[Show abstract][Hide abstract] ABSTRACT: Background
The human KIR genes are arranged in at least six major gene-content haplotypes, all of which are combinations of four centromeric and two telomeric motifs. Several less frequent or minor haplotypes also exist, including insertions, deletions, and hybridization of KIR genes derived from the major haplotypes. These haplotype structures and their concomitant linkage disequilibrium among KIR genes suggest that more meaningful correlative data from studies of KIR genetics and complex disease may be achieved by measuring haplotypes of the KIR region in total.
Towards that end, we developed a KIR haplotyping method that reports unambiguous combinations of KIR gene-content haplotypes, including both phase and copy number for each KIR. A total of 37 different gene content haplotypes were detected from 4,512 individuals and new sequence data was derived from haplotypes where the detailed structure was not previously available.
These new structures suggest a number of specific recombinant events during the course of KIR evolution, and add to an expanding diversity of potential new KIR haplotypes derived from gene duplication, deletion, and hybridization.
[Show abstract][Hide abstract] ABSTRACT: Next-generation sequencing technologies have led to rapid progress in the fields of human and nonhuman primate (NHP) genomics. The less expensive and more efficient technologies have enabled the sequencing of human genomes from multiple populations and the sequencing of many NHP species. NHP genomes have been sequenced for two main reasons: (1) their importance as animal models in biomedical research and (2) their phylogenetic relationship to humans and use in derivative evolutionary studies. NHPs are valuable animal models for a variety of diseases, most notably for human immunodeficiency virus/acquired immunodeficiency syndrome research, and for vaccine development. Knowledge about the variation in primate immune response loci can provide essential insights into relevant immune function. However, perhaps ironically considering their central role in infectious disease, the accumulation of sequence detail from genomic regions harboring immune response loci, such as the major histocompatibility complex and killer immunoglobulin-like receptors, has been slow. This deficiency is, at least in part, due to the highly repetitive and polymorphic nature of these regions and is being addressed by the application of special approaches to targeted sequencing of the immune response genomic regions. We discuss one such targeting approach that has successfully yielded complete phased genomic sequences from complex genomic regions and is now being used to resequence macaque and other primate major histocompatibility complex regions. The essential detail contained within the genomics of the NHP immune response is now being assembled, and the realization of precise comparisons between NHP and human immune genomics is close at hand, further enhancing the NHP animal model in the search for effective treatments for human disease.
ILAR journal / National Research Council, Institute of Laboratory Animal Resources 01/2013; 54(2):181-95. DOI:10.1093/ilar/ilt043 · 1.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The fast evolving human KIR gene family encodes variable lymphocyte receptors specific for polymorphic HLA class I determinants. Nucleotide sequences for 24 representative human KIR haplotypes were determined. With three previously defined haplotypes, this gave a set of 12 group A and 15 group B haplotypes for assessment of KIR variation. The seven gene-content haplotypes are all combinations of four centromeric and two telomeric motifs. 2DL5, 2DS5 and 2DS3 can be present in centromeric and telomeric locations. With one exception, haplotypes having identical gene content differed in their combinations of KIR alleles. Sequence diversity varied between haplotype groups and between centromeric and telomeric halves of the KIR locus. The most variable A haplotype genes are in the telomeric half, whereas the most variable genes characterizing B haplotypes are in the centromeric half. Of the highly polymorphic genes, only the 3DL3 framework gene exhibits a similar diversity when carried by A and B haplotypes. Phylogenetic analysis and divergence time estimates, point to the centromeric gene-content motifs that distinguish A and B haplotypes having emerged ~6 million years ago, contemporaneously with the separation of human and chimpanzee ancestors. In contrast, the telomeric motifs that distinguish A and B haplotypes emerged more recently, ~1.7 million years ago, before the emergence of Homo sapiens. Thus the centromeric and telomeric motifs that typify A and B haplotypes have likely been present throughout human evolution. The results suggest the common ancestor of A and B haplotypes combined a B-like centromeric region with an A-like telomeric region.
PLoS ONE 12/2010; 5(12):e15115. DOI:10.1371/journal.pone.0015115 · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We carried out a resequencing project that examined 552 kb of sequence from each of 46 individual HLA haplotypes representing a diversity of HLA allele types, generating nearly 27 Mb of fully phased genomic sequence. Haplotype blocks were defined extending from telomeric of HLA-F to centromeric of HLA-DP including in total 5186 MHC SNPs. To investigate basic questions about the evolutionary origin of common HLA haplotypes, and to obtain an estimate of rare variation in the MHC, we similarly examined two additional sets of samples. In 19 independent HLA-A1, B8, DR3 chromosomes, the most common HLA haplotype in Northern European Caucasians, variation was found at 11 SNP positions in the 3600-kb region from HLA-A to DR. Partial resequencing of 282 individuals in the gene-dense class III region identified significant variability beyond what could have been detected by linkage to common SNPs.
[Show abstract][Hide abstract] ABSTRACT: The innate antiviral factor TRIM5alpha restricts the replication of some retroviruses through its interaction with the viral capsid protein, leading to abortive infection. While overexpression of human TRIM5alpha results in modest restriction of human immunodeficiency virus type 1 (HIV-1), this inhibition is insufficient to block productive infection of human cells. We hypothesized that polymorphisms within TRIM5 may result in increased restriction of HIV-1 infection. We sequenced the TRIM5 gene (excluding exon 5) and the 4.8-kb 5' putative regulatory region in genomic DNA from 110 HIV-1-infected subjects and 96 exposed seronegative persons, along with targeted gene sequencing in a further 30 HIV-1-infected individuals. Forty-eight single nucleotide polymorphisms (SNPs), including 20 with allele frequencies of >1.0%, were identified. Among these were two synonymous and eight nonsynonymous coding polymorphisms. We observed no association between TRIM5 polymorphism in HIV-1-infected subjects and their set-point viral load after acute infection, although one TRIM5 haplotype was weakly associated with more rapid CD4(+) T-cell loss. Importantly, a TRIM5 haplotype containing the nonsynonymous SNP R136Q showed increased frequency among HIV-1-infected subjects relative to exposed seronegative persons, with an odds ratio of 5.49 (95% confidence interval = 1.83 to 16.45; P = 0.002). Nonetheless, we observed no effect of individual TRIM5alpha nonsynonymous mutations on the in vitro HIV-1 susceptibility of CD4(+) T cells. Therefore, any effect of TRIM5alpha polymorphism on HIV-1 infection in primary lymphocytes may depend on combinations of SNPs or on DNA sequences in linkage disequilibrium with the TRIM5alpha coding sequence.
Journal of Virology 03/2006; 80(5):2463-71. DOI:10.1128/JVI.80.5.2463-2471.2006 · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: With the advent of modern genomic sequencing technology the ability to obtain new sequence data and to acquire allelic polymorphism data from a broad range of samples has become routine. In this regard, our investigations have started with the most polymorphic of genetic regions fundamental to the immune response in the major histocompatibility complex (MHC). Starting with the completed human MHC genomic sequence, we have developed a resource of methods and information that provide ready access to a large portion of human and nonhuman primate MHCs. This resource consists of a set of primer pairs or amplicons that can be used to isolate about 15% of the 4.0 Mb MHC. Essentially similar studies are now being carried out on a set of immune response loci to broaden the usefulness of the data and tools developed. A panel of 100 genes involved in the immune response have been targeted for single nucleotide polymorphism (SNP) discovery efforts that will analyze 120 Mb of sequence data for the presence of immune-related SNPs. The SNP data provided from the MHC and from the immune response panel has been adapted for use in studies of evolution, MHC disease associations, and clinical transplantation.
[Show abstract][Hide abstract] ABSTRACT: Modern genetic analysis can be divided into three main areas of investigation. The first is data acquisition, in the form of genomic sequence and the cataloguing of polymorphism data of the single nucleotide polymorphism variety (so called SNPs). Once identified, such genetic information can be adapted into high throughput tests to examine genetic information in large populations, making the analysis of sufficiently large numbers both cost and time effective so that relatively low-penetrant genetic effects can be accurately detected. The third step is correlating variation with phenotype (e.g. disease susceptibility or resistance) for a variety of disorders is paramount in our motivation and indeed is a common goal of modern human genetic analysis. While the technology to acquire vast amounts of genetic data is now well established and continues to expand, the ability to deal with such data, from the process of acquisition, storage, and analysis depends fundamentally on a solid informatics infrastructure as an essential component. Indeed, most of the major gains in productivity in this field are to be realized on the informatics front, and involve automating data acquisition, defining and sorting data in databases for quality control and analysis and facilitating access to data for the large variety of data analyses. Informatics-related issues including those relating to data acquisition, database structure, and analysis tools are summarized here in an effort to define some of the issues relevant to establishing informatics infrastructure in a small genetics laboratory focused on resequencing human immune response genes. From inherited diseases to drug efficacy to the specific genetic changes occurring during tumor development, this new field of medical genetics promises a profound impact on the state of human health. Ultimately, any and all advances in this field will continue to depend on major investments in informatics.
[Show abstract][Hide abstract] ABSTRACT: Here we report the first complete sequence and gene map of a
human major histocompatibility complex (MHC), a region on
chromosome 6 which is essential to the immune system (reviewed
in ref. 1).When it was discovered over 50 years ago the region was
thought to specify histocompatibility genes, but their nature has
been resolved only in the last two decades. Although many of the
224 identified gene loci (128 predicted to be expressed) are still of
unknown function, we estimate that about 40% of the expressed
genes have immune system function. Over 50% of the MHC has
been sequenced twice, in different haplotypes, giving insight into
the extraordinary polymorphism and evolution of this region.
Several genes, particularly of theMHCclass II and III regions, can
be traced by sequence similarity and synteny to over 700 million
years ago, clearly predating the emergence of the adaptive
immune system some 400 million years ago. The sequence is
expected to be invaluable for the identification of many common
disease loci. In the past, the search for these loci has been
hampered by the complexity of high gene density and linkage
[Show abstract][Hide abstract] ABSTRACT: Knowledge of DNA sequence variation may help us understand how genetic variability gives rise to functional variability and, in so doing, revolutionize the development of strategies to combat and prevent disease. Single nucleotide polymorphisms (SNPs) are stable, inherited, biallelic, single base pair differences which are present in the human genome at a density of 1 to 10 per 1,000 nucleotides. It is anticipated that SNPs will account for much of the functional heterogeneity in gene expression and protein activity exhibited in the human population. Susceptibility to or protection from a number of diseases, particularly those of autoimmune etiology, has been associated with specific alleles of the human leukocyte antigen (HLA) complex. Interestingly, the precise molecular defects in the HLA genes are unknown and the notion that non-HLA genes, within the same chromosomal region, are involved remains a formal possibility. We have determined the nucleotide sequence of a contiguous 2.2 Mbp segment of chromosome six that includes all of the HLA class I region, and have identified over 10,000 SNPs therein. Because of the derivative knowledge of gene and SNP content and position, the scientific community is now uniquely poised to identify disease-contributory SNPs that lie within the MHC.