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Variation in the ciliary neurotrophic factor gene and muscle strength in older Caucasian women.

OBJECTIVES: To determine whether genetic variants in the ciliary neurotrophic factor (CNTF) gene are associated with muscle strength in older women. DESIGN: Cross-sectional analysis of baseline data from the Women's Health and Aging Studies I (1992) and II (1994), complementary population-based studies. SETTING: Twelve contiguous ZIP code areas in Baltimore, Maryland. PARTICIPANTS: Three hundred sixty-three Caucasian, community-dwelling women aged 70 to 79. MEASUREMENTS: Participants were genotyped at the CNTF locus for eight single nucleotide polymorphisms (SNPs), including the null allele rs1800169. The dependent variables were grip strength and the frailty syndrome, identified as presence of three or more of five frailty indicators (weakness, slowness, weight loss, low physical activity, exhaustion). In addition to genotypes, independent variables of body mass index (BMI) and osteoarthritis of the hands were included. RESULTS: Using multivariate linear regression, single SNP analysis identified five SNPs significantly associated with grip strength (P<.05), after adjusting for age, BMI, and osteoarthritis. Haplotype analysis was performed, and a single haplotype associated with grip strength was identified (P<.01). The rs1800169 null allele fully explained the association between this haplotype and grip strength under a recessive model, with individuals homozygous for the null allele exhibiting a 3.80-kg lower (95% confidence interval=1.01-6.58) grip strength. No association was seen between the CNTF null allele and frailty. CONCLUSION: Individuals homozygous for the CNTF null allele had significantly lower grip strength but did not exhibit overt frailty. Larger prospective studies are needed to confirm this finding and extend it to additional populations.

Aged↗

Genetic predisposition to sporadic cancer: how to handle major effects of minor genes?

Predisposition to non-familial, sporadic cancer is strongly influenced by multiple tumor susceptibility genes (TSGs), each with apparently minor effects on the cancer phenotype. Sequence analysis of the human genome has yielded numerous single nucleotide polymorphisms (SNPs), raising the expectation that new low-penetrance TSGs will be identified that can be used to estimate an individuals cancer risk. However, mouse models for human cancer showed that the effects of many low-penetrance TSGs are highly variable due to their involvement in epistatic interactions. Together, these interacting TSGs form large molecular networks, which represent cancer-associated biological modules that influence the tumorigenic process. As a consequence, although allelic variation in one TSG on a permissive genetic background can have major effects on tumor development, the net effect of allelic variation in multiple interacting TSGs remains hard to predict. Therefore, the predictive value of SNP-analysis to estimate an individuals cancer risk will be restricted to those TSGs that exhibit single-gene effects. New strategies need to be developed to evaluate cancer risk associated with biological modules that are influenced by TSG-networks.

Adenomatous Polyposis Coli↗

Comparative genomic analysis of Chlamydia trachomatis oculotropic and genitotropic strains.

Chlamydia trachomatis infection is an important cause of preventable blindness and sexually transmitted disease (STD) in humans. C. trachomatis exists as multiple serovariants that exhibit distinct organotropism for the eye or urogenital tract. We previously reported tissue-tropic correlations with the presence or absence of a functional tryptophan synthase and a putative GTPase-inactivating domain of the chlamydial toxin gene. This suggested that these genes may be the primary factors responsible for chlamydial disease organotropism. To test this hypothesis, the genome of an oculotropic trachoma isolate (A/HAR-13) was sequenced and compared to the genome of a genitotropic (D/UW-3) isolate. Remarkably, the genomes share 99.6% identity, supporting the conclusion that a functional tryptophan synthase enzyme and toxin might be the principal virulence factors underlying disease organotropism. Tarp (translocated actin-recruiting phosphoprotein) was identified to have variable numbers of repeat units within the N and C portions of the protein. A correlation exists between lymphogranuloma venereum serovars and the number of N-terminal repeats. Single-nucleotide polymorphism (SNP) analysis between the two genomes highlighted the minimal genetic variation. A disproportionate number of SNPs were observed within some members of the polymorphic membrane protein (pmp) autotransporter gene family that corresponded to predicted T-cell epitopes that bind HLA class I and II alleles. These results implicate Pmps as novel immune targets, which could advance future chlamydial vaccine strategies. Lastly, a novel target for PCR diagnostics was discovered that can discriminate between ocular and genital strains. This discovery will enhance epidemiological investigations in nations where both trachoma and chlamydial STD are endemic.

Amino Acid Sequence↗

ETHE1 mutations are specific to ethylmalonic encephalopathy.

Mutations in ETHE1, a gene located at chromosome 19q13, have recently been identified in patients affected by ethylmalonic encephalopathy (EE). EE is a devastating infantile metabolic disorder, characterised by widespread lesions in the brain, hyperlactic acidaemia, petechiae, orthostatic acrocyanosis, and high levels of ethylmalonic acid in body fluids. To investigate to what extent ETHE1 is responsible for EE, we analysed this gene in 29 patients with typical EE and in 11 patients presenting with early onset progressive encephalopathy with ethylmalonic aciduria (non-EE EMA). Frameshift, stop, splice site, and missense mutations of ETHE1 were detected in all the typical EE patients analysed. Western blot analysis of the ETHE1 protein indicated that some of the missense mutations are associated with the presence of the protein, suggesting that the corresponding wild type amino acid residues have a catalytic function. No ETHE1 mutations were identified in non-EE EMA patients. Experiments based on two dimensional blue native electrophoresis indicated that ETHE1 protein works as a supramolecular, presumably homodimeric, complex, and a three dimensional model of the protein suggests that it is likely to be a mitochondrial matrix thioesterase acting on a still unknown substrate. Finally, the 625G-->A single nucleotide polymorphism in the gene encoding the short chain acyl-coenzyme A dehydrogenase (SCAD) was previously proposed as a co-factor in the aetiology of EE and other EMA syndromes. SNP analysis in our patients ruled out a pathogenic role of SCAD variants in EE, but did show a highly significant prevalence of the 625A alleles in non-EE EMA patients.

Alleles↗

Comparison of whole genome assemblies of the human genome.

A fundamental problem in the human genome project is uncovering the correct assembly of the human genome. Many studies, including transcriptional analysis, SNP detection and characterization, gene finding and EST clustering, use genome assemblies as templates so it is important to determine the consistency among the various whole genome assemblies. A comparison of the order and orientation of the GenBank entries used to construct the NCBI and UCSC Goldenpath assemblies was made. In addition, a sequence level comparison was performed using MULTI, an efficient database search tool developed to make whole genome comparisons possible. The resulting comparisons show significant discrepancies in the sequence as well as in the order and orientation of GenBank entries used in constructing the NCBI and UCSC assemblies.

Chromosomes, Human↗

Excavating Y-chromosome haplotype strata in Anatolia.

Analysis of 89 biallelic polymorphisms in 523 Turkish Y chromosomes revealed 52 distinct haplotypes with considerable haplogroup substructure, as exemplified by their respective levels of accumulated diversity at ten short tandem repeat (STR) loci. The major components (haplogroups E3b, G, J, I, L, N, K2, and R1; 94.1%) are shared with European and neighboring Near Eastern populations and contrast with only a minor share of haplogroups related to Central Asian (C, Q and O; 3.4%), Indian (H, R2; 1.5%) and African (A, E3*, E3a; 1%) affinity. The expansion times for 20 haplogroup assemblages was estimated from associated STR diversity. This comprehensive characterization of Y-chromosome heritage addresses many multifaceted aspects of Anatolian prehistory, including: (1) the most frequent haplogroup, J, splits into two sub-clades, one of which (J2) shows decreasing variances with increasing latitude, compatible with a northward expansion; (2) haplogroups G1 and L show affinities with south Caucasus populations in their geographic distribution as well as STR motifs; (3) frequency of haplogroup I, which originated in Europe, declines with increasing longitude, indicating gene flow arriving from Europe; (4) conversely, haplogroup G2 radiates towards Europe; (5) haplogroup E3b3 displays a latitudinal correlation with decreasing frequency northward; (6) haplogroup R1b3 emanates from Turkey towards Southeast Europe and Caucasia and; (7) high resolution SNP analysis provides evidence of a detectable yet weak signal (<9%) of recent paternal gene flow from Central Asia. The variety of Turkish haplotypes is witness to Turkey being both an important source and recipient of gene flow.

Africa, Northern↗

PAR1 deletions downstream of SHOX are the most frequent defect in a Spanish cohort of Léri-Weill dyschondrosteosis (LWD) probands.

Léri-Weill dyschondrosteosis (LWD) is a skeletal dysplasia characterized by disproportionate short stature and Madelung deformity. Mutations or deletions of the SHOX gene have been previously identified as the main cause of LWD. We recently identified the existence of a second class of pseudoautosomal region 1 (PAR1) deletions which do not include SHOX, implicated in the etiopathogenesis of LWD. The deletions map at least 30-250 kb downstream of SHOX, are variable in size and clearly cosegregate with the LWD phenotype. In order to determine the frequency of this new type of deletions in the Spanish population we analyzed the distribution of PAR1 defects, including the screening of SHOX deletions, mutations, and PAR1 deletions downstream of SHOX, in a total of 26 LWD probands by a combination of MLPA, microsatellite analysis, SNP genotyping, dHPLC, and DNA sequencing. A molecular defect was identified in 16/26 LWD patients (61.5%): 10 PAR1 deletions downstream of SHOX, four SHOX encompassing deletions, and two SHOX mutations. No apparent phenotypic differences were observed between patients with SHOX defects and those with PAR1 deletions downstream of SHOX. In the examined cohort of Spanish LWD probands, PAR1 deletions downstream of SHOX represent the highest proportion of identified mutations (38%) compared to SHOX deletions (15%) and mutations (8%). As a consequence of our findings, the screening of this region should be included in the routine genetic testing of LWD. Also, LWD patients who tested negative for SHOX defects should be re-evaluated for PAR1 deletions downstream of SHOX.

Adolescent↗

Single-nucleotide polymorphism in repetitive sequences of the human deleted in azoospermia complex.

A simple and inexpensive single-nucleotide polymorphism (SNP) analysis procedure is described that uses the Fotodyne Analyst System equipped with the Gel-Pro Analysis software to compare the relative fluorescent intensity of ethidium bromide stained and MboI restricted amplicons from male individuals. The different intensity ratios reflect the ratio of repetitive elements with and without an MboI restriction enzyme site. The polymerase chain reaction (PCR) products represent a reiterated sequence within the Y-linked deleted in azoospermia (DAZ) complex involved in male fertility in humans. This procedure was utilized to determine the ratio of MboI(+) and MboI(-) repetitive sequences in 32 male individuals from two human populations, the Buryat from Mongolia and the Mayan from Yucatan. The proportion of wildtype to mutant amplicons was found to vary from 0 to 100% among individuals. This technique is well suited for large-scale analysis of the locus investigated in this manuscript and other similar polymorphisms. This approach may contribute to the study of recent human evolution based on Y-chromosome analysis as well as medical and developmental issues concerning the significance of these repetitive elements in male infertility.

Base Sequence↗

Multiplex high-throughput solid-phase minisequencing by capillary electrophoresis and liquid core waveguide fluorescence detection.

Minisequencing, solid-phase single-nucleotide primer extension reaction, is a robust method for performing multiplex single-nucleotide polymorphism (SNP) analysis. We have combined this technology with capillary gel electrophoresis in a multicapillary format, using liquid core waveguide (LCW) fluorescence detection. Polymerase chain reaction (PCR) amplification of multiple DNA targets is performed with one primer for each target biotinylated. Separation of the complementary strands, minisequencing and washing steps are carried out using streptavidin-coated magnetic beads. Dideoxynucleotides analogues labelled with different fluorophores are used for the extension of the minisequencing primers. The extended oligonucleotides, the length of which defines the position on the target and the color the identity of the polymorphism, are then separated in a gel-filled array of capillaries, coated on the outside with a layer of a fluoropolymer to provide the liquid core waveguide characteristics. The technology has a potential for extremely high throughputs when a combination of multiplex PCR-minisequencing is used together with a large array of capillaries, four-color detection and high-speed separation.

DNA↗

Significant association of BDNF haplotypes in European-American male smokers but not in European-American female or African-American smokers.

Brain-derived neurotrophic factor (BDNF) influences dopamine and serotonin neurotransmission in the brain, both of which are involved in the reward system of addiction. The BDNF gene is located in a genomic region on chromosome 11p where we and others have found 'significant' linkage to nicotine dependence (ND). We tested the potential role of variants within BDNF in vulnerability to ND, which was assessed by Smoking Quantity (SQ), the Heaviness of Smoking Index (HSI), and the Fagerström Test for ND (FTND). Six single nucleotide polymorphisms (SNPs) in BDNF were analyzed in an extensively phenotyped cohort of 602 nuclear families with smokers and non-smokers of African-American (AA) or European-American (EA) ancestry. Individual SNP analysis revealed that two SNPs in the pooled male and three SNPs in the EA male samples were significantly associated with at least one adjusted ND measure. However, none of these associations remained significant after correction for multiple testing. Haplotype analysis of rs6484320-rs988748-rs2030324-rs7934165 revealed that a major T-C-T-G haplotype was significantly associated, even after Bonferroni correction, with the three ND measures in the pooled and EA male samples (maximum Z = 3.00, P = 0.002 and maximum Z = 3.13, P = 0.0009 for SQ, respectively). No significant association of a major haplotype with ND was found in the AA or EA female smokers. The significant association of BDNF variants with ND implies that this gene plays a role in the etiology of ND in EAs and that its involvement is gender specific. BDNF may warrant further investigation in ND.

Adult↗

Admixture and Selection Driven by El Ni&#xf1;o-Southern Oscillation Events Shape the Genetic Structure of Octopus mimus-O. hubbsorum Complex Across the Humboldt and South Equatorial Current Transition Zone.

Marine transition zones, where contrasting water masses converge, can function as natural laboratories for studying admixture and early stages of speciation. The genomic structure of the eastern Pacific Octopus mimus-O. hubbsorum complex was investigated by analyzing whole-genome sequencing data from 67 individuals sampled along the west coast of the Americas, spanning Mexico and the Peruvian coast. This includes the South Equatorial Current, the transition zone, and the Humboldt Current System. The mitochondrial genomes fell into two major genetic clades that largely corresponded to the warm-water northern (O. hubbsorum) and cold-water southern (O. mimus) lineages. Analyses of the nuclear genomes revealed the same bipartite structure but also identified a broad admixture zone characterized by two different admixed clades (Admixed-Cold and Admixed-Warm). The results suggest that episodic relaxation of oceanographic barriers during El Ni&#xf1;o-Southern Oscillation (ENSO) events promotes secondary contact and gene flow, resulting in admixed individuals recurrently during ENSO years. However, the survival of these admixed individuals depends on the adaptive genetic composition of each organism and the prevailing environmental conditions. Outlier SNP analysis supports these findings, where the Admixed-Cold cluster shares mainly the adaptive genetic component identified as outliers in O. mimus, while Admixed-Warm is linked to those in O. hubbsorum. The O. mimus-O. hubbsorum complex is currently occupying a gray zone of speciation, in which selection and climate-driven connectivity act in tandem to shape genomic divergence.

gene flow↗

Multiple sample amplification and genotyping integrated on a single electronic microarray.

We report a novel method that allows simultaneous in situ amplification and then genotyping of single nucleotide polymorphism (SNP) for multiple samples on a single electronic microarray. The locus coding for one of the common inherited thrombosis risk factors, Factor V Leiden (FVL), was chosen as a model system for SNP analysis. This method combines strand displacement amplification (SDA) with electrophoretic movement and concentration of DNA on electronic microarrays to provide a single platform for DNA amplification and analysis. The method includes: electronic anchoring of allele-specific SDA amplifiable primers (APs) and a nonamplifiable primer (NAP) to different electrodes, electronic hybridization of genomic DNA from different samples to those primers, in situ amplification of target DNA, and genotyping of FVL. Compared to previous anchored SDA methods, the addition of a NAP improves detection signals by at least 20-fold. The sensitivity of this method is dependent on the amplification time. Using this method, nine different genomic DNA samples with known FVL genotypes were amplified and correctly genotyped on a single electronic microarray without any contamination between samples. The present method could streamline development of nucleic acid-based assays in applications of molecular diagnostic, point-of-care testing, and forensic detection, which often require the capability to analyze multiple samples efficiently.

Base Sequence↗

Long- and short-haired Weimaraner dogs represent two populations of one breed.

Weimaraners represent an old breed of hunting dogs. Today, two coat types are commonly distinguished, the more common short-hair (SH) and the long-hair (LH) variety, the latter having arisen from the SH Weimaraners. In order to analyze genetic variation in the coat varieties, we genotyped nine single nucleotide polymorphisms (SNPs) of the ABCA4 gene locus as well as six highly variable microsatellites scattered over the canine genome in the SH and LH populations. Three out of nine SNPs showed two alleles, allelic frequencies at two of these polymorphic sites differed significantly between SH and LH Weimaraners. Haplotype diversities for the three informative SNPs revealed higher estimates for the SH (0.515) than for the LH variety (0.364). In addition, two of six microsatellite markers showed significant differences in allelic frequencies between SH and LH Weimaraners. Unexpectedly, genetic diversities for all but one microsatellite were greater in LH than in SH Weimaraners. Similarly, the mean intra-individual genetic distance based on microsatellite markers was more pronounced in the LH population (0.62 for SH vs. 0.65 for LH) suggesting again closer genetic relationships among SH than LH Weimaraners. Taken together, the results of SNP analysis can be interpreted as reflections of early breed development whereas microsatellites mirror rather recent breeding strategies in the Weimaraner populations.

Animals↗

rSNP_Guide: an integrated database-tools system for studying SNPs and site-directed mutations in transcription factor binding sites.

Since the human genome was sequenced in draft, single nucleotide polymorphism (SNP) analysis has become one of the keynote fields of bioinformatics. We have developed an integrated database-tools system, rSNP_Guide (http://wwwmgs.bionet.nsc.ru/mgs/systems/rsnp/), devoted to prediction of transcription factor (TF) binding sites, alterations of which could be associated with disease phenotype. By inputting data on alterations in DNA sequence and in DNA binding pattern of an unknown TF, rSNP_Guide searches for a known TF with alterations in the recognition score calculated on the basis of TF site's sequence and consistent with the input alterations in DNA binding to the unknown TF. Our system has been tested on many relationships between known TF sites and diseases, as well as on site-directed mutagenesis data. Experimental verification of rSNP_Guide system was made on functionally important SNPs in human TDO2and mouse K-ras genes. Additional examples of analysis are reported involving variants in the human gammaA-globin (HBG1), hsp70(HSPA1A), and Factor IX (F9) gene promoters.

Animals↗

Polymorphisms in the CYP1A1 gene are associated with prostate cancer risk.

CYP1A1 is likely to play an important role in the etiology of CaP through its function in activating environmental procarcinogens and catalyzing the oxidative metabolites of estrogens. To test the hypothesis that genetic polymorphisms in the CYP1A1 gene may be associated with the risk for CaP, we compared the allele, genotype and haplotype frequencies of 3 SNPs (3801T>C, 2455A>G and 2453C>A) of CYP1A1 among 159 HPC probands, 245 sporadic CaP cases and 222 unaffected men. Two SNPs (3801T>C and 2455A>G) were each individually associated with CaP risk when the allele and genotype frequencies were compared between CaP patients and unaffected controls. Furthermore, a combined SNP analysis using a haplotype approach revealed an even stronger association in Caucasians. Specifically, 4 major haplotypes (T-A-C, C-A-C, C-G-C and T-A-A) accounted for 99.8% of all observed haplotypes. These 4 haplotypes correspond to the previously described nomenclature (CYP1A1*1A, CYP1A1*2A, CYP1A1*2B and CYP1A1*4). The frequencies of these 4 haplotypes were significantly different among CaP patients and controls. The haplotype T-A-C (CYP1A1*1A) was significantly associated with increased risk for CaP, and the haplotype C-A-C (CYP1A1*2A) was significantly associated with decreased risk for CaP. These findings suggest that genetic polymorphisms in CYP1A1 may modify the risk for CaP.

Biomarkers, Tumor↗

Single nucleotide polymorphism, haplotype diversity and recombination in the Isa gene of barley.

The Isa gene from barley--an intronless gene expressed in maternal tissues of the seed--has a likely role in defence against pathogens. The protein product--bi-functional alpha-amylase/subtilisin inhibitor--inhibits the seed's own amylase in addition to the bacterial protease subtilisin and fungal xylanase. Sixteen barley genotypes were targeted to amplify and sequence the Isa gene region to detect sequence polymorphisms, since little is known about genetic diversity at this locus. A total of 80 single nucleotide polymorphisms (SNPs) and 23 indels were detected in 2,164 bp of sequence containing the Isa transcript, promoter and 3' non-transcribed region (overall one SNP per 27 bp and one indel per 94 bp), with eight sequence-based haplotypes distinguishable amongst the 16 varieties. Sequencing a polymorphic region in the promoter in an additional 27 barley genotypes increased the number of sequence-based haplotypes discovered to 11. However there is low haplotype diversity amongst the cultivated barley varieties sampled, with most varieties represented by a single haplotype. There was minor amino acid diversity in the protein, with five out of ten SNP sites in the coding region predicted to produce amino acid substitutions. SNP analysis indicated a history of recombination events--a minimum of seven based on the initial eight haplotypes from the whole sequenced region. Most of the recombination events occurred in the highly polymorphic regions, the 3' non-transcribed region and sequences flanking a microsatellite in the Isa promoter.

Base Sequence↗

Label-free characterisation of oligonucleotide hybridisation using reflectometric interference spectroscopy.

The potential of a label-free detection method, reflectometric interference spectroscopy (RIfS), for temperature-dependent DNA hybridisation experiments (for example in single nucleotide polymorphism (SNP) analysis) is investigated. Hybridisations of DNA, peptide nucleic acid (PNA), and locked nucleic acid (LNA) to a single stranded DNA were measured for several temperatures, and the melting curves and temperatures were calculated from the changes in optical thickness obtained. These measurements were performed by hybridising surface-immobilised single stranded oligomers with their complementary ssDNA or with ssDNA containing SNPs at different temperatures. DNA was compared to its analogue oligomers PNA and LNA due to their stability against nuclease. A comparison of melting temperatures demonstrated the higher binding affinities of the DNA analogues. Moreover, a continuous melting curve was obtained by first hybridising the functionalised surface with its complementary DNA at room temperature and then heating up in-flow. Measurement of the continuous melting curve was only possible due to the insensitivity of the RIfS method towards temperature changes. This is an advantage over other label-free detection methods, which are based on determining the refractive index.

Base Sequence↗

Fatal intoxication cases: cytochrome P450 2D6 and 2C19 genotype distributions.

OBJECTIVE: Many commonly used pharmaceuticals, such as antidepressants and neuroleptics as well as some illegal drugs, are metabolised by the cytochrome P450 enzyme debrisoquine 4-hydroxylase (CYP2D6). Of Caucasians, 7-10% lack this enzyme, which can, upon administration of drugs in normal therapeutic doses, lead to adverse reactions and unexpected intoxication, leading in turn even to a fatal outcome in some cases. METHODS: Individuals (n=242) who had died due to intoxication by pharmaceuticals were genotyped for CYP2D6 and CYP2C19 and compared with a reference group of 281 blood donors. A single nucleotide polymorphism (SNP) method was used to identify five CYP2D6 alleles: *1 (wt), *2, *3, *4 and *6. The allele *5, a complete gene deletion, was identified by a multiplex amplification of long DNA fragments. Four CYP2C19 alleles *1 (wt), *2, *3 and *4 were also identified by SNP analysis. RESULTS: The prevalence of the CYP2D6 poor metaboliser (PM) genotypes in individuals with fatal intoxication was lower (4.7%) than expected from the frequencies of these genotypes in the blood donors (8.5%). A significantly lower frequency P<0.005 (0.03 with correction according to Bonferroni) was found for the CYP2D6*4 allele among the fatal intoxication cases. The CYP2C19 genotype analyses showed the same results for the fatal intoxication cases and for the blood donors. CONCLUSIONS: The findings in this study confirm our earlier observations of a lower frequency of CYP2D6 PM genotypes in cases of fatal intoxication. To our knowledge, it has not been shown previously that intoxication victims might have a lower frequency of PMs than the general population.

Aryl Hydrocarbon Hydroxylases↗