Analysis of the HFE gene (C282Y, H63D and S65C) mutations in a general Chinese Han population

Human DNA Mutations and their Impact on Genetic Disorders

DNA is a remarkably precise medium for copying and storing biological information. It serves as a design for cellular machinery that permits cells, organs, and even whole organisms to work. The fidelity of DNA replication results from the action of hundreds of genes involved in proofreading and damage repair. All human cells can acquire genetic changes in their DNA all over life. Genetic mutations are changes to the DNA sequence that happen during cell division when the cells make copies of themselves. Mutations in the DNA can cause genetic illnesses such as cancer, or they could help humans better adapt to their environment over time. The endogenous reactive metabolites, therapeutic medicines, and an excess of environmental mutagens, such as UV rays all continuously damage DNA, compromising its integrity. One or more chromosomal alterations and point mutations at a single site (monogenic mutation) including deletions, duplications, and inversions illustrate such DNA mutations. Genetic conditions can occur when an altered gene is inherited from parents, which increases the risk of developing that particular condition, or some gene alterations can happen randomly. Moreover, symptoms of genetic conditions depend on which gene has a mutation. There are many different diseases and conditions caused by mutations. Some of the most common genetic conditions are Alzheimer's disease, some cancers, cystic fibrosis, Down syndrome, and sickle cell disease. Interestingly, scientists find that DNA mutations are more common than formerly thought. This review outlines the main DNA mutations that occur along the human genome and their influence on human health. The subject of patents pertaining to DNA mutations and genetic disorders has been brought up.

HFE-Related Hemochromatosis in a Chinese Patient: The First Reported Case

HFE-related Hemochromatosis is the most common genetic iron overload disease in European populations, particularly of Nordic or Celtic ancestry. It is reported that the HFE p.C282Y mutation is present in 1/10 people of northern European descent, resulting in one in two hundred people will be homozygous. However, the HFE p.C282Y heterozygosity is virtually absent among East Asians, including Japanese, Koreans, and Chinese. In this article, we report a case of HFE-related hemochromatosis caused by compound heterozygosity HFE p.C282Y/p.R71X. This is the first report of hemochromatosis associated with HFE p.C282Y mutation in China.

Interactive Effects between Chronic Lead Exposure and the Homeostatic Iron Regulator Transport HFE Polymorphism on the Human Red Blood Cell Mean Corpuscular Volume (MCV)

Research has shown that long-term exposure to lead harms the hematological system. The homeostatic iron regulator HFE (hemochromatosis) mutation, which has been shown to affect iron absorption and iron overload, is hypothesized to be related to lead intoxication in vulnerable individuals. The aim of our study was to investigate whether the HFE genotype modifies the blood lead levels that affect the distributions of serum iron and other red blood cell indices. Overall, 121 lead workers and 117 unexposed age-matched subjects were recruited for the study. The collected data included the blood lead levels, complete blood count, serum iron, total iron binding capacity, transferrin, and ferritin, which were measured during regular physical examinations. All subjects filled out questionnaires that included demographic information, medical history, and alcohol and tobacco consumption. HFE genotyping for C282Y and H63D was determined using polymerase chain reaction and restriction fragment length polymorphism (PCR/RFLP). The mean blood lead level in lead workers was 19.75 µg/dL and was 2.86 µg/dL in unexposed subjects. Of 238 subjects, 221 (92.9%) subjects were wild-type (CCHH) for HFE C282Y and H63D, and 17 (7.1%) subjects were heterozygous for a H63D mutation (CCHD). Multiple linear regression analysis showed that blood lead was significantly negatively associated with hemoglobin (Hb), mean corpuscular hemoglobin concentration (MCHC), and mean corpuscular volume (MCV), whereas the HFE variant was associated negatively with MCV and positively with ferritin. An interactive influence on MCV was identified between blood lead and HFE variants. Our research found a significant modifying effect of the HFE variant, which possibly affected MCV. The HFE H63D heterozygous (CCHD) variant seemed to provide a protective factor against lead toxicity. Future studies should focus on competing binding proteins between iron and lead influenced by gene variation.

Late-onset Hemochromatosis: Co-inheritance of β-thalassemia and Hereditary Hemochromatosis in a Chinese Family: A Case Report and Epidemiological Analysis of Diverse Populations

Hereditary hemochromatosis and β-thalassemia can both result in the inappropriately low production of the hormone hepcidin, which leads to an increase in intestinal absorption and excessive iron deposition in the parenchymal cells. To the best of our knowledge, there have been no reports on the coexistence of the two disorders in China. We herein report a case in a Chinese who presented with late-onset hepatic cirrhosis with hereditary hemochromatosis and β-thalassemia. We analyzed the pedigree of the two disorders and the iron status in his family members. Our case supports that a heterozygous H63D mutation can interact with β-thalassemia, leading to late-onset hemochromatosis.

Hemochromatosis as Junctional Tachycardia, a Rare Presentation

We present here a 45-year-old male with no past medical problem who presented with palpitations. He was found to have supraventricular tachycardia intractable to medical therapy. Later his rhythm converted to junctional tachycardia. Further workup revealed hemochromatosis to be primary etiology causing the arrhythmia. The low index of suspicion for additional workup is key to diagnosis and successful outcome.

Recent advance in the molecular genetics of Wilson disease and hereditary hemochromatosis

Metabolic liver diseases such as Wilson disease (WD) and hereditary hemochromatosis (HH) possess complicated pathogenesis and typical hereditary characteristics with the hallmarks of a deficiency in metal metabolism. Mutations in genes encoding ATPase, Cu + transporting, beta polypeptide (ATP7B) and hemochromatosis (HFE) or several non-HFE genes are considered to be causative for WD and HH, respectively. Although the identification of novel mutations in ATP7B for WD and HFE or the non-HFE genes for HH has increased, especially with the application of whole genome sequencing technology in recent years, the biological function of the identified mutations, as well as genotype-phenotype correlations remain to be explored. Further analysis of the causative gene mutation would be critical to clarify the mechanisms underlying specific disease phenotypes. In this review, we therefore summarize the recent advances in the molecular genetics of WD and HH including the updated mutation spectrums and the correlation between genotype and phenotype, with an emphasis on biological functional studies of the individual mutations identified in WD and HH. The weakness of the current functional studies and analysis for the clinical association of the individual mutation was also discussed. These works are essential for the understanding of the association between genotypes and phenotypes of these inherited metabolic liver diseases.

Effect of the Hemochromatosis Mutations on Iron Overload among the Indian β Thalassemia Carriers

BACKGROUND

Hereditary hemochromatosis is a disorder of iron metabolism characterized by increased iron absorption.HFE gene mutations C282Y and H63D are responsible for the majority of hereditary hemochromatosis cases.

METHODS

We tried to look at the effect of HFE mutations on the iron status. A total of 100 β thalassemia traits (BTT) with 100 normal individuals were screened for the C282Y and H63D mutations using PCR-RFLP. The serum ferritin levels were determined using ELISA kit.

RESULTS

We did not find the C282Y mutation in our study group. The allelic frequencies for H63D mutation did not differ significantly between β-thalassemia traits (8.5%) and normal controls (9%). ΒΤΤ with H63D genotype of H/D (143.16 ± 80.3 ng/ml) and D/D (504 ng/ml) showed higher ferritin levels as against H/H genotype (88.64 ± 92.43 ng/ml). The statistically significant difference was observed in the mean serum ferritin levels among the individuals showing H/H and D/D genotypes (P < 0.002) and H/D and D/D genotype (P < 0.01) in both the groups.

CONCLUSION

This suggests that iron load in BTT tends to aggravated with the co-inheritance of the H63D mutation. The mutant H63D gene showed the presence of haplotype 6 which is reported in the European population suggesting a common origin.

Non-Heme Iron Absorption and Utilization from Typical Whole Chinese Diets in Young Chinese Urban Men Measured by a Double-Labeled Stable Isotope Technique

BACKGROUND

This study was to observe the non-heme iron absorption and biological utilization from typical whole Chinese diets in young Chinese healthy urban men, and to observe if the iron absorption and utilization could be affected by the staple food patterns of Southern and Northern China.

MATERIALS AND METHODS

Twenty-two young urban men aged 18-24 years were recruited and randomly assigned to two groups in which the staple food was rice and steamed buns, respectively. Each subject received 3 meals containing approximately 3.25 mg stable 57FeSO4 (the ratio of 57Fe content in breakfast, lunch and dinner was 1:2:2) daily for 2 consecutive days. In addition, approximately 2.4 mg 58FeSO4 was administered intravenously to each subject at 30-60 min after dinner each day. Blood samples were collected from each subject to measure the enrichment of the 57Fe and 58Fe. Fourteen days after the experimental diet, non-heme iron absorption was assessed by measuring 57Fe incorporation into red blood cells, and absorbed iron utilization was determined according to the red blood cell incorporation of intravenously infused 58Fe SO4.

RESULTS

Non-heme iron intake values overall, and in the rice and steamed buns groups were 12.8 ±2.1, 11.3±1.3 and 14.3±1.5 mg, respectively; the mean 57Fe absorption rates were 11±7%, 13±7%, and 8±4%, respectively; and the mean infused 58Fe utilization rates were 85±8%, 84±6%, and 85±10%, respectively. There was no significantly difference in the iron intakes, and 57Fe absorption and infused 58Fe utilization rates between rice and steamed buns groups (all P>0.05).

CONCLUSION

We present the non-heme iron absorption and utilization rates from typical whole Chinese diets among young Chinese healthy urban men, which was not affected by the representative staple food patterns of Southern and Northern China. This study will provide a basis for the setting of Chinese iron DRIs.

Carriers of the Complex Allele HFE c.[187C>G;340+4T>C] Have Increased Risk of Iron Overload in São Miguel Island Population (Azores, Portugal)

Iron overload is associated with acquired and genetic conditions, the most common being hereditary hemochromatosis (HH) type-I, caused by HFE mutations. Here, we conducted a hospital-based case-control study of 41 patients from the São Miguel Island (Azores, Portugal), six belonging to a family with HH type-I pseudodominant inheritance, and 35 unrelated individuals fulfilling the biochemical criteria of iron overload compatible with HH type-I. For this purpose, we analyzed the most common HFE mutations– c.845G>A [p.Cys282Tyr], c.187C>G [p.His63Asp], and c.193A>T [p.Ser65Cys]. Results revealed that the family’s HH pseudodominant pattern is due to consanguineous marriage of HFE-c.845G>A carriers, and to marriage with a genetically unrelated spouse that is a -c.187G carrier. Regarding unrelated patients, six were homozygous for c.845A, and three were c.845A/c.187G compound heterozygous. We then performed sequencing of HFE exons 2, 4, 5 and their intron-flanking regions. No other mutations were observed, but we identified the -c.340+4C [IVS2+4C] splice variant in 26 (74.3%) patients. Functionally, the c.340+4C may generate alternative splicing by HFE exon 2 skipping and consequently, a protein missing the α1-domain essential for HFE/ transferrin receptor-1 interactions. Finally, we investigated HFE mutations configuration with iron overload by determining haplotypes and genotypic profiles. Results evidenced that carriers of HFE-c.187G allele also carry -c.340+4C, suggesting in-cis configuration. This data is corroborated by the association analysis where carriers of the complex allele HFE-c.[187C>G;340+4T>C] have an increased iron overload risk (RR = 2.08, 95% CI = 1.40−2.94, p<0.001). Therefore, homozygous for this complex allele are at risk of having iron overload because they will produce two altered proteins—the p.63Asp [c.187G], and the protein lacking 88 amino acids encoded by exon 2. In summary, we provide evidence that the complex allele HFE-c.[187C>G;340+4T>C] has a role, as genetic predisposition factor, on iron overload in the São Miguel population. Independent replication studies in other populations are needed to confirm this association.

Nutritional determinants of anemia among adults in Eastern China

Historically, Eastern China has the highest prevalence of anemia among adults in China. It is commonly believed that iron deficiency is the main cause of anemia in China. Iron fortified soysauce is used to prevent anemia. Findings from Jiangsu Nutrition Study suggest that diet is related to anemia in this region. However, iron deficiency is not the main cause. Micronutrients other than iron (e.g., riboflavin) need to be considered in the prevention of anemia in the region.

High serum iron is associated with increased cancer risk

Epidemiologic studies linking high serum iron with cancer risks are limited and inconclusive, despite evidence implicating body iron in human carcinogenesis. A cohort of 309,443 adults in Taiwan who had no history of cancer had serum iron levels tested at the time of recruitment (1997-2008). Initially measured iron levels were associated with subsequent cancer risk by linking individuals with the National Cancer Registry and National Death File. HRs were calculated by the Cox model. One third of males (35%) and one fifth of females (18%) had high serum iron (≥120 μg/dL), which was associated with a 25% increase in risk for incidence of all cancers [HR, 1.25; 95% confidence interval (CI), 1.16-1.35] and with a 39% increase in risk for mortality from all cancers (HR, 1.39; 95% CI, 1.23-1.57). The relationship between serum iron and cancer risk was a J-shaped one, with higher cancer risk at both ends, either at lower than 60 μg/dL or higher than 120 μg/dL. At the higher end, cancer risk increased by 4% for every 10 μg/dL increment above 80 μg/dL, showing a dose-response relationship, with 60 to 79 μg/dL as a reference level. In a sensitivity analysis, the increases in risk were still observed after the first 5 years of cancer cases were excluded. Liver cancer risk was increased in HBV (-) non-hepatitis B carrier (3-fold) and HBV (+) hepatitis B carrier (24-fold). Lifestyle risks such as smoking, drinking, or inactivity interacted synergistically with high serum iron and significantly increased the cancer risks. The liver (HR, 2.49; 95% CI, 1.97-3.16) and the breast (HR, 1.31; 95% CI, 1.01-1.70) were the two major cancer sites where significant cancer risks were observed for serum iron either ≥120 μg/dL or ≥140 μg/dL, respectively. This study reveals that high serum iron is both a common disorder and a marker of increased risk for several cancers.

The effect of the hemochromatosis (HFE) genotype on lead load and iron metabolism among lead smelter workers

Background

Both an excess of toxic lead (Pb) and an essential iron disorder have been implicated in many diseases and public health problems. Iron metabolism genes, such as the hemochromatosis (HFE) gene, have been reported to be modifiers for lead absorption and storage. However, the HFE gene studies among the Asian population with occupationally high lead exposure are lacking.

Objectives

To explore the modifying effects of the HFE genotype (wild-type, H63D variant and C282Y variant) on the Pb load and iron metabolism among Asian Pb-workers with high occupational exposure.

Methods

Seven hundred and seventy-one employees from a lead smelter manufacturing company were tested to determine their Pb intoxication parameters, iron metabolic indexes and identify the HFE genotype. Descriptive and multivariate analyses were conducted.

Results

Forty-five H63D variant carriers and no C282Y variant carrier were found among the 771 subjects. Compared with subjects with the wild-type genotype, H63D variant carriers had higher blood lead levels, even after controlling for factors such as age, sex, marriage, education, smoking and lead exposure levels. Multivariate analyses also showed that the H63D genotype modifies the associations between the blood lead levels and the body iron burden/transferrin.

Conclusions

No C282Y variant was found in this Asian population. The H63D genotype modified the association between the lead and iron metabolism such that increased blood lead is associated with a higher body iron content or a lower transferrin in the H63D variant. It is indicated that H63D variant carriers may be a potentially highly vulnerable sub-population if they are exposed to high lead levels occupationally.

Characterization of HLA-F polymorphism in four distinct populations in Mainland China

Currently, there is a lack of information on polymorphism of human leucocyte antigen-F (HLA-F) gene in ethnically diverse human populations. In this study, HLA-F allelic typing was performed for 690 individuals representing two southern Chinese Han populations (Hunan Han and Guangdong Han) and two northern Chinese populations (Inner Mongolia Han and Inner Mongolia Mongol), using polymerase chain reaction-sequence-specific priming (PCR-SSP) and PCR-sequencing methods. Our results showed that (i) HLA-F*01 : 01 predominated in each population with a frequency >0.94 and HLA-F*01 : 03 was relatively more common in the two northern Chinese populations with a frequency of approximately 0.05; (ii) both geographical and ethnical factors are related to HLA-F allelic distribution, as evidenced by the significant difference in HLA-F allelic distribution between the Hunan Han population and the two northern Chinese populations; (iii) significant linkage disequilibrium (LD) was observed for haplotype HLA-A*03-F*01 : 03 in three populations. In most cases, this haplotype extended to HLA-E*01 : 03; and (iv) Ewens-Watterson homozygosity statistic at the HLA-F locus did not depart significantly from expectation in each of the four populations. Our data revealed a low level of HLA-F allelic variation in Chinese populations, suggesting that HLA-F gene may have existed before some of the HLA-A polymorphism and have been evolving under neutrality.

Clinical impact of HFE mutations in Japanese patients with chronic hepatitis C

BACKGROUND AND AIM

HFE mutations, a common cause of hereditary hemochromatosis (HH), are reportedly associated with hepatic iron overload, severe liver fibrosis, and good response to interferon treatment in European patients with chronic hepatitis C (CHC). HH shows ethnicity-based differences and little is known about the effects of HH mutations on CHC in the Japanese. Thus, the aim of this study was to clarify the clinical influence of HFE mutations in Japanese CHC patients.

METHODS

In a total of 251 patients with CHC, we analyzed the frequencies of H63D and S65C mutations in the HFE gene, and the influence of these mutations on clinical parameters and response to pegylated-interferon-alpha 2b (PEG-IFN) plus ribavirin therapy.

RESULTS

Fourteen patients (5.6%) carried the H63D mutation; all were heterozygotes. No S65C mutations were found. Only hemoglobin levels in the H63D heterozygotes were higher than in wild-type patients. Eleven of 14 H63D heterozygotes achieved sustained virological response (SVR). On univariate analysis, factors associated with SVR were interleukin 28B (IL28B) polymorphism, age, hepatitis C virus (HCV) genotype, HCV viral load, white blood cell count, stage of fibrosis and H63D mutation. All patients with both TT genotype in IL28B (rs8099917) and H63D mutation in HFE (n = 10) achieved SVR.

CONCLUSIONS

The H63D mutation has little impact on the clinical characteristics of CHC, but is related to favorable response to PEG-IFN plus ribavirin therapy, particularly in patients with the TT allele in IL28B.

An association study of HFE gene mutation with idiopathic male infertility in the Chinese Han population

Mutations in the haemochromatosis gene (HFE) influence iron status in the general population of Northern Europe, and excess iron is associated with the impairment of spermatogenesis. The aim of this study is to investigate the association between three mutations (C282Y, H63D and S65C) in the HFE gene with idiopathic male infertility in the Chinese Han population. Two groups of Chinese men were recruited: 444 infertile men (including 169 with idiopathic azoospermia) and 423 controls with proven fertility. The HFE gene was detected using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The experimental results demonstrated that no C282Y or S65C mutations were detected. Idiopathic male infertility was not significantly associated with heterozygous H63D mutation (odds ratio=0.801, 95% confidence interval=0.452-1.421, χ(2)=0.577, P=0.448). The H63D mutation frequency did not correlate significantly with the serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone (T) levels in infertile men (P=0.896, P=0.404 and P=0.05, respectively). Our data suggest that the HFE H63D mutation is not associated with idiopathic male reproductive dysfunction.

HFE genotype and iron metabolism in Chinese patients with myelodysplastic syndromes and aplastic anemia

The incidence of HFE gene mutations in myelodysplastic syndrome (MDS) cases remains controversial. In this study, we examined the HFE C282Y and H63D mutations in 271 Chinese patients with MDS, 402 with aplastic anemia (AA) and 1,615 healthy controls by polymerase chain reaction-restriction fragment length polymorphism in combination with DNA sequencing. No C282Y mutations were observed in the entire cohort. The distribution of H63D heterozygous and homozygous genotypes was not significantly different between the AA cases and the controls (9.7% versus 10.2%, 0.25% versus 0.24%, respectively). While the H63D heterozygous genotype in MDS patients was significantly lower than that in the controls (4.1% versus 10.2%, p = 0.002), the H63D homozygous genotype was not detected in the MDS patients. The results suggest that HFE gene mutations are not common genetic factors in Chinese patients with MDS and AA. We also compared iron metabolic parameters, including serum ferritin, serum iron, and transferrin saturation values, between HFE mutant and HFE wild-type groups in the absence of transfusion iron overload, but no significant difference was found in either MDS or AA patients except that the level of serum iron in AA patients was significantly higher in mutant carriers than in those with wild-type HFE (p = 0.011). Similarly, there was no significant difference between HFE mutant and HFE wild-type MDS and AA patients in clinical indices such as alanine aminotransferase, aspartate aminotransferase, fasting blood sugar values, and electrocardiogram. The results suggest that H63D mutations may not have clinical significance in Chinese patients with MDS and AA.