Biology subjects

Bhatt, D. N.

Publications and source records attributed to Bhatt, D. N..

3 recordsLinked to original sources

bioRxiv2026

The CTCF Paralog BORIS Contributes to the Ovarian Cancer Transcriptional Program by Relaxing CTCF-mediated 3D Genome Organization

Disruption of three-dimensional genome architecture is a major driver of cancer initiation and progression, frequently arising from genetic and epigenetic alterations at CTCF- and cohesin-bound chromatin anchors. These same chromatin loop anchors can also be occupied by the germ cell-specific CTCF paralog CTCFL (BORIS), which is aberrantly activated in multiple malignancies. Here, we show that in ovarian cancer cells, BORIS activation establishes a distinct transcriptional program that collapses following loss of BORIS chromatin binding and is accompanied by widespread changes in CTCF and cohesin occupancy, histone modifications, and chromatin accessibility. These BORIS-dependent transcriptional alterations occur in long-range genomic clusters, resulting in the coordinated activation or repression of neighboring genes, including hormonally regulated gene families. BORIS loss also increases topologically associating domain (TAD) insulation, strengthens A/B compartment segregation and chromatin loop interactions, and results in a more compact and constrained chromatin architecture. Together, our findings suggest that aberrant BORIS activation promotes transcriptional reprogramming by weakening CTCF-mediated chromatin insulation and relaxing three-dimensional genome organization in ovarian cancer. SignificanceHigh-grade serous ovarian carcinoma, the most common subtype of ovarian cancer, remains one of the deadliest gynecological malignancies because of its late diagnosis, extensive genomic instability, and frequent therapeutic resistance. The lack of reliable biomarkers for early detection underscores the need to identify new molecular drivers of disease initiation and progression. Here, we show that the germline-specific gene CTCFL (BORIS) is aberrantly activated in high-grade serous ovarian carcinoma, where it remodels transcriptional, epigenetic, and three-dimensional genome organization by occupying CTCF-bound chromatin loop anchors and weakening CTCF-mediated chromatin insulation. These findings identify BORIS as a key regulator of transcriptional reprogramming in ovarian cancer and support its further investigation as both a prognostic biomarker and a potential therapeutic target.

cancer biology↗

bioRxiv2025

Incomplete developmental silencing of cancer-testis antigen BORIS in humanized mouse model promotes cancer susceptibility

Cancer-testis antigens are genes normally restricted to the germline but aberrantly activated in many cancers, where their role in tumorigenesis remains unclear. BORIS (CTCFL), a testis-specific paralog of the chromatin organizer CTCF, is one such antigen that shows limited conservation between humans and mice, complicating in vivo functional studies. Here, we generated humanized mice in which both alleles of the endogenous Boris locus are replaced with the full-length human BORIS gene, including its highly diverged cis-regulatory elements. These fully humanized mice maintain normal fertility, indicating accurate germline expression and preserved BORIS function despite evolutionary divergence. However, unlike the strictly testis-specific expression of mouse Boris, human BORIS escapes complete somatic silencing, producing mosaic expression in a minority of mouse somatic cells. This ectopic expression is associated with reduced survival, increased tumor incidence and a shift of tumor spectrum toward aggressive lymphomas. Transcriptomic and chromatin profiling revealed that ectopic human BORIS reactivates testes-specific genes in the soma, including regulators of meiosis and DNA repair, through direct chromatin binding. This transcriptional reprogramming was consistent across tissues and clonal cell lines, revealing a dominant tissue-independent gene activation program. These findings demonstrate that when human BORIS escapes epigenetic silencing in somatic cells, it connects aberrant germline gene activation with increased cancer susceptibility in vivo.

cancer biology↗

bioRxiv2024

CTCF binding landscape is established by the epigenetic status of the nucleosome, well-positioned relative to CTCF motif orientation

CTCF binding sites serve as anchors for the 3D chromatin architecture in vertebrates. The functionality of these anchors is influenced by the residence time of CTCF on chromatin, which is determined by its binding affinity and its interactions with nucleosomes and other chromatin-associated factors. In this study, we demonstrate that CTCF occupancy is driven by CTCF motifs, strategically positioned at the entry sides of a well-positioned nucleosome, such that, upon binding, the N-terminus of CTCF is oriented towards the nucleosome. We refer to this nucleosome as the CTCF priming nucleosome (CPN). CTCF recognizes its binding sites if they are not methylated. It can then displace the CPN, provided the nucleosome is not marked by CpG methylation or repressive histone modifications. Under these permissive conditions, the N-terminus of CTCF recruits SMARCA5 to reposition the CPN downstream, thereby creating nucleosome-free regions that enhance CTCF occupancy and cohesin stalling. In contrast, when CPNs carry repressive epigenetic marks, CTCF binding is transient, without nucleosome displacement or chromatin opening. In such cases, cohesin is not effectively retained at CTCF binding sites. We propose that the epigenetic status of CPNs shapes cell-specific CTCF binding patterns, ensuring the maintenance of chromatin architecture throughout the cell cycle. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/614770v2_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@105f34eorg.highwire.dtl.DTLVardef@1a88a82org.highwire.dtl.DTLVardef@1d90f2org.highwire.dtl.DTLVardef@1170e49_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗