The Role of Neural Derived Lamb2 in the Retina

Abstract

Purpose : Two retinal basement membranes (BM) exist, one vascular and the other neural. Global deletion of Lamb2 from them results in serious neural and vascular defects. It is not known if these BMs are distinct compartments or can exchange molecular components. In this study, we analyzed a neural specific ablation of Lamb2.

Methods : Control Lamb2^loxP/loxP(CTL), conditional Lamb2^loxP/loxP,dkk3-cre(cKO^dkk3) and Lamb2^loxP/loxP,six3-cre(cKO^six3) mice were used. The Lamb2 targeting was confirmed using Gt(ROSA)26Sor^tdTomato. BM assembly, astrocyte distribution and vascular network were visualized by IHC. Individual animals were followed with OCT and segmentation analysis assayed degeneration.

Results : Dkk3-cre recombination (reporter) was seen in neuroepithelium and lens at e13.5. In contrast, at e13.5 six3-cre recombination was seen robustly in the central neuroepithelium only and no expression in the lens. No recombination was seen in the vasculature. In cKO^dkk3 retina, no b2-laminin was seen in the ILM or lens at any ages (e13.5 – adult) but was seen in the vascular BM. In cKO^six3 retinae b2 laminin deposition was low in the peripheral ILM at e13.5 and from the peripheral to midperiphery at 1 month. b2laminin was seen in cKO^six3 lens. In both conditional KOs the ILM was disrupted, as judged by laminin and nidogen IHC. The astrocyte distribution was significantly altered in both lines with numerous vascular abnormalities. The total retinal and ONL thickness showed no significant differences in young animals (P20) among the genotypes but signs of a progressive retinal degeneration emerged in the cKO^dkk3 animals only (see Table 1). In addition, cKO^dkk3 retina had retinoschisis and mild to severe cases of retinal detachment by 5 to 12mo.

Conclusions : These data demonstrate that targeting neural sources of b2 chain disrupted deposition of laminin into the ILM but not in the vascular BM demonstrating that these compartments are functionally and biochemical isolated despite their physical proximity. These data demonstrated that neural-derived laminins are necessary for normal astrocyte migration and vascular development. With complete ablation of neural b2-laminins (in Dkk3cre), there is a slow progressive retinal degeneration is seen in cKO^dkk3 animals.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.