Two complementary studies explain how Eurasian common shrews (Sorex araneus) shrink and then regrow their brains and other organs each year, a seasonal change known as Dehnel’s phenomenon. Researchers combined a chromosome-scale genome assembly with seasonal brain transcriptomes to tie genome structure to shifts in gene activity across seasons.
The Genome Research paper describes regulatory shifts from autumn into winter: reduced oxidative phosphorylation alongside increased fatty acid metabolism, a profile similar to hibernating species. Winter samples also showed elevated expression of genes for gluconeogenesis, the production of glucose from non-carbohydrate sources, and an increase in FOXO signaling, a cellular pathway linked to metabolic regulation and homeostasis. The authors argue that gluconeogenesis together with overexpression of FOXO is central to the observed brain and organ shrinkage.
The Molecular Biology and Evolution paper focuses on chromosome arrangement as a facilitator of this plasticity. The team discovered previously unknown seasonal gene expression changes and reports that genes under positive selection and differentially expressed in the hippocampus are concentrated at open chromosome regions that experience more breaks. They suggest that chromosomal rearrangements contribute to adaptive evolution and to the regulation of brain-size plasticity.
Lead researchers note an unexpected link between chromosome rearrangements and the genes that change during the shrinking and regrowth cycle. They also point out that many of the same genes exist in humans, so studying shrew energy management and brain regrowth may help researchers understand metabolism and brain health.
- Collaborators: John Jay College of Criminal Justice
- Max Planck Institute of Animal Behavior
- Aalborg University
- Universitat Autonoma de Barcelona
Difficult words
- transcriptome — complete set of RNA molecules in a tissuetranscriptomes
- oxidative phosphorylation — process in cells that produces most energy
- gluconeogenesis — production of glucose from non-carbohydrate sources
- FOXO signaling — cell pathway involved in metabolic regulation and homeostasis
- rearrangement — change in the order or structure of chromosomesrearrangements
- positive selection — evolutionary process favoring beneficial genetic variants
- hippocampus — brain region important for memory and spatial navigation
- plasticity — ability of an organ to change form or function
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Discussion questions
- What possible benefits could arise from studying shrew energy management and brain regrowth for human medicine?
- What difficulties might scientists face when applying findings from shrews to human biology?
- How could chromosome rearrangements influence adaptation and plasticity in other animal species?
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