Levels of post-translationally modified histones in ground squirrel livers are altered during deep torpor

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) are obligate hibernators capable of reducing their metabolic rates by up to 99 % during winter. Their ability to remain dormant without food for an extended period in cold conditions has made them compelling subjects for research. Developing a clearer understanding of mechanisms surrounding the pre-transcriptional control of hibernating tissues is crucial for cryobiological applications such as organ preservation. Thus, we investigated the differential expression of 24 modified histones (MH) in the livers of torpid and euthermic free-ranging ground squirrels by immunoblotting histone-enriched extracts (p < 0.05). We identified the torpor-responsive downregulation of multiple permissive MHs (H2BK5ac, H3K18ac, H3K23ac, H3K27ac, H3K4me2, H3K4me3, H4K20me1, H4R3me2s), including total H2B and H4, while the linker histone H1.0 was the only histone species that was upregulated. The present study provides valuable insights into the involvement of histone post-translational modifications in the epigenetic landscape of deeply torpid ground squirrel livers.