Figure 8.

Melanocytes that lack functional Tyrp1 are less sensitive to 4-TBP compared with normal melanocytes. Human melanocyte and fibroblast cultures were established from foreskin of three normally pigmented individuals (HM/HF) and one null for Tyrp1 (OCA3 mol/L/OCA3F). Left: Melanocytes were plated in 96-well plates. After 24 hours, the culture medium was replaced with medium containing 4-TBP. Viability was determined after 72 hours. There was a significant difference in sensitivity to 4-TBP between melanocytes isolated from normally pigmented individuals compared with melanocytes from an individual with OCA3 (*P < 0.01, **P < 0.05). Right: Fibroblasts were plated and allowed to attach overnight. HF10b is the unaffected twin of the individual with OCA3.33 Cells were dosed with 4-TBP and viability determined after 72 hours. Viability is shown relative to cells treated with vehicle alone. There is no significant difference in sensitivity to 4-TBP between fibroblasts isolated from normally pigmented individuals compared with fibroblasts from an individual with OCA3. Error bars indicate SD. The experiment was performed in triplicate, and a representative experiment is shown.