Different NK cell surface phenotypes defined by the DX9 antibody are due to KIR3DL1 gene polymorphism.
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KIR3DL1 and KIR3DL2 are NK cell receptors for polymorphic HLA-B and -A determinants. The proportion of NK cells that bind anti-KIR3DL1-specific Ab DX9 and their level of binding vary between individuals. To determine whether these differences are due to KIR polymorphism, we assessed KIR3D gene diversity in unrelated individuals and families. Both KIR3DL1 and KIR3DL2 are highly polymorphic genes, with KIR3DS1 segregating like an allele of KIR3DL1. A KIR haplotype lacking KIR3DL1 and KIR3DS1 was defined. The two KIR3DL1 alleles of a heterozygous donor were expressed by different, but overlapping, subsets of NK cell clones. Sequence variation in KIR3DL1 and KIR3DL2 appear distinct; recombination is more evident in KIR3DL1, and point mutation is more evident in KIR3DL2. The KIR3DL1 genotype correlates well with levels of DX9 binding by NK cells, but not with the frequency of DX9-binding cells. Different KIR3DL1 alleles determine high, low, and no binding of DX9 Ab. Consequently, heterozygotes for high and low binding KIR3DL1 alleles have distinct subpopulations of NK cells that bind DX9 at high and low levels, giving characteristic bimodal distributions in flow cytometry. The Z27 Ab gave binding patterns similar to those of DX9. Four KIR3DL1 alleles producing high DX9 binding phenotypes were distinguished from four alleles producing low or no binding phenotypes by substitution at one or more of four positions in the encoded protein: 182 and 283 in the extracellular Ig-like domains, 320 in the transmembrane region, and 373 in the cytoplasmic tail. (+info)
Premature atherosclerosis associated with monogenic insulin resistance.
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BACKGROUND: The common insulin resistance syndrome, with obesity, dyslipidemia, hyperglycemia, and hypertension, is associated with increased risk of atherosclerosis. Early atherosclerosis in rare monogenic forms of insulin resistance, however, has not been extensively documented. Cardiovascular end points were thus evaluated in subjects with Dunnigan-type familial partial lipodystrophy (FPLD) due to mutations at LMNA codon 482. METHODS AND RESULTS: FPLD subjects >/=35 years old were stratified by genotype for either the LMNA R482Q or R482W mutation. Twenty-three subjects were heterozygous mutation carriers, and 17 were R482/R482 homozygous family control subjects. All LMNA mutation carriers had FPLD with insulin resistance. In addition, LMNA mutation carriers had significantly more type 2 diabetes, hypertension, and dyslipidemia than normal family control subjects. Eight LMNA mutation carriers had coronary heart disease (CHD), compared with 1 normal control subject (OR 5.9, 95% CI 1.2 to 30.2). Six LMNA mutation carriers had CHD end points before age 55 years, and 4 of these, all women, had been hospitalized for CABG surgery between the ages of 35 and 54 years. CONCLUSIONS: Rare LMNA mutations that underlie FPLD with insulin resistance and hyperinsulinemia are also associated with early CHD, notably in women. This suggests that abnormalities of the nuclear envelope can result in a phenotype that recapitulates most of the important attributes of the common insulin resistance syndrome, including accelerated cardiovascular disease. FPLD thus appears to be an appropriate human monogenic model for the common insulin resistance syndrome. (+info)
Complement component C3 is not required for full expression of immune complex glomerulonephritis in MRL/lpr mice.
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Complement activation and tissue deposition of complement fragments occur during disease progression in lupus nephritis. Genetic deficiency of some complement components (e.g., Factor B) and infusion of complement inhibitors (e.g., Crry, anti-C5 Ab) protect against inflammatory renal disease. Paradoxically, genetic deficiencies of early components of the classical complement pathway (e.g., C1q, C4, and C2) are associated with an increased incidence of lupus in humans and lupus-like disease in murine knockout strains. Complement protein C3 is the converging point for activation of all three complement pathways and thus plays a critical role in biologic processes mediated by complement activation. To define the role of C3 in lupus nephritis, mice rendered C3 deficient by targeted deletion were backcrossed for eight generations to MRL/lpr mice, a mouse strain that spontaneously develops lupus-like disease. We derived homozygous knockout (C3(-/-)), heterozygous (C3(+/-)), and C3 wild-type (C3(+/+)) MRL/lpr mice. Serum levels of autoantibodies and circulating immune complexes were similar among the three groups. However, there was earlier and significantly greater albuminuria in the C3(-/-) mice compared with the other two groups. Glomerular IgG deposition was also significantly greater in the C3(-/-) mice than in the other two groups, although overall pathologic renal scores were similar. These results indicate that C3 and/or activation of C3 is not required for full expression of immune complex renal disease in MRL/lpr mice and may in fact play a beneficial role via clearance of immune complexes. (+info)
An insertion/deletion polymorphism in the alpha2B-adrenergic receptor gene is a novel genetic risk factor for acute coronary events.
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OBJECTIVES: Our aim was to study whether an insertion/deletion (I/D) polymorphism in the alpha2B-adrenoceptor gene is associated with the risk for cardiovascular diseases. BACKGROUND: alpha2-adrenoceptors mediate contraction of vascular smooth muscle and induce coronary vasoconstriction in humans. The alpha2-adrenoceptor subtype B mediates vasoconstriction in mice. A variant of the human alpha2B-adrenoceptor gene that encodes a D of three residues in an intracellular acidic motif has been shown to confer decreased receptor desensitization. This receptor variant could, therefore, be involved in diseases associated with enhanced vasoconstriction. METHODS: This study was part of a prospective population-based study investigating risk factors for cardiovascular diseases in a cohort of middle-aged men from eastern Finland. Nine hundred twelve men aged 46 to 64 years were followed for an average time of 4.5 years. RESULTS: In this study population, 192 men (21%) had the D/D genotype; 256 (28%) had the I/I genotype, and 464 (51%) had a heterozygous genotype. In a Cox model adjusting for other coronary risk factors, men with the D/D genotype had 2.2 times (95% confidence interval: 1.1 to 4.4, p = 0.02) the risk to experience an acute coronary event (n = 15 for D/D, 10 for I/I and 12 for I/D) compared with men carrying either of the other two genotypes. The alpha2B-adrenoceptor genotype was not associated with hypertension in this study population. CONCLUSIONS: The D/D genotype of the alpha2B-adrenoceptor is a novel genetic risk factor for acute coronary events, but not for hypertension. (+info)
CDX2 mutations do not account for juvenile polyposis or Peutz-Jeghers syndrome and occur infrequently in sporadic colorectal cancers.
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Peutz-Jeghers syndrome (PJS) and juvenile polyposis (JPS) are both characterized by the presence of hamartomatous polyps and increased risk of malignancy in the gastrointestinal tract. Mutations of the LKB1 and SMAD4 genes have been shown recently to cause a number of PJS and JPS cases respectively, but there remains considerable uncharacterized genetic heterogeneity in these syndromes, particularly JPS. The mouse homologue of CDX2 has been shown to give rise to a phenotype which includes hamartomatous-like polyps in the colon and is therefore a good candidate for JPS and PJS cases which are not accounted for by the SMAD4 and LKB1 genes. By analogy with SMAD4, CDX2 is also a candidate for somatic mutation in sporadic colorectal cancer. We have screened 37 JPS families/cases without known SMAD4 mutations, 10 Peutz-Jeghers cases without known LKB1 mutations and 49 sporadic colorectal cancers for mutations in CDX2. Although polymorphic variants and rare variants of unlikely significance were detected, no pathogenic CDX2 mutations were found in any case of JPS or PJS, or in any of the sporadic cancers. (+info)
Cytochrome P450 2E1 polymorphism and nasopharyngeal carcinoma development in Thailand: a correlative study.
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BACKGROUND: Nasopharyngeal carcinoma (NPC) is a rare tumor in most parts of the world but occurs at relatively high frequency among people of Chinese descent. The cytochrome P450 2E1 enzyme (CYP2E1) is responsible for the metabolic activation of nitrosamines, and has been shown to be a susceptibility gene for NPC development in Taiwan [RR = 2.6; 95%CI = 1.2-5.7]. Since there has been only one report of this link, it was decided to investigate the susceptibility of CYP2E1 to NPC development in other populations. Therefore, the correlation between the RsaI polymorphism of this gene and NPC was studied in-patients including Thai and Chinese in Thailand. The present study comprised 217 cases diagnosed with NPC and 297 healthy controls. RESULTS: Similar to the result found in Taiwanese, a homozygous uncut genotype demonstrated a higher relative risk both when all cases were analyzed [RR = 2.19; 95%CI = 0.62-8.68] or individual racial groups, Thai [RR = 1.51; 95%CI = 0.08-90.06] or Chinese [RR = 1.99; 95%CI = 0.39-10.87]. The ethnicity-adjusted odds ratio is 2.39 with 95%CI, 0.72-7.89. CONCLUSIONS: Though our finding was not statistically significant due to the moderate sample size of the study, similarity to the study in Taiwan with only a slight loss in precision was demonstrated. The higher RR found for the same genotype in distinct populations confirmed that CYP2E1 is one of several NPC susceptibility genes and that the RsaI minus variant is one mutation that affects phenotype. (+info)
Cost-effectiveness of screening and extended anticoagulation for carriers of both factor V Leiden and prothrombin G20210A.
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Carriers of a double thrombophilic mutation (factor V Leiden and prothrombin G20210A) are at high risk of a recurrent venous thromboembolism (VTE), and may benefit from a longer course of secondary prophylaxis. We examined the costs and health benefits of screening for both the mutations, provided that double heterozygotes undergo 2 years of anticoagulation as compared to the standard 6 months. We thus pooled the available evidence and calculated that the OR for recurrence in double heterozygotes was 5.9 (95% CI 2.65-13.20). A Markov model tracked patients' health lifelong, and calculated that prolonged prophylaxis saved 26 quality-adjusted days of life and $410 per double heterozygote treated. Screening all the patients with venous thromboembolism thus provided one additional day of life at the cost of 13624 $/QALY (95% CI 12 965-22 889). Screening was not cost-effective in those cohorts with a low prevalence of the mutations, a high bleeding risk or in those where prophylaxis prevented <65% of recurrences. Screening for factor V Leiden and prothrombin G20210A, with prolonged prophylaxis of double carriers, is cost-effective in most patients with VTE. (+info)
Role of the serotonin transporter gene in the behavioral expression of autism.
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The promoter polymorphism of the serotonin transporter gene (HTT, locus SLC6A4) is of special interest in autism given the well-replicated platelet hyperserotonemia of autism, treatment effects of serotonin reuptake inhibitors, and the role of serotonin in limbic functioning and neurodevelopment. Parent-offspring transmission of the long (l) and short (s) alleles of the deletion/insertion polymorphism in the HTT promoter region was examined in families of 71 children with autism using the transmission test for linkage disequilibrium (TDT). Transmission of HTT promoter alleles did not differ between probands with autism and their unaffected siblings. However, allelic transmission in probands was dependent upon severity of impairments in the social and communication domains, with greater s allele transmission in severely impaired individuals and greater l transmission in mild/moderately impaired individuals. This relationship between HTT promoter alleles and severity of autistic impairment was also seen when ratings of social and communication behaviors were compared across genotypes. The data indicate that HTT promoter alleles by themselves do not convey risk for autism, but, rather, modify the severity of autistic behaviors in the social and communication domains. The results require replication and, given the size of the groups and subgroups examined, must be considered still preliminary. The results suggest that future research on the genetics of autism should carefully assess each of the major behavioral domains and seriously consider the possible role of modifying loci. (+info)