Molecular diagnosis of hereditary hemochromatosis: application of a newly-developed reverse-hybridization assay in the South African population
CLINICAL GENETICS
Authors: Kotze, MJ; de Villiers, JNP; Bouwens, CSH; Warnich, L; Zaahl, MG; van der Merwe, S; Oberkanins, C
Abstract
A recently developed strip-assay for hemochromatosis provides a rapid method for simultaneous detection of multiple mutations, which among others includes the HFE gene mutations V53M, V59M, H63D, H63H, S65C, Q127H, E168Q, and C282Y, previously detected in the general South African population using gel-based mutation-screening methods. The objective of the study was to determine the frequency of the relatively rare mutations in samples selected for altered iron parameters or a family history of hereditary hemochromatosis (HH) as part of the validation process of the assay for routine diagnostic purposes. The study population consisted of 451 individuals previously screened for mutations C282Y and H63D by restriction enzyme analysis in order to confirm or possibly exclude a diagnosis of HH. These individuals were subjected to mutation screening using the commercially available hemochromatosis strip-assay. Previous positive results for mutations C282Y and H63D in 233 individuals confirmed the accuracy of the reverse-hybridization assay. Mutation S65C was detected in 13 Caucasians, including three compound heterozygotes. These constituted 2% (13/600) of the chromosomes without mutations C282Y or H63D. The African-specific HFE mutation V53M was detected in one out of 11 (9%) African subjects screened. Mutation E168Q was detected in a single Caucasian individual together with mutation H63D. Our data demonstrate the value of the strip-based technology in providing a rapid and reliable comprehensive test for simultaneous analysis of multiple mutations.
Expression of hepcidin is down-regulated in TfR2 mutant mice manifesting a phenotype of hereditary hemochromatosis
BLOOD
Authors: Kawabata, H; Fleming, RE; Gui, D; Moon, SY; Saitoh, T; O'Kelly, J; Umehara, Y; Wano, Y; Said, JW; Koeffler, HP
Abstract
Transferrin receptor 2 (TfR2) is a membrane glycoprotein that mediates cellular iron uptake from holotransferrin. Homozygous mutations of this gene cause one form of hereditary hemochromatosis in humans. We recently reported that homozygous TfR2(Y245X) mutant mice, which correspond to the TfR2(Y250X) mutation in humans, showed a phenotype similar to hereditary hemochromatosis. In this study, we further analyzed the phenotype as well as iron-related gene expression in these mice by comparing the TfR2-mutant and wild-type siblings. Northern blot analyses showed that the levels of expression of hepcidin mRNA in the liver were generally lower, whereas those of duodenal DMT1, the main transporter for uptake of dietary iron, were higher in the TfR2-mutant mice as compared to the wild-type siblings. Expression of hepcidin mRNA in the TfR2 mutant mice remained low even after intraperitoneal iron loading. In isolated hepatocytes from both wild-type and TfR2 mutant mice, interleukin-6 and lipopolysaccharide each induced expression of hepcidin mRNA. These results suggest that up-regulation of hepcidin expression by inflammatory stimuli is independent of TfR2 and that TfR2 is upstream of hepcidin in the regulatory pathway of body iron homeostasis. (C) 2005 by The American Society of Hematology.