Lamin B1 overexpression alters chromatin organization and gene expression

ABSTRACT

Peripheral heterochromatin positioning depends on nuclear envelope associated proteins and repressive histone modifications. Here we show that overexpression (OE) of Lamin B1 (LmnB1) leads to the redistribution of peripheral heterochromatin into heterochromatic foci within the nucleoplasm. These changes represent a perturbation of heterochromatin binding at the nuclear periphery (NP) through a mechanism independent from altering other heterochromatin anchors or histone post-translational modifications. We further show that LmnB1 OE alters gene expression. These changes do not correlate with different levels of H3K9me3, but a significant number of the misregulated genes were likely mislocalized away from the NP upon LmnB1 OE. We also observed an enrichment of developmental processes amongst the upregulated genes. ~74% of these genes were normally repressed in our cell type, suggesting that LmnB1 OE promotes gene de-repression. This demonstrates a broader consequence of LmnB1 OE on cell fate, and highlights the importance of maintaining proper levels of LmnB1.

KEYWORDS:

• Chromatin organization
• gene expression
• nuclear lamina
• nuclear envelope
• heterochromatin

Acknowledgments

We thank members of the Hetzer lab for critical review of the manuscript; Novogene for mRNA library preparation and sequencing; the Next-Generation Sequencing Core Facility at the Salk Institute, with funding from NIH-NCI CCSG: P30 014195, the Chapman Foundation, and the Helmsley Charitable Trust, for sequencing Cut&Run libraries; and the Waitt Advanced Biophotonics Core Facility at the Salk Institute, with funding from NIH-NCI CCSG: P30 014195, the Waitt Foundation, and the Chan-Zuckerberg Initiative Imaging Scientist Award, for electron microscopy sample preparation and imaging.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/19491034.2023.2202548

Additional information

Funding

The work was supported by the Glenn Foundation for Medical Research [none]; Salk Women & Science [none]; NIH [R24GM13720]; NIH-NCI CCSG [P30 014195]