Definition of ATM (cont.)
Mutations in the ATM gene cause ataxia-telangiectasia, an autosomal recessive disorder. (People with this disorder have two mutated copies of ATM.) The mutated ATM gene makes a protein that does not function properly because it is truncated (abnormally short). As a result, the cells are hypersensitive to radiation and do not respond correctly to DNA damage. Instead of activating DNA repair, the defective ATM protein allows mutations to accumulate in other genes. In addition, ATM mutations may allow cells to die inappropriately, particularly in the cerebellum (the part of the brain involved in coordinating movements).
People who have mutations in one copy of the ATM gene, particularly those who have at least one family member with ataxia-telangiectasia, may be at an increased risk of developing breast cancer.