COL4A2 and snowflake vitreoretinal degeneration: To provide insights into the pathological mechanisms underlying COL4A1/A2-related SVD, we established a human induced pluripotent stem cell (hiPSC)-based “disease in a dish” model from two individuals with two representative glycine substitutions in the G-X-Y repeat, one in COL4A1 (G755R) and the other in COL4A2 (G702D) gene (Murray et al., 2014; Shah et al., 2010).