Figure 2

The absence of at least one Ink4a-Arf allele overcomes the senescence of primary melanocytes in culture. Melanocytes from heterozygous YAC Tyr transgenic in homozygous Tyr ^c-32DSDbackground became large, flat, vacuolated and highly pigmented (A, B). No surviving melanocytes were detected in the culture dishes after the senescence step (C). Melanocytes from Ink4a-Arf ^+/- (G, H, I) and Ink4a-Arf ^-/- (J, K, L) mutant mice in a Tyrp1^Bbackground are black, small, bipolar, pale and without significant sings of senescence, as compared to wild type Ink4a-Arf ^+/+ melanocytes (D, E, F). A: culture at day 10; B: culture at day 18; C: culture at day 48; D, G, J: cultures at day 43; E, H, K: cultures at day 57; and, F, I, L: cultures at day 82. Scale ebars in C, D, G, J = 200 μm and in A, B, E, F, H, I, K, L = 150 μm.