Previous studies pertaining to Fz4′s role in the disease familial exudative vitreoretinopathy have suggested that the Fz4 receptor does not mediate Wnt/β-catenin signaling but rather elicits intracellular calcium flux that subsequently activates downstream calcium effector molecules [34,40]. This evidence concerns the gene FZD4 and Familial exudative vitreoretinopathy.