Biology subjects

McArthur, E.

Publications and source records attributed to McArthur, E..

11 recordsLinked to original sources

bioRxiv2024

Identifying deleterious noncoding variation through gain and loss of CTCF binding activity

Noncoding single nucleotide variants are the predominant class of genetic variation in whole genome sequencing and are key drivers of phenotypic variation. However, their functional annotation remains challenging. To address this, we develop a hypothesis-driven functional annotation scheme for CTCF binding sites given CTCFs critical roles in gene regulation and extensive profiling in regulatory datasets. We synthesize CTCFs binding patterns at 1,063,879 genomic loci across 214 biological contexts into a summary metric, which we refer to as binding activity. We find that binding activity is significantly enriched for both conserved nucleotides (Pearson R = 0.31, p < 2.2 x 10-16) and sequences that contain high-quality CTCF binding motifs (Pearson R = 0.63, p = 2.9 x 10-12). We then integrate binding activity with high confidence change in precision weight matrix scores. By applying this framework to 1,253,330 SNVs in gnomAD, we explore signatures of selection acting against the disruption of CTCF binding. We find a strong, positive relationship between the mutability adjusted proportion of singletons (MAPS) metric and the loss of CTCF binding at loci with high in vitro activity (Pearson R = 0.67, p = 1.5 x 10-14). To contextualize these findings, we apply MAPS to other functional classes of variation and find that a subset of 198,149 loss of CTCF binding variants are observed as infrequently as missense variants. This work implicates these thousands of rare, noncoding variants that disrupt CTCF binding for further functional studies while providing a blueprint for the interpretable annotation of noncoding variants.

genetics↗

bioRxiv2023

Machine learning reveals the diversity of human 3D chromatin contact patterns

Understanding variation in chromatin contact patterns across human populations is critical for interpreting non-coding variants and their ultimate effects on gene expression and phenotypes. However, experimental determination of chromatin contacts at a population-scale is prohibitively expensive. To overcome this challenge, we develop and validate a machine learning method to quantify the diversity 3D chromatin contacts at 2 kilobase resolution from genome sequence alone. We then apply this approach to thousands of diverse modern humans and the inferred human-archaic hominin ancestral genome. While patterns of 3D contact divergence genome-wide are qualitatively similar to patterns of sequence divergence, we find that 3D divergence in local 1-megabase genomic windows does not follow sequence divergence. In particular, we identify 392 windows with significantly greater 3D divergence than expected from sequence. Moreover, 26% of genomic windows have rare 3D contact variation observed in a small number of individuals. Using in silico mutagenesis we find that most sequence changes to do not result in changes to 3D chromatin contacts. However in windows with substantial 3D divergence, just one or a few variants can lead to divergent 3D chromatin contacts without the individuals carrying those variants having high sequence divergence. In summary, inferring 3D chromatin contact maps across human populations reveals diverse contact patterns. We anticipate that these genetically diverse maps of 3D chromatin contact will provide a reference for future work on the function and evolution of 3D chromatin contact variation across human populations.

genomics↗

bioRxiv2023

Sequence-based machine learning reveals 3D genome differences between bonobos and chimpanzees

Phenotypic divergence between closely related species, including bonobos and chimpanzees (genus Pan), is largely driven by variation in gene regulation. The 3D structure of the genome mediates gene expression; however, genome folding differences in Pan are not well understood. Here, we apply machine learning to predict genome-wide 3D genome contact maps from DNA sequence for 56 bonobos and chimpanzees, encompassing all five extant lineages. We use a pairwise approach to estimate 3D divergence between individuals from the resulting contact maps in 4,420 1 Mb genomic windows. While most pairs were similar,[~] 17% were predicted to be substantially divergent in genome folding. The most dissimilar maps were largely driven by single individuals with rare variants that pro-duce unique 3D genome folding in a region. We also identified 89 genomic windows where bonobo and chimpanzee contact maps substantially diverged, including several windows harboring genes associated with traits implicated in Pan phenotypic divergence. We used in silico mutagenesis to identify 51 3D-modifying variants in these bonobo-chimpanzee diver-gent windows, finding that 34 or 66.67% induce genome folding changes via CTCF binding motif disruption. Our results reveal 3D genome variation at the population-level and identify genomic regions where changes in 3D folding may contribute to phenotypic differences in our closest living relatives.

genomics↗

bioRxiv2023

Comparing chromatin contact maps at scale: methods and insights

Comparing chromatin contact maps is an essential step in quantifying how three-dimensional (3D) genome organization shapes development, evolution, and disease. However, no gold standard exists for comparing contact maps, and even simple methods often disagree. In this study, we propose novel comparison methods and evaluate them alongside existing approaches using genome-wide Hi-C data and 22,500 in silico predicted contact maps. We also quantify the robustness of methods to common sources of biological and technical variation, such as boundary size and noise. We find that simple difference-based methods such as mean squared error are suitable for initial screening, but biologically informed methods are necessary to identify why maps diverge and propose specific functional hypotheses. We provide a reference guide, codebase, and benchmark for rapidly comparing chromatin contact maps at scale to enable biological insights into the 3D organization of the genome.

bioinformatics↗

bioRxiv2023

Neanderthal Introgression Shaped Human Circadian Traits

IntroductionWhen the ancestors of modern Eurasians migrated out of Africa and interbred with Eurasian archaic hominins, namely Neanderthals and Denisovans, DNA of archaic ancestry integrated into the genomes of anatomically modern humans. This process potentially accelerated adaptation to Eurasian environmental factors, including reduced ultra-violet radiation and increased variation in seasonal dynamics. However, whether these groups differed substantially in circadian biology, and whether archaic introgression adaptively contributed to human chronotypes remains unknown. ResultsHere we traced the evolution of chronotype based on genomes from archaic hominins and present-day humans. First, we inferred differences in circadian gene sequences, splicing, and regulation between archaic hominins and modern humans. We identified 28 circadian genes containing variants with potential to alter splicing in archaics (e.g., CLOCK, PER2, RORB, RORC), and 16 circadian genes likely divergently regulated between present-day humans and archaic hominins, including RORA. These differences suggest the potential for introgression to modify circadian gene expression. Testing this hypothesis, we found that introgressed variants are enriched among eQTLs for circadian genes. Supporting the functional relevance of these regulatory effects, we found that many introgressed alleles have associations with chronotype. Strikingly, the strongest introgressed effects on chronotype increase morningness, consistent with adaptations to high latitude in other species. Finally, we identified several circadian loci with evidence of adaptive introgression or latitudinal clines in allele frequency. ConclusionsThese findings identify differences in circadian gene regulation between modern humans and archaic hominins and support the contribution of introgression via coordinated effects on variation in human chronotype. SIGNIFICANCE STATEMENTInterbreeding between humans and Neanderthals created the potential for adaptive introgression as humans moved into environments that had been populated by Neanderthals for hundreds of thousands of years. Here we discover lineage-specific genetic differences in circadian genes and their regulatory elements between humans and Neanderthals. We show that introgressed alleles are enriched for effects on circadian gene regulation, consistently increase propensity for morningness in Europeans, and show evidence of adaptive introgression or associations between latitude and frequency. These results expand our understanding of how the genomes of humans and our closest relatives responded to environments with different light/dark cycles, and demonstrate a coordinated contribution of admixture to human chronotype in a direction that is consistent with adaptation to higher latitudes.

evolutionary biology↗

bioRxiv2022

Cross-tissue patterns of DNA hypomethylation reveal genetically distinct histories of cell development

Establishment of DNA methylation (DNAme) patterns is essential for balanced multi-lineage cellular differentiation, but exactly how these patterns drive cellular phenotypes is unclear. While >80% of CpG sites are stably methylated, tens of thousands of discrete CpG loci form hypomethylated regions (HMRs). Because they lack DNAme, HMRs are considered transcriptionally permissive, but not all HMRs actively regulate genes. Unlike promoter HMRs, a subset of non-coding HMRs is cell-type specific and enriched for tissue specific gene regulatory functions. Our data further argues not only that HMR establishment is an important step in enforcing cell identity, but also that complex HMR patterns are functionally instructive to gene regulation. To understand the significance of non-coding HMRs, we systematically dissected HMR patterns across diverse human cell types and developmental timepoints, including embryonic, fetal, and adult tissues. Unsupervised clustering of 102,390 distinct HMRs revealed that levels of HMR specificity reflects a developmental hierarchy supported by enrichment of stage-specific transcription factors and gene ontologies. Using a pseudo-time course of development from embryonic stem cells to adult stem and mature hematopoietic cells, we find that most HMRs observed in differentiated cells (~70-75%) are established at early developmental stages and accumulate as development progresses. HMRs that arise during differentiation frequently (~35%) establish near existing HMRs ([≤] 6kb away), leading to the formation of HMR clusters associated with stronger enhancer activity. Using SNP-based partitioned heritability from GWAS summary statistics across diverse traits and clinical lab values, we discovered that genetic contribution to trait heritability is enriched within HMRs. Moreover, the contribution of heritability to cell-relevant traits increases with both increasing developmental specificity and HMR clustering, supporting the role of distinct HMR subsets in regulating normal cell function. Altogether, our findings reveal that HMRs can predict cellular phenotypes by providing genetically distinct historical records of a cells journey through development. AUTHOR SUMMARYStudies aiming to understand the relationship between DNA methylation patterns and phenotypic outcomes have focused largely on individual differentially methylated regions without consideration of combinatorial changes that drive phenotypes. In non-disease contexts, most of the human genome is stably methylated, except for thousands of discrete DNA hypomethylated regions (HMRs) coinciding with gene regulatory elements. Here, we comprehensively characterize HMR relationships both within and between developmentally diverse cell types to understand the functional significance of complex HMR patterns. We show that levels of HMR specificity across cell-types captures time-point specific branchpoints of development. Our analysis further reveals that HMRs form clusters in proximity to cell identity genes and are associated with stronger gene enhancer activity. This is a wide-spread phenomenon and only a very small subset of HMR clusters is explained by overlapping super-enhancer annotations. Partitioned heritability revealed the functional significance of different HMR patterns linked to specific phenotypic outcomes and indicates a quantitative relationship between HMR patterns and complex trait heritability. Altogether, our findings reveal that HMRs can predict cellular phenotypes by providing genetically distinct historical records of a cells journey through development, ultimately providing novel insights into how DNA hypo-methylation mediates genome function.

genomics↗

bioRxiv2022

Reconstructing the 3D genome organization of Neanderthals reveals that chromatin folding shaped phenotypic and sequence divergence

Changes in gene regulation were a major driver of the divergence of archaic hominins (AHs)--Neanderthals and Denisovans--and modern humans (MHs). The three-dimensional (3D) folding of the genome is critical for regulating gene expression; however, its role in recent human evolution has not been explored because the degradation of ancient samples does not permit experimental determination of AH 3D genome folding. To fill this gap, we apply novel deep learning methods for inferring 3D genome organization from DNA sequence to Neanderthal, Denisovan, and diverse MH genomes. Using the resulting 3D contact maps across the genome, we identify 167 distinct regions with diverged 3D genome organization between AHs and MHs. We show that these 3D-diverged loci are enriched for genes related to the function and morphology of the eye, supra-orbital ridges, hair, lungs, immune response, and cognition. Despite these specific diverged loci, the 3D genome of AHs and MHs is more similar than expected based on sequence divergence, suggesting that the pressure to maintain 3D genome organization constrained hominin sequence evolution. We also find that 3D genome organization constrained the landscape of AH ancestry in MHs today: regions more tolerant of 3D variation are enriched for introgression in modern Eurasians. Finally, we identify loci where modern Eurasians have inherited novel 3D genome folding patterns from AH ancestors and validate folding differences in a high-frequency locus using Hi-C, revealing a putative molecular mechanism for phenotypes associated with archaic introgression. In summary, our application of deep learning to predict archaic 3D genome organization illustrates the potential of inferring molecular phenotypes from ancient DNA to reveal previously unobservable biological differences.

evolutionary biology↗

bioRxiv2020

Quantifying the contribution of Neanderthal introgression to the heritability of complex traits

BackgroundNearly all Eurasians have [~]2% Neanderthal ancestry due to several events of inbreeding between anatomically modern humans and archaic hominins. Previous studies characterizing the legacy of Neanderthal ancestry in modern Eurasians have identified examples of both adaptive and deleterious effects of admixture. However, we lack a comprehensive understanding of the genome-wide influence of Neanderthal introgression on modern human diseases and traits. ResultsWe integrate recent maps of Neanderthal ancestry with well-powered association studies for more than 400 diverse traits to estimate heritability enrichment patterns in regions of the human genome tolerant of Neanderthal ancestry and in introgressed Neanderthal variants themselves. First, we find that variants in regions tolerant of Neanderthal ancestry are depleted of heritability for all traits considered, except skin and hair-related traits. Second, the introgressed variants remaining in modern Europeans are depleted of heritability for most traits; however, we discover that they are enriched for heritability of several traits with potential relevance to human adaptation to non-African environments, including hair and skin traits, autoimmunity, chronotype, bone density, lung capacity, and menopause age. To better understand the phenotypic consequences of these enrichments, we adapt recent methods to test for consistent directional effects of introgressed alleles, and we find directionality for several traits. Finally, we use a direction-of-effect-aware approach to highlight novel candidate introgressed variants that influence risk for disease. ConclusionOur results demonstrate that genomic regions retaining Neanderthal ancestry are not only less functional at the molecular-level, but are also depleted for variation influencing a diverse array of complex traits in modern humans. In spite of this depletion, we identify traits where introgression has an outsized effect. Integrating our results, we propose a framework for using quantification of trait heritability and direction of effect in introgressed regions to understand how Neanderthals were different from modern humans, how selection acted on different traits, and how introgression may have facilitated adaptation to non-African environments.

evolutionary biology↗

bioRxiv2020

Topologically associating domain (TAD) boundaries stable across diverse cell types are evolutionarily constrained and enriched for heritability

Topologically associating domains (TADs) are fundamental units of three-dimensional (3D) nuclear organization. The regions bordering TADs--TAD boundaries--contribute to the regulation of gene expression by restricting interactions of cis-regulatory sequences to their target genes. TAD and TAD boundary disruption have been implicated in rare disease pathogenesis; however, we have a limited framework for integrating TADs and their variation across cell types into the interpretation of common trait-associated variants. Here, we investigate an attribute of 3D genome architecture--the stability of TAD boundaries across cell types--and demonstrate its relevance to understanding how genetic variation in TADs contribute to complex disease. By synthesizing TAD maps across 37 diverse cell types with 41 genome-wide association studies (GWAS), we investigate the differences in functionality and evolutionary pressure on variation in TADs versus TAD boundaries. We quantify their contribution to trait heritability and sequence-level evolutionary constraint and demonstrate that genetic variation in TAD boundaries contributes more to complex trait heritability, especially for immunologic, hematologic, and metabolic traits. We also show that TAD boundaries are more evolutionarily constrained than TADs. Next, stratifying boundaries by their stability across cell types, we find substantial differences. Boundaries stable across cell types are further enriched for complex trait heritability, evolutionary constraint, CTCF binding, and housekeeping genes compared to boundaries unique to a specific cell type. This suggests greater functional importance for stable boundaries. Thus, considering TAD boundary stability across cell types provides valuable context for understanding the genomes functional landscape and enabling 3D-structure aware variant interpretation.

genomics↗

bioRxiv2019

Unravelling the genetic architecture of musical rhythm

Moving in synchrony to the beat is a fundamental component of musicality. Here, we conducted a genome-wide association study (GWAS) to identify common genetic variants associated with beat synchronization in 606,825 individuals. Beat synchronization exhibited a highly polygenic architecture, with sixty-nine loci reaching genome-wide significance (p<5x10-8) and SNP-based heritability (on the liability scale) of 13%-16%. Heritability was enriched for genes expressed in brain tissues, and for fetal and adult brain-specific gene regulatory elements, underscoring the role of central nervous system-expressed genes linked to the genetic basis of the trait. We performed validations of the self-report phenotype (through internet-based experiments) and of the GWAS (polygenic scores for beat synchronization were associated with patients algorithmically classified as musicians in medical records of a separate biobank). Genetic correlations with breathing function, motor function, processing speed, and chronotype suggest shared genetic architecture with beat synchronization and provide avenues for new phenotypic and genetic explorations.

genetics↗

bioRxiv2019

Neanderthal introgression reintroduced functional alleles lost in the human out of Africa bottleneck

Neanderthal ancestry remains across modern Eurasian genomes, and introgressed sequences influence diverse phenotypes, including immune, skin, and neuropsychiatric diseases. Interpretation of introgressed sequences has focused on alleles derived in the Neanderthal lineage. Here, we demonstrate that Neanderthal introgression also reintroduced thousands of ancestral hominin alleles lost in the Eurasian out of Africa bottleneck. Combining evolutionary simulations, expression quantitative trait loci (eQTL), massively parallel reporter assay (MPRA) data, and in vitro validation, we show that reintroduced alleles (RAs) have different fitness effects than Neanderthal-derived alleles (NDAs) and that some RAs regulate gene expression independent of NDAs. Illustrating the broad potential influence of RAs, we find that over 70% of known phenotype associations with NDAs are equally associated with RAs. Finally, we discover enrichment for RA eQTL activity in several tissues, with strongest enrichment in the brain. In summary, our study reveals that Neanderthal introgression supplied Eurasians with many lost functional variants and demonstrates that RAs must be considered when evaluating the effects of introgression. ONE SENTENCE SUMMARYNeanderthal interbreeding with modern humans restored to Eurasians, hundreds of thousands of ancient alleles that were lost in the out of Africa bottleneck.

evolutionary biology↗