Monitoring Gene Expression in Retina with synthetic serum markers

Gene expression underlies retinal development, function, and pathogenesis. However, monitoring retinal gene expression in vivo is challenging. In this study, we apply synthetic serum markers, called Released Markers of Activity, or RMAs, to quantify gene expression in an intact retina through a simple blood test. We show that RMAs can quantify transduction of multiple retinal cell-types and monitor cell implantation or cell loss. We found RMAs are sensitive enough to measure transduction of rare cell populations, such as retinal ganglion cells and could detect transplantation of as few as 100 stem cells. Expression of RMAs showed no evidence of cell loss or immune activation in the retina. Overall, these findings demonstrate that RMAs are highly sensitive, tissue non-destructive gene expression reporters that can continuously track gene delivery and cell survival in intact retina through a simple blood test.