Detection of the hereditary hemochromatosis gene mutation by real-time fluorescence polymerase chain reaction and peptide nucleic acid clamping.

Hereditary hemochromatosis (HH), an iron overload disease, is the most common known inheritable disease. The most prevalent form of HH is believed to be the result of a single base-pair mutation. We describe a rapid homogeneous mutation analysis method that does not require post-polymerase chain reaction (PCR) manipulations. This method is a marriage of three emerging technologies: rapid cycling PCR thermal cyclers, peptide nucleic acid (PNA) probes, and a new double-stranded DNA-selective fluorescent dye, Sybr Green I. The LightCycler is a rapid thermal cycler that fluorometrically monitors real-time formation of amplicon with Sybr Green I. PNAs are DNA mimics that are more sensitive to mismatches than DNA probes, and will not serve as primers for DNA polymerases. PNA probes were designed to compete with PCR primers hybridizing to the HH mutation site. Fully complemented PNA probes at an 18:1 ratio over DNA primers with a mismatch result in suppression of amplicon formation. Conversely, PNA probes with a mismatch will not impair the binding of a complementary primer, culminating in amplicon formation. A LightCycler-based rapid genetic assay has been developed to distinguish HH patients from HH carriers and normal individuals using PNA clamping technology.