Depletion of lamins B1 and B2 promotes chromatin mobility and induces differential gene expression by a mesoscale-motion-dependent mechanism

Emily M. Pujadas Liwag, Xiaolong Wei, Nicolas Acosta, Lucas M. Carter, Jiekun Yang, Luay M. Almassalha, Surbhi Jain, Ali Daneshkhah, Suhas S.P. Rao, Fidan Seker-Polat, Kyle L. MacQuarrie, Joe Ibarra, Vasundhara Agrawal, Erez Lieberman Aiden, Masato T. Kanemaki, Vadim Backman*, Mazhar Adli*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background: B-type lamins are critical nuclear envelope proteins that interact with the three-dimensional genomic architecture. However, identifying the direct roles of B-lamins on dynamic genome organization has been challenging as their joint depletion severely impacts cell viability. To overcome this, we engineered mammalian cells to rapidly and completely degrade endogenous B-type lamins using Auxin-inducible degron technology. Results: Using live-cell Dual Partial Wave Spectroscopic (Dual-PWS) microscopy, Stochastic Optical Reconstruction Microscopy (STORM), in situ Hi-C, CRISPR-Sirius, and fluorescence in situ hybridization (FISH), we demonstrate that lamin B1 and lamin B2 are critical structural components of the nuclear periphery that create a repressive compartment for peripheral-associated genes. Lamin B1 and lamin B2 depletion minimally alters higher-order chromatin folding but disrupts cell morphology, significantly increases chromatin mobility, redistributes both constitutive and facultative heterochromatin, and induces differential gene expression both within and near lamin-associated domain (LAD) boundaries. Critically, we demonstrate that chromatin territories expand as upregulated genes within LADs radially shift inwards. Our results indicate that the mechanism of action of B-type lamins comes from their role in constraining chromatin motion and spatial positioning of gene-specific loci, heterochromatin, and chromatin domains. Conclusions: Our findings suggest that, while B-type lamin degradation does not significantly change genome topology, it has major implications for three-dimensional chromatin conformation at the single-cell level both at the lamina-associated periphery and the non-LAD-associated nuclear interior with concomitant genome-wide transcriptional changes. This raises intriguing questions about the individual and overlapping roles of lamin B1 and lamin B2 in cellular function and disease.

Original languageEnglish (US)
Article number77
JournalGenome biology
Volume25
Issue number1
DOIs
StatePublished - Dec 2024

Keywords

  • 3D chromatin organization
  • Auxin-inducible degron system
  • CRISPR-Sirius; in situ Hi-C
  • Lamin-associated domains
  • Nuclear lamina
  • Partial Wave Spectroscopic Microscopy
  • Topologically associated domains

ASJC Scopus subject areas

  • Genetics
  • Ecology, Evolution, Behavior and Systematics
  • Cell Biology

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