Here’s a breakdown of the information from the provided text, answering the questions posed within it and summarizing the key findings:
What causes this brain shrinkage, and how do these animals avoid permanent damage?
The brain shrinkage is primarily caused by water loss, not by the loss of brain cells themselves. The animals avoid permanent damage through a combination of genetic factors:
* Upregulation of genes associated with brain cell creation: This suggests a preparation for regrowth.
* Increased expression of VEGFA: This gene increases blood-brain barrier permeability, potentially enhancing nutrient sensing.
* Abundance of genes associated with DNA repair and longevity: These genes help protect brain cells during the shrinkage and ensure they can recover.
* A “finely tuned system”: This allows for reversible regulation of brain shrinkage without the negative effects of neurodegeneration.
Key Findings & Summary:
* Dehnel’s Phenomenon: This is the seasonal reduction in brain size observed in certain mammals (shrews, moles, weasels, stoats) as a survival strategy during times of energy scarcity.
* Genetic Basis: Researchers mapped the genome of the common shrew and compared it to other mammals exhibiting the phenomenon to identify shared genetic traits.
* Water Loss is Key: The most significant discovery is that the shrinkage is due to water loss from the brain, not cell death.
* Potential for Human Applications: The genes involved in this process (especially those related to energy homeostasis and the blood-brain barrier) could potentially provide biomarkers and therapeutic targets for human neurodegenerative diseases, though caution is needed when extrapolating findings.
