Automated fragment analysis method for determining androgen receptor CAG repeat length

Abstract

Several studies have associated polymorphisms in the androgen receptor gene with the risk of developing hormone-dependent cancers. A highly polymorphic (CAG)n repeat in exon I encodes a polyglutamine tract of varying length. The determination of the number of CAG repeats in the androgen receptor has typically been performed on denaturing polyacrylamide gels with autoradiographic or fluorescent detection of differently sized alleles. Samples run on a capillary electrophoresis-based ABI PRISM® 310 Genetic Analyzer gave anomalous results when internal standards supplied by the manufacturer were used. Here we report a modified procedure for androgen receptor allele size determination that can be used on an automated capillary electrophoresis-based DNA sequencer equipped with the appropriate software. The assay is very precise, comparable to DNA sequencing, and is compatible with the latest generation of automated DNA sequencers.