Variation in coumarin 7-hydroxylase activity associated with genetic polymorphism of cytochrome P450 2A6 and the body status of iron stores in adult Thai males and females

The relationships between catalytic activity of cytochrome P450 2A6 (CYP2A6), polymorphism of CYP2A6 gene, gender and levels of body iron stores were analysed in a sample group of 202 apparently healthy Thais, aged 1947 years. Eleven individuals were found to have high activity of CYP2A6, judged by the relatively large amounts (11.2-14.6 mg) of 7-hydroyxcoumarin (7-OHC) excreted 3 h following administration of 15 mg of coumarin. Ten individuals, however, did not excrete any 7-OHC. Of these 10, four were found to have no CYP2A6 gene (whole gene deletion; CYP2A6*4 allele). The frequency of the CYP2A6 alleles; *1A, *1B and *4 in the whole sample group was 52, 40 and 8% while the frequency of the CYP2A6 gene types; *1A/* 1A, *1A/* 1B, *1B/* 1B, *1A/* 4, *1BI* 4, *4/* 4 was 29, 41, 16, 7, 5 and 2%. Subjects having CYP2A6* 1A/* 1B gene-type group were found to have higher rates of coumarin 7-hydroxylation compared with those of the CYP2A6* 1B/* 1B and CYP2A6* 1A/* 4 gene types. The inter-individual variability in CYP2A6 catalytic activity was therefore attributed in part to the CYP2A6 genetic polymorphism. Variation in CYP2A6 activity in this sample group was not associated with gender but, interestingly, it did show an inverse association with plasma ferritin; an indicator of body iron stores. Higher rates of coumarin 7-hydroxylation were found in individuals with low body iron stores (plasma ferritin < 20 μg/l) compared with subjects having normal body iron store status. Subjects (n = 16) with iron overload (plasma ferritin > 300 mug/l) also tended to have elevated rates of coumarin 7-hydroxylation. These results suggest an increased CYP2A6 expression in subjects who have excessive body iron stores. Further investigations into the underlying factors that may lead to increased expression of CYP2A6 in association with abnormal body iron stores are currently in progress in our laboratory. Pharmacogenetics 12:241-249 (C) 2002 Lippincott Williams Wilkins.

Knowledge-based system on optimum design of liquid retaining structures with genetic algorithms

This paper delineates the development of a prototype hybrid knowledge-based system for the optimum design of liquid retaining structures by coupling the blackboard architecture, an expert system shell VISUAL RULE STUDIO and genetic algorithm (GA). Through custom-built interactive graphical user interfaces under a user-friendly environment, the user is directed throughout the design process, which includes preliminary design, load specification, model generation, finite element analysis, code compliance checking, and member sizing optimization. For structural optimization, GA is applied to the minimum cost design of structural systems with discrete reinforced concrete sections. The design of a typical example of the liquid retaining structure is illustrated. The results demonstrate extraordinarily converging speed as near-optimal solutions are acquired after merely exploration of a small portion of the search space. This system can act as a consultant to assist novice designers in the design of liquid retaining structures.

Genetic influences on cognitive processes associated with distraction: An event-related potential study of the slow wave

The efficiency of inhibitory control processes has been proposed as a mechanism constraining working-memory capacity. In order to investigate genetic influences on processes that may reflect interference control, event-related potential (ER-P) activity recorded at frontal sites, during distracting and nondistracting conditions of a working-memory task, in a sample of 509 twin pairs was examined. The ERP component of interest was the slow wave (SW). Considerable overlap in source of genetic influence was found, with a common genetic factor accounting for 37 - 45% of SW variance irrespective of condition. However, 3 - 8 % of SW variance in the distracting condition was influenced by an independent genetic source. These results suggest that neural responses to irrelevant and distracting information, that may disrupt working-memory performance, differ in a fundamental way from perceptual and memory-based processing in a working-memory task. Furthermore, the results are consistent with the view that cognition is a complex genetic trait influenced by numerous genes of small influence.

Increased hepatic iron concentration in nonalcoholic steatohepatitis is associated with increased fibrosis

Background & Aims: Nonalcoholic steatohepatitis (NASH) is a chronic liver disease that occasionally progresses to cirrhosis but usually has a benign course. The aim of this study was to investigate the role of the hemochromatosis mutation Cys282Tyr in development of the mild hepatic iron overload found in some patients with NASH and its association with hepatic damage in these patients. Methods: Fifty-one patients with NASH were studied. The presence of the Cys282Tyr mutation was tested in all patients, and the data were analyzed with respect to the histological grade of steatosis, inflammation, Perls' staining, hepatic iron concentration (HIC), and serum iron indices. Results: Thirty-one percent of patients with NASH were either homozygous or heterozygous for the Cys282Tyr mutation. This mutation was significantly associated with Perls' stain grade (P < 0.005), HIC (P < 0.005), and transferrin saturation percentage (P < 0.005) but not with serum ferritin levels. Linear regression analysis showed that increased hepatic iron (Perls' stain or HIC) had the greatest association with the severity of fibrosis (P < 0.0001). Conclusions: The Cys282Tyr mutation is responsible for most of the mild iron overload found in NASH and thus has a significant association with hepatic damage in these patients. Heterozygosity for the hemochromatosis gene mutation therefore cannot always be considered benign.

HLA class II antigens positively and negatively associated with hepatosplenic schistosomiasis in a Chinese population

To identify possible associations between host genetic factors and the onset of liver fibrosis following Schistosoma japonicum infection, the major histocompatibility class II alleles of 84 individuals living on an island (Jishan) endemic for schistosomiasis japonica in the Poyang Lake Region of Southern China were determined. Forty patients exhibiting advanced schistosomiasis, characterised by extensive liver fibrosis, and 44 age and sex-matched control subjects were assessed for the class II haplotypes HLA-DRBI and HLA-DQB1. Two HLA-DRB1 alleles, HLA-DRB1*0901 (P = 0.012) and *1302 (P = 0.039), and two HLA-DQB1 alleles, HLA-DQB1*0303 (P = 0.012) and *0609 (P = 0.037), were found to be significantly associated with susceptibility to fibrosis. These associated DRB1 and DQB1 alleles are in very strong linkage disequilibrium, with DRB1*0901-DQB1*0303 and DRB1*1302-DQB1*0609 found as: common haplotypes in this population. In contrast, the alleles HLA-DRB1*1501 (P = 0.025) and HLA-DQB 1*0601 (P = 0.022) were found to be associated with resistance to hepatosplenic disease. Moreover, the alleles DQB1*0303 and DRB1*0901 did not increase susceptibility in the presence of DQB1*0601, indicating that DQB1*0601 is dominant over DQB1*0303 and DRB1*0901. The study has thus identified both positive and negative associations between HLA class II alleles and the risk of individuals developing moderate to severe liver fibrosis following schistosome infection. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.

Abnormal extracellular matrix protein transport associated with increased apoptosis of vascular smooth muscle cells in Marfan syndrome and bicuspid aortic valve thoracic aortic aneurysm

Background - Marfan syndrome (MS) is a genetic disorder caused by a mutation in the fibrillin gene FBN1. Bicuspid aortic valve (BAV) is a congenital heart malformation of unknown cause. Both conditions are associated with ascending aortic aneurysm and premature death. This study examined the relationship among the secretion of extracellular matrix proteins fibrillin, fibronectin, tenascin, and vascular smooth muscle cell (VSMC) apoptosis. The role of matrix metalloproteinase (MMP)- 2 in VSMC apoptosis was studied in MS aneurysm. Methods and Results - Aneurysm tissue was obtained from patients undergoing surgery ( MS: 4 M, 1 F, age 27 - 45 years; BAV: 3 M, 2 F, age 28 - 65 years). Normal aorta from subjects with nonaneurysm disease was also collected ( 4 M, 1 F, age 23 - 93 years). MS and BAV aneurysm histology showed areas of cystic medial necrosis (CMN) without inflammatory infiltrate. Immunohistochemical study of cultured MS and BAV VSMC showed intracellular accumulation and reduction of extracellular distribution of fibrillin, fibronectin, and tenascin. Western blot showed no increase in expression of fibrillin, fibronectin, or tenascin in MS or BAV VSMC and increased expression of MMP-2 in MS VSMCs. There was 4-fold increase in loss of cultured VSMC incubated in serum-free medium for 24 hours in both MS ( 27 +/- 8%) and BAV ( 32 +/- 14%) compared with control ( 7 +/- 5%). Conclusions - In MS and BAV there is alteration in both the amount and quality of secreted proteins and an increased degree of VSMC apoptosis. Up-regulation of MMP-2 might play a role in VSMC apoptosis in MS VSMC. The findings suggest the presence of a fundamental cellular abnormality in BAV thoracic aorta, possibly of genetic origin.

Dizygotic twinning is not associated with methylenetetrahydrofolate reductase haplotypes

Background: Folate metabolism is critical to embryonic development, influencing neural tube defects (NTD) and recurrent early pregnancy loss. Polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR) have been associated with dizygotic (DZ) twinning through pregnancy loss. Methods: The C677T and A1298C polymorphisms in MTHFR were genotyped in 258 Australasian families (1016 individuals) and 118 Dutch families (462 individuals) of mothers of DZ twins and a population sample of 462 adolescent twin families (1861 individuals). Haplotypes were constructed from the alleles, and transmission of the MTHFR haplotypes to mothers of DZ twins and from parents to twins in the adolescent twin families analysed. Results: The C677T and A1298C were common in all three populations (frequencies > 0.29). There was strong linkage disequilibrium (D'=1) between the variants, showing that specific combinations of alleles (haplotypes) were transmitted together. Three haplotypes accounted for nearly all the variation. There was no evidence of any association between MTHFR genotype and twinning in mothers of twins, or of the loss of specific MTHFR genotypes during twin pregnancies. Conclusions: It is concluded that variation in twinning frequency is not associated with MTHFR genotype.

The estrogen receptor 1 G594A polymorphism is associated with migraine susceptibility in two independent case/control groups

Migraine is a painful and debilitating disorder with a significant genetic component. Steroid hormones, in particular estrogen, have long been considered to play a role in migraine, as variations in hormone levels are associated with migraine onset in many sufferers of the disorder. Steroid hormones mediate their activity via hormone receptors, which have a wide tissue distribution. Estrogen receptors have been localized to the brain in regions considered to be involved in migraine pathogenesis. Hence it is possible that genetic variation in the estrogen receptor gene may play a role in migraine susceptibility. This study thus examined the estrogen receptor 1 (ESRalpha) gene for a potential role in migraine pathogenesis and susceptibility. A population-based cohort of 224 migraine sufferers and 224 matched controls were genotyped for the G594A polymorphism located in exon 8 of the ESR1 gene. Statistical analysis indicated a significant difference between migraineurs and non-migraineurs in both the allele frequencies (P=0.003) and genotype distributions (P=0.008) in this sample. An independent follow-up study was then undertaken using this marker in an additional population-based cohort of 260 migraine sufferers and 260 matched controls. This resulted in a significant association between the two groups with regard to allele frequencies (P=8x10(-6)) and genotype distributions (P=4x10(-5)). Our findings support the hypothesis that genetic variation in hormone receptors, in particular the ESR1 gene, may play a role in migraine.

Markers associated with stalk number and suckering in sugarcane colocate with tillering and rhizomatousness QTLs in sorghum

Two important factors influencing sugar yield, the primary focus of sugarcane plant breeding programs, are stalk number and suckering. Molecular markers linked to both of these traits are sought to assist in the identification of high sugar yield, high stalk number, low-suckering sugarcane clones. In this preliminary mapping study, 108 progeny from a biparental cross involving two elite Australian sugarcane clones were evaluated at two sites for two years for both stalk number and suckering. A total of 258 DNA markers, including both restriction fragment length polymorphisms (RFLPs) and radio-labelled amplified fragments (RAFs), were scored and evaluated using single-factor analysis. Sixteen (7 RFLPs and 9 RAFs) and 14 (6 RFLPs and 8 RAFs) markers were identified that were significantly associated (P < 0.01) with stalk number and suckering, respectively, across both years and sites. The seven and six RFLP markers associated with stalk number and suckering, respectively, were generated by eight different RFLP probes, of which seven had been mapped in sorghum and (or) sugarcane. Of significant interest was the observation that all seven RFLP probes could be shown to be located within or near QTLs associated with tillering and rhizomatousness in sorghum. This observation highlights the usefulness of comparative mapping between sorghum and sugarcane and suggests that the identification of useful markers for stalk number and suckering in sugarcane would be facilitated by focussing on sorghum QTLs associated with related traits.

Evaluation of haplotypes associated with copper toxicosis in Bedlington Terriers in Australia

Objective-To evaluate the haplotype distribution associated with the copper toxicosis gene and the segregation of the mutated allele in a Bedlington Terrier population in Australia. Animals-131 Bedlington Terriers. Procedure-Samples of DNA and RNA were obtained from each dog. Genetic status of each dog was evaluated by use of the DNA markers C04107; single nucleotide polymorphism (SNP), which was adjacent to exon 2 of Murr1; and a deletion marker for exon 2. A subgroup of the study population was evaluated by use of biochemical and histologic techniques to elucidate the correlation between genotype and phenotype. Results-We identified a recombination between the C04107 marker and Murr1 and a variation in a nucleotide in the splice site of exon 2 in our Bedlington Terrier cohort. Furthermore, we identified a novel haplotype associated with copper toxicosis in this cohort. Conclusions and Clinical Relevance-Our findings indicate that the deletion of exon 2 was not the sole cause of copper toxicosis, although only exon 2 deletion of Murr1 has been responsible for copper toxicosis in Bedlington Terriers. Although we failed to find a novel mutation in our cohort, we identified an affected dog family with an intact exon 2. Furthermore, we found that an SNP in the 5' splicing site of exon 2 may or may not be associated with a novel mutation of the Murr1 gene or other genes. Loss of linkage between the C04107 marker and the Murr1 gene was also identified in a certain family of dogs.

Trait physiology and crop modelling as a framework to link phenotypic complexity to underlying genetic systems

New tools derived from advances in molecular biology have not been widely adopted in plant breeding for complex traits because of the inability to connect information at gene level to the phenotype in a manner that is useful for selection. In this study, we explored whether physiological dissection and integrative modelling of complex traits could link phenotype complexity to underlying genetic systems in a way that enhanced the power of molecular breeding strategies. A crop and breeding system simulation study on sorghum, which involved variation in 4 key adaptive traits-phenology, osmotic adjustment, transpiration efficiency, stay-green-and a broad range of production environments in north-eastern Australia, was used. The full matrix of simulated phenotypes, which consisted of 547 location-season combinations and 4235 genotypic expression states, was analysed for genetic and environmental effects. The analysis was conducted in stages assuming gradually increased understanding of gene-to-phenotype relationships, which would arise from physiological dissection and modelling. It was found that environmental characterisation and physiological knowledge helped to explain and unravel gene and environment context dependencies in the data. Based on the analyses of gene effects, a range of marker-assisted selection breeding strategies was simulated. It was shown that the inclusion of knowledge resulting from trait physiology and modelling generated an enhanced rate of yield advance over cycles of selection. This occurred because the knowledge associated with component trait physiology and extrapolation to the target population of environments by modelling removed confounding effects associated with environment and gene context dependencies for the markers used. Developing and implementing this gene-to-phenotype capability in crop improvement requires enhanced attention to phenotyping, ecophysiological modelling, and validation studies to test the stability of candidate genetic regions.

Cell death mechanisms associated with G(2) radiosensitivity in patients with prostate cancer and benign prostatic hyperplasia

Cells respond to genotoxic insults such as ionizing radiation by halting in the G(2) phase of the cell cycle. Delayed cell death (mitotic death) can occur when the cell is released from G(2), and specific spindle defects form endopolyploid cells (endoreduplication/tetraploidy). Enhanced G(2) chromosomal radiosensitivity has been observed in many cancers and genomic instability syndromes, and it is manifested by radiation-induced chromatid aberrations observed in lymphocytes of patients. Here we compare the G(2) chromosomal radiosensitivity in prostate patients with benign prostatic hyperplasia (BPH) or prostate cancer with disease-free controls. We also investigated whether there is a correlation between G(2) chromosomal radiosensitivity and aneuploidy (tetraploidy and endoreduplication), which are indicative of mitotic cell death. The G(2) assay was carried out on all human blood samples. Metaphase analysis was conducted on the harvested chromosomes by counting the number of aberrations and the mitotic errors (endoreduplication/tetraploidy) separately per 100 metaphases. A total of 1/14 of the controls were radiosensitive in G(2) compared to 6/15 of the BPH patients and 15/17 of the prostate cancer patients. Radiation-induced mitotic inhibition was assessed to determine the efficacy of G(2) checkpoint control in the prostate patients. There was no significant correlation of G(2) radiosensitivity scores and mitotic inhibition in BPH patients (P = 0.057), in contrast to prostate cancer patients, who showed a small but significant positive correlation (P = 0.029). Furthermore, there was no significant correlation between G(2) radiosensitivity scores of BPH patients and endoreduplication/ tetraploidy (P = 0.136), which contrasted with an extremely significant correlation observed in prostate cancer patients (P < 0.0001). In conclusion, cells from prostate cancer patients show increased sensitivity to the induction of G(2) aberrations from ionizing radiation exposure but paradoxically show reduced mitotic indices and aneuploidy as a function of aberration frequency.