What's new in hemochromatosis

Hereditary hemochromatosis (HHC) is an inherited disorder of iron metabolism affecting approximately 1 in 200-300 individuals of Northern European descent. Over time, the continued deposition of iron in parenchymal cells of many organs can eventually lead to diabetes mellitus, cardiomyopathy, and hepatic cirrhosis, the last of which is frequently followed by hepatocellular carcinoma. Although the complications of HHC can be devastating, its clinical management is simple and effective if the disease is identified early in its progression. The recent elucidation of the HFE gene has provided insight into the pathogenesis of HHC and provided a means for the early identification of individuals in whom HHC may develop. Two mutations have been implicated in HHC: C282Y and H63D, The former occurs in a homozygous state seen in 75-100% of patients with HHC. The high correlation of HFE to HHC has caused it to be considered as a candidate gene for population-based genetic testing for diagnosis and detection of predisposition to HHC. In addition, mechanisms of iron transport and metabolism are unfolding and are providing clues to the enigma of iron homeostasis and the pathophysiology of iron overload, (C) 2001 Lippincott Williams & Wilkins, Inc.

Cloning and gastrointestinal expression of rat hephaestin: relationship to other iron transport proteins

The membrane-bound ceruloplasmin homolog hephaestin plays a critical role in intestinal iron absorption. The aims of this study were to clone the rat hephaestin gene and to examine its expression in the gastrointestinal tract in relation to other genes encoding iron transport proteins. The rat hephaestin gene was isolated from intestinal mRNA and was found to encode a protein 96% identical to mouse hephaestin. Analysis by ribonuclease protection assay and Western blotting showed that hephaestin was expressed at high levels throughout the small intestine and colon. Immunofluorescence localized the hephaestin protein to the mature villus enterocytes with little or no expression in the crypts. Variations in iron status had a small but nonsignificant effect on hephaestin expression in the duodenum. The high sequence conservation between rat and mouse hephaestin is consistent with this protein playing a central role in intestinal iron absorption, although its precise function remains to be determined.

Distinction between familial and sporadic forms of colorectal cancer showing DNA microsatellite instability

Attempts to classify colorectal cancer into subtypes based upon molecular characterisation are overshadowed by the classical stepwise model in which the adenoma-carcinoma sequence serves as the morphological counterpart. Clarity is achieved when cancers showing DNA microsatellite instability (MSI) are distinguished as sporadic MSI-low (MSI-L), sporadic MSI-high (MSI-H) and hereditary non-polyposis colorectal cancer (HNPCC). Divergence of the 'methylator' pathway into MSI-L and MSI-H is at least partly determined by the respective silencing of MGMT and hMLH1. Multiple differences can be demonstrated between sporadic and familial (HNPCC) MSI-H colorectal cancer with respect to early mechanisms, evolution, molecular characterisation, demographics and morphology. By acknowledging the existence of multiple pathways, rapid advances in the fields of basic and translational research will occur and this will lead to improved strategies for the prevention, early detection and treatment of colorectal cancer. (C) 2002 Elsevier Science Ltd. All rights reserved.

Evolution of colorectal cancer: Change of pace and change of direction

This review compiles evidence for an alternative to the classical adenoma-carcinoma sequence in the evolution of colorectal cancer. It is suggested that between 30 and 50% of colorectal cancers are not initiated by mutation of the tumor suppressor gene APC, but through the epigenetic silencing of genes implicated in the control of differentiation, cell cycle control and DNA repair proficiency. The precursor polyps are often characterized by a serrated architecture, and include hyperplastic polyps, admixed polyps and serrated adenomas. The alternative pathway is heterogeneous and may culminate in cancers showing low or high level DNA microsatellite instability (MSI-L and MSI-H, respectively), and in cancers that are microsatellite stable (MSS). Cancers showing DNA MSI may be characterized by an accelerated evolution. Cancers in hereditary non-polyposis colorectal cancer show features of both classical (adenoma and APC mutation) and alternative pathways (rapid evolution, MSI-H and lack of chromosomal instability). (C) 2001 Blackwell Science Asia Pty Ltd.

Emerging pathways in colorectal-cancer development

The past decade has seen the emergence of new pathways in the development of colorectal cancer. There is now clear evidence that subsets of these tumours do not show chromosomal instability and do not follow the suppressor pathway. Instead, about 15% of colorectal cancers are characterised by microsatellite instability (MSI). This feature arises through defective DNA mismatch repair, which is related either to a germline mutation (as in hereditary non-polyposis colorectal carcinoma) or to failure to express a mismatch-repair gene. CpG-island methylation has been linked to sporadic cancers with a high frequency of MSI. This type of methylation leads to loss of gene expression when it occurs in the promoter region of a gene. Tumours may have high or low type C (cancer-related) CpG-island methylation. When methylation affects hMLH1 (mismatch repair gene), the resultant cancer has high MSI.

A systematic study of the microwave and thermal cure kinetics of the DGEBA/DDS and DGEBA/DDM epoxy-amine resin systems

The microwave and thermal cure processes for the epoxy-amine systems (epoxy resin diglycidyl ether of bisphenol A, DGEBA) with 4,4'-diaminodiphenyl sulphone (DDS) and 4,4'-diaminodiphenyl methane (DDM) have been investigated for 1:1 stoichiometries by using fiber-optic FT-NIR spectroscopy. The DGEBA used was in the form of Ciba-Geigy GY260 resin. The DDM system was studied at a single cure temperature of 373 K and a single stoichiometry of 20.94 wt% and the DDS system was studied at a stoichiometry of 24.9 wt% and a range of temperatures between 393 and 443 K. The best values of the kinetic rate parameters for the consumption of amines have been determined by a least squares curve fit to a model for epoxy/amine cure. The activation energies for the polymerization of the DGEBA/DDS system were determined for both cure processes and found to be 66 and 69 kJ mol(-1) for the microwave and thermal cure processes, respectively. No evidence was found for any specific effect of the microwave radiation on the rate parameters, and the systems were both found to be characterized by a negative substitution effect. Copyright (C) 2002 John Wiley Sons, Ltd.

The Cys282Tyr polymorphism in the HFE gene in Australian Parkinson's disease patients

Iron homeostasis is altered in Parkinson's disease (PD). The HFE protein is an important regulator of cellular iron homeostasis and variations within this gene can result in iron overload and the disorder known as hereditary haemochromatosis. We studied the Cys282Tyr single nucleotide polymorphism as a genetic risk factor for PD in two distinct and separately collected cohorts of Australian PD patients and controls. In the combined cohort comprising 438 PD patients and 485 control subjects, we revealed an odds ratio for possession of the 282Tyr allele of 0.61 (95% confidence interval, Cl = 0.42-0.90, P = 0.011) from univariate chi-squared and 0.59 (95% Cl = 0.39-0.90, P = 0.014) after logistic regression analyses (correcting for potential confounding factors). These results suggest that possession of the 282Tyr allele may offer some protection against the development of PD. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

Familial adult renal neoplasia

Our understanding of the molecular mechanisms underlying the tumorigenesis of renal cell carcinoma (RCC) has partially come from studies of RCC related familial cancer syndromes such as von Hippel-Lindau (VHL) disease and hereditary papillary RCC (HPRC). These studies have led to the identification of RCC related genes, which, besides allowing accurate diagnosis of these diseases, have been found mutated or abnormally expressed in the sporadic counterparts of these familial renal tumours. To date, a number of renal tumour related syndromes have been described. We review recent advances in this field and discuss a genetic approach to managing familial cases of renal tumours occasionally encountered by cancer geneticists and urologists.

A population-based study of the biochemical and clinical expression of the H63D hemochromatosis mutation

Background & Aims: Two major mutations are defined within the hemochromatosis gene, HFE. Although the effects of the C282Y mutation have been well characterized, the effects of the H63D mutation remain unclear. We accessed a well-defined population in Busselton, Australia, and determined the frequency of the H63D mutation and its influence on total body iron stores. Methods: Serum transferrin saturation and ferritin levels were correlated with the H63D mutation in 2531 unrelated white subjects who did not possess the C282Y mutation. Results: Sixty-two subjects (2.1%) were homozygous for the H63D mutation, 711 (23.6%) were heterozygous, and 1758 (58.4%) were wild-type for the H63D mutation. Serum transferrin saturation was significantly increased in male and female H63D homozygotes and heterozygotes compared with wild-types. Serum ferritin levels within each gender were not influenced by H63D genotypes. Elevated transferrin saturation greater than or equal to45% was observed in a greater proportion of male H63D carriers than male wild-types. Male H63D homozygotes (9%) and heterozygotes (3%) were more likely to have both elevated transferrin saturation and elevated ferritin greater than or equal to300 ng/mL than male wild-types (0.7%). Homozygosity for H63D was not associated with the development of clinically significant iron overload. Conclusions: Presence of the H63D mutation results in a significant increase in serum transferrin saturation but does hot result in significant iron overload. In the absence of the C282Y mutation, the H63D mutation is not clinically significant.

Concordance of iron indices in homozygote and heterozygote sibling pairs in hemochromatosis families: implications for family screening

Background/Aims: Concordance of iron indices between same sex siblings homozygous for the cysteine-to-tyrosine substitution at amino acid 282 (C282Y) mutation suggests that the variable phenotype in hereditary hemochromatosis is caused by genetic factors. Concordance of iron indices between same-sex heterozygous sibling pairs would provide further evidence of genetic modifiers of disease expression, and guidance for family screening strategies of subjects heterozygous for the C282Y mutation. Methods: We compared the iron indices of 35 C282Y homozygous and 35 C282Y heterozygous same-sex sibling pairs. To clarify whether concordance between siblings was due to environmental or genetic factors we compared the iron indices of 164 C282Y homozygous-normal, same-sex dizygotic twins. Results: Serum ferritin (r = 0.50, P = 0.003), hepatic iron concentration (r = 0.61, P = 0.025) and hepatic iron index (r = 0.67, P = 0.01) were highly concordant in C282Y homozygotes. Heterozygote siblings were concordant for serum ferritin (r = 0.76, P = 0.0001) and transferrin saturation (r = 0.79, P = 0.0001). Homozygote-normal same-sex dizygotic twins were concordant for serum ferritin (r = 0.62, P = 0.0001) but not for transferrin saturation. Conclusions: Concordance of iron indices exists in C282Y homozygote and heterozygote sibling pairs. Siblings of expressing C282Y heterozygotes require phenotypic assessment. These data provide evidence for modifying genes influencing disease expression in hemochromatosis. (C) 2002 European Association for the Study of the Liver. Published by Elsevier Science B.V. All rights reserved.

Class benefits of AT1 antagonists in Type 2 diabetes with nephropathy

Diabetes mellitus has reached epidemic proportions in many countries and is the most common cause of end stage renal disease (ESRD). The angiotensin II receptor-1 (AT1) antagonists losartan and irbesartan have recently been evaluated as renoprotective agents in large clinical trials of patients with Type 2 diabetes and nephropathy. In the Reduction of End points in Non-insulin-dependent diabetes mellitus with the Angiotensin II Antagonist (RENAAL) study, losartan decreased the number of patients reaching the primary end point of a composite of measures of neuropathy. The relative risk reduction was ~ 15% with losartan and this was due to a reduction in both the doubling of creatinine concentration (25%) and of ESRD (28%) but not in death. In the Irbesartan Diabetic Nephropathy Trial (IDNT), the beneficial effect of irbesartan was mainly against the doubling of the baseline creatinine concentration (37% risk reduction) but there was also a 20% reduction in the onset of ESRD. Irbesartan had no effect on mortality. Beneficial effects occurred in addition to blood pressure being controlled by agents other than the AT1 antagonists. These clinical trials suggest that there may be a class renoprotective action with AT1 antagonists, although the mechanism is not clear. Patients with Type 2 diabetes and nephropathy should receive either an AT1 antagonist or the angiotensin converting enzyme inhibitor ramipril to ensure renoprotection.

Genetic structure of a population of Ganoderma boninense on oil palm

Ganoderma boninense (the causal agent of basal stem rot of oil palm in Papua New Guinea) has a tetrapolar mating system with multiple alleles. Investigations into the population structure of G. boninense, using interfertility between isolates as a marker, revealed that the population on oil palm was comprised predominantly of genetically distinct individuals, although a number of isolates were found to share single mating alleles. No direct hereditary relationship was found between isolates on neighbouring or spatially separated diseased palms, indicating that outcrossing had probably occurred over several generations in the founder population prior to colonization of oil palm. In this study, a total of 81 A and 83 B mating type alleles (factors) were detected with 18 allelic repeats at the A locus and 17 at the B locus. Alleles appeared to be randomly dispersed throughout the population in each study block, although there was a significantly (P

Tyrosinase-Cre mice for tissue-specific gene ablation in neural crest and neuroepithelial-derived tissues

This study describes the derivation of two new lines of transgenic mice that express Cre recombinase under the control of tyrosinase transcriptional elements. To determine the suitability of the Tyrosinase-Cre transgene for tissue-specific gene ablation studies, a fate map of Cre expression domains was determined using the Z/AP reporter strain. It was shown that Cre-expressing cells contribute to a wide array of neural crest and neuroepithelial-derived lineages. The melanocytes of the harderian gland and eye choroid, sympathetic cephalic ganglia, leptomeninges of the telencephalon, as well as cranial nerves (V), (VII), and (IX) are derived either fully or partly from Cre-expressing cephalic crest. The cells contributing to the cranial nerves were the first to exhibit Cre expression at E10.5 as they were migrating into the branchial arches. The melanocytes, chromaffin cells of the adrenal medulla, and dorsal root ganglia are derived from trunk neural crest that either express Cre or were derived from Cre-expressing precursors. An array of brain tissue including the basal forebrain, hippocampus, olfactory bulb, and the granule cell layer of the lateral cerebellum, as well as the retinal pigmented epithelium and glia of the optic nerve originate from Cre-expressing neuroepithelial cells. (C) 2003 Wiley-Liss, Inc.

Analysis of the mouse transcriptome for genes involved in the function of the nervous system

We analyzed the mouse Representative Transcript and Protein Set for molecules involved in brain function. We found full-length cDNAs of many known brain genes and discovered new members of known brain gene families, including Family 3 G-protein coupled receptors, voltage-gated channels, and connexins. We also identified previously unknown candidates for secreted neuroactive molecules. The existence of a large number of unique brain ESTs suggests an additional molecular complexity that remains to be explored. A list of genes containing CAG stretches in the coding region represents a first step in the potential identification of candidates for hereditary neurological disorders.

Disrupted hepcidin regulation in HFE-associated haemochromatosis and the liver as a regulator of body iron homoeostasis

Background The mechanisms responsible for disturbed iron homoeostasis in hereditary haemochromatosis are poorly understood. However, results of some studies indicate a link between hepcidin, a liver-derived peptide, and intestinal iron absorption, suggesting that this molecule could play a part in hepatic iron overload. To investigate this possible association, we studied the hepatic expression of the gene for hepcidin (HAMP) and a gene important in iron transport (IREG1) in patients with haemochromatosis, in normal controls, and in Hfe-knockout mice. Methods We extracted total RNA from the liver tissue of 27 patients with HFE-associated haemochromatosis, seven transplant donors (controls), and Hfe-knockout mice. HAMP and IREG1 mRNA concentrations were examined by ribonuclease protection assays and expressed relative to the housekeeping gene GAPD. Findings There was a significant decrease in HAMP expression in untreated patients compared with controls (5.4-fold, 95% CI 3.3-7.5; p