|Smelly Research Nets Two US Researchers the Nobel Prize|
By Ellen Kuwana|
Neuroscience for Kids Staff Writer
October 7, 2004
Axel and Buck tackled an area of research in which little was known previously: how the sense of smell, or olfaction, works. The numbers generated from their work speak for themselves. There are more than 1,000 different genes involved in the sense of smell; this, then, is the largest gene family known in the human genome. This represents 3% of the human genome, demonstrating how vital our sense of smell is to our survival; we need to detect food and discern if it's still edible (not rotten or poisonous), for example. Most animals use smell to find food, avoid predators and interpret their environment.
Once an odor is detected, an electrical signal travels along the neuron straight to the olfactory bulb in the brain. From the olfactory bulb, which is like the switchboard for smell information in the brain, the information is routed to other parts of the brain, including limbic areas. The sense of smell, therefore, is linked strongly to memories and emotion. By using chemicals in the lab to trace the pathways involved in smell, the researchers have been able to map how certain smells trigger the olfactory receptors, and how the information is conveyed by neuronal signals to the olfactory bulb and on to other parts of the brain.
Buck chose a novel approach to solve the mystery of how the nose-brain system recognizes the thousands of odor molecules (called "odorants") floating around us in the world. The question was: Did many very specific receptors detect the odorants, or only a few receptors, working overtime? The approach was: Search for the genes encoding receptors found only in the nose, instead of searching for the receptors themselves. Buck's former mentor, Axel, called this approach "an extremely clever twist."
The research to solve this receptor mystery borrowed clues from other studies on receptors.
Clue one: Many receptor proteins have a similar structure: they cross the cell membrane seven times, creating a zig-zag shape that resembles a snake.
Clue two: These proteins often interact with another type of protein, G-proteins, to transmit signals to the inside of the cell.
Clue three: These proteins often share stretches of DNA in common. These clues helped Buck to design probes (think of a fishing hook shaped for a certain fish) to identify these sequences in rodent DNA. The better you know what you are fishing for, the better you can design the "hook" to catch it.
By carefully designing the "hook," or probe, Buck saved years of work.
Once genes had been identified in rodent DNA, a similar approach was used to fish out the genes in collections of DNA from other species such as humans, mice, dogs, catfish and salamander.
Buck is expanding her research on odorant receptors to other types of receptors, such as those involved in bitter tastes, sweet tastes and pheromones. Pheromones are chemicals produced by animals to signal to others in their species. The first pheromone, identified in the 1950s, was an attractant signal for silkworm moth mating. Research on insects, though, is much easier than on humans, and the topic of human pheromones is controversial. Don't invest in that pheromone-enhanced perfume yet. The jury is still out on whether you can improve your attractiveness by exuding certain chemical signals. Animals have a vomeronasal organ (VNO) that responds to pheromones, but no such organ has been pinpointed in humans. Axel has noted that if humans have one, it's most likely disrupted by plastic surgery in those who have nose jobs.
Image courtesy of the Nobel Foundation
References and further information:|
|GO TO:||Neuroscience In The News||Explore the Nervous System||Table of Contents|
Fill out survey