How can tiny worms help solve the jigsaw puzzle of human behavior?

Department of Biophysics and Biochemistry — Iino Laboratory

Professor Yuichi Iino
Department of Biological Sciences
Graduate School of Science

Professor Iino graduated from the University of Tokyo’s Department of Biophysics and Biochemistry in 1982, and then obtained his Master’s Degree in Biochemistry in 1984 and Ph.D. in Biochemistry in 1987, both from the University of Tokyo. From 1987 to 1988 he was a Japan Society for the Promotion of Science Fellow, and from 1988 to 1990 took a postdoctoral position at Columbia University’s Center for Neurosicence and Behavior. He became an assistant professor at the University of Tokyo in the School of Science’s Department of Biochemistry in 1990, an instructor in the Graduate School of Science’s Biochemistry program in 1993, and an associate professor in the Molecular Genetics Research Laboratory in 1998. He took up his current position in 2007.

Why do humans behave the way they do? Every day we use our arms and legs to freely move about and interact with the world, but we rarely consider the details of how we do so. When we stop to consider this, many questions arise. For example, sometimes we find ourselves setting out to perform some task, but end up doing something else. An example would be heading toward your desk with the intent of studying, but finding yourself instead grabbing a book off your bookshelf. As Professor Yuichi Iino explains, “There are highly expedient factors related to our behavior and some very disorganized aspects, too. For example, through “learning” we can come to control previously impossible movements and through experience previously unremarkable smells and tastes can become unbearably foul. We want to know what’s behind that mechanism at the neuronal level.” Iino’s research tackles various mysteries related to the nervous system that regulate our behavior, such as how organisms sense physical and chemical stimuli, how those stimuli are recognized and evaluated, and where in the nervous system such information is encoded.

The Iino Laboratory uses the nematode Caenorhabditis elegans as its primary research specimen. These tiny organisms, only around 1 mm long, live in soil and feed on the bacteria present in decaying matter. They are excellent specimens for nervous system research because each and every one of their nerve cells and circuits has been identified and named.

One of representative research achievements made by Professor Iino was a study called “Let me taste that one more time.” While this may sound more like a jingle from a television commercial than a scientific study, the paper presented important research that elucidated the mechanism behind how nematodes store memories of taste. Experimenters fed and raised nematodes in environments with various salinity levels, then placed them in a different environment and observed their behavior. Doing so showed that nematodes have learning abilities—the worms would seek out areas where the salinity was similar to that where they were fed. In other words, worms raised in regions of high salinity learned to prefer salty places, and those raised in areas of low salinity preferred less salt in their environment.

Iino further demonstrated that when salinity was changed while nematodes were being raised, they would develop memories of their new environment in just a few hours. In experiments where individual nerve cells were investigated, it was found that this behavior was controlled by input from a single taste-sensing neuron, and that the diacylglycerol signaling pathway operating in this nerve celldetermines “tasting” behavior related to salinity levels.

Returning to our original question, how can investigating details of the nervous system in nematodes help us to understand the mechanisms underlying human behavior? “In the end, what we really want to understand is how the human brain works,” says Iino. “But even mice, let alone humans, have such a huge number of nerve cells that completely understanding how they work in harmony to transmit information is a very difficult task. It’s much easier to experiment with nematodes, for which we have a good understanding of how many cells are involved, and how they’re linked together.” Yet even in the case of nematodes, there remain many mysteries related to how nerves are networked, and how they transmit information. Currently, in joint research programs we are investigating in mice important molecular functions that were first identified in nematodes.

The Iino Laboratory places a high value on autonomy and “the moment of excitement.” Iino says, “If you just do as you’re told, then even if you discover something, it isn’t all that exciting. What’s exciting is when you think of an experiment yourself and produce good results from performing that experiment. That’s the experience I want my students to have.” Student Naoko Sakai (D2) says, “Here, everybody has their own research theme. That means each student performs their research with a sense of self-responsibility.”

Solving the puzzles that nerves present will require unending diligence and curiosity. But the longer it takes to solve a puzzle, the bigger the thrill when that last piece fits into place.

 

The nematode C. elegans (above) has 302 nerve cells. Each nerve cell has been identified and named (colored parts at bottom).

Student evaluations
“It’s interesting that despite being a bio lab, we have many researchers from IT-related fields.” (Yusuke Sato, D1)
“I like that we’re expected to think for ourselves and to perform experiments on our own.” (Naoko Sakai, D2)

― Office of Communication ―