Mouse Model of Congenital Nevi

Although NRAS mutations are uncommon in melanoma (found in ~20%), they are quite prevalent in congenital nevi (~80%). Because congenital nevi are known precursors to melanoma, the NRAS-driven pathway probably promotes both nevomelanocyte and melanoma growth. Investigators recently engineered a strain of oncogenic-Nras mice, reproducing the congenital nevus phenotype.

Melanocytic proliferation in the mice was localized to the dermis — probably less because of Nras effects and more a result of the absence of epidermal melanocytes in mice. Other genetic tricks are needed to induce melanocytes into epidermis. The investigators further found that Sox10, which also contributes to melanocyte formation, was highly expressed in both human and mouse c…