Modified Method for the Detection of the CAG Repeat Expansion in Huntington's Disease and Application to a Predictive...

Background: The identification of the CAG trinucleotide repeat expansion as the cause of Huntington's disease (HD) has dramatically altered the ease and uptake of testing. The direct test for the mutation allows testing of many more consultands, particularly those individuals whose family structure is not suitable for linkage analysis. Therefore, protocols that can rapidly handle a number of samples and give accurate reliable results are essential. Methods and Results: The HD1/HD2 set of primers, which amplify the variable CAG and polymorphic CCG repeats, and the HD1/HD3 set of primers, which amplify only the variable CAG repeat, were used. Comparison of internally labeled with end-labeled polymerase chain reaction product was made. "Lysates" made from blood were investigated as suitable material for the HD polymerase chain reaction. Conclusions: The conditions used for detection of the CAG repeat in the huntingtin gene by end labeling of one of the primers that amplifies only the CAG repeat were improved, and an efficient protocol that reduces sample preparation and storage by using lysates from blood rather than extracted purified genomic DNA was developed.