Figure 4

The effect of Ink4a-Arf locus on cell growth and Tyr enzymatic activity. (A) Cell growth of Ink4a-Arf ^-/- (open circles), Ink4a-Arf ^+/- (closed circles) and Ink4a-Arf ^+/+ (crosses) melanocytes. Each point represents one subculture step and represents the mean count of cells from three replicates. (B) Tyrosine hydroxylase activity in albino melan-c (white bars), [Ink4a-Arf ^+/-; Tyrp1 ^B/ Tyrp1 ^B] (dark-grey bars), [Ink4a-Arf ^-/- ; Tyrp1 ^B/ Tyrp1 ^B] (light-grey bars) and melan-a (black bars) cells. (C) Melanin content in the same cellular types, as in (B). Bars represent the mean value (+/- SD) from three replicates. Tyrosinase activity and melanin content were measured in melanocyte primary cultures at passage 8 (~day 70 of culture). Statistically significant differences (t-Student test) are indicated as follows: * p < 0,1; ** p < 0,01; *** p < 0,001.