The high frequency of B-raf mutations in melanomas may be related to a principal melanocyte-specific signalling pathway controlling proliferation and differentiation: α-melanocyte stimulating-hormone (α-MSH) and proopiomelanocortin-derived peptides, secreted by keratinocytes, bind to the melanocortin receptor I on melanocytes, leading to increased proliferation and melanogenesis in response to UVB radiation [33]. The gene discussed is BRAF; the disease is melanoma.