Non-canonical roles of CFH in retinal pigment epithelial cells revealed by dysfunctional rare CFH variants.

Complement factor H (CFH) common genetic variants have been associated with age-related macular degeneration (AMD). While most previous in vitro RPE studies focused on the common p.His402Tyr CFH variant, we characterized rare CFH variants that are highly penetrant for AMD using induced pluripotent stem-cell-derived retinal pigment epithelium (iPSC-RPE). Our results show that lower factor H (FH) levels are detected in AMD RPE, which potentially disrupt canonical and non-canonical roles of FH. Specifically, AMD RPE displays higher inflammation rate and a reduced set of differentially expressed genes compared to control RPE upon N-retinylidene-N-retinylethanolamine (A2E) and blue light challenge. Additionally, cholesterol efflux and photoreceptor outer segment (POS) phagocytosis defects, dysregulated complement levels, larger sub-RPE deposits, and increased mitochondrial stress were observed in AMD RPE. Thus, our study reveals new non-canonical roles for FH in regulating important RPE functions.