Morbidity risk in HFE associated hereditary hemochromatosis C282Y heterozygotes

Hereditary hemochromatosis (HHC) is a late-onset, autosomal recessive disorder leading to a chronic iron overload syndrome, finally causing diabetes, cardiomyopathy and liver disease. HHC is the most common single gene disorder in northern Europeans that occurs with a frequency of approximately 0.5%, and most of these patients carry the C282Y and H63D mutation in the HFE gene on chromosome 6p21.3. The vast majority of HHC patients are homozygous for the C282Y mutation, but HHC phenotypes are observed in other genotypes. Expression of the disease, in those homozygous for the C282Y mutation, is highly variable depending on the various features of the population studied. C282Y heterozygotes have slightly increased iron stores and in absence of other genetic and/or environmental factors do usually not develop the HHC phenotype. It is currently a matter of debate whether C282Y heterozygotes may have an increased risk for morbidity. Different studies investigating the association of C282Y heterozygocity with morbidity have given conflicting results, as is exemplified by extrahepatic cancers, cardiovascular diseases, alcoholic liver disease, and diabetes. However, there are examples of clear and unambiguous disease associations, such as with sporadic pophyria cutanea tarda. It remains to be seen whether a strong correlation between the C282Y heterozygous state and distinct pathological conditions will exist and large-scale genotyping studies will help to identify such potential risk groups in the future.

An unusual melting curve profile in LightCycler multiplex genotyping of the hemochromatosis H63D/C282Y gene mutations

OBJECTIVES

Real time polymerase chain reaction followed by melting curve analysis using hybridization probes has become an important tool in routine diagnosis of the HFE mutations, which are associated with hereditary hemochromatosis.

DESIGN AND METHODS

We used the LightCycler technology for simultaneous detection of the H63D and C282Y mutations of the HFE gene in patients with a higher prevalence for hemochromatosis.

RESULTS

In our cohort we identified two siblings with a variant pattern of the HFE-LightCycler melting profiles preventing allelic discrimination.

CONCLUSIONS

As a consequence, in these patients DNA sequencing or RFLP analysis is necessary to unequivocally assign the correct HFE genotype.

Semiautomated DNA Mutation Analysis Using a Robotic Workstation and Molecular Beacons

Background: Our increasing knowledge of the genetic basis of inheritable diseases requires the development of automated reliable methods for high-throughput analyses.

Methods: We investigated the combination of semiautomated DNA extraction from blood using a robotic workstation, followed by automated mutation detection using highly specific fluorescent DNA probes, so-called molecular beacons, which can discriminate between alleles with as little as one single-base mutation. We designed two molecular beacons, one recognizing the wild-type allele and the other the mutant allele, to determine genotypes in a single reaction. To evaluate this procedure, we examined the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene, which is associated with an increased risk for cardiovascular disease and neural tube defects. DNA was isolated from 10 μL of fresh EDTA-blood samples by use of a robotic workstation. The DNA samples were analyzed using molecular beacons as well as conventional methods.

Results: Both methods were compared, and no differences were found between outcomes of genotyping.

Conclusions: The described assay enables robust and automated extraction of DNA and analysis of up to 96 samples (10 μL of blood per sample) within 5 h. This is superior to conventional methods and makes it suitable for high-throughput analyses.