Regulatory activity and evolutionary co-option of cis-regulatory elements underlying bear hibernation.

Cis-regulatory elements in brown bears show dynamic activity shifts during hibernation, with many sharing homology to human enhancers but targeting different genes.

• Why it matters: Understanding the regulatory mechanisms behind hibernation can reveal how complex physiological adaptations evolve and are maintained across species, filling a key knowledge gap.
• What they did: Using capped-small RNA-sequencing from brown bear adipose tissue, the study identified putative enhancers with activity changes during hibernation and examined their sequence homology and gene targets, also exploring selection on these regulatory sequences.
• The result: Findings suggest regulatory co-option plays a role in hibernation evolution, and evidence of selection on cis-regulatory sequences indicates their importance in physiological adaptation across bears.