Human Genome Diversity Research Articles

Making and Measuring the Effect of Mutations on a Massive Scale

How does a protein's sequence encode its fold and function? How do changes in sequence influence disease risk, prognosis and treatment? How do gene expression patterns combine with protein activity to define cellular processes like growth, migration and communication? The Fowler lab is interested in developing new ways to probe the relationship between genotype and phenotype, enabling us to better answer these questions. In particular, we have applied large-scale mutagenesis to reveal a new mechanism of regulation in Src kinase involving a previously undiscovered interaction between Src's SH4 and catalytic domains. We have also used large-scale mutagenesis to better understand the meaning of variants in human genomes, particularly in the context of cancer-related genes. Finally, we employed large-scale mutagenesis data from diverse proteins to better understand and predict the impact of mutations.

Identifying and Interpreting Apparent Neanderthal Ancestry in African Individuals

Admixture has played a prominent role in shaping patterns of human genomic variation, including gene flow with now-extinct hominins like Neanderthals and Denisovans. Here, we describe a novel probabilistic method called IBDmix to identify introgressed hominin sequences, which, unlike existing approaches, does not use a modern reference population. We applied IBDmix to 2,504 individuals from geographically diverse populations to identify and analyze Neanderthal sequences segregating in modern humans. Strikingly, we find that African individuals carry a stronger signal of Neanderthal ancestry than previously thought. We show that this can be explained by genuine Neanderthal ancestry due to migrations back to Africa, predominately from ancestral Europeans, and gene flow into Neanderthals from an early dispersing group of humans out of Africa. Our results refine our understanding of Neanderthal ancestry in African and non-African populations and demonstrate that remnants of Neanderthal genomes survive in every modern human population studied to date.

Dating genomic variants and shared ancestry in population-scale sequencing data.

The origin and fate of new mutations within species is the fundamental process underlying evolution. However, while much attention has been focused on characterizing the presence, frequency, and phenotypic impact of genetic variation, the evolutionary histories of most variants are largely unexplored. We have developed a nonparametric approach for estimating the date of origin of genetic variants in large-scale sequencing data sets. The accuracy and robustness of the approach is demonstrated through simulation. Using data from two publicly available human genomic diversity resources, we estimated the age of more than 45 million single-nucleotide polymorphisms (SNPs) in the human genome and release the Atlas of Variant Age as a public online database. We characterize the relationship between variant age and frequency in different geographical regions and demonstrate the value of age information in interpreting variants of functional and selective importance. Finally, we use allele age estimates to power a rapid approach for inferring the ancestry shared between individual genomes and to quantify genealogical relationships at different points in the past, as well as to describe and explore the evolutionary history of modern human populations.

The Role of Natural Selection in the Formation of the Genetic Structure of Populations by SNP Markers in Association with Body Mass Index and Obesity

Obesity is one of the major challenges in modern society. More than a third of the world's population suffers froms overweight. This phenotype affects the quality of life and is associated with cardiovascular diseases, diabetes, cancer and reproductive disorders. The population variability of allele frequencies of 26 single nucleotide polymorphisms, in association with obesity and body mass index, according to data from genome-wide association studies (GWASs) is discussed in this study. Genetic variability was analyzed in populations of Northern Eurasia and populations from the human genome diversity project (HGDP). The population samples are characterized by high genetic diversity that correlates with climatic and geographical parameters. The results of the test for searching for natural selection signals revealed a selection effect for rs1167827 of the HIP1 gene, rs7138803 and rs7164727 located in the intergenic region, rs7141420 of the NRXN3 gene, rs7498665 of the SH2B1 gene, and rs7903146 of the TCF7L2 gene.

Impact of TLR9 gene polymorphism on cervical HPV infection and its progression to cervical cancer

Impact of TLR9 gene polymorphism on cervical HPV infection and its progression to cervical cancer - IJOGR- Print ISSN No: - 2394-2746 Online ISSN No:- 2394-2754 Article DOI No:- 10.18231/j.ijogr.2019.105, Indian Journal of Obstetrics and Gynecology Research-Indian J Obstet Gynecol Res

Variants of DNA mismatch repair genes derived from 33,998 Chinese individuals with and without cancer reveal their highly ethnic-specific nature

PurposeDNA mismatch repair (MMR) genes play important roles in maintaining genome stability. Mutations in MMR genes disrupt their mismatch repair function, cause genome instability and lead to increased risk of cancer in the mutation carriers as represented by Lynch Syndrome. Studies have identified a large number of MMR variants, mostly in the Caucasian population, whereas data from non-Caucasian populations remain poorly illustrated. With the population size of 1.4 billion, knowledge of MMR variants in the Chinese population can be valuable in understanding the roles of ethnic MMR variation and cancer and to further guide clinical applications in MMR-related cancer prevention and treatment in the Chinese population. In this study, we systematically analysed the MMR variants from the Chinese population. Experimental designWe performed a comprehensive MMR data mining and collected all the MMR variation data reported from 33,998 Chinese individuals consisting of 23,938 cancer and 10,060 non-cancer cases between January 1997 to May 2019. For the collected data, we performed standardisation following Human Genome Variation Society nomenclature and reannotated the MMR variant data following American College of Medical Genetics and Genomics guidelines and comparing with non-Chinese MMR data on various aspects. ResultsWe identified a total of 540 MMR variants in the Chinese population, including 194 in MLH1, 181 in MSH2, 59 in MSH6, 53 in PMS2 single-base/indel changes and 53 large deletions/duplications in MLH1, MSH2, MSH6 and PMS2, respectively. We determined that the pathogenic/likely pathogenic carrier rate in the Chinese population was 1.6%. Comparative analysis in variant spectrum, variant types, clinical classification and founder mutations showed substantial differences of MMR variation between Chinese and non-Chinese populations and the fact that over 90% of the variants were only present in the Chinese ethnicity reveals the highly ethnic-specific nature of the Chinese MMR variation . We also developed an open-access database, dbMMR-Chinese, to host all data (https://dbMMR-chinese.fhs.um.edu.mo). The rich MMR data from a large non-Caucasian population should be valuable to study MMR variation and its relationship with cancer and provide a valuable reference resource for MMR-related cancer prevention and treatment. ConclusionOur study provides the largest MMR data set from a single non-Caucasian population and reveals that MMR variation in the humans can be highly ethnic-specific.

The Alliance of Genome Resources: Building a Modern Data Ecosystem for Model Organism Databases.

Model organisms are essential experimental platforms for discovering gene functions, defining protein and genetic networks, uncovering functional consequences of human genome variation, and for modeling human disease. For decades, researchers who use model organisms have relied on Model Organism Databases (MODs) and the Gene Ontology Consortium (GOC) for expertly curated annotations, and for access to integrated genomic and biological information obtained from the scientific literature and public data archives. Through the development and enforcement of data and semantic standards, these genome resources provide rapid access to the collected knowledge of model organisms in human readable and computation-ready formats that would otherwise require countless hours for individual researchers to assemble on their own. Since their inception, the MODs for the predominant biomedical model organisms [Mus sp. (laboratory mouse), Saccharomyces cerevisiae, Drosophila melanogaster, Caenorhabditis elegans, Danio rerio, and Rattus norvegicus] along with the GOC have operated as a network of independent, highly collaborative genome resources. In 2016, these six MODs and the GOC joined forces as the Alliance of Genome Resources (the Alliance). By implementing shared programmatic access methods and data-specific web pages with a unified “look and feel,” the Alliance is tackling barriers that have limited the ability of researchers to easily compare common data types and annotations across model organisms. To adapt to the rapidly changing landscape for evaluating and funding core data resources, the Alliance is building a modern, extensible, and operationally efficient “knowledge commons” for model organisms using shared, modular infrastructure.

From Clinical Phenotype to Genotypic Modelling: Incidence and Prevalence of Recessive Dystrophic Epidermolysis Bullosa (RDEB).

BackgroundRecessive dystrophic epidermolysis bullosa (RDEB) is an inherited genetic disorder characterized by recurrent and chronic open wounds with significant morbidity, impaired quality of life, and early mortality. RDEB patients demonstrate reduction or structural alteration type VII collagen (C7) owing to mutations in the gene COL7A1, the main component of anchoring fibrils (AF) necessary to maintain epidermal-dermal cohesion. While over 700 alterations in COL7A1 have been reported to cause dystrophic epidermolysis bullosa (DEB), which may be inherited in an autosomal dominant (DDEB) or autosomal recessive pattern (RDEB), the incidence and prevalence of RDEB is not well defined. To date, the widely estimated incidence (0.2–6.65 per million births) and prevalence (3.5–20.4 per million people) of RDEB has been primarily characterized by limited analyses of clinical databases or registries.MethodsUsing a genetic modelling approach, we use whole exome and genome sequencing data to estimate the allele frequency of pathogenic variants. Through the ClinVar and NCBI database of human genome variants and phenotypes, DEB Register, and analyzing premature COL7A1 termination variants we built a model to predict the pathogenicity of previously unclassified variants. We applied the model to publicly available sequences from the Exome Aggregation Consortium (ExAC) and Genome Aggregation Database (gnomAD) and identified variants which were classified as pathogenic for RDEB from which we estimate disease incidence and prevalence.ResultsGenetic modelling applied to the whole exome and genome sequencing data resulted in the identification of predicted RDEB pathogenic alleles, from which our estimate of the incidence of RDEB is 95 per million live births, 30 times the 3.05 per million live birth incidence estimated by the National Epidermolysis Bullosa Registry (NEBR). Using a simulation approach, we estimate a mean of approximately 3,850 patients in the US who may benefit from COL7A1-mediated treatments in the US.ConclusionWe conclude that genetic allele frequency estimation may enhance the underdiagnosis of rare genetic diseases generally, and RDEB specifically, which may improve incidence and prevalence estimates of patients who may benefit from treatment.

Recovery of non-reference sequences missing from the human reference genome

BackgroundThe non-reference sequences (NRS) represent structure variations in human genome with potential functional significance. However, besides the known insertions, it is currently unknown whether other types of structure variations with NRS exist.ResultsHere, we compared 31 human de novo assemblies with the current reference genome to identify the NRS and their location. We resolved the precise location of 6113 NRS adding up to 12.8 Mb. Besides 1571 insertions, we detected 3041 alternate alleles, which were defined as having less than 90% (or none) identity with the reference alleles. These alternate alleles overlapped with 1143 protein-coding genes including a putative novel MHC haplotype. Further, we demonstrated that the alternate alleles and their flanking regions had high content of tandem repeats, indicating that their origin was associated with tandem repeats.ConclusionsOur study detected a large number of NRS including many alternate alleles which are previously uncharacterized. We suggested that the origin of alternate alleles was associated with tandem repeats. Our results enriched the spectrum of genetic variations in human genome.

Variation in nomenclature of somatic variants for selection of oncological therapies: Can we reach a consensus soon?

A standardized nomenclature for reporting oncology biomarker variants is key to avoid misinterpretation of results and unambiguous registration in clinical databases. External quality assessment (EQA) schemes have revealed a need for more consistent nomenclature use in clinical genetics. We evaluated the propensity of EQA for improvement of compliance with Human Genome Variation Society (HGVS) recommendations for reporting of predictive somatic variants in lung and colorectal cancer. Variant entries between 2012 and 2018 were collected from written reports and electronic results sheets. In total, 4,053 variants were assessed, of which 12.1% complied with HGVS recommendations. Compliance improved over time from 2.1% (2012) to 22.3% (2018), especially when laboratories participated in multiple EQA schemes. Compliance was better for next‐generation sequencing (20.9%) compared with targeted techniques (9.8%). In the 1792 reports, HGVS recommendations for reference sequences were met for 31.9% of reports, for 36.0% of noncommercial, and 26.5% of commercial test methods. Compliance improved from 16.7% (2012) to 33.1% (2018), and after repeated EQA participation. EQA participation improves compliance with HGVS recommendations. The residual percentage of errors in the most recent schemes suggests that laboratories, companies, and EQA providers need to collaborate for additional improvement of harmonization in clinical test reporting.

The International Genome Sample Resource (IGSR) collection of open human genomic variation resources.

To sustain and develop the largest fully open human genomic resources the International Genome Sample Resource (IGSR) (https://www.internationalgenome.org) was established. It is built on the foundation of the 1000 Genomes Project, which created the largest openly accessible catalogue of human genomic variation developed from samples spanning five continents. IGSR (i) maintains access to 1000 Genomes Project resources, (ii) updates 1000 Genomes Project resources to the GRCh38 human reference assembly, (iii) adds new data generated on 1000 Genomes Project cell lines, (iv) shares data from samples with a similarly open consent to increase the number of samples and populations represented in the resources and (v) provides support to users of these resources. Among recent updates are the release of variation calls from 1000 Genomes Project data calculated directly on GRCh38 and the addition of high coverage sequence data for the 2504 samples in the 1000 Genomes Project phase three panel. The data portal, which facilitates web-based exploration of the IGSR resources, has been updated to include samples which were not part of the 1000 Genomes Project and now presents a unified view of data and samples across almost 5000 samples from multiple studies. All data is fully open and publicly accessible.

Variation at DENND1B and Asthma on the Island of Tristan da Cunha.

A high prevalence of asthma has been documented among the inhabitants of Tristan da Cunha, an isolated island in the South Atlantic. The population derives from just 28 founders. We performed lung function testing, including methacholine inhalation challenge, allergen skin prick testing, and collected DNA from essentially all of the current island population (269 individuals), and genotyped a panel of 43 single-nucleotide polymorphisms (SNPs) reported as associated with asthma and atopy. We carried out a mixed-model association analysis using the known pedigree. There were 96 individuals diagnosed as asthmatic (36%), and heritability estimates were similar to those from nonisolated population samples (multifactorial threshold model, h2 = 48%). The first component from a genetic principal components analysis using the entire SNP panel was nonlinearly associated with asthma, with the maximum risk to those intermediate to reference (Human Genome Diversity Project) European and African samples means. The single most strongly associated SNP was rs2786098 (p = 5.5 × 10-5), known to regulate the gene DENND1B. This explained approximately one-third of the trait heritability, with an allelic odds ratio for the A allele of 2.6. Among A/A carriers, 10 out of 12 individuals were asthmatic. The rs2786098*A variant was initially reported to decrease the risk of childhood (atopic) asthma in European but slightly increase the risk in African-descended populations, and does significantly alter Th2 cell function. Despite an absence of overall association with this variant in recent asthma genome wide association studies meta-analyses, an effect may exist on the particular genetic background of the Tristan da Cunha population.

Diversity In Precision Medicine And Pharmacogenetics: Methodological And Conceptual Considerations For Broadening Participation.

Genome-wide association studies (GWAS) have revealed important links between genetic markers across the human genome and phenotypic traits, including risk factors for disease. Studies have shown that GWAS continue to be overwhelmingly conducted on people of primarily European descent, despite the fact that the vast majority of human genomic variation is present in non-European populations such as those in Africa. To enhance our understanding of diversity in the pharmacogenomics and precision medicine literature, this review provides a window into the representation of biogeographical populations that have been studied for pharmacogenetic traits, such as enzyme metabolism and adverse drug response. Using the Medical Subject Headings (MeSH) ontology search terms in PubMed, studies were identified that are either population-based, or include a description of the study population on the basis of biological or environmental diversity. The results of this scoping review indicate that the majority of relevant papers (>95% of studies tagged in PubMed with MeSH terms “precision medicine” or “pharmacogenetics”, N=23,701) are not annotated with the “population group” MeSH term, suggesting that the majority of studies in this literature are not population-based, or the authors chose not to describe the study population. Among those studies related to pharmacogenetics or precision medicine that are specific to human population groups (N=1006) and were included in the analysis after filtering and screening on eligibility criteria (N=192), the majority of single-population studies included individuals of African, Asian, and European origins, or genetic ancestry. Combining studies of single and multiple populations, 33% involve participants of Asian origin or ancestry; 30% European; 24% African; 10% Hispanic or Latino; and < 3% American Indian or Alaska Native. These data provide a baseline for future comparison, indicating which biogeographic groups have informed the pharmacogenomic knowledgebase specific to diverse human populations. Challenges and potential solutions to improve diversity in the field and in genetics research more broadly are discussed.

Ancestral analysis of a Native American Ecuadorian family with congenital insensitivity to pain with anhidrosis

Congenital insensitivity to pain with anhidrosis (CIPA) is an extremely rare autosomal recessive disorder characterized by self-mutilating behavior, unexplained fever, inability to sweat and intellectual disability. CIPA pathogenesis is associated with genetic loss-of-function mutations of the NTRK1 gene, which is auto phosphorylated activating intracellular signaling transduction such as cell survival, growth and differentiation. CIPA occurs with an incidence of 1 in 125 million newborns, and only some hundreds of cases have been reported worldwide. Most of cases have been reported in Asian countries. Here, we estimate the ancestral proportions of a family with consanguinity background affected with CIPA, who carries the missense pathogenic mutations rs80356677 (Asp674Tyr) in the kinase domain of NTRK1 and rs324420 (Pro129Thr) in the FAAH gene. The ancestral proportion was calculated through 45 ancestry informative markers (AIMs) and the comparison was done through the Human Genome Diversity Project panel. The resulting allele frequencies in CIPA family indicate a prevalence of the Native American ancestral component with 87.9%, and minor proportion for the European (8.9%) and African (3%) components. In conclusion, the genetic variations expressing CIPA in a Native American Ecuadorian family could have been caused by the insertion of certain genetic characteristics, which have been passed down from common ancestors as consequence of migration towards South America.

Massively parallel sequencing of autosomal STRs and identity-informative SNPs highlights consanguinity in Saudi Arabia

While many studies have been undertaken of Middle Eastern populations using autosomal STR profiling by capillary electrophoresis, little has so far been published from this region on the forensic use of massively parallel sequencing (MPS). Here, we carried out MPS of 27 autosomal STRs and 91 identity-informative SNPs (iiSNPs) with the Verogen ForenSeq™ DNA Signature Prep Kit on a representative sample of 89 Saudi Arabian males, and analysed the resulting sequence data using Verogen’s ForenSeq Universal Analysis Software (UAS) v1.3 and STRait Razor v3.0. This revealed sequence variation in the composition of complex STR arrays, and SNPs in their flanking regions, which raised the number of STR alleles from 238 distinct length variants to 357 sequence sub-variants. Similarly, between one and three additional polymorphic sites were observed within the amplicons of 37 of the 91 iiSNPs, forming up to six microhaplotypes per locus. These further enhance discrimination compared to the biallelic target SNP data presented by the primary UAS interface. In total, we observed twenty-two STR alleles previously unrecognised in the STRait Razor v3.0 default allele list, along with nine SNPs flanking target iiSNPs that were not highlighted by the UAS. Sequencing reduced the STR-based random match probability (RMP) from 2.62E-30 to 3.49E-34, and analysis of the iiSNP microhaplotypes reduced RMP from 9.97E-37 to 6.83E-40. The lack of significant linkage disequilibrium between STRs and target iiSNPs allowed the two marker types to be combined using the product rule, yielding a RMP of 2.39E-73. Evidence of consanguinity was apparent from both marker types. While TPOX was the only locus displaying a significant deviation from Hardy-Weinberg equilibrium, 23 out of 27 STRs and 63 out of 91 iiSNPs showed fewer than expected heterozygotes, demonstrating an overall homozygote excess probably reflecting the high frequency of first-cousin marriages in Saudi Arabia. We placed our data in a global context by considering the same markers in the Human Genome Diversity Panel (HGDP), revealing that the Saudi sample was typical of Middle Eastern populations, with a higher level of inbreeding than is seen in most European, African and Central/South Asian populations, correlating with known patterns of endogamy. Given reduced levels of diversity within endogamous groups, the ability to combine the discrimination power of both STRs and SNPs offers significant benefits in the analysis of forensic evidence in Saudi Arabia and the Middle East region more generally.

The Interplay of Human and Mycobacterium Tuberculosis Genomic Variability.

Tuberculosis (TB), caused by the human pathogens Mycobacterium tuberculosis (Mtb) and Mycobacterium africanum, has plagued humanity for millennia and remains the deadliest infectious disease in the modern world. Mycobacterium tuberculosis and M. africanum can be subdivided phylogenetically into seven lineages exhibiting a low but significant degree of genomic diversity and preferential geographic distributions. Human genetic variability impacts all stages of TB pathogenesis ranging from susceptibility to infection with Mtb, progression of infection to disease, and the development of distinct clinical subtypes. The genetic study of severe childhood TB identified strong inborn single-gene errors revealing crucial pathways of vulnerability to TB. However, the identification of major TB-susceptibility genes on the population level has remained elusive. In particular, the replication of findings from candidate and genome-wide association studies across distinct human populations has proven difficult, thus hampering the characterization of reliable host molecular markers of susceptibility. Among the possible confounding factors of genetic association studies is Mtb genomic variability, which generally was not taken into account by human genetic studies. In support of this possibility, Mtb lineage was found to be a contributing factor to clinical presentation of TB and epidemiological spread of Mtb in exposed populations. The confluence of pathogen and human host genetic variability to TB pathogenesis led to the consideration of a possible coadaptation of Mtb strains and their human hosts, which should reveal itself in significant interaction effects between Mtb strain and TB-susceptibility/resistance alleles. Here, we present some of the most consistent findings of genetic susceptibility factors in human TB and review studies that point to genome-to-genome interaction between humans and Mtb lineages. The limited results available so far suggest that analyses considering joint human–Mtb genomic variability may provide improved power for the discovery of pathogenic drivers of the ongoing TB epidemic.

Reclassification of Variants of Uncertain Significance in Children with Inherited Arrhythmia Syndromes is Predicted by Clinical Factors.

Genetic testing is important to augment clinical diagnosis and inform management of inherited arrhythmias syndromes (IAS), but variants of uncertain significance (VUS) are common and remain a challenge in clinical practice. In 2015, American College of Medical Genetics (ACMG) published updated guidelines for interpretation of genetic results. Despite increasing understanding of human genomic variation, there are no guidelines for reinterpretation of prior genetic test results. Patients at a single tertiary children's hospital with genetic testing for an IAS that demonstrated a VUS were re-evaluated using 2015 ACMG guidelines, clinical information, and publically available databases. Search of the electronic medical record identified 116 patients with genetic testing results available, and 24/116 (21%) harbored a VUS for an IAS. 23 unique VUS were evaluated from 12 genes. Over half of the VUS (12/23 (52%)) were reclassified using 2015 criteria, and 8 (35%) changed to pathogenic and 4 (17%) to benign. Relative risk of reclassification of VUS to a pathogenic variant in a patient with confirmed clinical diagnosis was 4.1 (95% CI 1.23-15.4). Reclassification was not associated with initial testing year. These data demonstrate 52% of VUS in children with IAS are reclassified with application of 2015 ACMG guidelines. Strength of phenotyping is associated with eventual pathogenic classification of genetic variants and periodic re-evaluation of VUS identified on genetic testing for IAS is warranted.

Identification of Structural Variation from NGS-Based Non-Invasive Prenatal Testing.

Copy number variants (CNVs) are an important type of human genome variation, which play a significant role in evolution contribute to population diversity and human genetic diseases. In recent years, next generation sequencing has become a valuable tool for clinical diagnostics and to provide sensitive and accurate approaches for detecting CNVs. In our previous work, we described a non-invasive prenatal test (NIPT) based on low-coverage massively parallel whole-genome sequencing of total plasma DNA for detection of CNV aberrations ≥600 kbp. We reanalyzed NIPT genomic data from 5018 patients to evaluate CNV aberrations in the Slovak population. Our analysis of autosomal chromosomes identified 225 maternal CNVs (47 deletions; 178 duplications) ranging from 600 to 7820 kbp. According to the ClinVar database, 137 CNVs (60.89%) were fully overlapping with previously annotated variants, 66 CNVs (29.33%) were in partial overlap, and 22 CNVs (9.78%) did not overlap with any previously described variant. Identified variants were further classified with the AnnotSV method. In summary, we identified 129 likely benign variants, 13 variants of uncertain significance, and 83 likely pathogenic variants. In this study, we use NIPT as a valuable source of population specific data. Our results suggest the utility of genomic data from commercial CNV analysis test as background for a population study.

The Impact of Natural Selection on the Evolution and Function of Placentally Expressed Galectins.

Immunity genes have repeatedly experienced natural selection during mammalian evolution. Galectins are carbohydrate-binding proteins that regulate diverse immune responses, including maternal–fetal immune tolerance in placental pregnancy. Seven human galectins, four conserved across vertebrates and three specific to primates, are involved in placental development. To comprehensively study the molecular evolution of these galectins, both across mammals and within humans, we conducted a series of between- and within-species evolutionary analyses. By examining patterns of sequence evolution between species, we found that primate-specific galectins showed uniformly high substitution rates, whereas two of the four other galectins experienced accelerated evolution in primates. By examining human population genomic variation, we found that galectin genes and variants, including variants previously linked to immune diseases, showed signatures of recent positive selection in specific human populations. By examining one nonsynonymous variant in Galectin-8 previously associated with autoimmune diseases, we further discovered that it is tightly linked to three other nonsynonymous variants; surprisingly, the global frequency of this four-variant haplotype is ∼50%. To begin understanding the impact of this major haplotype on Galectin-8 protein structure, we modeled its 3D protein structure and found that it differed substantially from the reference protein structure. These results suggest that placentally expressed galectins experienced both ancient and more recent selection in a lineage- and population-specific manner. Furthermore, our discovery that the major Galectin-8 haplotype is structurally distinct from and more commonly found than the reference haplotype illustrates the significance of understanding the evolutionary processes that sculpted variants associated with human genetic disease.

Searching for Signatures of Cold Climate Adaptation in TRPM8 Gene in Populations of East Asian Ancestry.

Dispersal of Homo sapiens across the globe during the last 200,000 years was accompanied by adaptation to local climatic conditions, with severe winter temperatures being probably one of the most significant selective forces. The TRPM8 gene codes for a cold-sensing ion channel, and adaptation to low temperatures is the major determinant of its molecular evolution. Here, our aim was to search for signatures of cold climate adaptation in TRPM8 gene using a combined data set of 19 populations of East Asian ancestry from the 1000 Genomes Project and Human Genome Diversity Project. As a result, out of a total of 60 markers under study, none showed significant association with the average winter temperatures at the locations of the studied populations considering the multiple testing thresholds. This might suggest that the principal mode of TRPM8 evolution may be different from widespread models, where adaptive alleles are additive, dominant or recessive, at least in populations with the predominant East Asian component. For example, evolution by means of selectively preferable epistatic interactions among amino acids may have taken place. Despite the lack of strong signals of association, however, a very promising single nucleotide polymorphism (SNP) was found. The SNP rs7577262 is considered the best candidate based on its allelic correlations with winter temperatures, signatures of selective sweep and physiological evidences. The second top SNP, rs17862920, may participate in adaptation as well. Additionally, to assist in interpreting the nominal associations, the other markers reached, we performed SNP prioritization based on functional evidences found in literature and on evolutionary conservativeness.