2019-10-13 20:10:25
One of the external conditions that can exert the greatest influence on all kinds of beings is temperature.
All external stimuli capable of being detected induce neuronal activation that transmits the information to the brain. Sensor neurons need molecules arranged in their outer membrane capable of biochemically detecting these stimuli. These molecules on the cell membrane are called receptors.
Just as temperature expands or contracts bodies, it can also change the structure of molecules. This change in the structure of the temperature receptor molecules is what triggers the signal that neurons send to the brain.
The signal must be proportional to the stimulus and must distinguish it from others. For example, freshness is not the same as intense cold. Receptors capable of generating a sensation of freshness are known. However, the receptors of the intense cold had not been able to be identified. For this reason, some scientists speculated that they did not exist and that it was the combined activity (or absence of it) of the different heat and coolness detectors that would generate the sensation of intense cold.
The search for cold receptor genes also did not reveal the existence of any. To search for them, the scientists focused on finding genes similar to those of the other receptors, and using this method they could not find any. It seemed, therefore, that the receiver of the cold did not exist.
However, all the possibilities to conclude this had not yet been exhausted. In particular, no genomic searches had been performed on cold-insensitive mutant organisms.
To conduct this search, researchers from the University of Michigan, USA, use the laboratory worm Caenorhabditis elegans. This is a worm only one millimeter long, made up of around a thousand cells, which is, like us, capable of detecting the cold and avoiding it by moving towards warmer areas.
The researchers looked for mutant worms unable to react to intense cold, suggesting that the mutation would have affected at least one of the genes required for this ability. After analyzing the genome of these worms incapable of reacting to cold, the researchers identified mutations in a gene that produces a known receptor called glr-3. What was not known at all was that the receptor participated in the detection of cold and in the transmission of that information to the central nervous system.
To make sure that this indeed was the cold receptor gene, the researchers checked that this gene is conserved throughout evolution from worm to human, which should be the case for a gene that performs such a basic mission. . And second, they introduce the mouse gene into the genome of the mutant worms, which have lost their normal glr-3 gene, and find that the mouse gene restores the worms’ ability to sense cold. Indeed, the gene, conserved in evolution from worms to mammals, functions in a similar way in both organisms.
There is no doubt, animals have at least one receptor for intense cold. Let’s hope that global warming doesn’t end up making it irrelevant.
Referencia: Jianke Gong et al. (2019) A Cold-Sensing Receptor Encoded by a Glutamate Receptor Gene.
Jorge Laborda, October 13, 2019
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