Identification of the HSP gene family in wild Daurian ground squirrel (Spermophilus dauricus) and analysis of their expression during different hibernation stages.

Hibernation is an extreme form of seasonal heterothermy that enables animals to survive under harsh environmental conditions and provides valuable natural models for investigating the physiological mechanisms underlying stress tolerance. The Daurian ground squirrel (Spermophilus dauricus) is a small burrowing mammal that exhibits pronounced seasonal changes in activity and naturally undergoes hibernation, making it a useful model for elucidating the molecular mechanisms underlying hibernation. Heat shock proteins (HSPs) are highly conserved molecular chaperones involved in protein homeostasis and cellular stress responses. A total of 40 HSP genes were identified in the Daurian ground squirrel and grouped into six subfamilies, consisting of three small HSPs (sHSPs), 26 HSP40s, six HSP70s, three HSP90s, one HSP60, and one HSP110. Comprehensive analyses of molecular characteristics, conserved domains, gene structures, phylogenetic relationships, and chromosomal distributions revealed substantial evolutionary diversity within the HSP40 family. Although members of the DNAJA, DNAJB, and DNAJC subfamilies shared several conserved structural features, differences were also observed in their molecular characteristics and evolutionary relationships. To investigate their expression dynamics during hibernation, the transcript levels of HSP40 genes in the liver tissues of the Daurian ground squirrels at different hibernation stages were quantified using the real-time quantitative polymerase chain reaction (RT-qPCR). Most of the HSP40 genes examined exhibited broadly similar expression trends throughout the hibernation cycle, although individual genes showed different temporal expression profiles. These findings suggest that HSP40 genes undergo differential transcriptional regulation during hibernation and may be involved in the physiological responses associated with hepatic adaptation to the hibernation state. Collectively, this study provides a systematic characterization of the HSP gene family in a natural mammalian hibernator and offers valuable insights into the potential involvement of HSPs in proteostasis regulation during hibernation.