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Prevalence of the H63D mutation of the HFE in north India: its presence does not cause iron overload in beta thalassemia trait.

OBJECTIVES: To determine the allele frequency in the north Indian population of the two mutations in the HFE gene, the C282Y and H63D, which are responsible for causing hereditary haemochromatosis particularly in Caucasians of north European descent. We also wanted to correlate these mutations with the iron status in beta thalassemia traits. PATIENTS AND METHODS: Sixty normal subjects and 215 individuals with beta thalassemia trait from north India were screened for the C282Y and H63D by polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP). We studied the iron status in these subjects and correlated the same with the HFE gene mutations. RESULTS: On screening for the C282Y gene mutation, all individuals were detected to be of the wild-type. The overall allele frequency of H63D was 9.09% with three individuals being homozygous for 63D. No statistically significant difference in the iron status was detected between the individuals of the wild-type and mutant for H63D. Haplotyping of the homozygous 63D alleles revealed the pattern to be identical to the Europeans. CONCLUSIONS: Our study shows that H63D is prevalent and C282Y is rare in north Indians and the presence of 63D mutation does not increase body iron as measured by serum ferritin in beta thalassemia traits. Haplotype of H63D gene mutation is of an European haplotype, indicating a common origin.

Alleles↗

Iron overload in mice expressing HFE exclusively in the intestinal villi provides evidence that HFE regulates a functional cross-talk between crypt and villi enterocytes.

Hereditary hemochromatosis (HH), a common autosomal recessive disorder due to a mutation in HFE, which encodes an atypical MHC class I glycoprotein, is characterized by excessive absorption of dietary iron. Little is known however of the apparently complex pathophysiology of HFE involvement in the process of iron influx. Here, in order to tackle the issue in vivo, we decided to target HFE expression exclusively to the relevant tissue, intestinal epithelium. This was achieved by putting HFE under transcriptional control of the rat fatty acid binding protein (Fabpi) promoter. Quite unexpectedly, Fabpi-HFE mice had significantly elevated serum transferrin saturation levels in comparison to those of normal littermates. By a careful, layer by layer analysis of transgene expression along the crypt-villus axis, we were able to affirm that the ectopic expression of transgenic HFE in the differentiated villi enterocytes was responsible for ferric hyperabsorption, a phenomenon exacerbated in the absence of endogenous HFE expression, which we assessed by crossing the transgene onto an HFE(-/-) (knockout) background. This forced dichotomy between the absence of HFE in the crypt and expression in the villi provides experimental support that HFE functions as a "gatekeeper," regulating the cross-talk between the crypt and villi enterocytes and thereby modulating the avidity of mature enterocytes for dietary iron.

Animals↗

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 microg 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 micromol 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.

Blood Donors↗

A prospective randomized controlled trial on the safety and efficacy of alternating deferoxamine and deferiprone in the treatment of iron overload in patients with thalassemia.

We compared the safety and efficacy of alternating deferoxamine and deferiprone with that of deferoxamine monotherapy. Sixty transfusion-dependent thalassemia patients regularly treated with deferoxamine were randomized to continue deferoxamine alone or to receive an alternating therapy for one year. Both arms resulted in equivalent decreases of serum ferritin and liver iron concentration. There was no significant difference in the proportion of patients with adverse events in the two therapy groups although the nature of the adverse events differed according to the chelation regimen.

Adolescent↗