Prevalence of HFE mutations in people from North Africa living in southern France

The role of genetic factors in patients with hepatocellular carcinoma and iron overload - a prospective series of 234 patients

BACKGROUND & AIMS

Iron overload (IO) in HFE-related hereditary haemochromatosis is associated with increased risk of liver cancer. This study aimed to investigate the role of other genes involved in hereditary IO among patients with hepatocellular carcinoma (HCC).

METHODS

Patients with HCC diagnosed in our institution were included in this prospective study. Those with ferritin levels ≥300 μg/L (males) or ≥200 μg/L (females) and/or transferrin saturation ≥50% (males) or ≥45% (females) had liver iron concentration (LIC) evaluated by MRI. HFE C282Y and H63D mutations were screened. Genetic analyses of genes involved in hereditary IO (HFE, HJV/HFE2, HAMP, TFR2, SLC40A1, GNPAT) were performed in patients with increased LIC.

RESULTS

A total of 234 patients were included; 215 (92%) had common acquired risk factors of HCC (mainly alcoholism or chronic viral hepatitis). 119 patients had abnormal iron parameters. Twelve (5.1%) were C282Y homozygotes, three were compound C282Y/H63D heterozygotes. LIC was measured by MRI in 100 patients. Thirteen patients with a LIC>70 μmol/g were enrolled in further genetic analyses: two unrelated patients bore the HAMP:c.-153C>T mutation at the heterozygous state, which is associated with increased risk of IO and severe haemochromatosis. Specific haplotypes of SLC40A1 were also studied.

CONCLUSIONS

Additional genetic risk factors of IO were found in 18 patients (7.7%) among a large series of 234 HCC patients. Screening for IO and the associated at-risk genotypes in patients who have developed HCC, is useful for both determining etiologic diagnosis and enabling family screening and possibly primary prevention in relatives.

Ancestral association between HLA and HFE H63D and C282Y gene mutations from northwest Colombia

A significant association between HFE gene mutations and the HLA-A*03-B*07 and HLA-A*29-B*44 haplotypes has been reported in the Spanish population. It has been proposed that these mutations are probably connected with Celtic and North African ancestry, respectively. We aimed to find the possible ancestral association between HLA alleles and haplotypes associated with the HFE gene (C282Y and H63D) mutations in 214 subjects from Antioquia, Colombia. These were 18 individuals with presumed hereditary hemochromatosis (“HH”) and 196 controls. The HLA-B*07 allele was in linkage disequilibrium (LD) with C282Y, while HLA-A*23, A*29, HLA-B*44, and B*49 were in LD with H63D. Altogether, our results show that, although the H63D mutation is more common in the Antioquia population, it is not associated with any particular HLA haplotype, whereas the C282Y mutation is associated with HLA-A*03-B*07, this supporting a northern Spaniard ancestry.

Telomere length and elevated iron: the influence of phenotype and HFE genotype

Elevated body iron stores are associated with morbidity and mortality due to oxidative stress. Hereditary hemochromatosis, a common condition caused by HFE gene mutations, can lead to excess iron storage and disease but clinical penetrance of HFE gene mutations is low and many people with elevated iron stores lack HFE mutations. We analyzed data from the Hemochromatosis and Iron Overload Screening Study to assess the relationship among HFE genotype (individuals with either homozygous or compound heterozygous status for C282Y and/or H63D HFE mutations were defined as genotype positive, or G+), elevated iron phenotype (individuals exceeding gender-specific transferrin saturation and serum ferritin threshold levels were considered phenotype positive, or P+), and leukocyte telomere length, a marker of biological aging and cumulative oxidative stress. In unadjusted analyses in comparison to individuals who were G-P-, G+P- were not significantly different (OR 0.74; 95% CI 0.26-2.04), while the G+P+ (OR 2.03; 95% CI 1.15-3.56), and G-P+ (OR 2.24; 95% CI 1.5-3.29) had increased risk of short telomeres (<=25th percentile) rather than long telomeres (>=75th percentile). In analyses adjusting for age, gender, and race/ethnicity, the effect of individuals with elevated iron phenotypes having short telomeres persisted with G+P+ individuals (OR 1.94; 95% CI 1.02-3.72), and G-P+ individuals (OR 2.17; 95% CI 1.39-3.39) being significantly different from the G-P- group. In conclusion, elevated iron phenotype, but not HFE genotype, was associated with shortened telomeres. Further studies will be needed to determine whether telomere length provides a marker for morbidities specifically associated with iron overload.

The Southern French registry of genetic hemochromatosis: a tool for determining clinical prevalence of the disorder and genotype penetrance

BACKGROUND

Despite great progress in understanding the mechanisms underlying genetic hemochromatosis, data on the prevalence and the penetrance of the disorder are conflicting.

DESIGN AND METHODS

A registry of patients with genetic hemochromatosis was established in the South of France and a regional health network was developed to allow the inclusion of all the diagnosed patients. C282Y homozygous patients classified in stages 2 (biological iron overload), 3 and 4 (clinical manifestations of iron overload, stage 4 being the more severe) according to the classification of the French National Authority for Health were included in the registry over a 6-year period.

RESULTS

A total of 352 symptomatic C282Y homozygotes were identified, resulting in a total prevalence of 1.83 per 10,000 (95% CI: 1.63 to 2.02) in subjects over 20 years and 2.40 per 10,000 (95% CI, 2.15 to 2.65) among subjects of European descent. Among Europeans, the total calculated penetrance was 15.8% in stage 2 or higher, 12.1% in stage 3 or 4 and 2.9% in stage 4. The penetrance was slightly higher in males (18.7%) than in females (13.2%). It was 19.9% for individuals over 40 years of age (24.1% and 16.3% in males and females, respectively) with a maximum of 31% in subjects between 50 and 54 years old. Among 249 patients with complete records, 24% were in stage 2, the majority (58%) were in stage 3, and 18% in stage 4. There was a higher proportion of males, and excessive alcohol intake was more prevalent in stage 4 than in stages 2 and 3 combined.

CONCLUSIONS

A French Mediterranean regional hemochromatosis registry with strict inclusion criteria is a useful tool for characterizing the history of this disease, particularly for the most severely affected patients, as defined by the disease severity classification. The total prevalence of symptomatic C282Y homozygotes in the region was found to be low. However, clinical penetrance (stages 3 and 4) was not negligible.

Prevalence of common HFE and SERPINA1 mutations in patients with hepatocellular carcinoma in a Moroccan population

BACKGROUND

Hereditary hemochromatosis and SERPINA1 mutation were reported to affect liver functions. Our objective was to estimate the prevalence of HFE and SERPINA1 (formerly known as alpha1-antitrypsin, AAT) mutations and assess their influence on hepatocellular carcinoma development.

METHODS

This study included 222 controls and 96 cases with hepatocellular carcinoma. PCR-RFLP was used to characterize S and Z alleles in SERPINA1, as well as C282Y/H63D alleles of HFE.

RESULTS

In healthy subjects and hepatocellular carcinoma patients as well, no homozygotes for the C282Y mutation were found. In controls, heterozygosity and homozygosity for the H63D mutation were 27 and 0.9%, respectively. Among patients, homozygosity for the H63D mutation was 3.1%, whereas heterozygosity for C282Y and H63D was 2.1 and 35.4%, respectively. Interestingly, albeit it does not reach significance (p=0.062), H63D was more prevalent in hepatocellular carcinoma patients than in controls (38.5 vs. 27.9%, respectively). The association was stronger when considering only male patients with hepatocellular carcinoma (47.1 vs. 23.6, p=0.001). Allele frequencies of S and Z in controls were 0.45% (95% CI=0.2-1.07) and 0.22% (95% CI=0.2-0.6), respectively, and 1 for S and 0% for Z in HCC. No significant difference was found between cases and controls.

CONCLUSIONS

We provide a novel appraisal of HFE and SERPINA1 mutations prevalence in the Moroccan population. Results are consistent with the worldwide spread of the H63D and S mutation and the north European restriction of the C282Y and Z. Our results show that H63D carriage is increased among hepatocellular carcinoma patients, suggesting that it may confer an increased susceptibility to hepatocellular carcinoma even in a heterozygous state. On the contrary, HFE C282Y and SERPINA1 mutations do not contribute to hepatocellular carcinoma development.

Prevalence of HFE mutations in California newborns

Advances in molecular diagnostics have led to an increased interest in expanding population-based screening to include genetic diseases that occur outside the newborn period. Hereditary hemochromatosis may be a candidate for large-scale screening in populations with a high prevalence of the common HFE mutations. To determine race-specific frequencies of the HFE mutations, C282Y and H63D, the authors applied an automated, high-throughput genotyping method to dried blood spot samples from a representative population of California newborns. In this sample of 3989 newborns, C282Y and H63D allele frequencies were highest in white (C282Y: 5.5 +/- 0.5%; H63D: 13.4 +/- 0.76%) and Hispanic (C282Y: 1.8 +/- 0.29%; H63D: 11.9 +/- 0.72%) newborns, and lowest in black (C282Y: 1.3 +/- 0.25%; H63D: 3.0 +/- 0.38%) and Asian (C282Y 0.5 +/- 0.16%; H63D 2.9 +/- 0.37%) newborns. The estimated prevalence of C282Y homozygotes in this multiracial population is 1.4/1000. As additional genetic and environmental risk factors for HHC are identified, neonatal screening may become an acceptable strategy to follow susceptible individuals and prevent clinical disease.

Prevalence of the C282Y, H63D, and S65C Mutations of theHFEGene in 1,146 Newborns from a Region of Northern Spain

In Spain, 85% of patients with genetic hemochromatosis (GH) are homozygous for the C282Y mutation of the HFE gene. H63D and S65C mutations of HFE may also play some role in the disease. The aim of this study was to establish the prevalence of C282Y, H63D, and S65C mutations of the HFE gene in newborns in Catalonia, Spain. One thousand one hundred forty-six newborn screening cards were selected randomly. DNA from these cards was extracted and HFE mutations were analyzed with the LightCycler equipment (Roche Diagnostics Gmbh, Mannheim, Germany). Sufficient DNA sample was obtained to screen for the three mutations in 1,043 cases (91%). The allelic frequencies of C282Y, H63D, and S65C mutations were 0.03 (IC 95% 0.022-0.037), 0.2 (IC 95% 0.19-0.22), and 0.01 (95% confidence interval [CI] 0.006-0.015), respectively. The frequency of C282Y homozygous newborns was 0.001 (95% CI 0.0005-0.0014). The frequencies of newborns doubly heterozygous for C282Y/H63D and C282Y/S65C were 0.01 (95% CI 0.005-0.02) and 0.002 (95% CI 0.0002-0.01), respectively. The allelic frequency of C282Y mutation is similar to that observed in Southern France, in the Czech Republic and in some areas of Italy. The allelic frequency of H63D mutation in Catalonia is the highest reported to date. Nevertheless, S65C is infrequent. These data should be kept in mind when designing hemochromatosis genotypic screening programs in Catalonia.

High heterogeneity of CFTR mutations and unexpected low incidence of cystic fibrosis in the Mediterranean France

In this report, we present updated spectrum and frequency of mutations of the CFTR gene that are responsible for cystic fibrosis (CF) in Languedoc-Roussillon (L-R), the southwestern part of France. A total of 75 different mutations were identified by DGGE in 215 families, accounting for 97.6% of CF genes and generating 88 different mutational genotypes. The frequency of p.F508del was 60.23% in L-R versus 67.18% in the whole country and only five other mutations (p.G542X, p.N1303K, p.R334W, c.1717-1G>A, c.711+1G>T) had a frequency higher than 1%. The mutations were scattered over 20 exons or their border. This sample representing only 5.7% of French CF patients contributed to 24% of CFTR mutations reported in France. This is one of the highest molecular allelic heterogeneity reported so far in CF. We also present the result of a neonatal screening program based on a two-tiered approach "IRT/20 mutations/IRT" analysis on blood spots, implemented in France with the aim to improve survival and quality of life of patients diagnosed before clinical onset. This 18-month pilot project showed an unexpected low incidence of CF (1/8885) in South of France, with only six CF children detected among 43,489 neonates born in L-R, and 13 among 125,339 neonates born in Provence-Alpes-Côte-d'Azur (PACA).

Prevalence of C282Y and H63D mutations in the haemochromatosis (HFE) gene in Tunisian population

The studies of the HFE mutations: H63D and C282Y in North African populations have revealed the extreme rarity or even the absence of the C282Y mutation. We have examined 1140 chromosomes (570 Tunisian people) for the presence of the two HFE mutations by PCR-RFLP analysis. We have found that the allele frequencies are, respectively, 15.17% (+/-2.1%) for the H63D and 0.09% (+/-0.17%) for the C282Y. These results are consistent with the worldwide spread of the H63D mutation and the north European restriction of the C282Y. This study will be completed by determining whether homozygote trait for H63D and associated risk factors (beta thalassémia) can lead to iron overload in Tunisia.

Molecular epidemiology of DFNB1 deafness in France

Background

Mutations in the GJB2 gene have been established as a major cause of inherited non syndromic deafness in different populations. A high number of sequence variations have been described in the GJB2 gene and the associated pathogenic effects are not always clearly established. The prevalence of a number of mutations is known to be population specific, and therefore population specific testing should be a prerequisite step when molecular diagnosis is offered. Moreover, population studies are needed to determine the contribution of GJB2 variants to deafness. We present our findings from the molecular diagnostic screening of the GJB2 and GJB6 genes over a three year period, together with a population-based study of GJB2 variants.

Methods and results

Molecular studies were performed using denaturing High Performance Liquid Chromatograghy (DHPLC) and sequencing of the GJB2 gene. Over the last 3 years we have studied 159 families presenting sensorineural hearing loss, including 84 with non syndromic, stable, bilateral deafness. Thirty families were genotyped with causative mutations. In parallel, we have performed a molecular epidemiology study on more than 3000 dried blood spots and established the frequency of the GJB2 variants in our population. Finally, we have compared the prevalence of the variants in the hearing impaired population with the general population.

Conclusion

Although a high heterogeneity of sequence variation was observed in patients and controls, the 35delG mutation remains the most common pathogenic mutation in our population. Genetic counseling is dependent on the knowledge of the pathogenicity of the mutations and remains difficult in a number of cases. By comparing the sequence variations observed in hearing impaired patients with those sequence variants observed in general population, from the same ethnic background, we show that the M34T, V37I and R127H variants can not be responsible for profound or severe deafness.