Furthermore, Ccl2/Cx3cr1 double knockout mice have been described as developing a more accelerated and severe, early onset retinal phenotype with high penetrance of rapid photoreceptor loss and RPE defects, which suggested that the combined knockout of both chemokine signalling pathways might act synergistically and may thus lead to an early onset retinal degeneration [41]. Here, CX3CR1 is linked to retinal degeneration.