Biology subjects

Kalluchi, A.

Publications and source records attributed to Kalluchi, A..

8 recordsLinked to original sources

bioRxiv2026

Kilobase-scale compartments enabled by CRUSH reveal regulatory programs across cell types, single-cells, and ancient mammoths

How chromatin is spatially organized in the nucleus has long been studied through the lens of large-scale A/B compartments, but whether these sizes reflect true biological units or analytical artifacts has remained unclear. We find that limits imposed by the conventional eigenvector-based compartment calling have required extreme sequencing depth and coarse resolution, obscuring regulatory-scale organization. We developed CRUSH to iteratively refine compartments to 1 kb resolution without the need for extreme sequencing depth, we show that kilobase-scale A/B segregation (micro-compartments) is evident across cell types. Across these maps, we demonstrate that RNA polymerase II pausing contributes to a sub-genic compartment signature at the transcription start site and that active enhancers almost universally occupy the A compartment. We then show that fine-scale compartment maps can resolve cancer subtype-specific regulatory programs, single-cell tissue identity, and cold-adaptation regulomes in a 52,000-year-old woolly mammoth. These findings establish chromatin compartmentalization as a gene-scale regulatory feature with broad implications for development, disease, and genome evolution. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC="FIGDIR/small/719469v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@15c1992org.highwire.dtl.DTLVardef@192f541org.highwire.dtl.DTLVardef@123a737org.highwire.dtl.DTLVardef@1b7292f_HPS_FORMAT_FIGEXP M_FIG C_FIG CRUSH uses iterative resolution walking to identify and correct A/B compartment measurements. This allows identification of A/B compartments at kilobase resolution with low sequencing depth and consistency across methodologies. Kilobase-scale compartments reveal sub-genic compartment organization, compartment identities in single-cells, and a distinct cold-adapted regulome in mammoths.

genomics↗

bioRxiv2025

ECD functions as a novel RNA-binding protein to regulate mRNA splicing

Human ecdysoneless protein (ECD) plays an essential role in regulating cell cycle progression and cell survival. ECD has previously been implicated in RNA splicing through its association with spliceosomal proteins. Here, using EMSA, fluorescence polarization assays, and mutational analysis, we demonstrate that ECD directly binds to RNA. Enhanced CLIP-seq analysis identified a broad repertoire of mRNAs bound to ECD in cells. RNA-seq analyses revealed that ECD depletion leads to widespread splicing aberrations and altered gene expression. ECD binding to RNAs was enriched near splice sites, and a substantial fraction of ECD-bound transcripts exhibited splicing defects upon ECD depletion. ECD associates with and stabilizes the U5 snRNP complex specific proteins. While depletion of ECD reduced the levels of key U5-specifc proteins, these proteins exhibited an increased association with the R2TP complex in knockout cells. Notably, we found ECD to directly bind to U5 snRNA, and an RNA binding defective mutant of ECD ({Delta}135-148) failed to rescue the reduced levels of U5-specific proteins or the proliferation defect induced by ECD depletion. Collectively, these findings demonstrate that ECD binds to RNAs, including the U5 snRNA, and that RNA-binding is required for ECD to stabilize the U5 snRNP and for cellular functions. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/634785v4_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@f5aa4forg.highwire.dtl.DTLVardef@80606borg.highwire.dtl.DTLVardef@3a4c8eorg.highwire.dtl.DTLVardef@1780b0f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

HiCrayon reveals distinct layers of multi-state 3D chromatin organization

The co-visualization of chromatin conformation with 1D omics data is key to the multi-omics driven data analysis of 3D genome organization. Chromatin contact maps are often shown as 2D heatmaps and visually compared to 1D genomic data by simple juxtaposition. While common, this strategy is imprecise, placing the onus on the reader to align features with each other. To remedy this, we developed HiCrayon, an interactive tool that facilitates the integration of 3D chromatin organization maps and 1D datasets. This visualization method integrates data from genomic assays directly into the chromatin contact map by coloring interactions according to 1D signal. HiCrayon is implemented using R shiny and python to create a graphical user interface (GUI) application, available in both web or containerized format to promote accessibility. HiCrayon is implemented in R, and includes a graphical user interface (GUI), as well as a slimmed-down web-based version that lets users quickly produce publication-ready images. We demonstrate the utility of HiCrayon in visualizing the effectiveness of compartment calling and the relationship between ChIP-seq and various features of chromatin organization. We also demonstrate the improved visualization of other 3D genomic phenomena, such as differences between loops associated with CTCF/cohesin vs. those associated with H3K27ac. We then demonstrate HiCrayons visualization of organizational changes that occur during differentiation and use HiCrayon to detect compartment patterns that cannot be assigned to either A or B compartments, revealing a distinct 3rd chromatin compartment. Overall, we demonstrate the utility of co-visualizing 2D chromatin conformation with 1D genomic signals within the same matrix to reveal fundamental aspects of genome organization. Local version: https://github.com/JRowleyLab/HiCrayon Web version: https://jrowleylab.com/HiCrayon

genomics↗

bioRxiv2024

Novel spirocyclic dimer, SpiD3, targets chronic lymphocytic leukemia survival pathways with potent preclinical effects

Chronic lymphocytic leukemia (CLL) cell survival and growth is fueled by the induction of B-cell receptor (BCR) signaling within the tumor microenvironment (TME) driving activation of NF- {kappa}B signaling and the unfolded protein response (UPR). Malignant cells have higher basal levels of UPR posing a unique therapeutic window to combat CLL cell growth using pharmacological agents that induce accumulation of misfolded proteins. Frontline CLL therapeutics that directly target BCR signaling such as Bruton-tyrosine kinase (BTK) inhibitors (e.g., ibrutinib) have enhanced patient survival. However, resistance mechanisms wherein tumor cells bypass BTK inhibition through acquired BTK mutations, and/or activation of alternative survival mechanisms have rendered ibrutinib ineffective, imposing the need for novel therapeutics. We evaluated SpiD3, a novel spirocyclic dimer, in CLL cell lines, patient-derived CLL samples, ibrutinib-resistant CLL cells, and in the E{micro}-TCL1 mouse model. Our integrated multi-omics and functional analyses revealed BCR signaling, NF-{kappa}B signaling, and endoplasmic reticulum stress among the top pathways modulated by SpiD3. This was accompanied by marked upregulation of the UPR and inhibition of global protein synthesis in CLL cell lines and patient-derived CLL cells. In ibrutinib-resistant CLL cells, SpiD3 retained its anti-leukemic effects, mirrored in reduced activation of key proliferative pathways (e.g., PRAS, ERK, MYC). Translationally, we observed reduced tumor burden in SpiD3-treated E{micro}-TCL1 mice. Our findings reveal that SpiD3 exploits critical vulnerabilities in CLL cells including NF-{kappa}B signaling and the UPR, culminating in profound anti-tumor properties independent of TME stimuli. STATEMENT OF SIGNIFICANCESpiD3 demonstrates cytotoxicity in CLL partially through inhibition of NF-{kappa}B signaling independent of tumor-supportive stimuli. By inducing the accumulation of unfolded proteins, SpiD3 activates the UPR and hinders protein synthesis in CLL cells. Overall, SpiD3 exploits critical CLL vulnerabilities (i.e., the NF-{kappa}B pathway and UPR) highlighting its use in drug-resistant CLL. VISUAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=137 HEIGHT=200 SRC="FIGDIR/small/578283v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1dd7a38org.highwire.dtl.DTLVardef@1831c85org.highwire.dtl.DTLVardef@c571f9org.highwire.dtl.DTLVardef@bdce53_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

Three-dimensional genome architecture persists in a 52,000-year-old woolly mammoth skin sample

Ancient DNA (aDNA) sequencing analysis typically involves alignment to a modern reference genome assembly from a related species. Since aDNA molecules are fragmentary, these alignments yield information about small-scale differences, but provide no information about larger features such as the chromosome structure of ancient species. We report the genome assembly of a female Late Pleistocene woolly mammoth (Mammuthus primigenius) with twenty-eight chromosome-length scaffolds, generated using mammoth skin preserved in permafrost for roughly 52,000 years. We began by creating a modified Hi-C protocol, dubbed PaleoHi-C, optimized for ancient samples, and using it to map chromatin contacts in a woolly mammoth. Next, we developed "reference-assisted 3D genome assembly," which begins with a reference genome assembly from a related species, and uses Hi-C and DNA-Seq data from a target species to split, order, orient, and correct sequences on the basis of their 3D proximity, yielding accurate chromosome-length scaffolds for the target species. By means of this reference-assisted 3D genome assembly, PaleoHi-C data reveals the 3D architecture of a woolly mammoth genome, including chromosome territories, compartments, domains, and loops. The active (A) and inactive (B) genome compartments in mammoth skin more closely resemble those observed in Asian elephant skin than the compartmentalization patterns seen in other Asian elephant tissues. Differences in compartmentalization between these skin samples reveal sequences whose transcription was potentially altered in mammoth. We observe a tetradic structure for the inactive X chromosome in mammoth, distinct from the bipartite architecture seen in human and mouse. Generating chromosome-length genome assemblies for two other elephantids (Asian and African elephant), we find that the overall karyotype, and this tetradic Xi structure, are conserved throughout the clade. These results illustrate that cell-type specific epigenetic information can be preserved in ancient samples, in the form of DNA geometry, and that it may be feasible to perform de novo genome assembly of some extinct species.

genomics↗

bioRxiv2023

EHD1-dependent traffic of IGF-1 receptor to the cell surface is essential for Ewing sarcoma tumorigenesis and metastasis

Overexpression of EPS15 Homology Domain containing 1 (EHD1) has been linked to tumorigenesis but whether its core function as a regulator of intracellular traffic of cell surface receptors plays a role in oncogenesis remains unknown. We establish that EHD1 is overexpressed in Ewing sarcoma (EWS), with high EHD mRNA expression specifying shorter patient survival. ShRNA and CRISPR-knockout with mouse Ehd1 rescue established a requirement of EHD1 for tumorigenesis and metastasis. RTK antibody arrays identified the IGF-1R as a target of EHD1 regulation in EWS. Mechanistically, we demonstrate a requirement of EHD1 for endocytic recycling and Golgi to plasma membrane traffic of IGF-1R to maintain its surface expression and downstream signaling. Conversely, EHD1 overexpression-dependent exaggerated oncogenic traits require IGF-1R expression and kinase activity. Our findings define the RTK traffic regulation as a proximal mechanism of EHD1 overexpression-dependent oncogenesis that impinges on IGF-1R in EWS, supporting the potential of IGF-1R and EHD1 co-targeting.

cancer biology↗

bioRxiv2021

Fine-mapping of nuclear compartments using ultra-deep Hi-C shows that active promoter and enhancer elements localize in the active A compartment even when adjacent sequences do not

Megabase-scale intervals of active, gene-rich and inactive, gene-poor chromatin are known to segregate, forming the A and B compartments. Fine mapping of the contents of these A and B compartments has been hitherto impossible, owing to the extraordinary sequencing depths required to distinguish between the long-range contact patterns of individual loci, and to the computational complexity of the associated calculations. Here, we generate the largest published in situ Hi-C map to date, spanning 33 billion contacts. We also develop a computational method, dubbed PCA of Sparse, SUper Massive Matrices (POSSUMM), that is capable of efficiently calculating eigenvectors for sparse matrices with millions of rows and columns. Applying POSSUMM to our Hi-C dataset makes it possible to assign loci to the A and B compartment at 500 bp resolution. We find that loci frequently alternate between compartments as one moves along the contour of the genome, such that the median compartment interval is only 12.5 kb long. Contrary to the findings in coarse-resolution compartment profiles, we find that individual genes are not uniformly positioned in either the A compartment or the B compartment. Instead, essentially all (95%) active gene promoters localize in the A compartment, but the likelihood of localizing in the A compartment declines along the body of active genes, such that the transcriptional termini of long genes (>60 kb) tend to localize in the B compartment. Similarly, nearly all active enhancers elements (95%) localize in the A compartment, even when the flanking sequences are comprised entirely of inactive chromatin and localize in the B compartment. These results are consistent with a model in which DNA-bound regulatory complexes give rise to phase separation at the scale of individual DNA elements.

genomics↗

bioRxiv2021

Sex-specific multi-level 3D genome dynamics in the mouse brain

The female mammalian brain exhibits sex-hormone-driven plasticity during the reproductive period. Evidence implicates chromatin dynamics in gene regulation underlying this plasticity. However, whether ovarian hormones impact higher-order chromatin organization in post-mitotic neurons in vivo is unknown. Here, we mapped 3D genome of ventral hippocampal neurons across the estrous cycle and by sex in mice. In females, we found cycle-driven dynamism in 3D chromatin organization, including in estrogen-response-elements-enriched X-chromosome compartments, autosomal CTCF loops, and enhancer-promoter interactions. With rising estrogen levels, the female 3D genome becomes more similar to the male genome. Cyclical enhancer-promoter interactions are partially associated with gene expression and enriched for brain disorder-relevant genes. Our study reveals unique 3D genome dynamics in the female brain relevant to female-specific gene regulation, neuroplasticity, and disease risk.

neuroscience↗