Adrenal gene expression dynamics support hibernation in 13-lined ground squirrels.

Area of Science:

• Physiology
• Molecular Biology
• Genomics

Background:

• Hibernation presents extreme physiological challenges, including drastic temperature and oxygen fluctuations.
• Understanding molecular mechanisms of homeostasis during hibernation is crucial for mammalian survival.
• Adrenal glands play a key role in stress response and metabolic regulation, vital during hibernation.

Purpose of the Study:

• To investigate adrenal gland gene expression dynamics in hibernating 13-lined ground squirrels.
• To identify molecular mechanisms supporting homeostasis during seasonal hibernation and torpor-arousal cycles.
• To elucidate the role of gene expression in adrenal function during extreme physiological states.

Main Methods:

• RNA sequencing (RNA-seq) of adrenal glands from 13-lined ground squirrels at six key timepoints.
• Analysis of gene expression patterns across seasonal changes and torpor-arousal cycles.
• Integration of gene expression data with body temperature telemetry and morphometric analyses.

Main Results:

• Significant seasonal and torpor-arousal cycle effects on adrenal gland gene expression were identified.
• Steroidogenesis gene expression decreased seasonally, suggesting preservation of mineralocorticoids and suppression of glucocorticoids/androgens.
• A serial gene expression program, including immediate early response genes, was observed during arousal, initiating proteostasis and restoring cellular function.

Conclusions:

• Hibernation involves seasonal reorganization of steroidogenesis in adrenal glands, prioritizing mineralocorticoid preservation.
• A coordinated gene expression program during arousal facilitates cellular repair, proteostasis, and survival during hibernation.
• These findings provide insights into the molecular strategies enabling mammals to withstand extreme physiological challenges during hibernation.