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Ancestral haplotypes carry haplotypic and haplospecific polymorphisms of BAT1: possible relevance to autoimmune disease.

The human BAT1 gene, located in the central MHC region (approximately 170 kb centrometric of HLA-B), is polymorphic and the polymorphism correlates with MHC ancestral haplotypes. Allelic RFLP patterns have been assigned to several ancestral haplotypes and have been shown to be 'haplotypic' (i.e. found on all examples of the same ancestral haplotype) and in some cases 'haplospecific' (i.e. unique to one ancestral haplotype). The relevance of the BAT1 polymorphism to susceptibility to Myasthenia Gravis (MG) has been investigated. The frequency of the BAT1 B allelic pattern is increased in patients with MG (n = 16) compared to an equal number of control subjects. The increase is due to the association between MG and the 8.1 ancestral haplotype (HLA A1, Cw7, B8, BfS, C4AQ0, C4B1, DR3, DQw2).

Autoimmune Diseases↗

Haplotype reconstruction and estimation of haplotype frequencies from nuclear families with only one parent available.

Recent literature has suggested that haplotype inference through close relatives, especially from nuclear families can be an alternative strategy in determining the linkage phase. In this paper, haplotype reconstruction and estimation of haplotype frequencies via expectation maximization (EM) algorithm including nuclear families with only one parent available is proposed. Parent and his (her) child are treated as parent-child pair with one shared haplotype. This reduces the number of potential haplotype pairs for both parent and child separately, resulting in a higher accuracy of the estimation. In a series of simulations, the comparisons of PHASE, GENEHUNTER, EM-based approach for complete nuclear families and our approach are carried out. In all situations, EM-based approach for trio data is comparable but slightly worse error rate than PHASE, our approach is slightly better and much faster than PHASE for incomplete trios, the performance of GENEHUNTER is very bad in simple nuclear family settings and dramatically decreased with the number of markers being increased. On the other hand, the comparison result of different sampling designs demonstrates that sampling trios is the most efficient design to estimate haplotype frequencies in populations under same genotyping cost.

Child↗

Y chromosome probe p49a detects complex PvuII haplotypes and many new TaqI haplotypes in southern African populations.

Y-specific 49a/TaqI haplotypes were determined for 831 individuals drawn from 21 different southern African populations. A total of 31 new haplotypes were observed, some of which contained new alleles or allelic variants. Duplication, in addition to CpG mutation, is implicated in the generation of certain allelic variants. Cluster analysis of genetic distances between the populations, calculated using the 49a/TaqI haplotype frequencies, revealed a basic split between African and non-African populations. Hybrid groups cluster with the caucasoid groups, indicating that male gene flow has occurred from the latter into the former. Clustering of the negroid and Khoisan groups is not what might have been expected from the known linguistic affinities. It is suggested that the 49a/TaqI haplotype analysis of these populations is not sufficiently sensitive to distinguish between many of the populations. The Y-specific 49a/PvuII polymorphism was studied in 127 individuals from southern African populations, and 17 polymorphic fragments ranging in size from 3.6 kb to greater than 48 kb were identified. A total of 53 PvuII haplotypes were observed, corresponding to only 30 TaqI haplotypes. There appears to be poor correlation between the two polymorphisms.

Africa, Southern↗

Maximum likelihood estimation of haplotype effects and haplotype-environment interactions in association studies.

The associations between haplotypes and disease phenotypes offer valuable clues about the genetic determinants of complex diseases. It is highly challenging to make statistical inferences about these associations because of the unknown gametic phase in genotype data. We describe a general likelihood-based approach to inferring haplotype-disease associations in studies of unrelated individuals. We consider all possible phenotypes (including disease indicator, quantitative trait, and potentially censored age at onset of disease) and all commonly used study designs (including cross-sectional, case-control, cohort, nested case-control, and case-cohort). The effects of haplotypes on phenotype are characterized by appropriate regression models, which allow various genetic mechanisms and gene-environment interactions. We present the likelihood functions for all study designs and disease phenotypes under Hardy-Weinberg disequilibrium. The corresponding maximum likelihood estimators are approximately unbiased, normally distributed, and statistically efficient. We provide simple and efficient numerical algorithms to calculate the maximum likelihood estimators and their variances, and implement these algorithms in a freely available computer program. Extensive simulation studies demonstrate that the proposed methods perform well in realistic situations. An application to the Carolina Breast Cancer Study reveals significant haplotype effects and haplotype-smoking interactions in the development of breast cancer.

Algorithms↗

High-Density SNP genotyping defines 17 distinct haplotypes of the TNF block in the Caucasian population: implications for haplotype tagging.

The region spanning the tumor necrosis factor (TNF) cluster in the human major histocompatibility complex (MHC) has been implicated in susceptibility to numerous immunopathological diseases, including type 1 diabetes mellitus and rheumatoid arthritis. However, strong linkage disequilibrium across the MHC has hampered the identification of the precise genes involved. In addition, the observation of "blocks" of DNA in the MHC within which recombination is very rare, limits the resolution that may be obtained by genotyping individual SNPs. Hence a greater understanding of the haplotypes of the block spanning the TNF cluster is necessary. To this end, we genotyped 32 human leukocyte antigen (HLA)-homozygous workshop cell lines and 300 healthy control samples for 19 coding and promoter region SNPs spanning 45 kb in the central MHC near the TNF genes. The workshop cell lines defined 11 SNP haplotypes that account for approximately 80% of the haplotypes observed in the 300 control individuals. Using the control individuals, we defined a further six haplotypes that account for an additional 10% of donors. We show that the 17 haplotypes of the "TNF block" can be identified using 15 SNPs.

Cell Line, Transformed↗

Haplotypes of CYP3A4 and their close linkage with CYP3A5 haplotypes in a Japanese population.

In order to identify single nucleotide polymorphisms (SNPs) and haplotype frequencies of CYP3A4 in a Japanese population, the distal enhancer and proximal promoter regions, all exons, and the surrounding introns were sequenced from genomic DNA of 416 Japanese subjects. We found 24 SNPs, including 17 novel ones: two in the distal enhancer, four in the proximal promoter, one in the 5'-untranslated region (UTR), seven in the introns, and three in the 3'-UTR. The most common SNP was c.1026+12G>A (IVS10+12G>A), with a 0.249 frequency. Four non-synonymous SNPs, c.554C>G (p.T185S, CYP3A4(*)16), c.830_831insA (p.E277fsX8, (*)6), c.878T>C (p.L293P, (*)18), and c.1088 C>T (p.T363M, (*)11) were found with frequencies of 0.014, 0.001, 0.028, and 0.002, respectively. No SNP was found in the known nuclear transcriptional factor-binding sites in the enhancer and promoter regions. Using these 24 SNPs, 16 haplotypes were unambiguously identified, and nine haplotypes were inferred by aid of an expectation-maximization-based program. In addition, using data from 186 subjects enabled a close linkage to be found between CYP3A4 and CYP3A5 SNPs, especially among the SNPs at c.1026+12 in CYP3A4 and c.219-237 (IVS3-237, a key SNP site for CYP3A5(*)3), c.865+77 (IVS9+77) and c.1523 in CYP3A5. This result suggested that CYP3A4 and CYP3A5 are within the same gene block. Haplotype analysis between CYP3A4 and CYP3A5 revealed several major haplotype combinations in the CYP3A4-CYP3A5 block. Our findings provide fundamental and useful information for genotyping CYP3A4 (and CYP3A5) in the Japanese, and probably Asian populations.

Cytochrome P-450 CYP3A↗

Detecting genome wide haplotype sharing using SNP or microsatellite haplotype data.

Genome wide association studies using high throughput technology are already being conducted despite the significant hurdles that need to be overcome (Nat Rev Genet 6:95-108, 2005; Nat Rev Genet 6:109-118, 2005). Methods for detecting haplotype association signals in genome wide haplotype datasets are as yet very limited. Much methodological research has already been devoted to linkage disequilibrium (LD) fine mapping where the focus is the identification of the disease locus rather than the detection of a disease signal. Applications of these approaches to genome wide scanning are limited by the strong model assumptions of the sharing process, which lead to computational complexity. We describe a new algorithm for the initial identification of disease susceptibility loci in genome wide haplotype association studies. Excess sharing of ancestral haplotypes, which indicates the presence of a disease locus, is detected with a simple, easy to interpret, chi2 based statistic. The method allows genome wide scanning for qualitative traits within reasonable computational timeframes and can serve as a first pass analysis prior to the usage of likelihood based methods, providing candidate regions and inferred susceptibility haplotypes. Our method makes no assumptions regarding the population history or the pattern of background LD. Statistical significance is evaluated with permutation tests. The method is illustrated on simulated and real data where it is applied to simple (cystic fibrosis) and complex disease (multiple sclerosis) examples. The statistic has low type I error and greater power to map disease loci over conventional single marker tests for low to moderate levels of LD.

Algorithms↗

Evolution of human and non-human primate CC chemokine receptor 5 gene and mRNA. Potential roles for haplotype and mRNA diversity, differential haplotype-specific transcriptional activity, and altered transcription factor binding to polymorphic nucleotides in the pathogenesis of HIV-1 and simian immunodeficiency virus.

Polymorphisms in CC chemokine receptor 5 (CCR5), the major coreceptor of human immunodeficiency virus 1 (HIV-1) and simian immunodeficiency virus (SIV), have a major influence on HIV-1 transmission and disease progression. The effects of these polymorphisms may, in part, account for the differential pathogenesis of HIV-1 (immunosuppression) and SIV (natural resistance) in humans and non-human primates, respectively. Thus, understanding the genetic basis underlying species-specific responses to HIV-1 and SIV could reveal new anti-HIV-1 therapeutic strategies for humans. To this end, we compared CCR5 structure/evolution and regulation among humans, apes, Old World Monkeys, and New World Monkeys. The evolution of the CCR5 cis-regulatory region versus the open reading frame as well as among different domains of the open reading frame differed from one another. CCR5 cis-regulatory region sequence variation in humans was substantially higher than anticipated. Based on this variation, CCR5 haplotypes could be organized into seven evolutionarily distinct human haplogroups (HH) that we designated HHA, -B, -C, -D, -E, -F, and -G. HHA haplotypes were defined as ancestral to all other haplotypes by comparison to the CCR5 haplotypes of non-human primates. Different human and non-human primate CCR5 haplotypes were associated with differential transcriptional regulation, and various polymorphisms resulted in modified DNA-nuclear protein interactions, including altered binding of members of the NF-kappaB family of transcription factors. We identified novel CCR5 untranslated mRNA sequences that were conserved in human and non-human primates. In some primates, mutations at exon-intron boundaries caused loss of expression of selected CCR5 mRNA isoforms or production of novel mRNA isoforms. Collectively, these findings suggest that the response to HIV-1 and SIV infection in primates may have been driven, in part, by evolution of the elements controlling CCR5 transcription and translation.

Animals↗

Plotting haplotype-specific linkage disequilibrium patterns by extended haplotype homozygosity.

UNLABELLED: Association studies may request more details of a specific haplotype. Haplotype-specific decay of linkage disequilibrium is such a crucial and versatile characteristic. It may be used, e.g. to search for signals of natural selection in a risk haplotype. Here, we present a web-based tool to explore the relationship between population frequency and extended linkage disequilibrium measured as haplotype homozygosity of observed haplotypes within a specified candidate region. AVAILABILITY: The web-tool is available at http://ihg.gsf.de/cgi-bin/mueller/webehh.pl

Algorithms↗

Molecular haplotyping by linking emulsion PCR: analysis of paraoxonase 1 haplotypes and phenotypes.

Linking emulsion PCR (LE-PCR) enables formation of minichromosomes preserving phase information of two polymorphic loci, hence the haplotype. Emulsion PCR confines two amplicons of two linked polymorphic sites on a single template molecule to one aqueous-phase droplet. Linking PCR uses biotinylated, overlapping linking primers to connect these amplicons in the droplet. After LE-PCR, unlinked amplicons are removed on streptavidin-coated magnetic beads and single-stranded runoff products are capped by primer extension. Quantitative ASPCR can then be used to ascertain the haplotypes of the two polymorphic loci on the minichromosomes. Using LE-PCR, we determined the human paraoxonase-1 [PON1] molecular haplotypes at three loci (-909g>c, L55M, Q192R) in women who were compound heterozygotes for -909g>c/L55M (n = 89), -909g>c/Q192R (n = 77) and L55M/Q192R (n = 68). We observed a strong association between PON1 substrate specificity (paraoxon/phenylacetate substrate activity ratios) and -909g>c/Q192R haplotype. We have demonstrated here a powerful molecular haplotyping technology that can be applied in population studies.

Aryldialkylphosphatase↗

Clone-based systematic haplotyping (CSH): a procedure for physical haplotyping of whole genomes.

We present a novel methodology to determine the phase of single-nucleotide polymorphisms (SNPs) on a chromosome, which we term clone-based systematic haplotyping (CSH). The CSH procedure is based on separating the allelic chromosomes of a diploid genome by fosmid/cosmid cloning, and subsequent SNP typing of 96 clone pools, each representing approximately 10% of the genome. The pools are screened by PCR for the sequence of interest, followed by SNP typing on the PCR products using the GOOD assay. We demonstrate that by CSH, the haplotype of SNPs separated by more than 50 kilobases can definitely be assigned. We propose this method as being suitable for constructing maps of ancestral haplotypes, analysis of complex diseases, and for diagnosis of rare defects in which the molecular haplotype is crucial. In addition, by amplifying the initial DNA by many orders of magnitude, the original DNA resource is effectively immortalized, enabling the haplotyping of hundreds of thousands of SNPs per individual.

Cloning, Molecular↗

The S haplotype-specific F-box protein gene, SFB, is defective in self-compatible haplotypes of Prunus avium and P. mume.

Many Prunus species, including sweet cherry and Japanese apricot, of the Rosaceae, display an S-RNase-based gametophytic self-incompatibility (GSI). The specificity of this outcrossing mechanism is determined by a minimum of two genes that are located in a multigene complex, termed the S locus, which controls the pistil and pollen specificities. SFB, a gene located in the S locus region, encodes an F-box protein that has appropriate S haplotype-specific variation to be the pollen determinant in the self-incompatibility reaction. This study characterizes SFBs of two self-compatible (SC) haplotypes, S(4') and S(f), of Prunus. S(4') of sweet cherry is a pollen-part mutant (PPM) that was produced by X-ray irradiation, while S(f) of Japanese apricot is a naturally occurring SC haplotype that is considered to be a PPM. DNA sequence analysis revealed defects in both SFB(4') and SFB(f). A 4 bp deletion upstream from the HVa coding region of SFB(4') causes a frame-shift that produces transcripts of a defective SFB lacking the two hypervariable regions, HVa and HVb. Similarly, the presence of a 6.8 kbp insertion in the middle of the SFB(f) coding region leads to transcripts for a defective SFB lacking the C-terminal half that contains HVa and HVb. As all reported SFBs of functional S haplotypes encode intact SFB, the fact that the partial loss-of-function mutations in SFB are present in SC mutant haplotypes of Prunus provides additional evidence that SFB is the pollen S gene in GSI in Prunus.

Amino Acid Sequence↗

Haplotype analysis of Norwegian and Swedish patients with acute intermittent porphyria (AIP): Extreme haplotype heterogeneity for the mutation R116W.

Acute intermittent porphyria (AIP), the most common of the acute porphyrias, is caused by mutations in the gene encoding hydroxymethylbilane synthase (HMBS) also called porphobilinogen deaminase (PBGD). The mutation spectrum in the HMBS gene is characterized by a majority of family specific mutations. Among the exceptions are R116W and W198X, with high prevalence in both the Dutch and Swedish populations. These two mutations were also detected in unrelated Norwegian patients. Thus, Norwegian and Swedish patients were haplotyped using closely linked flanking microsatellites and intragenic single nucleotide polymorphisms (SNPs) to see if the high frequency of these two mutations is due to a founder effect. Twelve intragenic SNPs were determined by a method based on fluorescent restriction enzyme fingerprinting single-strand conformation polymorphism (F-REF-SSCP). W198X occurred exclusively on one haplotype in both Norwegian and Swedish patients, showing that it has originated from a common gene source. In contrast, R116W was found on three different haplotypes in three Norwegian families, and in five Swedish families on four or five haplotypes. This extreme haplotype heterogeneity indicates that R116W is a recurrent mutation, maybe explained by the high mutability of CpG dinucleotides. This can also explain why it is the only AIP mutation reported to occur in seven different populations (Norway, Sweden, Finland, Netherlands, France, Spain and South Africa).

Founder Effect↗

Asian-specific HLA haplotypes reveal heterogeneity of the contribution of HLA-DR and -DQ haplotypes to susceptibility to type 1 diabetes.

To assess the effect of Asian-specific HLA haplotypes on susceptibility to type 1 diabetes, we investigated the association of genotypic combinations of DRB1-DQB1 haplotypes with susceptibility to type 1 diabetes. We studied 132 Japanese patients with type 1 diabetes and 157 control subjects, along with 67 Korean patients and 109 control subjects. DRB1*0405-DQB1*0401 and DRB1*0901-DQB1*0303 were confirmed to be two major susceptible HLA haplotypes in the Japanese population. The frequencies of heterozygotes and homozygotes with DRB1*0405-DQB1*0401 were similarly higher in patients than in control subjects (homozygotes, 5.3% vs. 3.8%; heterozygotes, 48.5% vs. 26.1%). In contrast, homozygotes, but not heterozygotes, with DRB1*0901-DQB1*0303 were more frequent in patients with type 1 diabetes than in control subjects (homozygotes, 12.9% vs. 0.6%; heterozygotes, 22.0% vs. 24.8%). A similar tendency was also observed in the Korean population. In multiple logistic regression analysis, DRB1*0405-DQB1*0401 fitted a dominant model and DRB1*0901-DQB1*0303 fitted a recessive model. These data, which indicate that the contribution of HLA haplotypes to the genetic susceptibility to type 1 diabetes differs depending on the genotypic combination of HLA haplotypes, suggest the importance of extensive analysis of genotypes in studies on HLA and disease association in general.

Adolescent↗

[Two loci HLA haplotypes in celiac children. Linkage imbalance and haplotype frequencies. Comparative study with a control population].

OBJECTIVE: Celiac disease is closely correlated with certain human lymphocyte antigen (HLA) alleles. The aim of this study was to compare linkage disequilibrium parameters and the frequencies of the two loci haplotypes: HLA A/B, A/C, A/DR, A/DQ; HLA B/C, B/DR, B/DQ; HLA C/DR, C/DQ and HLA DR/DQ in children with celiac disease and in a control population within the same geographical area. METHODS: Thirty-eight children with celiac disease, aged 5months to 18years at diagnosis, were HLA typed by microlymphocytotoxicity assay using T and Bcells separated by monoclonal antibody labeled immunomagnetic particles. The frequency of each haplotype of two loci (Hij) depends on the frequency of each allele (pi and pj) and on a correction factor delta, according to the formula: Hij5 Dij1(pi3pj). The existence of a correction factor delta, or linkage disequilibrium, was assessed by a chi square test using 2 X 2contingency tables for gametic association. RESULTS: Among children with celiac disease the most frequent and significant haplotypes were A1/B8, A9/B5, A19/B12, A28/B22, A28/Cw1, A9/DQ3, B8/Cw7, B18/Cw5, B22/Cw1, B5/DR5, B8/DR3, B12/DR7, B5/DQ3, DR3/DQ2, DR4/DQ8 (3) and DR5/DQ3, showing a positive linkage disequilibrium. Negative linkage disequilibrium was found between B18/Cw7, B12/DR3, Cw4/DR3 and DR3/DQ3. CONCLUSIONS: Our findings show that the frequency of A1/B8,A19/B12, B8/DR3,B12/DR7 and DR3/DQ2 haplotypes is higher in children with celiac disease than in the control population and suggest that these two loci haplotypes confer susceptibility to celiac disease.

Adolescent↗

C4 polymorphism and major histocompatibility complex haplotypes in IgA deficiency: association with C4A null haplotypes.

IgA-deficient individuals (n = 110) and six families comprising 9 cases of IgA deficiency were typed for HLA-A, -B, -DR, C4 and factor B. Phenotype frequencies were increased for HLA-B8 (p = 0.004), HLA-DR3 (p = 0.001) and homozygous C4AQ0 (p = 0.01) and decreased for HLA-B7 (p = 0.004), HLA-DR2 (p = 0.0001) and C4A3 (p = 0.00007) compared to controls. Homozygous C4A deficiency was found in 20% of IgA-deficient persons. As clearly suggested by investigation of families, the findings could be attributed to high prevalence of the extended major histocompatibility complex (MHC) haplotype [HLA-A1, B8, C4AQ0, C4B1, BfS, DR3] in IgA deficiency. All but 1 of the 9 IgA-deficient persons included in the family study carried this haplotype and 4 of them were homozygous. In the families, 3 persons with normal serum IgA concentrations had the same MHC haplotypes as their IgA-deficient relatives. The findings were also consistent with possible overrepresentation of other MHC haplotypes with aberrant C4 gene organization in IgA deficiency. As previously suggested, the presence of two MHC haplotypes associated with IgA deficiency appears to be a necessary but not sufficient requirement for manifestation of the condition. The putative existence of a recessive gene in the MHC with regulatory function with regard to IgA gene expression is consistent with the findings.

Complement C4↗

Comparison of haplotypes of the major histocompatibility complex in the rat. II. Serological analysis of the haplotypes H-1a (Ag-B4), H-1d (Ag-B9) and H-1f (Ag-B10).

The strongly cross-reacting haplotypes of the inbred strains DA, ACI, ACP, MR, BD V and AS2, and of the congenic lines LEW.1A, LEW.1D and LEW.1F, were explored. All of these inbred strains and these congenic lines type with anti-Ag-B4 antisera raised against the DA strain, which behaved as operationally mono-specific in previously reported studies of the eight currently defined Ag-B haplotypes. Serological analyses showed that this cross-reactivity was due to antibodies against public antigenic specificities which were not previously recognized as being in the anti-Ag-B4 antisera, due to the fact that the LEW.1D and LEW.1F animals were not available for testing. With the use of appropriate antisera and of absorption studies, two haplotypes in the H-1 system were found not to have been previously identified in the Ag-B system. The animals carrying the H-1d haplotype (MR, BD V and LEW.1D) have been designated as Ag-B9, and those carrying the H-1f haplotype (AS2 and LEW.1F) have been designated as Ag-B10. With the proper absorptions, an anti-Ag-B4 antiserum can be prepared which reacts only with the DA, ACI and ACP strains, and it will henceforth be used as the operationally mono-specific Ag-B4 typing reagent. A variety of typing experiments showed that the results using antisera raised in Pittsburgh and in Prague and using the Ficoll and dextran haemagglutination methods were the same.

Alleles↗

Haplotypic variation of the transporter associated with antigen processing (TAP) genes and their extension of HLA class II region haplotypes.

Stable cell surface presentation of HLA class I molecules requires active transport of antigenic peptides across the endoplasmic reticulum by products of two genes, TAP1 and TAP2, which map in the major histocompatibility complex class II region. Alleles of each gene are derived from a combination of variable sites at each locus. In this study, TAP1 and TAP2 alleles were identified in homozygous typing cell (HTC) lines, allowing resolution of specific haplotypes in conjunction with the highly polymorphic HLA class II region haplotypes. Three alleles at each TAP locus were found from which eight haplotypes could be assigned. Determination of TAP1 and TAP2 alleles in cell lines homozygous at DR, DQ, and DP created eight additional haplotypes beyond the number observed with these class II genes alone. Complete analysis of DR, DQ, TAP, and DP genotypes in 66 HTCs resulted in the following groups: 1) 46 homozygotes; 2) nine homozygous at DR, DQ, and TAP, but heterozygous at DP; 3) four homozygous at DR, DQ, and DP, but heterozygous at one or both TAP genes; 4) four homozygous at DR and DQ, but heterozygous at TAP and DP; and 5) three complex genotypes heterozygous at DP, TAP, and at least one of DQA1, DQB1, or DRB1 loci. TAP1 and TAP2 genes map in an area of frequent recombination. TAP alleles were determined in five DQB1, DPB1 recombinant individuals, three of which were informative. Recombination was found between DQB1 and the TAP loci in two individuals and between TAP and DPB1 in the other individual.

ATP Binding Cassette Transporter, Subfamily B, Mem↗