Loss of CBX2 induces genome instability and senescence-associated chromosomal rearrangements

Polycomb group proteins play important roles in developmental and cell proliferation processes. We demonstrate that the PRC1 protein CBX2 is critical for heterochromatin homeostasis, chromosome stability and the prevention of premature cellular senescence. Purpose: Use of Next-generation sequencing (NGS) to assess transcriptional (RNAseq) profiles and changes in chromatin accessibility in WT and Cbx2-/- fibroblasts prior to the onset of premature senescence. Overall design: Methods: RNA-seq and ATAC-seq profiles of Passage 2 mouse embryonic fibroblasts (MEFs) from wild-type (WT) and Cbx2 knockout (Cbx2-/-) mice were maintained in high glucose DMEM (Gibco/Thermo Fisher, Waltham, MA, USA) supplemented with 10% FBS (Hyclone, GE Healthcare, Chicago, IL, USA), 1/100 (v/v) sodium pyruvate, 1/100 (v/v) L-Glutamine and 1/100 (v/v) Penicillin/Streptomycin (all Gibco/Thermo Fisher) before cell collection for ATAC-seq and RNAseq. Results: Integrative transcriptome analysis and ATAC-seq revealed a significant dysregulation of transcripts involved in DNA repair, chromocenter formation and tumorigenesis in addition to changes in chromatin accessibility of genes involved in amyotrophic lateral sclerosis, basal transcription factors and folate metabolism. Conclusions: The presence of transcriptional dysregulation and altered chromatin accessibility at key loci in Cbx2-/- cells combined with extensive centromere and telomere defects suggest a prominent role for CBX2 in heterochromatin homeostasis and the regulation of nuclear architecture.