For Ccl2−/− and Ccr2−/− knockout mice, one study has reported that RPE and choroidal changes occur from an age of about 9 months and are followed by subsequent retinal degeneration around 16 months of age (Ambati et al., 2003), while a second report describes the development of specific RPE lesions with a variable penetrance of 40% in Ccl2−/− and 25% in CCR2−/− mice that are aged between 18 and 27 months (Chen et al., 2011). The gene discussed is CCR2; the disease is retinal degeneration.