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Roni Hazim, David S Williams; Mutations in CFH perturb RPE homeostasis in vitro. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6046.
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© ARVO (1962-2015); The Authors (2016-present)
Single nucleotide polymorphisms (SNPs) in the complement factor H gene (CFH) are closely linked with increased risk of age-related macular degeneration (AMD). In particular, SNPs in exons 2 and 9, responsible for I62V and Y402H amino acid substitutions, respectively, constitute a genetic haplotype that increases the risk of developing AMD in late adulthood by 7-fold. Individually, both of these SNPs have been shown to compromise the function of CFH. Although most abundant in the circulating plasma, CFH is locally expressed and secreted by the retinal pigment epithelium (RPE), a primary site of insult in AMD pathogenesis. Numerous models have been made to elucidate the role of CFH, yet the full extent of CFH function and the underlying cellular mechanisms responsible for perturbing RPE homeostasis remain elusive. The purpose of this study is to investigate the role of CFH, in relation to RPE biology and pathology, using an in vitro model of human RPE cells.
We used the genome-editing technology of the CRISPR/Cas9 system to specifically target and modify the CFH locus in an immortalized human RPE cell line (ARPE-19). Two stable cell lines were generated, one of which exhibited a knockdown of CFH while the other expressed the mutated form of the protein (VV62, HH402). Brightfield microscopy was used to assess the morphology of the stable cell lines, and immunocytochemistry and western blotting were used to analyze cytoskeletal organization and to test for signs of inflammation and cellular stress.
Sanger sequencing verified the genetic modifications to the CFH locus, and western blotting confirmed the reduction in CFH protein levels in the CFH-knockdown line. Brightfield microscopy revealed a striking morphological phenotype in the CFH-knockdown line, which exhibited an elongated, fusiform shape. Immunolabeling of α-tubulin confirmed an abnormal arrangement of the microtubule cytoskeleton in these cells. Additionally, both CFH-mutant cell lines were found to possess an aberrant expression of ZO-1, a tight junction protein known to associate with actin filaments. Characteristics of AMD, including inflammation and cellular stress, were also more prominent in the CFH-knockdown line, as indicated by increased expression of C5b-9 and 3-NT, respectively.
Our results indicate that compromised CFH function has a significant effect on RPE morphology, as well as increasing inflammation and cellular stress.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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