Epigenetic patterns in a complete human genome

Complete sequencing of ape genomes

The most dynamic and repetitive regions of great ape genomes have traditionally been excluded from comparative studies1-3. Consequently, our understanding of the evolution of our species is incomplete. Here we present haplotype-resolved reference genomes and comparative analyses of six ape species: chimpanzee, bonobo, gorilla, Bornean orangutan, Sumatran orangutan and siamang. We achieve chromosome-level contiguity with substantial sequence accuracy (<1 error in 2.7 megabases) and completely sequence 215 gapless chromosomes telomere-to-telomere. We resolve challenging regions, such as the major histocompatibility complex and immunoglobulin loci, to provide in-depth evolutionary insights. Comparative analyses enabled investigations of the evolution and diversity of regions previously uncharacterized or incompletely studied without bias from mapping to the human reference genome. Such regions include newly minted gene families in lineage-specific segmental duplications, centromeric DNA, acrocentric chromosomes and subterminal heterochromatin. This resource serves as a comprehensive baseline for future evolutionary studies of humans and our closest living ape relatives.

Human de novo mutation rates from a four-generation pedigree reference

Understanding the human de novo mutation (DNM) rate requires complete sequence information1. Here using five complementary short-read and long-read sequencing technologies, we phased and assembled more than 95% of each diploid human genome in a four-generation, twenty-eight-member family (CEPH 1463). We estimate 98-206 DNMs per transmission, including 74.5 de novo single-nucleotide variants, 7.4 non-tandem repeat indels, 65.3 de novo indels or structural variants originating from tandem repeats, and 4.4 centromeric DNMs. Among male individuals, we find 12.4 de novo Y chromosome events per generation. Short tandem repeats and variable-number tandem repeats are the most mutable, with 32 loci exhibiting recurrent mutation through the generations. We accurately assemble 288 centromeres and six Y chromosomes across the generations and demonstrate that the DNM rate varies by an order of magnitude depending on repeat content, length and sequence identity. We show a strong paternal bias (75-81%) for all forms of germline DNM, yet we estimate that 16% of de novo single-nucleotide variants are postzygotic in origin with no paternal bias, including early germline mosaic mutations. We place all this variation in the context of a high-resolution recombination map (~3.4 kb breakpoint resolution) and find no correlation between meiotic crossover and de novo structural variants. These near-telomere-to-telomere familial genomes provide a truth set to understand the most fundamental processes underlying human genetic variation.

Unraveling the hidden complexity of cancer through long-read sequencing

Cancer is fundamentally a disease of the genome, characterized by extensive genomic, transcriptomic, and epigenomic alterations. Most current studies predominantly use short-read sequencing, gene panels, or microarrays to explore these alterations; however, these technologies can systematically miss or misrepresent certain types of alterations, especially structural variants, complex rearrangements, and alterations within repetitive regions. Long-read sequencing is rapidly emerging as a transformative technology for cancer research by providing a comprehensive view across the genome, transcriptome, and epigenome, including the ability to detect alterations that previous technologies have overlooked. In this Perspective, we explore the current applications of long-read sequencing for both germline and somatic cancer analysis. We provide an overview of the computational methodologies tailored to long-read data and highlight key discoveries and resources within cancer genomics that were previously inaccessible with prior technologies. We also address future opportunities and persistent challenges, including the experimental and computational requirements needed to scale to larger sample sizes, the hurdles in sequencing and analyzing complex cancer genomes, and opportunities for leveraging machine learning and artificial intelligence technologies for cancer informatics. We further discuss how the telomere-to-telomere genome and the emerging human pangenome could enhance the resolution of cancer genome analysis, potentially revolutionizing early detection and disease monitoring in patients. Finally, we outline strategies for transitioning long-read sequencing from research applications to routine clinical practice.

Expanded methylome and quantitative trait loci detection by long-read profiling of personal DNA

Structural variants (SVs) are omnipresent in human DNA, yet their genotype and methylation statuses are rarely characterized due to previous limitations in genome assembly and detection of modified nucleotides. Also, the extent to which SVs act as methylation quantitative trait loci (SV-mQTLs) is largely unknown. Here, we generated a pangenome graph summarizing SVs in 782 de novo assemblies obtained from Genomic Answers for Kids, capturing 14.6 million CpG dinucleotides that are absent from the CHM13v2 reference (SV-CpGs), thus expanding their number by 43.6%. Using 435 methylomes, we genotyped 4.06 million SV-CpGs, of which 3.93 million (96.8%) are methylated at least once. Nonrepeat sequences contribute 1.59 × 106 novel SV-CpGs, followed by centromeric satellites (6.57 × 105), simple repeats (5.40 × 105), Alu elements (5.07 × 105), satellites (2.17 × 105), LINE-1s (1.83 × 105), and SVA (SINE-VNTR-Alu) elements (1.50 × 105). Centromeric satellites, simple repeats, and SVAs are overrepresented in SV-CpGs versus reference CpGs. Similarly, methylation levels in SV-CpGs are more variable than in reference CpGs. To explore if SVs are potentially causal for functional variation, we measured SV-mQTLs. This revealed over 230,464 methylation bins where the methylation is associated with common SVs within 100 kbp. Finally, we identified 65,659 methylation bins (28.5%) where the leading QTL variant is an SV. In conclusion, we demonstrate that graph pangenomes provide full SV structures, the associated methylation variation, and reveal tens of thousands of SV-mQTLs, underscoring the importance of assembly based analyses of human traits.

Evolution of genome-wide methylation profiling technologies

In this mini-review, we explore the advancements in genome-wide DNA methylation profiling, tracing the evolution from traditional methods such as methylation arrays and whole-genome bisulfite sequencing to the cutting-edge single-molecule profiling enabled by long-read sequencing (LRS) technologies. We highlight how LRS is transforming clinical and translational research, particularly by its ability to simultaneously measure genetic and epigenetic information, providing a more comprehensive understanding of complex disease mechanisms. We discuss current challenges and future directions in the field, emphasizing the need for innovative computational tools and robust, reproducible approaches to fully harness the capabilities of LRS in molecular diagnostics.

A Hitchhiker's Guide to long-read genomic analysis

Over the past decade, long-read sequencing has evolved into a pivotal technology for uncovering the hidden and complex regions of the genome. Significant cost efficiency, scalability, and accuracy advancements have driven this evolution. Concurrently, novel analytical methods have emerged to harness the full potential of long reads. These advancements have enabled milestones such as the first fully completed human genome, enhanced identification and understanding of complex genomic variants, and deeper insights into the interplay between epigenetics and genomic variation. This mini-review provides a comprehensive overview of the latest developments in long-read DNA sequencing analysis, encompassing reference-based and de novo assembly approaches. We explore the entire workflow, from initial data processing to variant calling and annotation, focusing on how these methods improve our ability to interpret a wide array of genomic variants. Additionally, we discuss the current challenges, limitations, and future directions in the field, offering a detailed examination of the state-of-the-art bioinformatics methods for long-read sequencing.

The impact of long-read sequencing on human population-scale genomics

Long-read sequencing technologies, particularly those from Pacific Biosciences and Oxford Nanopore Technologies, are revolutionizing genome research by providing high-resolution insights into complex and repetitive regions of the human genome that were previously inaccessible. These advances have been particularly enabling for the comprehensive detection of genomic structural variants (SVs), which is critical for linking genotype to phenotype in population-scale and rare disease studies, as well as in cancer. Recent developments in sequencing throughput and computational methods, such as pangenome graphs and haplotype-resolved assemblies, are paving the way for the future inclusion of long-read sequencing in clinical cohort studies and disease diagnostics. DNA methylation signals directly obtained from long reads enhance the utility of single-molecule long-read sequencing technologies by enabling molecular phenotypes to be interpreted, and by allowing the identification of the parent of origin of de novo mutations. Despite this recent progress, challenges remain in scaling long-read technologies to large populations due to cost, computational complexity, and the lack of tools to facilitate the efficient interpretation of SVs in graphs. This perspective provides a succinct review on the current state of long-read sequencing in genomics by highlighting its transformative potential and key hurdles, and emphasizing future opportunities for advancing the understanding of human genetic diversity and diseases through population-scale long-read analysis.

Non-canonical DNA in human and other ape telomere-to-telomere genomes

Non-canonical (non-B) DNA structures-e.g. bent DNA, hairpins, G-quadruplexes (G4s), Z-DNA, etc.-which form at certain sequence motifs (e.g. A-phased repeats, inverted repeats, etc.), have emerged as important regulators of cellular processes and drivers of genome evolution. Yet, they have been understudied due to their repetitive nature and potentially inaccurate sequences generated with short-read technologies. Here we comprehensively characterize such motifs in the long-read telomere-to-telomere (T2T) genomes of human, bonobo, chimpanzee, gorilla, Bornean orangutan, Sumatran orangutan, and siamang. Non-B DNA motifs are enriched at the genomic regions added to T2T assemblies and occupy 9%-15%, 9%-11%, and 12%-38% of autosomes and chromosomes X and Y, respectively. G4s and Z-DNA are enriched at promoters and enhancers, as well as at origins of replication. Repetitive sequences harbor more non-B DNA motifs than non-repetitive sequences, especially in the short arms of acrocentric chromosomes. Most centromeres and/or their flanking regions are enriched in at least one non-B DNA motif type, consistent with a potential role of non-B structures in determining centromeres. Our results highlight the uneven distribution of predicted non-B DNA structures across ape genomes and suggest their novel functions in previously inaccessible genomic regions.

Conservation of dichromatin organization along regional centromeres

The attachment of the kinetochore to the centromere is essential for genome maintenance, yet the highly repetitive nature of satellite regional centromeres limits our understanding of their chromatin organization. We demonstrate that single-molecule chromatin fiber sequencing (Fiber-seq) can uniquely co-resolve kinetochore and surrounding chromatin architectures along point centromeres, revealing largely homogeneous single-molecule kinetochore occupancy. In contrast, the application of Fiber-seq to regional centromeres exposed marked per-molecule heterogeneity in their chromatin organization. Regional centromere cores uniquely contain a dichotomous chromatin organization (dichromatin) composed of compacted nucleosome arrays punctuated with highly accessible chromatin patches. CENP-B occupancy phases dichromatin to the underlying alpha-satellite repeat within centromere cores but is not necessary for dichromatin formation. Centromere core dichromatin is conserved between humans and primates, including along regional centromeres lacking satellite repeats. Overall, the chromatin organization of regional centromeres is defined by marked per-molecule heterogeneity, buffering kinetochore attachment against sequence and structural variability within regional centromeres.

Centromeric transposable elements and epigenetic status drive karyotypic variation in the eastern hoolock gibbon

Great apes have maintained a stable karyotype with few large-scale rearrangements; in contrast, gibbons have undergone a high rate of chromosomal rearrangements coincident with rapid centromere turnover. Here, we characterize fully assembled centromeres in the eastern hoolock gibbon, Hoolock leuconedys (HLE), finding a diverse group of transposable elements (TEs) that differ from the canonical alpha-satellites found across centromeres of other apes. We find that HLE centromeres contain a CpG methylation centromere dip region, providing evidence that this epigenetic feature is conserved in the absence of satellite arrays. We uncovered a variety of atypical centromeric features, including protein-coding genes and mismatched replication timing. Further, we identify duplications and deletions in HLE centromeres that distinguish them from other gibbons. Finally, we observed differentially methylated TEs, topologically associated domain boundaries, and segmental duplications at chromosomal breakpoints, and thus propose that a combination of multiple genomic attributes with propensities for chromosome instability shaped gibbon centromere evolution.

Evolution and instability of human centromeres are accelerated by heterochromatin boundary loss and CENP-A overexpression

Centromere location is specified by CENP-A, a centromere-specific histone that epigenetically defines centromere identity. How CENP-A is maintained at one location in rapidly evolving centromeric DNA is unknown. Using single-cell-derived clones of human cell lines, we demonstrate single-cell heterogeneity in CENP-A position within cell populations at neocentromeres and a native centromere. CENP-A heterogeneity is accompanied by unique DNA methylation and H3K9me3 patterns, with DNA methylation shifting according to CENP-A position. We further demonstrate centromere epigenetic evolution over prolonged proliferation, with native centromeres maintaining stable heterochromatin boundaries, but neocentromeres exhibiting DNA methylation instability, H3K9me3 gain, boundary loss and fragility. Lastly, prolonged CENP-A and HJURP overexpression leads to centromere and neocentromere expansion, gradual CENP-A depletion, neocentromere destabilization and CENP-A re-localization that is accompanied by local heterochromatin remodeling. This study reveals the naturally evolving epigenetic plasticity of human centromeres and neocentromeres and highlights the importance of repressive chromatin boundaries in maintaining centromere stability.

A telomere-to-telomere genome assembly of cotton provides insights into centromere evolution and short-season adaptation

Cotton (Gossypium hirsutum L.) is a key allopolyploid crop with global economic importance. Here we present a telomere-to-telomere assembly of the elite variety Zhongmian 113. Leveraging technologies including PacBio HiFi, Oxford Nanopore Technology (ONT) ultralong-read sequencing and Hi-C, our assembly surpasses previous genomes in contiguity and completeness, resolving 26 centromeric and 52 telomeric regions, 5S rDNA clusters and nucleolar organizer regions. A phylogenetically recent centromere repositioning on chromosome D08 was discovered specific to G. hirsutum, involving deactivation of an ancestral centromere and the formation of a unique, satellite repeat-based centromere. Genomic analyses evaluated favorable allele aggregation for key agronomic traits and uncovered an early-maturing haplotype derived from an 11 Mb pericentric inversion that evolved early during G. hirsutum domestication. Our study sheds light on the genomic origins of short-season adaptation, potentially involving introgression of an inversion from primitively domesticated forms, followed by subsequent haplotype differentiation in modern breeding programs.

Uncalled4 improves nanopore DNA and RNA modification detection via fast and accurate signal alignment

Nanopore signal analysis enables detection of nucleotide modifications from native DNA and RNA sequencing, providing both accurate genetic or transcriptomic and epigenetic information without additional library preparation. At present, only a limited set of modifications can be directly basecalled (for example, 5-methylcytosine), while most others require exploratory methods that often begin with alignment of nanopore signal to a nucleotide reference. We present Uncalled4, a toolkit for nanopore signal alignment, analysis and visualization. Uncalled4 features an efficient banded signal alignment algorithm, BAM signal alignment file format, statistics for comparing signal alignment methods and a reproducible de novo training method for k-mer-based pore models, revealing potential errors in Oxford Nanopore Technologies' state-of-the-art DNA model. We apply Uncalled4 to RNA 6-methyladenine (m6A) detection in seven human cell lines, identifying 26% more modifications than Nanopolish using m6Anet, including in several genes where m6A has known implications in cancer. Uncalled4 is available open source at github.com/skovaka/uncalled4 .

Computational analysis of DNA methylation from long-read sequencing

DNA methylation is a critical epigenetic mechanism in numerous biological processes, including gene regulation, development, ageing and the onset of various diseases such as cancer. Studies of methylation are increasingly using single-molecule long-read sequencing technologies to simultaneously measure epigenetic states such as DNA methylation with genomic variation. These long-read data sets have spurred the continuous development of advanced computational methods to gain insights into the roles of methylation in regulating chromatin structure and gene regulation. In this Review, we discuss the computational methods for calling methylation signals, contrasting methylation between samples, analysing cell-type diversity and gaining additional genomic insights, and then further discuss the challenges and future perspectives of tool development for DNA methylation research.

Genomic context-dependent histone H3K36 methylation by three Drosophila methyltransferases and implications for dedicated chromatin readers

Methylation of histone H3 at lysine 36 (H3K36me3) marks active chromatin. The mark is interpreted by epigenetic readers that assist transcription and safeguard chromatin fiber integrity. In Drosophila, the chromodomain protein MSL3 binds H3K36me3 at X-chromosomal genes to implement dosage compensation. The PWWP-domain protein JASPer recruits the JIL1 kinase to active chromatin on all chromosomes. Because depletion of K36me3 had variable, locus-specific effects on the interactions of those readers, we systematically studied K36 methylation in a defined cellular model. Contrasting prevailing models, we found that K36me1, K36me2, and K36me3 each contribute to distinct chromatin states. Monitoring the changing K36 methylation landscape upon depletion of the three methyltransferases Set2, NSD, and Ash1 revealed local, context-specific methylation signatures. Each methyltransferase governs K36 methylation in dedicated genomic regions, with minor overlaps. Set2 catalyzes K36me3 predominantly at transcriptionally active euchromatin. NSD places K36me2/3 at defined loci within pericentric heterochromatin and on weakly transcribed euchromatic genes. Ash1 deposits K36me1 at putative enhancers. The mapping of MSL3 and JASPer suggested that they bind K36me2 in addition to K36me3, which was confirmed by direct affinity measurement. This dual specificity attracts the readers to a broader range of chromosomal locations and increases the robustness of their actions.

An evolutionarily conserved constellation of functional cis-elements programs the virus-responsive fate of the human (epi)genome

Human health depends on perplexing defensive cellular responses against microbial pathogens like Viruses. Despite the major effort undertaken, the (epi)genomic mechanisms that human cells utilize to tailor defensive gene expression programs against microbial attacks have remained inadequately understood, mainly due to a significant lack of recording of the in vivo functional cis-regulatory modules (CRMs) of the human genome. Here, we introduce the virus-responsive fate of the human (epi)genome as characterized in naïve and infected cells by functional genomics, computational biology, DNA evolution, and DNA Grammar and Syntax investigations. We discovered that multitudes of novel functional virus-responsive CRMs (vrCRMs) compose typical enhancers (tEs), super-enhancers (SEs), repetitive-DNA enhancers (rDEs), and stand-alone functional genomic stretches that grant human cells regulatory underpinnings for layering basal immunity and eliminating illogical/harmful defensive responses under homeostasis, yet stimulating virus-responsive genes and transposable elements (TEs) upon infection. Moreover, extensive epigenomic reprogramming of previously unknown SE landscapes marks the transition from naïve to antiviral human cell states and involves the functions of the antimicrobial transcription factors (TFs), including interferon response factor 3 (IRF3) and nuclear factor-κB (NF-κB), as well as coactivators and transcriptional apparatus, along with intensive modifications/alterations in histone marks and chromatin accessibility. Considering the polyphyletic evolutionary fingerprints of the composite DNA sequences of the vrCRMs assessed by TFs-STARR-seq, ranging from the animal to microbial kingdoms, the conserved features of antimicrobial TFs and chromatin complexes, and their pluripotent stimulus-induced activation, these findings shed light on how mammalian (epi)genomes evolved their functions to interpret the exogenous stress inflicted and program defensive transcriptional responses against microbial agents. Crucially, many known human short variants, e.g. single-nucleotide polymorphisms (SNPs), insertions, deletions etc., and quantitative trait loci (QTLs) linked to autoimmune diseases, such as multiple sclerosis (MS), systemic lupus erythematosus (SLE), Crohn's disease (CD) etc., were mapped within or vastly proximal (±2.5 kb) to the novel in vivo functional SEs and vrCRMs discovered, thus underscoring the impact of their (mal)functions on human physiology and disease development. Hence, we delved into the virus-responsive fate of the human (epi)genome and illuminated its architecture, function, evolutionary origins, and its significance for cellular homeostasis. These results allow us to chart the "Human hyper-Atlas of virus-infection", an integrated "molecular in silico" encyclopedia situated in the UCSC Genome Browser that benefits our mechanistic understanding of human infectious/(auto)immune diseases development and can facilitate the generation of in vivo preclinical animal models, drug design, and evolution of therapeutic applications.

Non-canonical DNA in human and other ape telomere-to-telomere genomes

Non-canonical (non-B) DNA structures-e.g., bent DNA, hairpins, G-quadruplexes (G4s), Z-DNA, etc.-which form at certain sequence motifs (e.g., A-phased repeats, inverted repeats, etc.), have emerged as important regulators of cellular processes and drivers of genome evolution. Yet, they have been understudied due to their repetitive nature and potentially inaccurate sequences generated with short-read technologies. Here we comprehensively characterize such motifs in the long-read telomere-to-telomere (T2T) genomes of human, bonobo, chimpanzee, gorilla, Bornean orangutan, Sumatran orangutan, and siamang. Non-B DNA motifs are enriched at the genomic regions added to T2T assemblies, and occupy 9-15%, 9-11%, and 12-38% of autosomes, and chromosomes X and Y, respectively. G4s and Z-DNA are enriched at promoters and enhancers, as well as at origins of replication. Repetitive sequences harbor more non-B DNA motifs than non-repetitive sequences, especially in the short arms of acrocentric chromosomes. Most centromeres and/or their flanking regions are enriched in at least one non-B DNA motif type, consistent with a potential role of non-B structures in determining centromeres. Our results highlight the uneven distribution of predicted non-B DNA structures across ape genomes and suggest their novel functions in previously inaccessible genomic regions.

Centromeric chromatin clearings demarcate the site of kinetochore formation

The centromere is the chromosomal locus that recruits the kinetochore, directing faithful propagation of the genome during cell division. Using cryo-ET on human mitotic chromosomes, we reveal a distinctive architecture at the centromere: clustered 20- to 25-nm nucleosome-associated complexes within chromatin clearings that delineate them from surrounding chromatin. Centromere components CENP-C and CENP-N are each required for the integrity of the complexes, while CENP-C is also required to maintain the chromatin clearing. We find that CENP-C is required in mitosis, not just for kinetochore assembly, likely reflecting its role in organizing the inner kinetochore during chromosome segregation. We further visualize the scaffold of the fibrous corona, a structure amplified at unattached kinetochores, revealing crescent-shaped parallel arrays of fibrils extending >1 μm. Thus, we reveal how the organization of centromeric chromatin creates a clearing at the site of kinetochore formation as well as the nature of kinetochore amplification mediated by corona fibrils.

Reconstruction of diploid higher-order human 3D genome interactions from noisy Pore-C data using Dip3D

Differential high-order chromatin interactions between homologous chromosomes affect many biological processes. Traditional chromatin conformation capture genome analysis methods mainly identify two-way interactions and cannot provide comprehensive haplotype information, especially for low-heterozygosity organisms such as human. Here, we present a pipeline of methods to delineate diploid high-order chromatin interactions from noisy Pore-C outputs. We trained a previously published single-nucleotide variant (SNV)-calling deep learning model, Clair3, on Pore-C data to achieve superior SNV calling, applied a filtering strategy to tag reads for haplotypes and established a haplotype imputation strategy for high-order concatemers. Learning the haplotype characteristics of high-order concatemers from high-heterozygosity mouse allowed us to devise a progressive haplotype imputation strategy, which improved the haplotype-informative Pore-C contact rate 14.1-fold to 76% in the HG001 cell line. Overall, the diploid three-dimensional (3D) genome interactions we derived using Dip3D surpassed conventional methods in noise reduction and contact distribution uniformity, with better haplotype-informative contact density and genomic coverage rates. Dip3D identified previously unresolved haplotype high-order interactions, in addition to an understanding of their relationship with allele-specific expression, such as in X-chromosome inactivation. These results lead us to conclude that Dip3D is a robust pipeline for the high-quality reconstruction of diploid high-order 3D genome interactions.

Nanopore Long-Read Sequencing Unveils Genomic Disruptions in Alzheimer's Disease

Studies in laboratory models and postmortem human brain tissue from patients with Alzheimer's disease have revealed disruption of basic cellular processes such as DNA repair and epigenetic control as drivers of neurodegeneration. While genomic alterations in regions of the genome that are rich in repetitive sequences, often termed "dark regions," are difficult to resolve using traditional sequencing approaches, long-read technologies offer promising new avenues to explore previously inaccessible regions of the genome. In the current study, we leverage nanopore-based long-read whole-genome sequencing of DNA extracted from postmortem human frontal cortex at early and late stages of Alzheimer's disease, as well as age-matched controls, to analyze retrotransposon insertion events, non-allelic homologous recombination (NAHR), structural variants and DNA methylation within retrotransposon loci and other repetitive/dark regions of the human genome. Interestingly, we find that retrotransposon insertion events and repetitive element-associated NAHR are particularly enriched within centromeric and pericentromeric regions of DNA in the aged human brain, and that ribosomal DNA (rDNA) is subject to a high degree of NAHR compared to other regions of the genome. We detect a trending increase in potential somatic retrotransposition events of the small interfering nuclear element (SINE) AluY in late-stage Alzheimer's disease, and differential changes in methylation within repetitive elements and retrotransposons according to disease stage. Taken together, our analysis provides the first long-read DNA sequencing-based analysis of retrotransposon sequences, NAHR, structural variants, and DNA methylation in the aged brain, and points toward transposable elements, centromeric/pericentromeric regions and rDNA as hotspots for genomic variation.

Rapid brain tumor classification from sparse epigenomic data

Although the intraoperative molecular diagnosis of the approximately 100 known brain tumor entities described to date has been a goal of neuropathology for the past decade, achieving this within a clinically relevant timeframe of under 1 h after biopsy collection remains elusive. Advances in third-generation sequencing have brought this goal closer, but established machine learning techniques rely on computationally intensive methods, making them impractical for live diagnostic workflows in clinical applications. Here we present MethyLYZR, a naive Bayesian framework enabling fully tractable, live classification of cancer epigenomes. For evaluation, we used nanopore sequencing to classify over 200 brain tumor samples, including 10 sequenced in a clinical setting next to the operating room, achieving highly accurate results within 15 min of sequencing. MethyLYZR can be run in parallel with an ongoing nanopore experiment with negligible computational overhead. Therefore, the only limiting factors for even faster time to results are DNA extraction time and the nanopore sequencer's maximum parallel throughput. Although more evidence from prospective studies is needed, our study suggests the potential applicability of MethyLYZR for live molecular classification of nervous system malignancies using nanopore sequencing not only for the neurosurgical intraoperative use case but also for other oncologic indications and the classification of tumors from cell-free DNA in liquid biopsies.

A refined analysis of Neanderthal-introgressed sequences in modern humans with a complete reference genome

BACKGROUND

Leveraging long-read sequencing technologies, the first complete human reference genome, T2T-CHM13, corrects assembly errors in previous references and resolves the remaining 8% of the genome. While studies on archaic admixture in modern humans have so far relied on the GRCh37 reference due to the availability of archaic genome data, the impact of T2T-CHM13 in this field remains unexplored.

RESULTS

We remap the sequencing reads of the high-quality Altai Neanderthal and Denisovan genomes onto GRCh38 and T2T-CHM13. Compared to GRCh37, we find that T2T-CHM13 significantly improves read mapping quality in archaic samples. We then apply IBDmix to identify Neanderthal-introgressed sequences in 2504 individuals from 26 geographically diverse populations using different reference genomes. We observe that commonly used pre-phasing filtering strategies in public datasets substantially influence archaic ancestry determination, underscoring the need for careful filter selection. Our analysis identifies approximately 51 Mb of Neanderthal sequences unique to T2T-CHM13, predominantly in genomic regions where GRCh38 and T2T-CHM13 assemblies diverge. Additionally, we uncover novel instances of population-specific archaic introgression in diverse populations, spanning genes involved in metabolism, olfaction, and ion-channel function. Finally, to facilitate the exploration of archaic alleles and adaptive signals in human genomics and evolutionary research, we integrate these introgressed sequences and adaptive signals across all reference genomes into a visualization database, ASH ( www.arcseqhub.com ).

CONCLUSIONS

Our study enhances the detection of archaic variations in modern humans, highlights the importance of utilizing the T2T-CHM13 reference, and provides novel insights into the functional consequences of archaic hominin admixture.

Label-Free and Sequence-Independent Isothermal Amplification Strategy for the Simultaneous Detection of Genomic 5-Methylcytosine and 5-Hydroxymethylcytosine

5-Methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) are crucial epigenetic modifications in eukaryotic genomic DNA that regulate gene expression and are associated with the occurrence of various cancers. Here, we combined bisulfite conversion with 4-acetamido-2,2,6,6-tetramethyl-1-oxopiperridinium tetrafluoroborate (ACT+BF4-, TCI) oxidation to develop a label-free and sequence-independent isothermal amplification (BTIA) assay for a genome-wide 5mC and 5hmC analysis. The BTIA strategy can distinguish 5mC and 5hmC signatures from other bases with high sensitivity and good specificity, avoiding sophisticated chemical modifications and expensive protein labeling. Moreover, the utilization of terminal deoxynucleotidyl transferase (TdT) enables the proposed strategy to detect global 5mC and 5hmC without sequence dependence. With only 78 ng of input of genomic DNA, global 5mC and 5hmC levels were accurately quantified in cells (including cancer cells of A549, T47D, and K562 and normal cells of HEK-293T, CHO, and NRK-52E) and clinical whole blood samples (including healthy control, precancerous cervical cancer, and confirmed cervical cancer) within 18 h. The detection results suggested that 5mC was highly expressed in cancer cells. More importantly, a significant increase in 5mC was observed in precancerous cervical cancer and further upregulation in confirmed cervical cancer, suggesting a correlation between 5mC and cancer occurrence and development. However, 5hmC showed the reverse result in these tested cells and clinical samples. Collectively, the BTIA strategy can be easily performed on the ordinary heating apparatus in almost all research and medical laboratories, showing a significant application in the early screening of cervical cancer in the clinic.

Bridging scales in chromatin organization: Computational models of loop formation and their implications for genome function

Chromatin loop formation plays a crucial role in 3D genome interactions, with misfolding potentially leading to irregular gene expression and various diseases. While experimental tools such as Hi-C have advanced our understanding of genome interactions, the biophysical principles underlying chromatin loop formation remain elusive. This review examines computational approaches to chromatin folding, focusing on polymer models that elucidate chromatin loop mechanics. We discuss three key models: (1) the multi-loop-subcompartment model, which investigates the structural effects of loops on chromatin conformation; (2) the strings and binders switch model, capturing thermodynamic chromatin aggregation; and (3) the loop extrusion model, revealing the role of structural maintenance of chromosome complexes. In addition, we explore advanced models that address chromatin clustering heterogeneity in biological processes and disease progression. The review concludes with an outlook on open questions and current trends in chromatin loop formation and genome interactions, emphasizing the physical and computational challenges in the field.

Genome Assembly of a Living Fossil, the Atlantic Horseshoe Crab Limulus polyphemus, Reveals Lineage-Specific Whole-Genome Duplications, Transposable Element-Based Centromeres, and a ZW Sex Chromosome System

Horseshoe crabs, considered living fossils with a stable morphotype spanning ∼445 million years, are evolutionarily, ecologically, and biomedically important species experiencing rapid population decline. Of the four extant species of horseshoe crabs, the Atlantic horseshoe crab, Limulus polyphemus, has become an essential component of the modern medicine toolkit. Here, we present the first chromosome-level genome assembly, and the most contiguous and complete assembly to date, for L. polyphemus using nanopore long-read sequencing and chromatin conformation analysis. We find support for three horseshoe crab-specific whole-genome duplications, but none shared with Arachnopulmonata (spiders and scorpions). Moreover, we discovered tandem duplicates of endotoxin detection pathway components Factors C and G, identify candidate centromeres consisting of Gypsy retroelements, and classify the ZW sex chromosome system for this species and a sister taxon, Carcinoscorpius rotundicauda. Finally, we revealed this species has been experiencing a steep population decline over the last 5 million years, highlighting the need for international conservation interventions and fisheries-based management for this critical species.

YHSeqY3000 panel captures all founding lineages in the Chinese paternal genomic diversity database

BACKGROUND

The advancements in second-/third-generation sequencing technologies, alongside computational innovations, have significantly enhanced our understanding of the genomic structure of Y-chromosomes and their unique phylogenetic characteristics. These researches, despite the challenges posed by the lack of population-scale genomic databases, have the potential to revolutionize our approach to high-resolution, population-specific Y-chromosome panels and databases for anthropological and forensic applications.

OBJECTIVES

This study aimed to develop the highest-resolution Y-targeted sequencing panel, utilizing time-stamped, core phylogenetic informative mutations identified from high-coverage sequences in the YanHuang cohort. This panel is intended to provide a new tool for forensic complex pedigree search and paternal biogeographical ancestry inference, as well as explore the general patterns of the fine-scale paternal evolutionary history of ethnolinguistically diverse Chinese populations.

RESULTS

The sequencing performance of the East Asian-specific Y-chromosomal panel, including 2999-core SNP variants, was found to be robust and reliable. The YHSeqY3000 panel was designed to capture the genetic diversity of Chinese paternal lineages from 3500 years ago, identifying 408 terminal lineages in 2097 individuals across 41 genetically and geographically distinct populations. We identified a fine-scale paternal substructure that was correlating with ancient population migrations and expansions. New evidence was provided for extensive gene flow events between minority ethnic groups and Han Chinese people, based on the integrative Chinese Paternal Genomic Diversity Database.

CONCLUSIONS

This work successfully integrated Y-chromosome-related basic genomic science with forensic and anthropological translational applications, emphasizing the necessity of comprehensively characterizing Y-chromosome genomic diversity from genomically under-representative populations. This is particularly important in the second phase of our population-specific medical or anthropological genomic cohorts, where dense sampling strategies are employed.

CRISPR-Cas technology in forensic investigations: Principles, applications, and ethical considerations

CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated proteins) systems are adaptive immune systems originally present in bacteria, where they are essential to protect against external genetic elements, including viruses and plasmids. Taking advantage of this system, CRISPR-Cas-based technologies have emerged as incredible tools for precise genome editing, thus significantly advancing several research fields. Forensic sciences represent a multidisciplinary field that explores scientific methods to investigate and resolve legal issues, particularly criminal investigations and subject identification. Consequently, it plays a critical role in the justice system, providing scientific evidence to support judicial investigations. Although less explored, CRISPR-Cas-based methodologies demonstrate strong potential in the field of forensic sciences due to their high accuracy and sensitivity, including DNA profiling and identification, interpretation of crime scene investigations, detection of food contamination or fraud, and other aspects related to environmental forensics. However, using CRISPR-Cas-based methodologies in human samples raises several ethical issues and concerns regarding the potential misuse of individual genetic information. In this manuscript, we provide an overview of potential applications of CRISPR-Cas-based methodologies in several areas of forensic sciences and discuss the legal implications that challenge their routine implementation in this research field.

Advances in forensic genetics: Exploring the potential of long read sequencing

DNA-based technologies have been used in forensic practice since the mid-1980s. While PCR-based STR genotyping using Capillary Electrophoresis remains the gold standard for generating DNA profiles in routine casework worldwide, the research community is continually seeking alternative methods capable of providing additional information to enhance discrimination power or contribute with new investigative leads. Oxford Nanopore Technologies (ONT) and PacBio third-generation sequencing have revolutionized the field, offering real-time capabilities, single-molecule resolution, and long-read sequencing (LRS). ONT, the pioneer of nanopore sequencing, uses biological nanopores to analyze nucleic acids in real-time. Its devices have revolutionized sequencing and may represent an interesting alternative for forensic research and routine casework, given that it offers unparalleled flexibility in a portable size: it enables sequencing approaches that range widely from PCR-amplified short target regions (e.g., CODIS STRs) to PCR-free whole transcriptome or even ultra-long whole genome sequencing. Despite its higher error rate compared to Illumina sequencing, it can significantly improve accuracy in read alignment against a reference genome or de novo genome assembly. This is achieved by generating long contiguous sequences that correctly assemble repetitive sections and regions with structural variation. Moreover, it allows real-time determination of DNA methylation status from native DNA without the need for bisulfite conversion. LRS enables the analysis of thousands of markers at once, providing phasing information and eliminating the need for multiple assays. This maximizes the information retrieved from a single invaluable sample. In this review, we explore the potential use of LRS in different forensic genetics approaches.

Telomere-to-telomere sheep genome assembly identifies variants associated with wool fineness

Ongoing efforts to improve sheep reference genome assemblies still leave many gaps and incomplete regions, resulting in a few common failures and errors in genomic studies. Here, we report a 2.85-Gb gap-free telomere-to-telomere genome of a ram (T2T-sheep1.0), including all autosomes and the X and Y chromosomes. This genome adds 220.05 Mb of previously unresolved regions and 754 new genes to the most updated reference assembly ARS-UI_Ramb_v3.0; it contains four types of repeat units (SatI, SatII, SatIII and CenY) in centromeric regions. T2T-sheep1.0 has a base accuracy of more than 99.999%, corrects several structural errors in previous reference assemblies and improves structural variant detection in repetitive sequences. Alignment of whole-genome short-read sequences of global domestic and wild sheep against T2T-sheep1.0 identifies 2,664,979 new single-nucleotide polymorphisms in previously unresolved regions, which improves the population genetic analyses and detection of selective signals for domestication (for example, ABCC4) and wool fineness (for example, FOXQ1).

Identification and annotation of centromeric hypomethylated regions with CDR-Finder

MOTIVATION

Centromeres are chromosomal regions historically understudied with sequencing technologies due to their repetitive nature and short-read mapping limitations. However, recent improvements in long-read sequencing allow for the investigation of complex regions of the genome at the sequence and epigenetic levels.

RESULTS

Here, we present Centromere Dip Region (CDR)-Finder: a tool to identify regions of hypomethylation within the centromeres of high-quality, contiguous genome assemblies. These regions are typically associated with a unique type of chromatin containing the histone H3 variant CENP-A, which marks the location of the kinetochore. CDR-Finder identifies the CDRs in large and short centromeres and generates a BED file indicating the location of the CDRs within the centromere. It also outputs a plot for visualization, validation, and downstream analysis.

AVAILABILITY AND IMPLEMENTATION

CDR-Finder is available at https://github.com/EichlerLab/CDR-Finder.

SatXplor-a comprehensive pipeline for satellite DNA analyses in complex genome assemblies

Satellite DNAs (satDNAs) are tandemly repeated sequences that make up a significant portion of almost all eukaryotic genomes. Although satDNAs have been shown to play an important role in genome organization and evolution, they are relatively poorly analyzed, even in model organisms. One of the main reasons for the current lack of in-depth studies on satDNAs is their underrepresentation in genome assemblies. Due to complexity, abundance, and highly repetitive nature of satDNAs, their analysis is challenging, requiring efficient tools that ensure accurate annotation and comprehensive genome-wide analysis. We present a novel pipeline, named satellite DNA Exploration (SatXplor), designed to robustly characterize satDNA elements and analyze their arrays and flanking regions. SatXplor is benchmarked against other tools and curated satDNA datasets from diverse species, including mice and humans, showcase its versatility across genomes with varying complexities and satDNA profiles. Component algorithms excel in the identification of tandemly repeated sequences and, for the first time, enable evaluation of satDNA variation and array annotation with the addition of information about surrounding genomic landscape. SatXplor is an innovative pipeline for satDNA analysis that can be paired with any tool used for satDNA detection, offering insights into the structural characteristics, array determination, and genomic context of satDNA elements. By integrating various computational techniques, from sequence analysis and homology investigation to advanced clustering and graph-based methods, it provides a versatile and comprehensive approach to explore the complexity of satDNA organization and understand the underlying mechanisms and evolutionary aspects. It is open-source and freely accessible at https://github.com/mvolar/SatXplor.

Leveraging the power of long reads for targeted sequencing

Long-read sequencing technologies have improved the contiguity and, as a result, the quality of genome assemblies by generating reads long enough to span and resolve complex or repetitive regions of the genome. Several groups have shown the power of long reads in detecting thousands of genomic and epigenomic features that were previously missed by short-read sequencing approaches. While these studies demonstrate how long reads can help resolve repetitive and complex regions of the genome, they also highlight the throughput and coverage requirements needed to accurately resolve variant alleles across large populations using these platforms. At the time of this review, whole-genome long-read sequencing is more expensive than short-read sequencing on the highest throughput short-read instruments; thus, achieving sufficient coverage to detect low-frequency variants (such as somatic variation) in heterogenous samples remains challenging. Targeted sequencing, on the other hand, provides the depth necessary to detect these low-frequency variants in heterogeneous populations. Here, we review currently used and recently developed targeted sequencing strategies that leverage existing long-read technologies to increase the resolution with which we can look at nucleic acids in a variety of biological contexts.

Gapless assembly of complete human and plant chromosomes using only nanopore sequencing

The combination of ultra-long (UL) Oxford Nanopore Technologies (ONT) sequencing reads with long, accurate Pacific Bioscience (PacBio) High Fidelity (HiFi) reads has enabled the completion of a human genome and spurred similar efforts to complete the genomes of many other species. However, this approach for complete, "telomere-to-telomere" genome assembly relies on multiple sequencing platforms, limiting its accessibility. ONT "Duplex" sequencing reads, where both strands of the DNA are read to improve quality, promise high per-base accuracy. To evaluate this new data type, we generated ONT Duplex data for three widely studied genomes: human HG002, Solanum lycopersicum Heinz 1706 (tomato), and Zea mays B73 (maize). For the diploid, heterozygous HG002 genome, we also used "Pore-C" chromatin contact mapping to completely phase the haplotypes. We found the accuracy of Duplex data to be similar to HiFi sequencing, but with read lengths tens of kilobases longer, and the Pore-C data to be compatible with existing diploid assembly algorithms. This combination of read length and accuracy enables the construction of a high-quality initial assembly, which can then be further resolved using the UL reads, and finally phased into chromosome-scale haplotypes with Pore-C. The resulting assemblies have a base accuracy exceeding 99.999% (Q50) and near-perfect continuity, with most chromosomes assembled as single contigs. We conclude that ONT sequencing is a viable alternative to HiFi sequencing for de novo genome assembly, and provides a multirun single-instrument solution for the reconstruction of complete genomes.

Train and Reprogram Your Brain: Effects of Physical Exercise at Different Stages of Life on Brain Functions Saved in Epigenetic Modifications

Multiple studies have demonstrated the significant effects of physical exercise on brain plasticity, the enhancement of memory and cognition, and mood improvement. Although the beneficial impact of exercise on brain functions and mental health is well established, the exact mechanisms underlying this phenomenon are currently under thorough investigation. Several hypotheses have emerged suggesting various possible mechanisms, including the effects of hormones, neurotrophins, neurotransmitters, and more recently also other compounds such as lactate or irisin, which are released under the exercise circumstances and act both locally or/and on distant tissues, triggering systemic body reactions. Nevertheless, none of these actually explain the long-lasting effect of exercise, which can persist for years or even be passed on to subsequent generations. It is believed that these long-lasting effects are mediated through epigenetic modifications, influencing the expression of particular genes and the translation and modification of specific proteins. This review explores the impact of regular physical exercise on brain function and brain plasticity and the associated occurrence of epigenetic modifications. It examines how these changes contribute to the prevention and treatment of neuropsychiatric and neurological disorders, as well as their influence on the natural aging process and mental health.

Evolutionary Dynamics of G-Quadruplexes in Human and Other Great Ape Telomere-to-Telomere Genomes

G-quadruplexes (G4s) are non-canonical DNA structures that can form at approximately 1% of the human genome. G4s contribute to point mutations and structural variation and thus facilitate genomic instability. They play important roles in regulating replication, transcription, and telomere maintenance, and some of them evolve under purifying selection. Nevertheless, the evolutionary dynamics of G4s has remained underexplored. Here we conducted a comprehensive analysis of predicted G4s (pG4s) in the recently released, telomere-to-telomere (T2T) genomes of human and other great apes-bonobo, chimpanzee, gorilla, Bornean orangutan, and Sumatran orangutan. We annotated tens of thousands of new pG4s in T2T compared to previous ape genome assemblies, including 41,236 in the human genome. Analyzing species alignments, we found approximately one-third of pG4s shared by all apes studied and identified thousands of species- and genus-specific pG4s. pG4s accumulated and diverged at rates consistent with divergence times between the studied species. We observed a significant enrichment and hypomethylation of pG4 shared across species at regulatory regions, including promoters, 5' and 3'UTRs, and origins of replication, strongly suggesting their formation and functional role in these regions. pG4s shared among great apes displayed lower methylation levels compared to species-specific pG4s, suggesting evolutionary conservation of functional roles of the former. Many species-specific pG4s were located in the repetitive and satellite regions deciphered in the T2T genomes. Our findings illuminate the evolutionary dynamics of G4s, their role in gene regulation, and their potential contribution to species-specific adaptations in great apes, emphasizing the utility of high-resolution T2T genomes in uncovering previously elusive genomic features.

Identification and annotation of centromeric hypomethylated regions with Centromere Dip Region (CDR)-Finder

Centromeres are chromosomal regions historically understudied with sequencing technologies due to their repetitive nature and short-read mapping limitations. However, recent improvements in long-read sequencing allowed for the investigation of complex regions of the genome at the sequence and epigenetic levels. Here, we present Centromere Dip Region (CDR)-Finder: a tool to identify regions of hypomethylation within the centromeres of high-quality, contiguous genome assemblies. These regions are typically associated with a unique type of chromatin containing the histone H3 variant CENP-A, which marks the location of the kinetochore. CDR-Finder identifies the CDRs in large and short centromeres and generates a BED file indicating the location of the CDRs within the centromere. It also outputs a plot for visualization, validation, and downstream analysis. CDR-Finder is available at https://github.com/EichlerLab/CDR-Finder.

Microsatellite density landscapes illustrate short tandem repeats aggregation in the complete reference human genome

BACKGROUND

Microsatellites are increasingly realized to have biological significance in human genome and health in past decades, the assembled complete reference sequence of human genome T2T-CHM13 brought great help for a comprehensive study of short tandem repeats in the human genome.

RESULTS

Microsatellites density landscapes of all 24 chromosomes were built here for the first complete reference sequence of human genome T2T-CHM13. These landscapes showed that short tandem repeats (STRs) are prone to aggregate characteristically to form a large number of STRs density peaks. We classified 8,823 High Microsatellites Density Peaks (HMDPs), 35,257 Middle Microsatellites Density Peaks (MMDPs) and 199, 649 Low Microsatellites Density Peaks (LMDPs) on the 24 chromosomes; and also classified the motif types of every microsatellites density peak. These STRs density aggregation peaks are mainly composing of a single motif, and AT is the most dominant motif, followed by AATGG and CCATT motifs. And 514 genomic regions were characterized by microsatellite density feature in the full T2T-CHM13 genome.

CONCLUSIONS

These landscape maps exhibited that microsatellites aggregate in many genomic positions to form a large number of microsatellite density peaks with composing of mainly single motif type in the complete reference genome, indicating that the local microsatellites density varies enormously along the every chromosome of T2T-CHM13.

Complete sequencing of ape genomes

We present haplotype-resolved reference genomes and comparative analyses of six ape species, namely: chimpanzee, bonobo, gorilla, Bornean orangutan, Sumatran orangutan, and siamang. We achieve chromosome-level contiguity with unparalleled sequence accuracy (<1 error in 500,000 base pairs), completely sequencing 215 gapless chromosomes telomere-to-telomere. We resolve challenging regions, such as the major histocompatibility complex and immunoglobulin loci, providing more in-depth evolutionary insights. Comparative analyses, including human, allow us to investigate the evolution and diversity of regions previously uncharacterized or incompletely studied without bias from mapping to the human reference. This includes newly minted gene families within lineage-specific segmental duplications, centromeric DNA, acrocentric chromosomes, and subterminal heterochromatin. This resource should serve as a definitive baseline for all future evolutionary studies of humans and our closest living ape relatives.

Fast Context-Aware Analysis of Genome Annotation Colocalization

An annotation is a set of genomic intervals sharing a particular function or property. Examples include genes or their exons, sequence repeats, regions with a particular epigenetic state, and copy number variants. A common task is to compare two annotations to determine if one is enriched or depleted in the regions covered by the other. We study the problem of assigning statistical significance to such a comparison based on a null model representing random unrelated annotations. To incorporate more background information into such analyses, we propose a new null model based on a Markov chain that differentiates among several genomic contexts. These contexts can capture various confounding factors, such as GC content or assembly gaps. We then develop a new algorithm for estimating p-values by computing the exact expectation and variance of the test statistic and then estimating the p-value using a normal approximation. Compared to the previous algorithm by Gafurov et al., the new algorithm provides three advances: (1) the running time is improved from quadratic to linear or quasi-linear, (2) the algorithm can handle two different test statistics, and (3) the algorithm can handle both simple and context-dependent Markov chain null models. We demonstrate the efficiency and accuracy of our algorithm on synthetic and real data sets, including the recent human telomere-to-telomere assembly. In particular, our algorithm computed p-values for 450 pairs of human genome annotations using 24 threads in under three hours. Moreover, the use of genomic contexts to correct for GC bias resulted in the reversal of some previously published findings.

Deciphering the role of structural variation in human evolution: a functional perspective

Advances in sequencing technologies have enabled the comparison of high-quality genomes of diverse primate species, revealing vast amounts of divergence due to structural variation. Given their large size, structural variants (SVs) can simultaneously alter the function and regulation of multiple genes. Studies estimate that collectively more than 3.5% of the genome is divergent in humans versus other great apes, impacting thousands of genes. Functional genomics and gene-editing tools in various model systems recently emerged as an exciting frontier - investigating the wide-ranging impacts of SVs on molecular, cellular, and systems-level phenotypes. This review examines existing research and identifies future directions to broaden our understanding of the functional roles of SVs on phenotypic innovations and diversity impacting uniquely human features, ranging from cognition to metabolic adaptations.

Telomere-to-telomere assemblies of cattle and sheep Y-chromosomes uncover divergent structure and gene content

Reference genomes of cattle and sheep have lacked contiguous assemblies of the sex-determining Y chromosome. Here, we assemble complete and gapless telomere to telomere (T2T) Y chromosomes for these species. We find that the pseudo-autosomal regions are similar in length, but the total chromosome size is substantially different, with the cattle Y more than twice the length of the sheep Y. The length disparity is accounted for by expanded ampliconic region in cattle. The genic amplification in cattle contrasts with pseudogenization in sheep suggesting opposite evolutionary mechanisms since their divergence 19MYA. The centromeres also differ dramatically despite the close relationship between these species at the overall genome sequence level. These Y chromosomes have been added to the current reference assemblies in GenBank opening new opportunities for the study of evolution and variation while supporting efforts to improve sustainability in these important livestock species that generally use sire-driven genetic improvement strategies.

The formation and propagation of human Robertsonian chromosomes

Robertsonian chromosomes are a type of variant chromosome found commonly in nature. Present in one in 800 humans, these chromosomes can underlie infertility, trisomies, and increased cancer incidence. Recognized cytogenetically for more than a century, their origins have remained mysterious. Recent advances in genomics allowed us to assemble three human Robertsonian chromosomes completely. We identify a common breakpoint and epigenetic changes in centromeres that provide insight into the formation and propagation of common Robertsonian translocations. Further investigation of the assembled genomes of chimpanzee and bonobo highlights the structural features of the human genome that uniquely enable the specific crossover event that creates these chromosomes. Resolving the structure and epigenetic features of human Robertsonian chromosomes at a molecular level paves the way to understanding how chromosomal structural variation occurs more generally, and how chromosomes evolve.

Complex genetic variation in nearly complete human genomes

Diverse sets of complete human genomes are required to construct a pangenome reference and to understand the extent of complex structural variation. Here, we sequence 65 diverse human genomes and build 130 haplotype-resolved assemblies (130 Mbp median continuity), closing 92% of all previous assembly gaps1,2 and reaching telomere-to-telomere (T2T) status for 39% of the chromosomes. We highlight complete sequence continuity of complex loci, including the major histocompatibility complex (MHC), SMN1/SMN2, NBPF8, and AMY1/AMY2, and fully resolve 1,852 complex structural variants (SVs). In addition, we completely assemble and validate 1,246 human centromeres. We find up to 30-fold variation in α-satellite high-order repeat (HOR) array length and characterize the pattern of mobile element insertions into α-satellite HOR arrays. While most centromeres predict a single site of kinetochore attachment, epigenetic analysis suggests the presence of two hypomethylated regions for 7% of centromeres. Combining our data with the draft pangenome reference1 significantly enhances genotyping accuracy from short-read data, enabling whole-genome inference3 to a median quality value (QV) of 45. Using this approach, 26,115 SVs per sample are detected, substantially increasing the number of SVs now amenable to downstream disease association studies.

dHICA: a deep transformer-based model enables accurate histone imputation from chromatin accessibility

Histone modifications (HMs) are pivotal in various biological processes, including transcription, replication, and DNA repair, significantly impacting chromatin structure. These modifications underpin the molecular mechanisms of cell-type-specific gene expression and complex diseases. However, annotating HMs across different cell types solely using experimental approaches is impractical due to cost and time constraints. Herein, we present dHICA (deep histone imputation using chromatin accessibility), a novel deep learning framework that integrates DNA sequences and chromatin accessibility data to predict multiple HM tracks. Employing the transformer architecture alongside dilated convolutions, dHICA boasts an extensive receptive field and captures more cell-type-specific information. dHICA outperforms state-of-the-art baselines and achieves superior performance in cell-type-specific loci and gene elements, aligning with biological expectations. Furthermore, dHICA's imputations hold significant potential for downstream applications, including chromatin state segmentation and elucidating the functional implications of SNPs (Single Nucleotide Polymorphisms). In conclusion, dHICA serves as a valuable tool for advancing the understanding of chromatin dynamics, offering enhanced predictive capabilities and interpretability.

A systematic framework for understanding the microbiome in human health and disease: from basic principles to clinical translation

The human microbiome is a complex and dynamic system that plays important roles in human health and disease. However, there remain limitations and theoretical gaps in our current understanding of the intricate relationship between microbes and humans. In this narrative review, we integrate the knowledge and insights from various fields, including anatomy, physiology, immunology, histology, genetics, and evolution, to propose a systematic framework. It introduces key concepts such as the 'innate and adaptive genomes', which enhance genetic and evolutionary comprehension of the human genome. The 'germ-free syndrome' challenges the traditional 'microbes as pathogens' view, advocating for the necessity of microbes for health. The 'slave tissue' concept underscores the symbiotic intricacies between human tissues and their microbial counterparts, highlighting the dynamic health implications of microbial interactions. 'Acquired microbial immunity' positions the microbiome as an adjunct to human immune systems, providing a rationale for probiotic therapies and prudent antibiotic use. The 'homeostatic reprogramming hypothesis' integrates the microbiome into the internal environment theory, potentially explaining the change in homeostatic indicators post-industrialization. The 'cell-microbe co-ecology model' elucidates the symbiotic regulation affecting cellular balance, while the 'meta-host model' broadens the host definition to include symbiotic microbes. The 'health-illness conversion model' encapsulates the innate and adaptive genomes' interplay and dysbiosis patterns. The aim here is to provide a more focused and coherent understanding of microbiome and highlight future research avenues that could lead to a more effective and efficient healthcare system.

Addressing Technical Pitfalls in Pursuit of Molecular Factors That Mediate Immunoglobulin Gene Regulation

The expressed Ab repertoire is a critical determinant of immune-related phenotypes. Ab-encoding transcripts are distinct from other expressed genes because they are transcribed from somatically rearranged gene segments. Human Abs are composed of two identical H and L chain polypeptides derived from genes in IGH locus and one of two L chain loci. The combinatorial diversity that results from Ab gene rearrangement and the pairing of different H and L chains contributes to the immense diversity of the baseline Ab repertoire. During rearrangement, Ab gene selection is mediated by factors that influence chromatin architecture, promoter/enhancer activity, and V(D)J recombination. Interindividual variation in the composition of the Ab repertoire associates with germline variation in IGH, implicating polymorphism in Ab gene regulation. Determining how IGH variants directly mediate gene regulation will require integration of these variants with other functional genomic datasets. In this study, we argue that standard approaches using short reads have limited utility for characterizing regulatory regions in IGH at haplotype resolution. Using simulated and chromatin immunoprecipitation sequencing reads, we define features of IGH that limit use of short reads and a single reference genome, namely 1) the highly duplicated nature of the DNA sequence in IGH and 2) structural polymorphisms that are frequent in the population. We demonstrate that personalized diploid references enhance performance of short-read data for characterizing mappable portions of the locus, while also showing that long-read profiling tools will ultimately be needed to fully resolve functional impacts of IGH germline variation on expressed Ab repertoires.

DNA methylation governs the sensitivity of repeats to restriction by the HUSH-MORC2 corepressor

The human silencing hub (HUSH) complex binds to transcripts of LINE-1 retrotransposons (L1s) and other genomic repeats, recruiting MORC2 and other effectors to remodel chromatin. How HUSH and MORC2 operate alongside DNA methylation, a central epigenetic regulator of repeat transcription, remains largely unknown. Here we interrogate this relationship in human neural progenitor cells (hNPCs), a somatic model of brain development that tolerates removal of DNA methyltransferase DNMT1. Upon loss of MORC2 or HUSH subunit TASOR in hNPCs, L1s remain silenced by robust promoter methylation. However, genome demethylation and activation of evolutionarily-young L1s attracts MORC2 binding, and simultaneous depletion of DNMT1 and MORC2 causes massive accumulation of L1 transcripts. We identify the same mechanistic hierarchy at pericentromeric α-satellites and clustered protocadherin genes, repetitive elements important for chromosome structure and neurodevelopment respectively. Our data delineate the epigenetic control of repeats in somatic cells, with implications for understanding the vital functions of HUSH-MORC2 in hypomethylated contexts throughout human development.

Centromeric transposable elements and epigenetic status drive karyotypic variation in the eastern hoolock gibbon

Great apes have maintained a stable karyotype with few large-scale rearrangements; in contrast, gibbons have undergone a high rate of chromosomal rearrangements coincident with rapid centromere turnover. Here we characterize assembled centromeres in the Eastern hoolock gibbon, Hoolock leuconedys (HLE), finding a diverse group of transposable elements (TEs) that differ from the canonical alpha satellites found across centromeres of other apes. We find that HLE centromeres contain a CpG methylation centromere dip region, providing evidence this epigenetic feature is conserved in the absence of satellite arrays; nevertheless, we report a variety of atypical centromeric features, including protein-coding genes and mismatched replication timing. Further, large structural variations define HLE centromeres and distinguish them from other gibbons. Combined with differentially methylated TEs, topologically associated domain boundaries, and segmental duplications at chromosomal breakpoints, we propose that a "perfect storm" of multiple genomic attributes with propensities for chromosome instability shaped gibbon centromere evolution.

The ICF syndrome protein CDCA7 harbors a unique DNA binding domain that recognizes a CpG dyad in the context of a non-B DNA

CDCA7, encoding a protein with a carboxyl-terminal cysteine-rich domain (CRD), is mutated in immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome, a disease related to hypomethylation of juxtacentromeric satellite DNA. How CDCA7 directs DNA methylation to juxtacentromeric regions is unknown. Here, we show that the CDCA7 CRD adopts a unique zinc-binding structure that recognizes a CpG dyad in a non-B DNA formed by two sequence motifs. CDCA7, but not ICF mutants, preferentially binds the non-B DNA with strand-specific CpG hemi-methylation. The unmethylated sequence motif is highly enriched at centromeres of human chromosomes, whereas the methylated motif is distributed throughout the genome. At S phase, CDCA7, but not ICF mutants, is concentrated in constitutive heterochromatin foci, and the formation of such foci can be inhibited by exogenous hemi-methylated non-B DNA bound by the CRD. Binding of the non-B DNA formed in juxtacentromeric regions during DNA replication provides a mechanism by which CDCA7 controls the specificity of DNA methylation.