The MAP2K1 gene provides instructions for making a protein known as MEK1 protein kinase. This protein is part of a signaling pathway called the RAS/MAPK pathway. RAS/ MAPK signaling helps control the proliferation of cells, differentiation, migration, and apoptosis. At least 13 mutations in the MAP2K1 gene have been identified in people with cardiofaciocutaneous syndrome. This condition affects many parts of the body, particularly the heart, facial features, and the skin and hair.