Loss-of-function mutations in Norrin (an unconventional Wnt ligand), Wnt receptor Frizzled 4 (FZD4) or co-receptor LRP5, can cause familial exudative vitreoretinopathy (FEVR) in humans [4], [5], [6]. The gene discussed is LRP5; the disease is Familial exudative vitreoretinopathy.