Ataxia-telangiectasia: from a rare disorder to a paradigm for cell signalling and cancer.

First described over 80 years ago, ataxia-telangiectasia (A-T) was defined as a clinical entity 50 years ago. Although not encountered by most clinicians, it is a paradigm for cancer predisposition and neurodegenerative disorders and has a central role in our understanding of the DNA-damage response, signal transduction and cell-cycle control. The discovery of the protein A-T mutated (ATM) that is deficient in A-T paved the way for rapid progress on understanding how ATM functions with a host of other proteins to protect against genome instability and reduce the risk of cancer and other pathologies.