A GENE THAT ALLOWS HUMANS TO EXPERIENCE TOUCH HAS A ROLE IN THEIR SENSE OF SMELL, ACCORDING TO A NEW STUDY

 

The same gene that causes us to be lured to the lovely scent of roses also causes us to feel prickly when we unintentionally contact the thorns. SMU (Southern Methodist University) researchers discovered that a gene associated to experiencing touch could also be an olfactory gene. The result was reached after researching a tiny, translucent worm that resembles the human nervous system in many ways. The research was published in the 'Nucleic Acids Research' publication.

"This gene has previously been identified as a possible chronic pain treatment target. Now that we know the gene is involved in olfaction, it could be used to cure or understand olfactory disorders like the mysterious loss of smell that many COVID-19 patients have experienced "Adam D. Norris, a co-author of the study from SMU, said Norris is an assistant professor in the Department of Biological Sciences at SMU, where he holds the Floyd B. James Chair. He collaborated with the study's lead authors, SMU graduate students Xiaoyu Liang and Canyon Calovich-Benne.

Touch is one of the most crucial senses in the human body, but Norris says there's still a lot we don't know about it. When we touch anything, our nervous system turns the mechanical input from touch receptors in our skin into electrical signals for the brain, according to scientists. This is called mechanosensation, and it allows the brain to tell us a range of information about the object we touched, such as whether it was hot or cold, or sharp, as in the case of a rose's thorns.

However, because the human nervous system is so complicated, the specific mechanics of "what's going on beneath the hood" during this electrical response to touch are unknown. Because it is a much simpler species, scientists routinely study the neurological system of the worm Caenorhabditis elegans. Despite the fact that this worm's nervous system has just 302 nerve cells compared to the billions found in the human brain, many of the genes that produce these neurons in C. elegans have functional counterparts in humans.

The SMU researchers began with well-established knowledge: that in C. elegans, a gene called mec-2 is required for touch neuron activation. However, the SMU study team discovered that activating touch isn't its primary function. "In addition to turning genes on and off, isoforms are various (but functionally identical) versions of a single gene that can be used to alter a neuron's function. We looked for neurons that had varied isoforms of essential genes in them "Norris said. "This led to the basic discovery described in this paper: various isoforms of a single gene (mec-2) interact together to permit both mechanosensation and olfaction."

They discovered that the mec-2 isoform, which is responsible for mechanosensation, requires the activation of a gene called mec-8, according to Norris. Neurons have the ability to express a large number of genes within them. Instead, those who have the mec-8 gene generate the olfactory isoform of mec-2. He explained, "Mec-8 ensures that mec-2 is produced in the mechanosensory isoform."

Using cutting-edge techniques termed "deep single cell sequencing," SMU researchers discovered that without it, mec-2 genes create isoforms that are required for smell in C. elegans. "Single-cell sequencing allows scientists to examine all of the genes active in a single cell." "They can view the full gene, rather than just a little portion from the end of the gene," Norris added. "Deep single-cell sequencing identifies all of the genes and isoforms of those genes expressed in a single cell when used together."

"We were able to distinguish isoforms in single sensory neurons with extraordinary sensitivity, leading directly to these results," he stated. The next step for Norris Lab is to see if a human gene called stomatin can perform the same function as mec-2 in the sense of smell.

Not humans, but worms have the mec-2 gene. However, stomatin is a human gene that has been shown to be quite similar to mec-2 in terms of touch sensitivity in humans. If this is proved to be true for smell, Norris believes that similar treatments being tested to treat chronic pain might be used to treat COVID-19-related loss of scent.

Therapeutic medications functioned by locating a molecular target involved in a negative biological consequence. Once the target has been discovered, the next stage is to locate a chemical key that can attach to it and change its behaviour, preventing it from having its typical negative effect. This chemical key can then be used to make a medicinal medication. In the instance of the Norris team's research, scientists want to determine if they can manipulate mec-2 in worms — and eventually stomatin in people — to turn specific senses on and off. "The goal of preclinical trials is to reduce the sensitivity of mechanosensory neurons without clogging the sensory channels themselves by altering the activity of mec-2," Norris explained. "Perhaps, by doing so, mec-2 can be employed as a "sensory thermostat" to regulate sensory activity."

Norris, on the other hand, emphasised the need for deeper research into this notion. "Experiments in C. elegans and mice have yielded results that are consistent. It's easy to assume that comparable outcomes will occur with humans "he stated "However, that must be demonstrated."