Prevalence of HFE C282Y and H63D in Jewish populations and clinical implications of H63D homozygosity

The frequencies of C282Y and H63D mutations of the HFE gene vary between different populations. A previous study showed an unexpectedly high H63D frequency in Chuetas (a population of Jewish descent). The present study addressed the question of the distribution of these mutations in Jewish populations from different origins and studied the possible causes of the high H63D frequency in Chuetas. Moreover, to improve the understanding of the controversial relationship between H63D homozygosity and iron overload, a group of patients with altered iron metabolism were studied. The high frequency of H63D mutation in Chuetas is not due to a high prevalence of this mutation in Sephardic Jews. Jewish populations have low C282Y and moderate H63D frequencies, suggesting slight gene flow from their surrounding populations. In accordance with historical and demographic data, genetic drift is the most probable cause for the singular H63D frequency in Chuetas. Clinically, this study of H63D homozygotes supports the conclusion that this genotype must be taken into account, because it confers an increased risk of iron overload and therefore genetic susceptibility to developing hereditary hemochromatosis or to aggravating other diseases.     

A previously undescribed frameshift deletion mutation of HFE (c.del277; G93fs) associated with hemochromatosis and iron overload in a C282Y heterozygote

A 62-year-old white man with a hemochromatosis phenotype was found to be heterozygous for the C282Y mutation of the HFE gene. The H63D and S65C mutations of HFE were not present. As most C282Y heterozygotes do not develop a hemochromatosis phenotype, the coding region of the patient's HFE gene was sequenced and a previously undescribed frameshift mutation was identified in exon 2 (c.del277; G93fs) that resulted in a premature stop-codon. There were no coding region mutations of the ferroportin gene (FPN1). We performed human leukocyte antigen (HLA) typing of the patient and his brother who was heterozygous for the C282Y HFE mutation unassociated with a hemochromatosis phenotype. They shared only C282Y and the HLA haplotype A*03, B*14; hence, the c.del277 mutation was linked to the HLA haplotype A*02, B*44 and therefore not on the same chromosome as the C282Y mutation. Thus, the present patient's only intact HFE protein is C282Y, and this may explain his hemochromatosis phenotype.     

Distribution of HFE C282Y and H63D mutations in the Balearic Islands (NE Spain)

The HFE gene contains two main missense mutations: C282Y and H63D. Individuals with these mutations carry a risk of developing hereditary haemochromatosis (HH). The common form of this disease is due to homozygosity for the C282Y mutation. Population studies have shown the variation of the prevalence of these mutations in different countries and ethnic groups. The purposes of this current study were to determine the prevalence of the C282Y and H63D mutations in the Balearic Islands and the genotypic characterization of patients diagnosed with HH, as well as those with iron overload and liver diseases. A total of 1330 Balearic chromosomes were analyzed. The results showed that the populations of the Balearic Islands were not homogeneous. No C282Y carriers were observed in a group of descendants of Majorcan Jews (Chuetas) and the frequency was very low in Minorca (1.2%) in comparison with the other islands of Majorca (4.7%) and Ibiza (6.5%). The carrier frequency of the H63D mutation was similar in the three islands and very high (43.1%) in the descendants of Majorcan Jews. The study of patients was carried out in 129 individuals. The homozygous C282Y genotype was the principal one involved in hereditary haemochromatosis (90%), whereas the other HH patients were C282Y/H63D compound heterozygous and H63D homozygous.     

HFE基因与遗传性血色素沉着症

HFE基因发现于1996年，属于HLA I类样基因，是遗传性血色素沉着症侯选基因。HFE分子的功能可能是参与调节转铁蛋白与转铁蛋白受体间的相互作用。遗传性血色素沉着症是一种常染色体隐性遗传性铁异常沉积性疾病，高加索群体中发病率高，平均不到300人就有一个是该病患者。大量群体遗传学研究结果，提示HFE基因C282Y突变与遗传性血色素沉着症显著相关，HFE H63D突变对遗传性血色素沉着症影响较小。新近发现，HFE分子通过与转铁蛋白受体反应影响转铁蛋白与转铁蛋白受体间的相互作用，从而调节体内铁平衡。C282Y突变可使HFE分子不能与β2微球蛋白结合，不能转运到细胞表面，从而失去对转铁蛋白和转铁蛋白受体作用的调节功能。H63D突变影响功能的机理目前尚不清楚，现有研究提示H63D突变蛋白可与β2微球蛋白结合，并转过到细胞表面，突变对分子功能的影响可能也表现在不能调节转铁蛋白和转铁蛋白受体间的作用。     

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

Hereditary hemochromatosis (HH) is one of the most common autosomal recessive genetic disorders of iron metabolism in white populations, which leads to inappropriately high iron absorption. C282Y, H63D, and S65C are three major missense mutations of the hemochromatosis gene (HFE). In the present study, C282Y, H63D, and S65C mutations in 395 normal Chinese Han populations from Zhejiang province were investigated. No C282Y, S65C mutations, and H63D homozygote was observed, while the genotype frequency of H63D heterozygote was 4.6% and the allelic frequency 2.3% in this population. This was the first report to analyze the prevalence of C282Y, H63D, and S65C mutations in the HFE gene in a Chinese Han population. Low incidence of the HFE gene mutations could be a reason for the rarity of HH in the Chinese Han population studied.     

Elevated MCP-1 serum levels are associated with the H63D mutation and not the C282Y mutation in hereditary hemochromatosis

Monocyte chemoattractant protein-1 (MCP-1) is a major lymphocyte and inflammatory chemokine associated with persistent inflammatory states. Several abnormalities in the immune status of patients with hereditary hemochromatosis (HH) have been reported, suggesting an imbalance in their immune function. This may include persistent production of, or exposure to, inflammatory cytokines contributing to the pathogenesis of this disorder. The aim of this study was to assess MCP-1 levels in patients with HH and correlate these results with HFE status and iron indexes. One hundred and thirty-nine subjects diagnosed with HH (C282Y homozygotes = 87, C282Y/H63D = 26 heterozygotes, H63D homozygotes = 26), 27 healthy control subjects with no HFE mutation (N/N), and 18 normal subjects heterozygous for the H63D mutation served as age- and sex-matched controls. Ferritin and transferrin saturation and the presence of HFE mutation status were correlated with MCP-1 levels. Full white blood cell count analysis was also performed. We found a strongly significant decrease in MCP-1 protein levels in the C282Y homozygotes compared with the H63D homozygotes (P = 0.0009) and C282Y/H63D heterozygotes (P = 0.002). Similarly, MCP-1 protein levels in the C282Y homozygotes were decreased compared with the healthy controls (P = 0.00076). Furthermore, MCP-1 serum levels were elevated in H63D patients compared with the healthy controls (P = 0.0008). This study suggests for the first time that a differential expression of MCP-1 protein in patients with HH is associated with the specific HFE genetic component for iron overload. Therefore, these findings offer a possible explanation in the variable clinical spectrum of pathogenesis in patients with HH through abnormalities of an imbalance in the immune states of patients with HH.     

HFE H63D,C282Y and AGTR1 A1166C Polymorphisms and Brain White Matter Lesions in the Aging Brain

Abstract: Incidental white matter lesions (WML) are a common neuroradiological finding in elderly people and have been linked to dementia and depression. Various mechanisms including hypoxia and increased production of reactive oxygen species (ROS) are implicated in the etiology of WML. The hemochromatosis (HFE) gene p.H63D and p.C282Y polymorphisms have been linked to dysregulation of iron metabolism and increased levels of ROS, whereas Angiotensin II receptor 1 (AGTR1) c.1166A → C polymorphism is known as a vascular risk factor. These genetic polymorphisms were characterized in brains donated to the UK MRC Cognitive Function and Ageing Study (CFAS) to assess their potential role in the risk for development of age-related WML. The study cohort comprised 258 brain donated to CFAS. WML severity was assessed in the postmortem brain donations using magnetic resonance imaging (MRI) scans and scored using the Scheltens’ scale. Polymerase chain reaction (PCR) amplification of extracted DNA followed by restriction enzyme digestion was used to genotype the samples. Genotypes were validated using direct sequencing in a smaller sample. The results show that HFE p.H63D polymorphism is not associated with WML severity in the whole cohort. However, there is a significant association of the D allele with severity of WML in noncarriers of the APOE ε4 allele. No association is demonstrated between the HFE p.C282Y nor the AGTR1 c.1166A → C polymorphisms and WML severity. The HFE gene appears to be a genetic risk factor for severe aging WML independently of the APOE ε4 genotype. This would support the role of iron-related oxidative stress, in addition to previously studied factors, e.g., hypoxia as potential risk factors for developing prominent aging WML.     

Iron‐overload and genotypic expression of HFE mutations H63D/C282Y and transferrin receptor Hin6I and BanI polymorphism in German patients with hereditary haemochromatosis

Gene variations of HFE, a HLA‐class I like molecule, are highly associated with hereditary haemochromatosis (HH). Functional as well as molecular studies of the HFE protein have indicated that the molecule is involved in iron metabolism and that the HFE gene variations observed among HH patients affect its interaction with the transferrin receptor (TfR). In the present study, we have therefore analysed the relationship between the HFE gene variants, C282Y and H63D, and body iron status among 85 German HH patients. In addition, two TfR gene polymorphism, TfR‐Hin6I and TfR‐BanI, were typed that have been reported to define ethnically distinct haplotypes. As controls we used 251/159 healthy German blood donors. Seventy‐eight (92%) patients were C292Y homozygous, the H63D mutation was present in five (6%) patients with none of the patients being H63D homozygous. Serum transferrin, transferrin saturation and liver iron content were determined prior to therapeutic intervention. Among C282Y homozygous patients serum ferritin levels (2294 ± 3174 vs. 463 ± 224 µg L^?1, P < 0.0001) and transferrin saturation (86 ± 18% vs. 62 ± 25%, P = 0.048) were elevated significantly compared with C282Y and/or H63D heterozygous patients. In addition, the liver iron content (291 ± 165 vs. 138 ± 95 µmol g^?1, P = 0.028) and liver iron index (6.4 ± 2.8 vs. 3.2 ± 2.3, P = 0.019) were increased among C282Y homozygotes compared with C282Y heterozygotes. In contrast, no difference was observed between patients and controls regarding the distribution of TfR‐Hin6I and TfR‐BanI alleles. These data indicate that the iron intake is higher among C282Y homozygous patients compared with C282Y heterozygous or C282Y/H63D compound heterozygous individuals and supports the functional role of the HFE protein in iron metabolism whereas the TfR gene variants seem to have no influence on iron uptake.     

Homozygosity for Premature Stop Codon of the MHC Class I Chain-Related Gene A (MIC-A) Is Associated with Early Activation of Islet Autoimmunity of DR3/4-DQ2/8 High Risk DAISY Relatives

We hypothesized that homozygosity for the major histocompatibility complex (MHC) class I chain-related gene A (MIC-A)5.1 allele with premature stop codon would increase diabetes risk of individuals followed from infancy in the DAISY study (Diabetes Autoimmunity Study in the young). Forty five percent (10/22) of relatives (siblings and offspring cohort, SOC) who developed anti-islet autoantibodies were MIC-A5.1/5.1 homozygous. Of SOC individuals without autoantibodies, 12/58 (19%, p = 0.02) were MIC-A5.1 homozygous. By life table analysis of expression of autoantibodies, DR3-DQ2/ DR4-DQ8 more than 50% of MIC-A5.1 homozygous children became autoantibody positive by 7 years of age, compared to delayed development of autoantibodies for non-MIC-A5.1/5.1 DR3-DQ2/ DR4-DQ8 children (p = 0.005). For DR3-DQ2/DR4-DQ8 nonrelatives, the risk of activating anti-islet autoimmunity remained low even with MIC-A5.1 homozygosity suggesting that there are additional factors contributing to the marked risk of relatives compared to the general population with the DR3-DQ2/DR4-DQ8 genotype.     

Impact of genetic polymorphisms near the IL28B gene and amino acid substitutions in the hepatitis C virus core region on interferon sensitivity/resistance in patients with chronic hepatitis C

It has been reported that genetic polymorphisms near the IL28B gene or amino acid substitutions in hepatitis C virus (HCV) core protein are associated with the clinical outcome of peginterferon (PEG-IFN) and ribavirin combination therapy. The impact of these factors on the pure sensitivity/resistance to interferon was evaluated. Changes in the HCV RNA levels 24, 48, 72, and 120 hr after administering a single dose of standard interferon (IFN) were measured in 156 HCV-infected patients. The changes were compared based on the genetic polymorphisms near the IL28B gene or amino acid substitutions in the HCV core region. Among patients with HCV genotype 1b, there were differences in the reduction and subsequent increase in HCV RNA levels after administering IFN based on rs8099917 genetic polymorphisms. Amino acid substitutions at residue 70 were associated with differences in the changes in HCV RNA levels only in patients with TG/GG genotype. Multivariate analyses showed that genetic polymorphisms near the IL28B gene was the sole independent factor that was associated with the reduction in HCV RNA levels after administering IFN and the final response to the combination therapy. Among patients infected with HCV genotype 2a or 2b, there were no differences in the changes in HCV RNA levels based on the genetic polymorphisms near the IL28B gene. In HCV genotype 1b, genetic variations near the IL28B gene affected the sensitivity/resistance to IFN strongly. Genetic polymorphisms near the IL28B gene did not affect the sensitivity/resistance to IFN in HCV genotype 2.     

Age related macular degeneration and drusen: neuroinflammation in the retina

Inflammation protects from dangerous stimuli, restoring normal tissue homeostasis. Inflammatory response in the nervous system ("neuroinflammation") has distinct features, which are shared in several diseases. The retina is an immune-privileged site, and the tight balance of immune reaction can be disrupted and lead to age-related macular disease (AMD) and to its peculiar sign, the druse. Excessive activation of inflammatory and immunological cascade with subsequent induction of damage, persistent activation of resident immune cells, accumulation of byproducts that exceeds the normal capacity of clearance giving origin to a chronic local inflammation, alterations in the activation of the complement system, infiltration of macrophages, T-lymphocytes and mast-cells from the bloodstream, participate in the mechanisms which originate the drusen. In addition, aging of the retina and AMD involve also para-inflammation, by which immune cells react to persistent stressful stimuli generating low-grade inflammation, aimed at restoring function and maintaining tissue homeostasis by varying the set point in relation to the new altered conditions. This mechanism is also seen in the normal aging retina, but, in the presence of noxious stimuli as in AMD, it can become chronic and have an adverse outcome. Finally, autophagy may provide new insights to understand AMD pathology, due to its contribution in the removal of defective proteins. Therefore, the AMD retina can represent a valuable model to study neuroinflammation, its mechanisms and therapy in a restricted and controllable environment. Targeting these pathways could represent a new way to treat and prevent both exudative and dry forms of AMD.     

Protection against malaria is conferred by passive transferring rabbit F(ab)(2)' antibody fragments, induced by Plasmodium falciparum MSP-1 site-directed designed pseudopeptide-BSA conjugates assessed in a rodent model

F(ab)₂′-immunoglobulin (Ig) fragments induced by site-directed designed immunogens are emerging as novel tools of potential utility in the treatment of clinical episodes of transmissible diseases such as malaria. Immunogens based on reduced amide pseudopeptides based on site-directed molecular modifications represent structural probes that could be considered as novel vaccine candidates, as we have previously demonstrated.We have obtained F(ab)₂′-Ig rabbit antibodies induced against the N-terminal sequence of the native Merozoite Surface Protein-1 (MSP-1) of Plasmodium falciparum and a set of five MSP-1-derived reduced amide pseudopeptides. Pseudopeptides were designed for inducing functional neutralizing mono-specific polyclonal antibodies with potential applications in the control of malaria. Following a classical enzyme immunoglobulin fractionation, F(ab)₂′-Ig fragments were tested for their ability to suppress blood-stage parasitemia by passive immunization in malaria-infected mice. Some of these fragments proved totally effective in suppressing a lethal blood-stage challenge infection and others reduced malarial parasitemia.These data suggest that protection against Plasmodium yoelii malaria following passive transfer of structurally well-defined β-strand F(ab)₂′-Ig fragments can be associated with specific immunoglobulins induced by site-directed designed MSP-1 reduced amide pseudopeptides.