By studying how yeast ages, the MIT biologist obtained insights into the molecular basis of human aging, too.

Question: What attracted you to biology?

Leonard Guarente: I was actually more inclined towards chemistry, maybe mathematics, than biology. In fact, in high school I never studied biology at all because I found it much too soft as a science. Then it was characterization of taxonomy and species and phyla and stuff that I found totally boring. But in college, at MIT, when I was a freshman I was planning to major in possibly chemistry, but I learned that there was this new thing called molecular biology that was just emerging, and it was very exciting. So I decided to try it out. And I ended up majoring in biology while taking a lot of chemistry courses. And I think it was probably a very good decision, because I think the life sciences really have blossomed tremendously in the past 10, 20, 30 years, and this is really the golden age now for biology.

Question: What made you want to specialize in aging?

Leonard Guarente: That came a little bit later. So I had been on the faculty at MIT for about six, seven years. I had tenure, and it gave me an opportunity to think about doing something a little bit risky, sort of high-risk, high-reward. And I spent several years thinking what are some problems out there in biology now that would fit into that category? And I thought about a lot of things, including learning and memory. And I thought aging was interesting because obviously it's extremely important. And it wasn't being studied systematically. It was being studied from the point of view of comparing old and young, and mainly in the medical community. But in terms of the aging process itself, and moreover what might control the aging process, there wasn't very much known. There was a little bit known, but not much. So it looked like a perfect opportunity, but one that had considerable risk.

What made me decide to actually get into it is, it turned out -- so my lab was at that point studying the organism yeast, and I was a yeast biologist. And we had studied various aspects of cell and molecular biology in yeast, and that's really what gained me tenure at MIT. And it turned out that yeast cells get old; they age. So this was for me a perfect entry point to the problem. We could begin by studying how yeast cells get old, and that's what we did.

Question: So you studied yeast?

Leonard Guarente: We started bashing away at this problem in yeast with the idea that we could find genes, single genes, that could confer extra longevity to yeast cells that are dividing. So when yeast cells divide -- this is baker's yeast that I'm talking about, the kind of yeast you would use to make bread or wine or spirits -- and it turns out they're a very, very good system to study in the laboratory to look at cell biology. Now, when these cells divide, what you get -- interestingly, of course, you get two cells from one cell, but they're different. One is called the mother cell, and it's big; and the other is called the daughter cell, and it's small. And it turns out the daughter cell is all newly synthesized; all the material in the daughter is new. But the mother cell retains the old stuff. So that mother cell will then give another daughter and another daughter, and every generation it will be getting older. And it does that about 20 times, and then it hits the wall, and senesces, okay?

So it really -- there really was aging, albeit in a very baroque system. So we thought we would be able to make some headway potentially in identifying at least what controls this process in this exotic system. And that's really what intrigued me. I had at that point no plan to study aging more generally than yeast. That came as we got deeper and deeper into the problem.

Recorded on November 9, 2009