CEBPA: The CEBPA gene provides instructions for making a protein called CCAAT/enhancer-binding protein alpha. This protein is a transcription factor, which means that it attaches (binds) to specific regions of DNA and helps control the activity (expression) of certain genes. CCAAT/enhancer-binding protein alpha is involved in the maturation (differentiation) of certain blood cells. It is also believed to act as a tumor suppressor, which means that it is involved in cellular mechanisms that help prevent the cells from growing and dividing too rapidly or in an uncontrolled way. Mutations in the CEBPA gene have been identified in some people with a form of acute myeloid leukemia known as cytogenetically normal acute myeloid leukemia (CN-AML). While large chromosomal abnormalities can be involved in the development of acute myeloid leukemia, about half of cases do not have these abnormalities; these are classified as CN-AML. Mutations in this gene are found in approximately 18 percent of individuals with CN-AML. When associated with CEBPA gene mutations, this condition can be inherited, in which case it is called familial acute myeloid leukemia with mutated CEBPA (described above), or not inherited (sporadic acute myeloid leukemia with mutated CEBPA). Two types of CEBPA gene mutations can occur in both the inherited and non-inherited forms of CN-AML. One type leads to production of an abnormally short protein that interferes with the tumor suppressor function of normal versions of CCAAT/enhancer-binding protein alpha. The other type of mutation blocks the DNA-binding ability of CCAAT/enhancer-binding protein alpha. Impaired DNA binding interferes with the protein's ability to regulate gene expression and impairs its tumor suppressor function. Impairment of the tumor suppressor function of CCAAT/enhancer-binding protein alpha leads to the uncontrolled production of abnormal white blood cells that occurs in acute myeloid leukemia. Between 50 and 75 percent of all individuals who have acute myeloid leukemia with mutations in the CEBPA gene, both sporadic and familial, have two mutated CEBPA genes in each leukemia cell. The rest have only one CEBPA gene mutation. In the sporadic cases the mutation appears only in the leukemia cells, and in the familial cases it is present throughout the body. Somatic mutations in other genes can also contribute to the development of CN-AML.