Deciphering the role of lipid metabolism pathways in the RPE and their implications for AMD

University Of Pennsylvania, Philadelphia PA

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Abstract

PROJECT SUMMARY Age-related macular degeneration (AMD) is the leading cause of blindness among the elderly in the United States. Strong association between variants in the high-density lipoprotein (HDL) cholesterol pathway genes (hepatic lipase [LIPC] and cholesterol ester transfer protein [CETP]) and advanced AMD were found in recent genome-wide association studies. The current proposal aims to understand the mechanism underlying AMD caused by SNPs in LIPC and CETP genes, which are historically known to be associated with lipid biogenesis pathways. The research proposal tests the overall hypothesis that the SNPs in LIPC and CETP exert their effects through modulating ocular lipoprotein pathways that are critical for the maintenance of retinal cholesterol homeostasis, thus causing retinal pathology. In Aim 1, we propose to (i) characterize the complete lipoprotein secretion profile including HL and CETP in the apical and basal conditioned media derived from 2D polarized primary human fetal retinal pigment epithelial (hfRPE) cultures in normal and cholesterol loaded conditions, (ii) study the effect of HL and CETP knockdown or overexpression using CRISPR/Cas9 gene editing and viral gene delivery, respectively in hfRPE cultures, and understand their function in maintenance of lipid homeostatic pathways in the RPE. We will determine the function of HL and CETP in these cultures by performing lipid efflux and influx assays, lipid secretion profile among other assays. In Aim 2, we will establish the effect of AMD-associated SNPs on LIPC and CETP transcript expression by characterizing the presence of eQTLs in these genes. We propose to use patient derived induced pluripotent stem cells (iPSC) cultures harboring AMD-associated SNPs in these genes along with isogenic controls. The iPSCs will be differentiated into well-characterized RPE cultures. These iPSC-RPE cultures will be analyzed to establish and identify any SNPs in LIPC and CETP that can regulate their expression. Outcome of our studies will open new avenues to understand the molecular pathophysiology of AMD and address the importance of HDL cholesterol metabolism pathways in maintaining retinal health. Understanding the function of genes in these pathways will not only allow us to determine potential therapeutic targets to treat AMD but also enable us to use and/or warn against the use of already available drugs for treatment of Atherosclerosis.