Physiological And Anatomical Role Of Neural Derived Lamb2 In The Retina.

Abstract

Purpose : Global deletion of the gene encoding the laminin β2 chain, Lamb2, results leads to dysgenesis of retina and brain. However, both neural and non-neural sources of laminin contribute to these phenotypes. To isolate the role of neural-derived laminin we used tissue specific ablation of Lamb2.

Methods : We used a combination of optical techniques to examine Lamb2^loxP/loxP, dkk3-cre(CKO)and Lamb2^loxP/loxPcontrols (CTL) at 1 and 5 months of age. The thickness of individual retinal layers was measured from OCT scans in order to assess degeneration. Photoreceptor organization was examined immunohistologically in radial sections using rod and cone specific markers. Finally, we used light- and dark-adapted electroretinograms (ERGs) to test rod and cone function and to assess the inner retinal response. ERGs were obtained from the same mice within a week after performing OCT.

Results : In CKO mice, there were no significant changes in total retina thickness or retinal layer thickness at P21. However, by 5 months of age, there was significant thinning of the entire retina (CTL-184±6 vs CKO-133±23, P<0.001, N=5) as well as the peripheral ONL (CTL-58±3 vs CKO-36±7, P<0.001, N=9). Immunohistological examinations of the retina using antibodies against rhodopsin and S-opsin revealed disorganized rods and cones. ERG recordings were consistent with progressive photoreceptor degeneration: the scotopic a-wave of the CKO retina was decreased by 36% at 1 month (CTL N=4, CKO N=4) and by 50% at 5 months (CTL N=5, CKO N=5);b-wave was decreased by 50% at 1 month (CTL N=4, CKO N=4) and by 72% at 5 months (CTL N=5, CKO N=5). In addition, the photopic a-wave of the CKO retina was decreased by 33% at 1 month, and was not detectable at 5 months; the b-wave was decreased by 72% at 1 month, and was not detectable at 5 months. In contrast, oscillatory potentials of b-wave recordings were preserved at all ages.

Conclusions : The absence of neural-derived laminin β2 in the retina results in an age-dependent progressive disruption of retinal structure and function. Interestingly, despite the fact that photoreceptor organization and function are disrupted with aging, oscillatory potentials remain intact, indicating that inner retinal cell function is preserved.Our results demonstrate that neural-derived laminin β2 plays a specialized role in the overall function and maintenance of photoreceptors.

This is a 2020 ARVO Annual Meeting abstract.