Researchers at Stony Brook University, along with international collaborators, have published new findings on how the Eurasian common shrew (Sorex araneus) adapts to winter through a process known as Dehnel’s phenomenon. Unlike some mammals that hibernate, this shrew conserves energy by shrinking its brain and other organs during winter, then regrows them in spring.
The studies, published in Genome Research and Molecular Biology and Evolution, detail genetic and biological changes linked to this seasonal adaptation. The research team identified regulatory shifts in oxidative phosphorylation and increased fatty acid metabolism in shrews during autumn and winter—changes also seen in hibernating animals. However, they found that shrews uniquely increase the expression of genes involved in gluconeogenesis during winter.
The studies also highlight an increase in FOXO signaling—a cell regulatory process important for maintaining homeostasis—which researchers believe is essential to the shrinkage of the brain and organs.
Liliana M. Dávalos, professor in the Department of Ecology and Evolution at Stony Brook University and senior author on both papers, said: “In mammals, Dehnel’s phenomenon is an extreme example of how the same genetic information can result in varying structures, we call that genetic plasticity. Together, these studies show that how the genome is arranged contributes to both the plasticity and evolution or genetic adaptation that enable this tiny shrew to continue being active through the winter, even as it gets colder and food grows scarcer.”
By combining chromosome-scale genome assembly with seasonal brain transcriptomes, researchers discovered gene expression changes previously unknown to be involved in Dehnel’s phenomenon. They observed that genes selected for adaptation or showing differential expression are concentrated at open chromosomal regions prone to breaks. According to the authors: “that chromosomal rearrangements are integral to adaptive evolution and the regulation of brain size plasticity.”
William R. Thomas, lead author on both papers and post-doctoral associate at Stony Brook University’s Department of Ecology and Evolution stated: “Before I had even heard of Dehnel’s phenomenon, I knew these shrews had an unusual number of rearrangements in their chromosomes that evolutionary biologists have studied for decades. Yet I did not expect the rearrangements themselves had something to do with the genes that adapt in this species to generate Dehnel’s phenomenon, to the genes that express more during the cycle of shrinking and regrowing, or to genes that may help repair breaks in the genome.”
Thomas added: “This shows us how important the structure of the genome is to traits that make shrews unique. Plus, our findings are not confined to shrews. The same genes shrews use are also present in humans. How the shrew’s energy management links to brain regrowth can help us figure out how metabolism and brain health can work in people as well.”
Collaborators on these studies included researchers from John Jay College of Criminal Justice, Max Planck Institute of Animal Behavior, Aalborg University, and Universitat Autonoma de Barcelona.
