scholarly journals Improved Characterization of Balancing Selection Genome Wide and a Detailed Look at HLA Genes

2021 ◽  
Author(s):  
Tristan J Hayeck ◽  
Timothy L. Mosbruger ◽  
Jonathan P Bradfield ◽  
Adam G Gleason ◽  
George Damianos ◽  
...  
Keyword(s):  
Balancing Selection ◽  
Allelic Diversity ◽  
Exon 2 ◽  
Multiple Alleles ◽  
Bayesian Techniques ◽  
Hla Genes ◽  
Genome Wide ◽  
Evolutionary Simulation ◽  
Critical Regions

Balancing selection occurs when different evolutionary pressures impact the fitness of multiple alleles, resulting in increased allelic diversity in the population. A new statistical method was developed to test for selection, improving inference by using efficient Bayesian techniques to test for density and strength of linkage disequilibrium. Evolutionary simulation studies showed that the method consistently outperformed existing methods. Using this methodology, we tested for novel signals of balancing selection genome wide in 500 samples from phased trios. Several novel signals of selection appeared in CYP2A7, GPC6, and CNR2 across multiple ancestries. Additionally, tests in SIRPA demonstrate dramatically strong selection signal, significantly higher than previously observed. Well-known signals around olfactory genes and the MHC, containing HLA genes associated with the immune response, also demonstrated strong signatures of selection. So, utilizing data from the 17th IHIW, a follow up analysis was then performed by leveraging over seven thousand HLA typed samples by NGS; in contrast, the genome wide scan did not include a detailed characterization of the HLA genes. The strongest signals observed in the IHIW samples were in DQA1 and DQB1 in or around exon 2, the portion of the gene responsible for antigen presentation and most likely to be under environmental and evolutionary pressure. Our new statistical approach and analysis suggest novel evolutionary pressure in new regions and additionally highlight the importance of improved sequencing and characterization of variation across the extended MHC and other critical regions.

scholarly journals Population Differentiation at the HLA Genes

2017 ◽  
Author(s):  
Débora Y. C. Brandt ◽  
Jônatas César ◽  
Jérôme Goudet ◽  
Diogo Meyer
Keyword(s):  
Population Differentiation ◽  
Balancing Selection ◽  
Global Scale ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Hla Genes ◽  
Genome Wide ◽  
Different Populations ◽  
Genomic Regions

ABSTRACTBalancing selection is defined as a class of selective regimes that maintain polymorphism above what is expected under neutrality. Theory predicts that balancing selection reduces population differentiation, as measured by FST. However, balancing selection regimes in which different sets of alleles are maintained in different populations could increase population differentiation. To tackle this issue, we investigated population differentiation at the HLA genes, which constitute the most striking example of balancing selection in humans. We found that population differentiation of single nucleotide polymorphisms (SNPs) at the HLA genes is on average lower than that of SNPs in other genomic regions. However, this result depends on accounting for the differences in allele frequency between selected and putatively neutral sites. Our finding of reduced differentiation at SNPs within HLA genes suggests a predominant role of shared selective pressures among populations at a global scale. However, in pairs of closely related populations, where genome-wide differentiation is low, differentiation at HLA is higher than in other genomic regions. This pattern was reproduced in simulations of overdominant selection. We conclude that population differentiation at the HLA genes is generally lower than genome-wide, but it may be higher for recently diverged population pairs, and that this pattern can be explained by a simple overdominance regime.

scholarly journals Distinct evolutionary strategies of human leucocyte antigen loci in pathogen-rich environments

2012 ◽  
Vol 367 (1590) ◽  
pp. 830-839 ◽  
Author(s):  
Alicia Sanchez-Mazas ◽  
Jean-François Lemaître ◽  
Mathias Currat
Keyword(s):  
Genetic Diversity ◽  
Genetic Drift ◽  
Human Leucocyte Antigen ◽  
Balancing Selection ◽  
Allelic Diversity ◽  
Hla Class I ◽  
Significant Negative Correlation ◽  
Evolutionary Strategies ◽  
Hla Genes ◽  
Geographical Distances

Human leucocyte antigen (HLA) loci have a complex evolution where both stochastic (e.g. genetic drift) and deterministic (natural selection) forces are involved. Owing to their extraordinary level of polymorphism, HLA genes are useful markers for reconstructing human settlement history. However, HLA variation often deviates significantly from neutral expectations towards an excess of genetic diversity. Because HLA molecules play a crucial role in immunity, this observation is generally explained by pathogen-driven-balancing selection (PDBS). In this study, we investigate the PDBS model by analysing HLA allelic diversity on a large database of 535 populations in relation to pathogen richness. Our results confirm that geographical distances are excellent predictors of HLA genetic differentiation worldwide. We also find a significant positive correlation between genetic diversity and pathogen richness at two HLA class I loci (HLA-A and -B), as predicted by PDBS, and a significant negative correlation at one HLA class II locus (HLA-DQB1). Although these effects are weak, as shown by a loss of significance when populations submitted to rapid genetic drift are removed from the analysis, the inverse relationship between genetic diversity and pathogen richness at different loci indicates that HLA genes have adopted distinct evolutionary strategies to provide immune protection in pathogen-rich environments.

Genome-wide Characterization of Major Intrinsic Protein (MIP) Gene Family in Brachypodium distachyon

2018 ◽  
Vol 13 (5) ◽  
pp. 536-552 ◽  
Author(s):  
Ankush Ashok Saddhe ◽  
Shweta ◽  
Kareem A. Mosa ◽  
Kundan Kumar ◽  
Manoj Prasad ◽  
...  
Keyword(s):  
Gene Family ◽  
Brachypodium Distachyon ◽  
Major Intrinsic Protein ◽  
Intrinsic Protein ◽  
Genome Wide

Genome wide identification and characterization of abiotic stress responsive lncRNAs in Capsicum annuum

2021 ◽  
Author(s):  
Pooja Moni Baruah ◽  
Debasish B. Krishnatreya ◽  
Kuntala Sarma Bordoloi ◽  
Sarvajeet Singh Gill ◽  
Niraj Agarwala
Keyword(s):  
Abiotic Stress ◽  
Capsicum Annuum ◽  
Genome Wide ◽  
Identification And Characterization

scholarly journals Genome-Wide Identification and Characterization of Long Noncoding RNAs Involved in Chinese Wheat Mosaic Virus Infection of Nicotiana benthamiana

Biology ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 232
Author(s):  
Weiran Zheng ◽  
Haichao Hu ◽  
Qisen Lu ◽  
Peng Jin ◽  
Linna Cai ◽  
...  
Keyword(s):  
Virus Infection ◽  
Mosaic Virus ◽  
Nicotiana Benthamiana ◽  
Noncoding Rnas ◽  
Long Noncoding Rnas ◽  
Differentially Expressed ◽  
Genome Wide ◽  
Chinese Wheat

Recent studies have shown that a large number of long noncoding RNAs (lncRNAs) can regulate various biological processes in animals and plants. Although lncRNAs have been identified in many plants, they have not been reported in the model plant Nicotiana benthamiana. Particularly, the role of lncRNAs in plant virus infection remains unknown. In this study, we identified lncRNAs in N. benthamiana response to Chinese wheat mosaic virus (CWMV) infection by RNA sequencing. A total of 1175 lncRNAs, including 65 differentially expressed lncRNAs, were identified during CWMV infection. We then analyzed the functions of some of these differentially expressed lncRNAs. Interestingly, one differentially expressed lncRNA, XLOC_006393, was found to participate in CWMV infection as a precursor to microRNAs in N. benthamiana. These results suggest that lncRNAs play an important role in the regulatory network of N. benthamiana in response to CWMV infection.

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