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Ataxia- Telangiectasia and ATM Kenji Leonard 3/5/2004 Cancer Biology What is Ataxia-Telangiectasia A-T is a progressive neurodegenerative genetic disease. Cerebellar ataxia (In-coordination, lack of balance) Ocular telangiectasia (Widening of small blood vessels in conjunctiva) No cure and fatal by early 20s. Cerebellar Ataxia Ocular Telangiectasia www.indianpediatrics.net/ dec-99/99-dec-29.htm What Causes A-T? A mutated gene called ATM produces a mutated ATM protein (ataxia telangiectasia mutated) Found by genetic linkage analysis Gene in genomic location: bands according to Ensembl, locations according to GeneLoc (and/or LocusLink and/or Ensembl if different) Normal ATM protein Function A Serine-Protein Kinase Ex. p53, BRCA1 Senses Double Stranded Breaks in DNA Activates cell cycle checkpoints Abnormal ATM protein 70% of all mutated ATM protein is found to be truncated Missense mutations produce a dominant negative effect If heterozygous for mutated ATM gene, the cancer risk is 4X that of the general population Abnormal ATM protein Function ATM and cancer Main Points ATM, a serine kinase, senses DNA damage and activates cell cycle checkpoints to either arrest cell cycle or cause apoptosis. Mutant ATM causes A-T, a genomic instability syndrome, which is lethal by age 20. Mutant ATM heterozygotes have increased cancer risks.