Effects of knockdown or overexpression of PNPLA6 in human retinal pigment epithelial cell line ARPE-19

Although mutations in human patatin-like phospholipase PNPLA6 are associated with hereditary retinal degenerative diseases, its mechanistic action in the retina is poorly understood. Here, we uncover the molecular mechanism by which PNPLA6 dysfunction disturbs retinal homeostasis and visual function. PNPLA6, by acting as a phospholipase B, regulates choline mobilization from phosphatidylcholine and subsequent choline turnover for phosphatidylcholine regeneration in retinal pigment epithelial (RPE) cells. PNPLA6-driven choline is supplied from RPE cells to adjacent photoreceptor cells to support their survival. Inhibition of this pathway results in abnormal morphology, proliferation, metabolism, and functions of RPE and photoreceptor cells, and mice with retina-specific PNPLA6 deletion exhibit retinitis pigmentosa-like retinal degeneration. Notably, these abnormalities are entirely rescued by choline supplementation. Thus, PNPLA6 plays an essential role in retinal homeostasis by controlling choline availability for phospholipid recycling and provide a framework for the development of a novel ophthalmic drug target for retinal degeneration. Cells, ARPE-19 retinal pigment epithelial cell line; Condition, Human PNPLA6 knockdown (siRNA) and control, PNPLA6 overexpression and mock; RNA, total RNA samples pooled from individual cells for 4 wells