SIMPLE NONISOTOPIC ASSAYS FOR DETECTION OF (CAG)(N) REPEATS EXPANSIONS ASSOCIATED WITH 7 NEURODEGENERATIVE DISORDERS

To date, eight neurodegenerative diseases, including Huntington's dise ase, dentatorubral-pallidoluysian atrophy, spinal and bulbar muscular atrophy, and spinocerebellar ataxia (SCA) types 1, 2, 3, 6, and 7, hav e been proven to be caused by an expanded trinucleotide repeat (CAG)(n ) located within a specific gene for each of these diseases. Except in SCA 6, the CAG repeat is present in approximately 7 to 35 copies in t he normal population, whereas patients have CAG expansions of 40 to ap proximately 75 repeats. Sizing of the repeat length enables molecular diagnosis in affected patients and presymptomatic persons carrying a m utated allele. A molecular protocol for the diagnosis of these disease s was developed based on polymerase chain reaction, denaturing polyacr ylamide gel electrophoresis and staining with silver nitrate, and adap ted to each disease. This simple and rapid method gives a sensitivity of detection equal to current procedures but avoids isotopic manipulat ions. Therefore, shorter turnaround time, decreased cost per sample, a nd simplified screening of these neurodegenerative diseases by PCR-bas ed assays may be attainable using this protocol.