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At least 19 recordsLinked to original sources

Assessing reproducibility of Hi-C chromatin interactions using stratum-adjusted irreproducible discovery rate.

MOTIVATION: Hi-C is a powerful technology for mapping chromatin interactions genome-wide. However, interaction loops identified from Hi-C contact maps often vary across replicate experiments due to experimental noise, making reproducibility assessment essential. A major challenge lies in the genomic distance dependence of interaction strength, which systematically affects reproducibility but is overlooked by existing methods for reproducibility assessment. RESULTS: We introduce Stratum-Adjusted Irreproducible Discovery Rate (SIDR), a novel statistical model that integrates distance stratification into the widely-used Irreproducible Discovery Rate (IDR) framework. SIDR explicitly models the confounding effect of genomic distance, enabling global control of irreproducibility across interaction ranges. Through simulations and real Hi-C datasets, we demonstrate that SIDR improves discriminative power and recovers more biologically meaningful interactions than existing approaches, making it a valuable tool for robust and reproducible Hi-C analysis. AVAILABILITY: The R package SIDR is freely available on GitHub https://github.com/qunhualilab/SIDR.

Chromatin

map3C: a computational tool for processing multiomic single-cell Hi-C data.

SUMMARY: The emergence of multiomic single-cell Hi-C (scHi-C) methods, which simultaneously profile chromatin conformation and other modalities such as gene expression or DNA methylation, creates tremendous opportunities for studying the genome's structure-function relationships. Existing tools for processing multiomic scHi-C datasets lack certain key functions for downstream bioinformatics analysis. We present map3C, a software tool that incorporates additional key functions. Specifically, we demonstrate that map3C facilitates multiomic scHi-C processing, quality control, and identification of structural variant locations in the genome. AVAILABILITY AND IMPLEMENTATION: map3C is available at https://github.com/luogenomics/map3C and is archived at https://doi.org/10.5281/zenodo.20724719.

Software

Identification and characterization of ectopic chromosomal amplifications in acute myeloid leukemia cell limes using high-throughput chromosome conformation capture screening.

Despite advanced molecular diagnostics, improving outcomes for refractory acute myeloid leukemia (AML) remains challenging. Although many cancer-related genes are identified, their molecular mechanisms are not fully elucidated. Amplification is a mechanism of cancer-associated gene activation, and ectopic gene amplification may have particularly high pathological significance. However, research on ectopically amplified cancer-associated genes in leukemia remains limited. Here, we evaluated the usefulness of high-throughput chromosomal conformation capture (Hi-C) as a screening method for ectopic gene amplification and assessed whether ectopic amplification of cancer-associated genes may represent a general phenomenon in AML. We screened the U-937 and NB-4 cell lines using in situ Hi-C. Regions appearing as "high-intensity bands" in Hi-C contact maps were identified and validated using fluorescence in situ hybridization (FISH). Additionally, copy number variation analysis was performed using whole-genome sequencing (WGS) to extract cancer-associated genes with ectopic amplification. In the U-937, three genomic regions showing "high-intensity bands" were identified and confirmed as ectopic amplifications-including PDCD1LG2 (PD-L2), CD274 (PD-L1), and JAK2; that is, four copies were detected by WGS, and amplification signals were observed by FISH. In the NB-4, four such regions were detected, including MYC and KRAS, with expression level of 498 transcripts per million (TPM) and 34 TPM, respectively. Copy number variation analysis further identified multiple cancer-associated genes with ectopic amplification. Overall, these findings demonstrate the presence of ectopic amplification of cancer-associated genes in AML cell lines and support the usefulness of Hi-C as a screening method for detecting such genomic alterations.

Acute myeloid leukemia

Characterization of a draft chromosome-scale genome assembly for the mutton snapper, Lutjanus analis.

BACKGROUND: The mutton snapper (Lutjanus analis) is a reef fish commonly found in tropical waters of the Western Atlantic Ocean. Genomic studies of this species are needed to support conservation efforts and breeding programs. OBJECTIVE: Here, we report the development of a chromosome-scale reference assembly for the mutton snapper and conduct an initial comparative genomic analysis with other lutjanids. METHODS: The genome of one mutton snapper specimen was sequenced using PAC-Bio HiFi long reads and Illumina short reads. Contigs and scaffolds were assembled in the Flye pipeline and anchored using Hi-C proximity guided assembly. Gene prediction and functional annotations were obtained in AUGUSTUS and eggNOG-mapper, respectively. The mutton snapper genome was compared to those of other lutjanids to infer gene family evolution and chromosome synteny conservation. RESULTS: Assembly and polishing yielded 946 contigs and 926 scaffolds (N50 of 3.16 Mb, complete BUSCO score 98.1%) that were anchored using Hi-C scaffolding in 24 draft chromosomes. The anchored assembly featured a N50 of 42.47 Mb and contained 97.6% of the unanchored assembly length. The 24 mutton snapper chromosomes showed a one-to-one syntenic relationship with their counterparts in medaka, and other Lutjanids. AUGUSTUS predicted 29,023 genes, 24,335 of which (83.85%) could be functionally annotated. Gene family evolution analysis revealed 1,014 significantly expanded or contracted hierarchical ortholog groups in mutton snapper. Expansions and contractions were linked to several biological functions including growth, oocyte maturation, and response to exogenous stressors. CONCLUSION: The draft genome will be a valuable tool for forthcoming applied genomic studies of mutton snapper.

Animals

HiCPotts: An R/Bioconductor package to identify significant interactions in chromosome conformation capture data and model sources of bias.

MOTIVATION: Chromosome Conformation Capture methods, including Hi-C, micro-C or Capture-C, are used to map chromatin interactions genome-wide. Most of the existing computational methods do not account for sources of bias (such as DNA accessibility, GC content or TE content) in the data. RESULTS: We previously developed ZipHiC, a Bayesian method based on the hidden Markov random field (HMRF) model and the Approximate Bayesian Computation (ABC), that uses zero-inflated Poisson distribution to model the noise, signal and false signal of the data and showed that this approach was able to detect bias from DNA accessibility, GC content and TE content in both Hi-C and micro-C data. Here, we present HiCPotts, another Bayesian method based on the HMRF model and the ABC that uses a zero-inflated Negative Binomial distribution instead to model the noise and signal of the data. We systematically show that HiCPotts reduces false positives and increases recovery of true interactions compared to ZipHiC, but also compared to other methods such as FastHiC, Juicer and HiCExplorer. Most importantly, we provide an R/Bioconductor package that allows modelling the noise, signal and false signal using various distributions such as the zero-inflated Negative Binomial (ZINB) and the zero-inflated Poisson distribution (ZIP). AVAILABILITY AND IMPLEMENTATION: https://bioconductor.org/packages/HiCPotts/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Approximate Bayesian Computation

Charting host structural variations in cervical cancer by long-read sequencing pinpoints a functional deletion in PIAS1.

Host structural variations (SVs) are critical in cancer development but their landscape and interaction with HPV integration in cervical carcinogenesis remain unclear. In this study, we performed Nanopore long-read sequencing on five HPV-positive cervical cancer tissues and two cell lines to profile host SVs. We identified thousands of SVs and statistically demonstrated their significant enrichment in genomic windows ±25 to ±50 kb from HPV integration sites. Cross-sample analysis revealed 60 shared SVs, including a recurrent deletion within the PIAS1 gene. Multi-omics integration (Hi-C, H3K27ac ChIP-seq, and TCGA data) showed that this deletion is associated with reduced PIAS1 expression, disruption of local topologically associating domains, advanced pathological tumor stage, and poorer overall survival. Functional assays confirmed that PIAS1 deficiency inhibits cervical cancer cell proliferation and migration. Our findings identify a PIAS1 deletion as a candidate driver event, and underscore the pivotal role of host genomic instability in HPV-associated oncogenesis.

Cervical cancer

Genome assembly of Astatotilapia latifasciata uncovers B chromosome-linked chromatin reorganization.

B chromosomes (Bs) are supernumerary genomic elements found in many eukaryotes, yet their full sequence composition, functional potential, and regulatory impact on the host genome remain unclear. Here, we present a chromosome-level genome assembly of the cichlid fish Astatotilapia latifasciata, integrating PacBio long reads, Illumina short reads, and Hi-C chromatin contact maps to resolve both A and B chromosomes. The 0.93 Gb assembly (N50 = 36.2 Mb) includes a 34 Mb B chromosome containing 789 predicted protein-coding genes and a markedly higher density of transposable elements (TEs), especially long terminal repeats (LTR) retrotransposons. Transcriptome profiling revealed that B-linked genes are predominantly transcriptionally repressed relative to their A chromosome paralogs. Hi-C-based chromatin modeling uncovered distinct 3D structural configurations associated with the B chromosome, including fewer topologically associating domains (TADs), reduced loop formation, and altered compartmentalization. These changes are linked to long-range chromatin interactions and genomic rearrangements, suggesting that the B chromosome reshapes the nuclear architecture of the host genome. Our study proposes a potential regulatory role of Bs in genome and provides a genomic resource for investigating chromosome evolution in cichlids.

Animals

Allele-specific chromatin architecture shapes imprinted domains and coordinates a distal enhancer and antisense transcription at the mouse Mest-Copg2 domain.

Genomic imprinting results in parent-of-origin-dependent gene expression, but how three-dimensional genome organization contributes to imprinted gene regulation remains unclear. Using Capture Hi-C in mouse cortex and primary cortical neurons, we identified parental allele-specific chromatin architectures across multiple imprinted domains. These architectures largely originate from imprinting control regions and correlate with DNA methylation-sensitive CTCF binding. Active and inactive alleles of imprinted genes show distinct promoter interaction profiles and differential engagement with distal regulatory elements in both contact frequency and the epigenetic state of distal regions. A CRISPR interference screen identified a distal enhancer that regulates Mest-Copg2 imprinted expression through allele-specific chromatin interactions. In neurons, this enhancer activates Copg2 on the maternal allele, whereas on the paternal allele it drives Mest isoforms transcribed antisense to Copg2 and contributes to Copg2 repression. In summary, we show that allele-specific chromatin architecture coordinates maternal enhancer activity and paternal antisense transcription to control imprinted expression in neurons.

Animals

Chromosomal level genome assembly of medicinal plant Chrysosplenium macrophyllum.

Chrysosplenium macrophyllum Oliv., a perennial herb native to China, is widely used in traditional medicine for its notable therapeutic properties. However, the absence of a reference genome has constrained its full potential for research and application. This study presents the first chromosome-level de novo genome assembly of C. macrophyllum, constructed by integrating long reads from Oxford Nanopore Technologies (ONT), short reads from BGI, and Hi-C data. The final assembly spans 2.55 Gb, with a scaffold N50 of 93.38 Mb, and 83.70% of the genome has been assigned to 22 chromosomes. The mapping rate of the BGI short reads to the genome is approximately 97.94%, and BUSCO analysis reveals that 97.94% of the predicted genes are complete. A total of 62,921 protein-coding genes were predicted, with functional annotations for 93.67% of them. This chromosome-level genome assembly represents an important resource for expanding our understanding of Chrysosplenium species and supports future genomic studies and applications.

Genome, Plant

Near-complete reference genome assembly of Hoya carnosa.

Hoya R. Br. is the largest genus in the tribe Marsdenieae (Apocynaceae), comprising 350-450 species. Hoya species are popular in horticulture for their distinctive floral traits and fragrances, primarily sourced from domestication and mutation breeding. However, the lack of molecular analysis for floral morphological traits has limited their cultivation and application. In this study, we assembled a near-complete reference genome for H. carnosa, the model species of the genus, using PacBio HiFi reads and Hi-C method. The genome size was approximately 465.7 Mb with a contig N50 of 39.3 Mb. 99.7% of the sequences were anchored to 11 pseudochromosomes, and the assembly achieved a BUSCO score of 98.5%. We predicted 24,309 protein-coding genes, of which 90.2% (21,927) were functionally annotated. This high-quality genome provides a valuable reference for the research of evolution, conservation and molecular breeding in Hoya.

Genome, Plant

Chromosome level genome assembly and full-length transcriptome of blacktip trevally (Caranx heberi).

Caranx heberi (Bennett, 1830) commonly known as the blacktip trevally belongs to the family Carangidae and is a potential brackishwater aquaculture species. However, the limited genomic resources are hindering the efforts to study its genetic traits and their molecular basis. To bridge this gap, we generated a high-quality reference genome employing multiple sequencing strategies including PacBio Hifi reads (135x), Illumina short reads (150x), and Hi-C chromosome conformation capturing (180x). The high-quality genome assembly consisted of 159 scaffolds summing to 618.71 Mb and an N50 value of 26.72 Mb. Among these, 24 chromosome level scaffolds covered 97.5% of the total assembly. The genome contained 20.94% of repeat elements and 30,354 protein encoding genes. In addition, full-length transcriptomes were generated using the PacBio IsoSeq approach from seven tissues (gill, kidney, liver, muscle, heart, spleen, and intestine). The comprehensive genomic and transcriptomic resources developed in this study will facilitate the domestication and aquaculture development of C. heberi, as well as support research on its nutritional potential, ecological adaptations, and evolutionary biology.

Animals

A gap-free, telomere-to-telomere chromosome-scale genome assembly of the mangrove red snapper, Lutjanus argentimaculatus.

The mangrove red snapper (Lutjanus argentimaculatus) is a commercially important marine fish species in the Indo-Pacific region. Despite its significant economic value for aquaculture, existing genomic resources remain fragmented, limiting the advancement of molecular breeding and functional genomic studies. Here, we present a gap-free, telomere-to-telomere (T2T) genome assembly of L. argentimaculatus, generated using a hybrid approach combining PacBio HiFi, Oxford Nanopore ultra-long reads and Hi-C technology. The resulting assembly comprises exactly 24 scaffolds spanning 1.03 Gb, perfectly matching the haploid chromosome number with a contig N50 of 46.17 Mb. Notably, this assembly resolves all physical gaps present in previous versions, achieving a BUSCO completeness score of 98.2%. Comprehensive genome annotation successfully predicted 23,167 protein-coding genes. Among these, 22,067 genes (95.25%) were functionally annotated across major public databases, including eggNOG, InterPro, and Swiss-Prot. Furthermore, structural analysis successfully identified 19 telomeres and 20 centromeres, validating the chromosomal integrity. This high-fidelity, gap-free reference genome provides a robust foundation for comparative genomics, population genetics, and the genetic improvement of Lutjanidae species.

Animals

Integrative modeling of the genome structure and dynamics in fission yeast.

Genome organization in the nucleus is highly structured and dynamic. Recent advances in genomic technology have enabled the measurement of genome-wide architecture and locus-specific motion, yielding contact maps and live-cell trajectories. However, these outcomes are derived from different modalities and are not directly comparable, with their quantitative integration being a key challenge. Here we establish a genome-wide live-cell imaging platform in fission yeast Schizosaccharomyces pombe, tracking 131 chromosomal loci, along with the spindle pole body (SPB) and nucleolus, to construct a quantitative map of locus dynamics. By integrating these dynamics with contact data through polymer modeling of Hi-C data, we build a physics-based "digital twin" of the S. pombe genome consistent with the spatiotemporal dynamics of interphase chromatin. We validate it against genome-wide mobility patterns and known architectural features, including centromere and telomere clustering. The model also identifies distinct dynamical regimes: centromere- and telomere-proximal loci relax within [Formula: see text]150 s, whereas the remaining loci relax within [Formula: see text]70 s. We measure semiperiodic dynamics of SPB motion, including a characteristic peak near 225 s and [Formula: see text] fluctuations. We use the model with SPB-directed forcing to show how these low-frequency components propagate through the genome to drive genome-wide chromatin displacements. Together, this predictive physics-based modeling framework integrates genome structure and dynamics to reveal how nuclear mechanical driving forces shape chromosome motion, linking mechanically driven chromatin responses to genome maintenance and regulation.

Schizosaccharomyces

Chiron3D: an interpretable deep learning framework for understanding the DNA code of chromatin looping.

MOTIVATION: Three-dimensional folding of the genome into structures such as chromatin loops is essential for gene regulation. Current experimental methods for mapping these structures, like Hi-C and HiChIP, are labor-intensive and require repeated assays to test hypothesized mutation effects. This motivates the need for predictive approaches that reveal the sequence determinants of chromatin loops. RESULTS: In this work, we present a novel and interpretable computational pipeline for predicting CTCF-mediated chromatin loops. We propose Chiron3D, a DNA-only model trained in a cell-type specific manner to predict CTCF HiChIP contact maps. By leveraging pre-trained embeddings from a foundation model, our approach is competitive with baselines that take CTCF ChIP-seq as additional input, while enabling nucleotide-level attribution to the input DNA sequence. Using our framework, we provide likely mechanistic insights into the physical control of loop dynamics. Specifically, we find that the strength of the loop extrusion anchorage site is largely governed by the amount and binding affinity of CTCF sites at the boundaries. Furthermore, we reveal that loop stability is regulated by the amount of intra-loop CTCF binding sites, where fewer intra-loop sites are associated with greater loop stability. Using targeted, single-nucleotide edit simulations with Chiron3D, we show that both loop strength and stability can be precisely controlled. Together, these results provide novel mechanistic insights into the physical control of genome organization and highlight the potential of decoding the DNA sequence logic in silico. AVAILABILITY: The Chiron3D pipeline is made available at https://github.com/BoevaLab/Chiron3D.

Chromatin

A chromosome-level genome of the Nicobar pigeon, Caloenas nicobarica.

The Nicobar pigeon (Caloenas nicobarica), the closest living relative of the extinct Dodo (Raphus cucullatus), is endemic to Southeast Asia with a fragmented distribution across numerous small islands. It suffers from habitat loss, hunting, and predation from invasive species, resulting in its classification as Near Threatened by the International Union for the Conservation of Nature. We have generated a haplotype-resolved and chromosome-level genome assembly of the Nicobar pigeon using a combination of PacBio HiFi long-read sequencing and Arima Hi-C chromatin interaction mapping. This assembly includes two haplotypes, each spanning approximately 1.2 Gb. Haplotype 1 has a contig N50 of 25.2 Mb and a scaffold N50 of 79.7 Mb, whereas haplotype 2 has a contig N50 of 24.7 Mb and a scaffold N50 of 107.9 Mb. As the first high-quality genome assembly of any bird in the Columbidae Indo-Pacific clade, this resource provides valuable insights for phylogenetic studies. Furthermore, the phylogenetic proximity of the Nicobar pigeon to the Dodo (R. cucullatus) and the Rodrigues Solitaire (Pezophaps solitaria) offers a unique opportunity to study these extinct species, making this assembly a critical resource for evolutionary studies. It also offers a unique model for studying genetic diversity, adaptation, and speciation in island environments. This genomic resource will not only enhance our understanding of the evolutionary history of the Nicobar pigeon but also serve as a valuable tool for future conservation efforts aimed at preserving this unique species and its fragile island ecosystem.

Animals

Chromosome-Level Reference Genome of the Desert Night Lizard Xantusia vigilis.

We present a reference-quality genome assembly for the desert night lizard (Xantusia vigilis). The night lizards (Xantusiidae) are a family of small-bodied lizards found in North America (Xantusia), Central America (Lepidophyma), and Cuba (Cricosaura). The night lizard family has an independent evolutionary history of at least 80 million years from its sister taxa within Scincoidea. The Xantusiids have several unique ecological, behavioral and evolutionary characteristics. For instance, the family contains the only squamate species that form diploid, unisexual, parthenogenic lineages. In addition, most night lizards are viviparous and form stable kin groups that are maintained over multiple years, an unusual life history strategy among lizards. Combining PacBio long-read sequencing, Hi-C, and RNAseq data we developed a reference-quality genome for the desert night lizard, X. vigilis. We assembled a complete mitochondrion and ~ 2.2 Gb nuclear genome, with 20 scaffolds that correlate in size to the X. vigilis karyotype. In addition, we found that X. vigilis chromosome 1 aligns with gene content of both of macrochromosome 1 and microchromosome 9 from a genome assembly of a species in the sister family Cordylidae (Hemicordylus capensis).

Xantusia

Bridging-driven condensation by eukaryotic SMC complexes is a conserved feature of genome organization.

The Structural Maintenance of Chromosome (SMC) protein family plays a central role in higher-order genome organization through ATP-dependent DNA loop extrusion by cohesin and condensin and other processes. Whether these activities fully account for the complexity of chromosome architecture remains unknown. Here, we uncover a conserved ATP-independent mechanism of chromatin condensation by SMC complexes, occurring via biomolecular condensation. Using single-molecule fluorescence imaging, we show that a variety of SMCs form dynamic DNA-bound condensates that exhibit key features of biomolecular condensates, including droplet coalescence, fluorescence recovery after photobleaching, and rapid exchange with free SMC complexes. Atomic force microscopy analysis of human cohesin-DNA assemblies reveals DNA-length-dependent clustering, providing evidence for bridging-driven condensation. Analyses of in vivo super-resolution imaging and high-throughput chromosome conformation capture (Hi-C) data indicate that these condensates form chromatin-associated clusters with multi-loop structures. Together, our results establish that SMC complexes employ ATP-independent phase condensation as well as ATP-dependent activities to shape genome architecture. This work reveals a broadly conserved principle of chromosomal organization across eukaryotes.

Chromosomal Proteins, Non-Histone

Loss of SUMOylation drives aberrant PRC1 clustering and 3D genome rewiring independent of H3K27me3.

Polycomb repressive complex 1 (PRC1) forms nuclear condensates that organize target chromatin domains. SUMOylation modulates PRC1 clustering, but its impact on condensate properties and 3D genome architecture remains unclear. Here, we show that depletion of small ubiquitin-like modifier (SUMO) in Drosophila wing imaginal discs transforms PRC1 condensates into large structures with reduced molecular dynamics. Biophysical modeling suggests that the changes in PRC1 self-interactions are responsible for the formation of large PRC1 condensates when SUMO is depleted. Interestingly, this biophysical reorganization occurs without global loss of the H3K27me3 mark. Instead, Hi-C reveals widespread rewiring of topologically associating domain (TAD) interactions. PRC1-bound TADs lose specific long-range contacts with each other while gaining ectopic interactions with active chromatin. These topological shifts correlate with gene misregulation independently of changes in Polycomb histone modifications. Our results establish SUMOylation as a critical regulator of PRC1 condensates, demonstrating that post-translational control of biomolecular condensation modulates 3D genome architecture and transcriptional output through mechanisms separable from histone mark deposition.

Animals