The capacity to detect cold temperatures is essential for many living organisms because cold temperatures can cause detrimental effects like severe soft-tissue damage and hypothermia. Some organisms have evolved the presence of thermoreceptors, which are specific nerve endings that are sensitive to changes in temperature and exist in the skin, skeletal muscle, and the hypothalamus. Thermoreceptors relay electrical signals to the central nervous system (CNS). Glutamate receptors can create disturbances in the CNS if defected, causing neurological conditions ranging from epilepsy to neurodegenerative diseases. The researchers in this study used this notion to determine the function of GLR-3, a glutamate receptor, in the sensation of cold temperatures in the model organism C. elegans . It was already known that cold receptors are abundant in the intestine of C. elegans, and physiologically respond to cold by releasing calcium intracellularly .
Researchers designed an activity-based and unbiased genetic screen with mutant C. elegans, and isolated a specific mutant allele of the GLR-3 gene that encodes for a glutamate receptor. Wild type and mutant species were used for the experiment, the latter is defective in the gene encoding for the GLR-3 gene. A real-time PCR thermocycler was used to rapidly cool and heat the organisms, in addition to amplifying cDNA. Standard calcium imaging was performed using fluorescent microscopy to detect intestinal calcium levels.
Results showed that while wild-type nematodes would release intestinal calcium in response to temperature changes, mutant C. elegans did not. Further experiments showed that cooling caused normal C. elegans to swim away to evade the cold, whereas the individuals lacking cold receptors did not. Mutated C. elegans displayed a significant deficiency in this evolutionary behavioral response. This experiment highlights the evolutionary role of GLR-3 in the detection and avoidance of cold temperatures in numerous organisms. Nevertheless, future studies are necessary to determine the role of transduction channels apart from GLR-3 in cooling-evoked calcium release.
- J. Gong, et al., A cold-sensing receptor encoded by a glutamate receptor gene. CellPress 178, (2019). doi: 10.1016/j.cell.2019.07.034
- Image retrieved from: https://commons.wikimedia.org/wiki/File:Skin_Layers_Unlabeled.jpg