RESUMO
Although blood group variation was first described over a century ago, our understanding of the genetic variation affecting antigenic expression on the red blood cell surface in many populations is lacking. This deficit limits the ability to accurately type patients, especially as serological testing is not available for all described blood groups, and targeted genotyping panels may lack rare or population-specific variants. Here, we perform serological assays across 24 antigens and whole genome sequencing on 100 Omanis, a population underrepresented in genomic databases. We inferred blood group phenotypes using the most commonly typed genetic variants. The comparison of serological to inferred phenotypes resulted in an average concordance of 96.9%. Among the 22 discordances, we identify seven known variants in four blood groups that, to our knowledge, have not been previously reported in Omanis. Incorporating these variants for phenotype inference, concordance increases to 98.8%. Additionally, we describe five candidate variants in the Lewis, Lutheran, MNS, and P1 blood groups that may affect antigenic expression, although further functional confirmation is required. Notably, we identify several blood group alleles most common in African populations, likely introduced to Oman by gene flow over the last thousand years. These findings highlight the need to evaluate individual populations and their population history when considering variants to include in genotype panels for blood group typing. This research will inform future work in blood banks and transfusion services.
RESUMO
Leukocyte telomere length is a highly polygenic trait that has been associated with a complex range of lifestyle factors and disease risk. McQuillan et al.'s results comparing telomere length to malaria incidence rates suggest that infections may be another important factor, possibly through permanent shortening of telomeres in hematopoietic progenitor cells.
Assuntos
Leucócitos , Malária , Telômero , Humanos , Malária/epidemiologia , Doenças Endêmicas , Encurtamento do Telômero , IncidênciaRESUMO
Detection of microbial pathogens is a primary function of many mammalian immune proteins. This is accomplished through the recognition of diverse microbial-produced macromolecules including proteins, nucleic acids, and carbohydrates. Pathogens subvert host defenses by rapidly changing these structures to avoid detection, placing strong selective pressures on host immune proteins that repeatedly adapt to remain effective. Signatures of rapid evolution have been identified in numerous immunity proteins involved in the detection of pathogenic protein substrates, but whether similar signals can be observed in host proteins engaged in interactions with other types of pathogen-derived molecules has received less attention. This focus on protein-protein interfaces has largely obscured the study of fungi as contributors to host-pathogen conflicts, despite their importance as a formidable class of vertebrate pathogens. Here, we provide evidence that mammalian immune receptors involved in the detection of microbial glycans have been subject to recurrent positive selection. We find that rapidly evolving sites in these genes cluster in key functional domains involved in carbohydrate recognition. Further, we identify convergent patterns of substitution and evidence for balancing selection in one particular gene, MelLec, which plays a critical role in controlling invasive fungal disease. Our results also highlight the power of evolutionary analyses to reveal uncharacterized interfaces of host-pathogen conflict by identifying genes, like CLEC12A, with strong signals of positive selection across mammalian lineages. These results suggest that the realm of interfaces shaped by host-microbe conflicts extends beyond the world of host-viral protein-protein interactions and into the world of microbial glycans and fungi.
Assuntos
Proteínas de Transporte , Evolução Molecular , Animais , Proteínas de Transporte/genética , Mamíferos/genética , Fungos/genética , Polissacarídeos , Interações Hospedeiro-Patógeno/genéticaRESUMO
Host genetic factors can confer resistance against malaria1, raising the question of whether this has led to evolutionary adaptation of parasite populations. Here we searched for association between candidate host and parasite genetic variants in 3,346 Gambian and Kenyan children with severe malaria caused by Plasmodium falciparum. We identified a strong association between sickle haemoglobin (HbS) in the host and three regions of the parasite genome, which is not explained by population structure or other covariates, and which is replicated in additional samples. The HbS-associated alleles include nonsynonymous variants in the gene for the acyl-CoA synthetase family member2-4 PfACS8 on chromosome 2, in a second region of chromosome 2, and in a region containing structural variation on chromosome 11. The alleles are in strong linkage disequilibrium and have frequencies that covary with the frequency of HbS across populations, in particular being much more common in Africa than other parts of the world. The estimated protective effect of HbS against severe malaria, as determined by comparison of cases with population controls, varies greatly according to the parasite genotype at these three loci. These findings open up a new avenue of enquiry into the biological and epidemiological significance of the HbS-associated polymorphisms in the parasite genome and the evolutionary forces that have led to their high frequency and strong linkage disequilibrium in African P. falciparum populations.
Assuntos
Genótipo , Hemoglobina Falciforme/genética , Adaptação ao Hospedeiro/genética , Malária Falciparum/sangue , Malária Falciparum/parasitologia , Parasitos/genética , Plasmodium falciparum/genética , Alelos , Animais , Criança , Feminino , Gâmbia/epidemiologia , Genes de Protozoários/genética , Humanos , Quênia/epidemiologia , Desequilíbrio de Ligação , Malária Falciparum/epidemiologia , Masculino , Polimorfismo GenéticoRESUMO
Glycophorins are the most abundant sialoglycoproteins on the surface of human erythrocyte membranes. Genetic variation in glycophorin region of human chromosome 4 (containing GYPA, GYPB, and GYPE genes) is of interest because the gene products serve as receptors for pathogens of major public health interest, including Plasmodiumsp., Babesiasp., Influenza virus, Vibrio cholerae El Tor Hemolysin, and Escherichia coli. A large structural rearrangement and hybrid glycophorin variant, known as Dantu, which was identified in East African populations, has been linked with a 40% reduction in risk for severe malaria. Apart from Dantu, other large structural variants exist, with the most common being deletion of the whole GYPB gene and its surrounding region, resulting in multiple different deletion forms. In West Africa particularly, these deletions are estimated to account for between 5 and 15% of the variation in different populations, mostly attributed to the forms known as DEL1 and DEL2. Due to the lack of specific variant assays, little is known of the distribution of these variants. Here, we report a modification of a previous GYPB DEL1 assay and the development of a novel GYPB DEL2 assay as high-throughput PCR-RFLP assays, as well as the identification of the crossover/breakpoint for GYPB DEL2. Using 393 samples from three study sites in Ghana as well as samples from HapMap and 1000 G projects for validation, we show that our assays are sensitive and reliable for genotyping GYPB DEL1 and DEL2. To the best of our knowledge, this is the first report of such high-throughput genotyping assays by PCR-RFLP for identifying specific GYPB deletion types in populations. These assays will enable better identification of GYPB deletions for large genetic association studies and functional experiments to understand the role of this gene cluster region in susceptibility to malaria and other diseases.
Assuntos
Sequência de Bases , Técnicas de Genotipagem , Glicoforinas/genética , Polimorfismo de Fragmento de Restrição , Deleção de Sequência , Adulto , Criança , Pré-Escolar , Feminino , Gana , Humanos , Lactente , Malária/genética , MasculinoRESUMO
A new study reports genome-wide variation in 163 vervet monkeys from across their taxonomic and geographic ranges. The analysis suggests a complex history of admixture and identifies signals of repeated evolutionary selection, some of which may be linked to response to simian immunodeficiency virus.
Assuntos
Síndrome de Imunodeficiência Adquirida dos Símios , Vírus da Imunodeficiência Símia , Adaptação Fisiológica , Animais , Evolução Biológica , Chlorocebus aethiops , FilogeniaRESUMO
The malaria parasite Plasmodium falciparum invades human red blood cells by a series of interactions between host and parasite surface proteins. By analyzing genome sequence data from human populations, including 1269 individuals from sub-Saharan Africa, we identify a diverse array of large copy-number variants affecting the host invasion receptor genes GYPA and GYPB We find that a nearby association with severe malaria is explained by a complex structural rearrangement involving the loss of GYPB and gain of two GYPB-A hybrid genes, which encode a serologically distinct blood group antigen known as Dantu. This variant reduces the risk of severe malaria by 40% and has recently increased in frequency in parts of Kenya, yet it appears to be absent from west Africa. These findings link structural variation of red blood cell invasion receptors with natural resistance to severe malaria.
Assuntos
Resistência à Doença/genética , Eritrócitos/parasitologia , Glicoforinas , Interações Hospedeiro-Parasita/genética , Malária Falciparum/genética , Modelos Moleculares , Adulto , África Subsaariana , Criança , Variações do Número de Cópias de DNA/genética , Frequência do Gene , Genoma Humano/genética , Glicoforinas/química , Glicoforinas/genética , Glicoforinas/metabolismo , Humanos , Estrutura Secundária de Proteína , Receptores de Superfície Celular/química , Receptores de Superfície Celular/genéticaRESUMO
The DNA-binding protein PRDM9 has a critical role in specifying meiotic recombination hotspots in mice and apes, but it appears to be absent from other vertebrate species, including birds. To study the evolution and determinants of recombination in species lacking the gene that encodes PRDM9, we inferred fine-scale genetic maps from population resequencing data for two bird species: the zebra finch, Taeniopygia guttata, and the long-tailed finch, Poephila acuticauda. We found that both species have recombination hotspots, which are enriched near functional genomic elements. Unlike in mice and apes, most hotspots are shared between the two species, and their conservation seems to extend over tens of millions of years. These observations suggest that in the absence of PRDM9, recombination targets functional features that both enable access to the genome and constrain its evolution.
Assuntos
Evolução Molecular , Tentilhões/genética , Regulação da Expressão Gênica , Recombinação Genética , Proteínas Repressoras/genética , Animais , Mapeamento Cromossômico , Genoma , Especificidade da EspécieRESUMO
Instances in which natural selection maintains genetic variation in a population over millions of years are thought to be extremely rare. We conducted a genome-wide scan for long-lived balancing selection by looking for combinations of SNPs shared between humans and chimpanzees. In addition to the major histocompatibility complex, we identified 125 regions in which the same haplotypes are segregating in the two species, all but two of which are noncoding. In six cases, there is evidence for an ancestral polymorphism that persisted to the present in humans and chimpanzees. Regions with shared haplotypes are significantly enriched for membrane glycoproteins, and a similar trend is seen among shared coding polymorphisms. These findings indicate that ancient balancing selection has shaped human variation and point to genes involved in host-pathogen interactions as common targets.
Assuntos
Genoma Humano/genética , Interações Hospedeiro-Patógeno/genética , Pan troglodytes/genética , Seleção Genética , Animais , Sequência de Bases , Estudos de Associação Genética , Haplótipos , Humanos , Dados de Sequência Molecular , Linhagem , Polimorfismo de Nucleotídeo ÚnicoRESUMO
Understanding why some species have more genetic diversity than others is central to the study of ecology and evolution, and carries potentially important implications for conservation biology. Yet not only does this question remain unresolved, it has largely fallen into disregard. With the rapid decrease in sequencing costs, we argue that it is time to revive it.
Assuntos
Drosophila/genética , Variação Genética , Animais , Cromossomos de Insetos/genética , Ecossistema , Geografia , Modelos Biológicos , Nucleotídeos/genética , Filogenia , Seleção Genética , Cromossomos Sexuais/genética , Especificidade da EspécieRESUMO
To study the evolution of recombination rates in apes, we developed methodology to construct a fine-scale genetic map from high-throughput sequence data from 10 Western chimpanzees, Pan troglodytes verus. Compared to the human genetic map, broad-scale recombination rates tend to be conserved, but with exceptions, particularly in regions of chromosomal rearrangements and around the site of ancestral fusion in human chromosome 2. At fine scales, chimpanzee recombination is dominated by hotspots, which show no overlap with those of humans even though rates are similarly elevated around CpG islands and decreased within genes. The hotspot-specifying protein PRDM9 shows extensive variation among Western chimpanzees, and there is little evidence that any sequence motifs are enriched in hotspots. The contrasting locations of hotspots provide a natural experiment, which demonstrates the impact of recombination on base composition.