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Hydraulic model of myogenic autoregulation and the cerebrovascular bed: the effects of altering systemic arterial pressure.

Systemic arterial (Ps), cerebrospinal fluid (Pcsf), and sagittal sinus (Pss) pressures were measured in 39 dogs divided into eight groups in which Ps was altered pharmacologically or by bleeding. The pharmaceuticals used were norepinephrine (N-EP), dopamine (DOP), sodium nitroprusside (SNP), and nitroglycerin (NTG). SNP and NTG were examined with and without methohexital (MHX) anesthesia and during chronic infusion and bolus injection. The various pressures were subjected to systems analysis in accordance with a previously published model of myogenic autoregulation. Myogenic autoregulation seemed to be impaired only during infusions of N-EP, DOP, and SNP without MHX and during hypovolemic hypotension. The various observed changes in Pcsf are explained by using a hydraulic model of the cerebrovascular bed in which Pcsf represents the pressure drop across the outflow resistance of the bridging veins and lateral lacunae and myogenic autoregulation at the arteries and arterioles represents the major inflow resistance. Impaired myogenic autoregulation is associated with a rise in Pcsf. In addition, variation in pulse pressure is demonstrated to be related to the arterial pulse pressure and the degree of arterial and arteriolar vasodilation.

Animals↗

Bioinformatics approaches and resources for single nucleotide polymorphism functional analysis.

Since the initial sequencing of the human genome, many projects are underway to understand the effects of genetic variation between individuals. Predicting and understanding the downstream effects of genetic variation using computational methods are becoming increasingly important for single nucleotide polymorphism (SNP) selection in genetics studies and understanding the molecular basis of disease. According to the NIH, there are now more than four million validated SNPs in the human genome. The volume of known genetic variations lends itself well to an informatics approach. Bioinformaticians have become very good at functional inference methods derived from functional and structural genomics. This review will present a broad overview of the tools and resources available to collect and understand functional variation from the perspective of structure, expression, evolution and phenotype. Additionally, public resources available for SNP identification and characterisation are summarised.

Algorithms↗

Lowered pulmonary arterial pressure prevents edema after endotoxin in sheep.

Escherichia coli endotoxin causes increased capillary membrane permeability and increased pulmonary arterial pressure (PAP) in sheep. If the pulmonary hypertension extends to the level of the microvasculature, then the increased microvascular pressure may contribute to the pulmonary edema caused by endotoxin. We tested the hypothesis that reducing the pulmonary hypertension would reduce the amount of edema caused by endotoxin. Twelve sheep were chronically instrumented with catheters to measure PAP, left atrial pressure, and central venous pressure. The sheep were divided into two groups. One group (E) of six sheep received an intravenous infusion of 4 micrograms/kg of E. coli endotoxin. The second group (E + SNP) received the same dose of endotoxin as well as a continuous infusion of sodium nitroprusside (SNP) to reduce PAP. Three hours after the endotoxin infusions, the sheep were terminated and the extravascular fluid-to-blood-free dry weight ratios of the lungs were determined (EVF). The base-line PAP was 17.5 +/- 2.7 mmHg. A two-way analysis of variance demonstrated a significant difference (P less than 0.01) in PAP between the E and E + SNP groups. Although PAP in each group varied as a function of time, the difference between the two groups did not. The mean PAP for the E + SNP group (20.9 +/- 1.5 mmHg) was lower than the E group PAP of 27.3 +/- 2.1 mmHg after the endotoxin spike. Furthermore, the E + SNP group EVF (3.9 +/- 0.2) was significantly less than the EVF of the E group (4.7 +/- 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Haplotype transmission analysis provides evidence of association for DISC1 to schizophrenia and suggests sex-dependent effects.

We have previously reported a linkage peak on 1q42 in a Finnish schizophrenia sample. In this study we genotyped 28 single nucleotide polymorphisms (SNPs) from 1q42 covering the three candidate genes TRAX, DISC1 and DISC2, using a study sample of 458 Finnish families ascertained for schizophrenia. Two-point and haplotype association analysis revealed a significant region of interest within the DISC1 gene. A common haplotype (HEP3) was observed to be significantly under-transmitted to affected individuals (P=0.0031). HEP3 represents a two SNP haplotype spanning from intron 1 to exon 2 of DISC1. This haplotype also displayed sex differences in transmission distortion, the under-transmission being significant only to affected females (P=0.00024). Three other regions of interest were observed in the TRAX and DISC genes. However, analysis of only those families with complete genotype information specifically highlights the HEP3 haplotype as a true observation. The finding of a common under-transmitted SNP haplotype might imply that this particular allele offers some protection from the development of schizophrenia. Analysis of component-traits of schizophrenia, derived from the Operational Criteria Checklist of Psychotic Illness (OCCPI), displayed association of HEP3 to features of the general phenotype of schizophrenia, including traits representing delusions, hallucinations and negative symptoms. This study provides further evidence for the hypothesis that the DISC1 gene is involved in the aetiology of schizophrenia, and implies a putative sex difference for the effect of the gene. Our findings would also encourage more detailed analyses of the effect of DISC1 on the component-traits of schizophrenia.

Female↗

ARTS: a web-based tool for the set-up of high-throughput genome-wide mapping panels for the SNP genotyping of mouse mutants.

Genome-wide mapping in the identification of novel candidate genes has always been the standard method in genetics and genomics to correlate a clinically interesting phenotypic trait with a genotype. However, the performance of a mapping experiment using classical microsatellite approaches can be very time consuming. The high-throughput analysis of single-nucleotide polymorphisms (SNPs) has the potential of being the successor of microsatellite analysis routinely used for these mapping approaches, where one of the major obstacles is the design of the appropriate SNP marker set itself. Here we report on ARTS, an advanced retrieval tool for SNPs, which allows researchers to comb freely the public mouse dbSNP database for multiple reference and test strains. Several filters can be applied in order to improve the sensitivity and the specificity of the search results. By employing the panel generator function of this program, it is possible to abbreviate the extraction of reliable sequence data for a large marker panel including several different mouse strains from days to minutes. The concept of ARTS is easily adaptable to other species for which SNP databases are available, making it a versatile tool for the use of SNPs as markers for genotyping. The web interface is accessible at http://andromeda.gsf.de/arts.

Animals↗

Association study of 12 polymorphisms spanning the dopamine D(2) receptor gene and clozapine treatment response in two treatment refractory/intolerant populations.

RATIONALE: Dopamine D(2) receptor blockade is the major basis for the antipsychotic action of typical antipsychotic drugs (AP) and a necessary but not sufficient basis for the antipsychotic action of atypical APs such as clozapine and other multireceptor antagonists which rely, in part, upon 5-HT(2A) antagonism. Genetic factors affecting the density and/or function of D(2) receptors may therefore affect AP response. OBJECTIVES: This exploratory study investigates the effect of 12 single nucleotide polymorphisms (SNPs) spanning the entire dopamine D(2) gene on clozapine response in two distinct schizophrenic populations (Caucasian and African-American) refractory or intolerant to conventional APs. METHODS: This study included 183 Caucasian and 49 African-American DSM-III-R or DSM-IV schizophrenics. Genotyping was determined by 5'-exonuclease fluorescence assays. Within each population genotype, allele, allele +/-, and haplotype frequencies were compared between responders and non-responders by X (2) tests. Linkage disequilibrium analysis was also performed. RESULTS: In the Caucasian sample, no significant associations were found for individual SNP tests; however, two haplotypes were identified as having significant protective effects on treatment outcome. In the African-American sample, individual SNP tests identified the Taq1A, Taq1B, and rs1125394 markers as being predictive of clozapine response. Haplotype analyses identified four protective haplotypes containing these SNPs. In addition, no association between the -141C Ins/Del site and clozapine response was found in either population. CONCLUSIONS: Interindividual variability in clozapine response among treatment refractory/intolerant patients is still not fully understood and likely involves multiple factors. This exploratory analysis suggests that the D(2) receptor gene may be one such factor.

Adult↗

Generation of co-dominant PCR-based markers by duplex analysis on high resolution gels.

Rapid and efficient procedures for the detection of sequence polymorphisms are essential for chromosomal walking and mutation detection analyses. While DNA chip technology and denaturing high-performance liquid chromatography (DHPLC) are the methods of choice for large scale facilities, small laboratories are dependent on simple ready-to-use techniques. We show that heteroduplex analysis on high resolution gel matrices efficiently detects sequence polymorphism differing as little as a single base pair (e.g. single-nucleotide polymorphism, SNP) with standard laboratory equipment. Furthermore, the matrices also discerned differences between homoduplexes, a prerequisite for co-dominant markers. The markers thus generated are referred to as duplex analysis markers. We designed PCR primers for 36 Arabidopsis thaliana loci ranging in length from 230 bp to 1000 bp. Among three ecotypes, more than half (n = 19) of the loci examined were polymorphic; five of which contained three different alleles. This simple, high resolution technique can be used to rapidly convert sequence tagged sites into co-dominant PCR-based molecular markers for fine-scale mapping studies and chromosomal walking strategies as well as for the detection of mutations in particular genes.

Alleles↗

Genetic-epigenetic interactions (meQTLs) in orofacial clefts etiology.

Understanding how genetic variants influence disease risk through molecular mechanisms remains a central challenge in complex disease genetics. Nonsyndromic orofacial clefts (OFCs) exemplify this challenge, with most risk loci residing in non-coding regions. We hypothesized that common genetic variants influence OFC risk by modulating DNA methylation at regulatory elements through methylation quantitative trait loci (meQTLs). We analyzed 10 OFC-associated SNPs against genome-wide DNA methylation profiles in 409 cases and 456 controls, identifying 23 potential meQTLs. Findings were validated using 358 cleft-discordant sibling pairs with MethyLight assays. We performed formal mediation analysis, genotype-tissue interaction and cross-referenced with the mQTL Database to assess developmental timing. Nine meQTLs were validated, including rs987525 (8q24)-cg16561172 (MYC) (P = 9.6 × 10⁻⁶), which mapped to a mesendoderm-active enhancer upstream of MYC. Genotype × tissue interaction confirmed tissue-specificity (P = 1.00 × 10- 3), with stronger effects in oral-derived tissue (saliva). Additional validated SNP-CpG associations involved MAFB-PLCG1, NOG-PPM1E, FOXE1-FRZB, and SPRY2-LGR4. While effect sizes correlated between tissues (r = 0.81), formal mediation analysis indicated individual CpG sites do not fully mediate SNP-phenotype relationships, suggesting coordinated epigenetic mechanisms. Most associations showed peak effects during childhood, while 8q24 showed unique adult-specific patterns. We identified genetic variants influencing methylation at craniofacial regulatory elements, and provided a mechanistic link for a major risk locus, 8q24, with tissue-specific effects in saliva. While individual CpG sites did not fully mediate the genetic risk, our findings identified specific regulatory regions where coordinated epigenetic changes may contribute to OFC susceptibility.

Humans↗

Polymorphisms in the CYP19 gene confer increased risk for Alzheimer disease.

BACKGROUND: Brain aromatase may be neuroprotective by increasing the local estrogen levels in injured neurons. Aromatase is encoded by the CYP19 gene located at 15q21.1, a chromosomal region in linkage disequilibrium (LD) with Alzheimer disease (AD) in this sample. OBJECTIVE: To investigate whether nine single-nucleotide polymorphisms (SNP) spanning the CYP19 gene were associated with AD. METHODS: Three hundred ninety-four patients were compared with 469 nondemented control subjects using single-locus and haplotype approaches. Haplotypes were identified using the expectation/maximization algorithm and latent class analysis, which included additional information on age, sex, and APOE polymorphism. RESULTS: Allelic and genotypic frequencies for three adjacent SNP differed between AD and control groups. Both haplotype approaches identified an approximately 60% increase (p = 0.02) in the risk of AD for one haplotype and similar levels of excess risk irrespective of APOE polymorphism and gender. CONCLUSION: Genetic variation in the brain aromatase gene may modify the risk for AD.

Adult↗

Association of TCF7L2 and LEPR gene variants (rs7903146 and rs1137101) with primary knee osteoarthritis in a northern Mexican Mestizo population.

INTRODUCTION: There is a growing interest in the study of Obesity, Diabetes, and their genetic polymorphisms for the risk of developing osteoarthritis. This study analyzed the associations among the rs1137101 LEPR gene and rs7903146 polymorphisms TCF7L2 gene with primary knee osteoarthritis in a population from northern Mexico. METHODS: We conducted a case-control study with 438 Mexican Mestizo participants, selected non-randomly by convenience. We included age, diabetes, and body mass index for analysis. The presence of the TCF7L2 (n = 236) and LEPR (n = 405) gene genotypes was determined using real-time PCR with the rhAmpTM SNP Assay methodology. We performed comparisons between groups using the chi-square test, Fisher´s exact test, the Mann-Whitney U test, and adjusted regression model analysis. RESULTS: The CC genotype of the rs7903146 ​​polymorphism was significantly associated as risk factor with obesity (p = 0.043; OR 2.021, CI 1.023 - 3.989) and CT genotype as a protective factor (p = 0.016, p = 0.013, and p = 0.008); the CC genotype was significantly associated with primary KOA as a risk factor (p = 0.040; OR 2.061, CI 1.034 - 4.107) and the CT genotype as a protective factor (p = 0.039, and p = 0.041; OR 0.480, CI 0.237 - 0.970). No association was found between the genotypes for LEPR rs1137101 and KOA. CONCLUSION: This study suggests a possible role for the rs7903146 ​​polymorphism of the TCF7L2 gene, in the risk of primary KOA and obesity. We suggest conducting additional studies with a larger population sample, including other polymorphisms of the same genes in different ethnic groups, to corroborate the findings shown in this study. Key Points • We observed significant associations for obesity and primary knee osteoarthritis in the presence of the rs7903146 CC and CT genotypes.

LEPR↗

Distinct haplotype profiles and strong linkage disequilibrium at the MDR1 multidrug transporter gene locus in three ethnic Asian populations.

The MDR1 multidrug transporter plays a key role in determining drug bioavailability, and differences in drug response exist amongst different ethnic groups. Numerous studies have identified an association between the MDR1 single nucleotide polymorphism (SNP) exon 26 3435C>T and differences in MDR1 function. We performed a haplotype analysis of the MDR1 gene in three major ethnic groups (Chinese, Malays and Indians) by examining 10 intragenic SNPs. Four were polymorphic in all three ethnic groups: one occurring in the non-coding region and three occurring in coding exons. All three coding SNPs (exon 12 1236C>T, exon 21 2677G>T/A and exon 26 3435C>T) were present in high frequency in each ethnic group, and the derived haplotype profiles exhibited distinct differences between the groups. Fewer haplotypes were observed in the Malays (n = 6) compared to the Chinese (n = 10) and Indians (n = 9). Three major haplotypes (> 10% frequency) were observed in the Malays and Chinese; of these, two were observed in the Indians. Strong linkage disequilibrium (LD) was detected between the three SNPs in all three ethnic groups. The strongest LD was present in the Chinese, followed by Indians and Malays, with the corresponding LD blocks estimated to be approximately 80 kb, 60 kb and 40 kb, respectively. These data strongly support the hypothesis that strong LD between the neutral SNP exon 26 3435C>T and a nearby unobserved causal SNP underlies the observed associations between the neutral SNP and MDR1 functional differences. Furthermore, strong LD between exon 26 3435T and different unobserved causal SNPs in different study populations may provide a plausible explanation for conflicting reports associating the same exon 26 3435T allele with different MDR1 functional changes.

5' Untranslated Regions↗

Development of PCR-based SNP markers for rice blast resistance genes at the Piz locus.

We assessed the utility of single-nucleotide polymorphisms (SNPs) and small insertion/deletion polymorphisms (InDels) as DNA markers in genetic analysis and breeding of rice. Toward this end, we surveyed SNPs and InDels in the chromosomal region containing the Piz and Piz-t rice blast resistance genes and developed PCR-based markers for typing the SNPs. Analysis of sequences from a blast-susceptible Japanese cultivar and two cultivars each containing one of these genes revealed that SNPs are abundant in the Piz and Piz-t regions (on average, one SNP every 248 bp), but the number of InDels was much lower. The dense distribution of SNPs facilitated the generation of SNP markers in the vicinity of the genes. For typing these SNPs, we used a modified allele-specific PCR method. Of the 49 candidate allele-specific markers, 33 unambiguously and reproducibly discriminated between the two alleles. We used the markers for mapping the Piz and Piz-t genes and evaluating the size of DNA segments introgressed from the Piz donor cultivar in Japanese near-isogenic lines containing Piz. Our findings suggest that, because of its ability to generate numerous markers within a target region and its simplicity in assaying genotypes, SNP genotyping with allele-specific PCR is a valuable tool for gene mapping, map-based cloning, and marker-assisted selection in crops, especially rice.

Base Sequence↗

A novel single-nucleotide polymorphism in the 3'-untranslated region of the human dihydrofolate reductase gene with enhanced expression.

A novel single-nucleotide polymorphism (SNP), 829C-->T in the 3'-untranslated region of the human dihydrofolate reductase (DHFR) gene transcript, was identified in the study population of 37 patients with childhood leukemias/lymphomas and 83 healthy Japanese children. Frequencies of the DHFR 829C/C, 829C/T, and 829T/T genotypes were 83.8, 10.8, and 5.4%, respectively, in the cases and 74.7, 19.3, and 6.0% in the controls, showing no significant difference in genotype frequencies between the cases and controls. When determined by real-time quantitative reverse transcription-PCR analysis, the highest expression of the DHFR transcript was demonstrated in the samples with a DHFR 829T/T polymorphism (P < 0.001). Direct association of the presence of the SNP with methotrexate-related adverse events in each patient was not demonstrated in this limited analysis. These data suggest that the novel DHFR 829 polymorphism is associated with a positive role in gene expression and provide evidence of a functional SNP in the 3' regulatory region of the gene.

3' Untranslated Regions↗

Synergistic disaggregation of platelets by the products of endothelial cells or their analogs.

It is known that some products of endothelial cells or their analogs can attenuate the platelet aggregation response and initiate the platelet disaggregation response. Since platelets are involved in the initiation of many clinically important occlusive vascular diseases, we hypothesized that the endothelial cell products act synergistically to disperse platelet aggregates. In this study we examined the synergistic platelet disaggregating effects among the products of endothelial cells. We used urokinase, prostaglandin I2 (PGI2), and sodium nitroprusside (SNP) (which is the chemical substitute as nitric oxide(NO)-donor) for endothelium-derived relaxing factor (EDRF). Platelet disaggregation rate was increased in a dose-dependent manner and decreased in a time-dependent manner, and the combined use of two or three agents had synergistic effects on platelet disaggregation. Furthermore, flow cytometric analysis showed decreases in the binding of fibrinogen to activated platelets by the addition of PGI2 or SNP. These data revealed that these products or their analogs could inactivate the activated platelets or aggregated platelets by detaching fibrinogen from platelets. In addition our data revealed that PGI2 and SNP can act synergistically with fibrinolytic agents. These findings suggest a potential strategy for improving the efficacy of thrombolytic therapy by a combination of these products or their substitutes.

Adenosine Diphosphate↗

A new type 1 diabetes susceptibility locus containing the catalase gene (chromosome 11p13) in a Russian population.

BACKGROUND: Oxidative stress is involved in the origin of type 1 diabetes. Low efficiency of the scavenging antioxidant system has been shown to be related to the pathogenesis of the disease. This, therefore suggests that genes encoding catalase and other antioxidant enzymes may implicate in the development of type 1 diabetes. METHODS: Nine microsatellite markers that cover about 10 megabases around the catalase (CAT) gene on chromosome 11p13 were analyzed using polymerase chain reaction (PCR) and fluorescence-based genotyping on an automatic DNA sequencer. We also evaluated three single-nucleotide polymorphisms (SNP) within genes encoding catalase (T1667T and C(-262)T dimorphism) and ETS homologous factor (EHF) (C255T SNP) using a PCR-restriction fragment-length polymorphism approach. Multipont linkage analysis in 37 affected sibling pairs was performed using GENEHUNTER 2.1. We examined the markers for association with the disease by transmission disequilibrium tests in 57 discordant sibling pairs and by a case-control study in 258 unrelated healthy donors and 247 affected patients. RESULTS: We obtained close-to-suggestive evidence of linkage to type I diabetes, with the maximum linkage peak between markers D11S907 and D11S2008. Analysis of three SNPs at the CAT and EHF gene located within the region of maximum linkage showed that T1667T and C(-262)T markers of the CAT gene are strongly associated with the disease. CONCLUSION: Our findings support evidence of a new putative type 1 diabetes susceptibility locus on chromosome 11p13 and suggest that the CAT gene may play a role in conferring susceptibility to the disorder in Russian patients.

Adult↗

Improved use of SNP information to detect the role of genes.

A topical question in genetic association studies is the optimal use of the information provided by genotyped single-nucleotide polymorphisms (SNPs) in order to detect the role of a candidate gene in a multifactorial disease. We propose a strategy called "combination test" that tests the association between a quantitative trait and all possible phased combinations of various numbers of SNPs. We compare this strategy to two alternative strategies: the association test that considers each SNP separately, and a multilocus genotype-based test that considers the phased combination of all SNPs together. To compare these three tests, a quantitative trait was simulated under different models of correspondence between phenotype and genotype, including the extreme case when two SNPs interact with no marginal effects of each SNP. The genotypes were taken from a sample of 290 independent individuals genotyped for three genes with various number of SNPs (from 5-8 SNPs). The results show that the "combination test" is the only one able to detect the association when the two SNPs involved in disease susceptibility interact with no marginal effects. Interestingly, even in the case of a single etiological SNP, the "combination test" performed well. We apply the three tests to Genetic Analysis Workshop 12 (Almasy et al. [2001] Genet. Epidemiol. 21:332-338) simulated data, and show that although there was no interactions between the etiological SNPs, the "combination test" was preferable to the two other compared methods to detect the role of the candidate gene.

Genotype↗

Large-scale determination of SNP allele frequencies in DNA pools using MALDI-TOF mass spectrometry.

One of the major challenges in the near future is the identification of genes that contribute to complex disorders. Large scale association studies that utilize a dense map of single nucleotide polymorphisms (SNPs) have been considered as a valuable tool for this purpose. However, genome-wide screens are limited by costs of genotyping thousands of SNPs in a large number of individuals. Here we present a pooling strategy that enables high-throughput SNP validation and determination of allele frequencies in case and control populations. Quantitative analysis of allele frequencies of SNPs in DNA pools is based on matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry of primer extension assays. We demonstrate the accuracy and reliability of this approach on pools of eight previously genotyped individuals with an allele frequency representation in the range of 0.1 to 0.9. The accuracy of measured allele frequencies was shown in DNA pools of 142 to 186 individuals using additional markers. Allele frequencies determined from the pooled samples deviate from the real frequencies by about 3%. The described method reduces costs and time and enables genotyping of up to thousands of samples by taking advantage of the high-throughput MALDI-TOF technology.

DNA↗

Linkage and association analyses of the osteoprotegerin gene locus with human osteoporosis.

Osteoprotegerin (OPG), a secreted glycoprotein and a member of the tumor necrosis factor receptor superfamily, is considered to play an important role in the regulation of bone resorption by modifying osteoclast differentiation. Overexpression of OPG in mice has been reported to result in osteopetrosis, whereas targeted disruption of OPG in mice has been associated with osteoporosis. Accordingly, OPG could be a strong candidate gene for susceptibility to human osteoporosis. Here, we analyzed whether OPG is involved in the etiology of osteoporosis using both linkage and association analyses. We recruited 164 sib pairs in Gunma prefecture, which is located in the central part of Honshu (mainland Japan), for a linkage study, and 394 postmenopausal women in Akita prefecture, which is in the northern part of Honshu, for an association study. We identified two microsatellite polymorphisms in the linkage study, and six single-nucleotide polymorphisms (SNPs) in the OPG region for the association study. Although, no evidence of significant linkage between OPG and osteoporosis was found, a possible association of one SNP, located in the promoter region of the gene, was identified. A haplotype analysis with the six SNPs revealed that four major haplotypes account for 71% of the alleles in the Japanese population.

Base Sequence↗