ARHGEF18/p114RhoGEF is a Rho-specific guanine nucleotide exchanging factor involved in the regulation of the actin cytoskeleton in epithelial and endothelial cells. Mutations in ARHGEF18 gene have been associated with adult-onset retinal degeneration; however, the retinal cell types and molecular pathways affected are unknown. To identify the retinal cell roles of p114RhoGEF, we are investigating disease-relevant ocular cell types and are applying cell type-specific knockout mouse models. We use human RPE cells carrying two point mutations for p114RhoGEF, animal models of RPE with p114RhoGEF depletion, rod-specific, endothelial-specific knockout and PDGFRa models and assessed visual function and retinal degeneration. Thus, this work reveals p114RhoGEF is expressed by several retinal cell types, and plays different roles in different cell types.