in rod amplitude (p<0.005), but showed a slightly reduced cone flicker response (p=0.02). ApoER2Δexon19 mice were not significantly different from WT mice (p>0.1).
Keywords: electroretinography: non-clinical • retinal degenerations: cell biology • transgenics/knock-outs