Given that MITF is the known master regulator of pro-proliferative phenotype switching in melanoma, and given that the pro-proliferative effect of C21orf91 was not mediated by MITF, we hypothesized that C21orf91 could be an undescribed hub controlling pigment cell phenotype switching, and could therefore be downstream of MITF as well as downstream of PR70. The gene discussed is MITF; the disease is melanoma.