Analysis of Short Tandem Repeat Markers by Capillary Array Electrophoresis

The chapter describes the use of capillary array electrophoresis (CAE) for the detection of triplet repeat expansion at the
huntingtin
locus associated with autosomal dominant Huntington disease (HD), an adult-onset neuro-degenerative disorder. The regionof this gene that expands to disease-causing mutations consists of two adjacent tandemly repeated polymorphic triplet repeats:a diagnostic (CAG)n repeat immediately followed by a (CCG)n region. Early polymerase chain reaction (
PCR
)-based methods usedto genotype disease-causing mutations amplified through both of the repeat regions. More accurate diagnostic risk assessmentfor expansion is obtained when the (CAG)n and the (CCG)n repeats are amplified separately, as well as together in a singlereaction. However, these tests require three separate PCR amplifications to be run using conventional methods. The use ofmulticolor fluorescence detection and CAE can simplify this improved diagnostic test.