 news in the outstanding journals such as Cell, Development, Genetics, Nature, and Science. A major component of Dr. Kenyon's current research focuses on identifying and understanding the genes that function to establish longevity. This is what she is here to tell us about today. Now, if you're interested in how people come to what they do, like I am, you might wonder what drew Dr. Kenyon along the path she took to get where she is today. As an undergraduate at the University of Georgia, she was perhaps like a lot of students here at Gustavus. She knew she was interested in a major. The only trouble was, which one? In her first two years, she considered upwards of a dozen majors, including mathematics, Russian, veterinary, and dairy science. None seemed to be the right fit. She tells me a formative experience came for her through literature. Genetics eventually captivated her imagination as a result of a rena book that her mother brought home, Jim Watson's The Molecular Biology of the Gene. The logic apparent in the circuitry controlling genes fascinated her. She was hooked. Dr. Kenyon majored in chemistry and biochemistry at the University of Georgia and subsequently studied biology at Massachusetts Institute for Technology, where she obtained her PhD. Dr. Kenyon then spent several years at the Medical Research Council Laboratory of Molecular Biology, Cambridge University, England, working with Dr. Sidney Brenner, Nobel Laureate in Physiology or Medicine on developmental studies of the nematode C. elegans. Let me just say that if you like genetics of small worms, this was the place to be. Just a little background on this nematode may be helpful. C. elegans is an interesting model organism, especially if you're interested in questions of developmental biology, because biologists have essentially developed a map for the outcome of each cell division necessary to give rise to the body of this worm, which consists of 959 cells in the adult. A limited number of body cells and this map combined serve as an extremely useful tool for studying developmental decisions. Dr. Kenyon has used this tool for studying the role of genes and determining cell fate, though her current research focuses upon the role of genes in determining an individual worm's fate, or at least its longevity. Significantly, her research has revealed three independent, non-redundant molecular pathways that influence longevity in the nematode C. elegans. As you can no doubt imagine, this promises to be a very interesting topic. Please help me in welcoming Dr. Kenyon to the podium. Thank you so much for that lovely introduction. It's really a pleasure to be here. There is a certain magic to this place. It's really a special place and it's really an honor and a pleasure for me to come and visit here. I'm going to be talking about aging, so I'll be talking about genes that control aging, and as I guess you know for many, many years, even centuries, people have thought that aging is something that just happens. We wear out, like old cars. You know? Yeah. But you know, I started to think, is it possible that it's not so simple? Is that possible? The first thing that made me start thinking this is to just think about the life of a young girl. She grows up through childhood and suddenly when she's 10 or 12 or so, she goes through puberty. And then decades go by and suddenly she goes through menopause. How does this happen? Does this just happen? It seems so timed in a way. Does it just happen or not? Another thing is, here's the second thing, nothing in biology seems to just happen. We know that now. We've studied many other aspects of molecular biology and development and how cells become muscles or nerve cells or many other kind of processes, how genes are switched on and off. And many times it's been the case that people thought something just happened and then they found out that it was actually something that turned out to be controlled in a very precise way by the actions of specific genes in the DNA. So after this happens again and again, you see something that you thought just happened turn out to be controlled, you start thinking, well, maybe aging is too. Maybe it could be. Another thing that influenced my thinking was the following. Some kinds of animals can have very different lifespans. Here you see that a mouse lives two years, a canary 15, and a bat can live to be 50. Actually, my favorite example is a different one. Rats have a lifespan of about three years, but gray squirrels can live to be 25 years. Isn't that something? They're very different and yet they look the same in many ways. So something is making them different from one another, and obviously the things that makes these animals different from each other to begin with are their genes. Their genes are different. That's why they're different, and that must be why they have different lifespans. The other thing is that all of these animals arose during evolution from a common ancestor that must have aged at some rate. So that means that changes in genes that took place during evolution have to be responsible for the changes that they have in lifespan, or the differences between them now in their lifespans. So there have to be genes that influence aging. There just have to be. So basically what we decided to do was to see, so my idea was that maybe there was some control program for aging, something that controlled the rate at which animals aged. So for example, maybe this control system is present in the mouse and the bat, but it's set differently. It's set to run quickly in the mouse so the mouse gets old quickly, but more slowly in the bat so the bat can live longer. Now that's just a hypothesis and it could be wrong or it could be right. But one thing you can do is you can do experiments to ask if it could be true. What you can do is you can change the genes in a little organism and ask if there are genes that you can change that as a consequence will change the lifespan of the animal. So of course we didn't study people, instead we studied C. elegans. This is a small soil nematode. It looks very big here, but it's actually microscopic. And as you heard, it's very small, it has just a few cells in its body, just about a thousand cells, but it has all the major tissues and it moves towards things it likes and away from things it doesn't like. It's a real little animal. So we decided to look and see whether there might be genes in this animal that affected the rate of aging. And we were very optimistic when we started out that we might be able to learn something that told us not just about these little roundworms, but about all animals. So the question was, could C. elegans ever possibly lead us to the fountain of youth? So here you see little C. elegans, an elderly individual. And here's the fountain of youth. And so that's what we were wondering about. So the answer is yes, I think so. So we were optimistic. First because many biological mechanisms are known to have been conserved during evolution. So that means that now they're the same in lots of different kinds of animals. So for example, these little worms have nerve cells just like we do. And the nerve cells have the same kinds of nerve proteins in them. They make the same neurotransmitters, serotonin, acetylcholine, various other ones that you've probably, dopamine that you've probably heard of. And even the genes that cause a certain cell to become a neuron, these are informational kinds of genes. They're the same in the worms and people. It's really quite remarkable because they look so different from us. So it is. You would think they'd be totally different, but they're not. Actually the differences at the molecular level are dwarfed by the similarities. It's quite remarkable. So anyway, it seemed to me that maybe if there were genes that controlled aging in these little worms, there would also be genes that controlled aging in higher organisms. OK, the next thing is just a technical point, which is that these worms are very easy to study and they have very short lifespans. They just live a few weeks, as you'll see. And as you'll see, they get old. OK, so we were real optimistic and we were particularly optimistic because another researcher, Michael Klass, had found a mutant worm, a worm in which one gene was changed, was different, that seemed to live longer than normal, that lived about 50% longer than a normal worm. So we set out to look for genes that affect aging. So now what we did was we have a population of worms and we just changed the genes at random. We can make a gene work better, a gene work worse. We could just do it randomly. And then we sort through the population of worms with these possible changes in their genes, looking for individuals that lived longer than normal. And what we found was that mutations that damage a certain gene, a gene called DAF2, double the worm's lifespan. Changed one gene, lived twice as long. It was amazing. So this is a survival curve here. Here on this axis we have the fraction of worms that are still alive. And here we have time in days. And you can see here that normal worms start at the beginning, of course, they're all alive. But then they die after just a few weeks, so that by the time the month has passed, they're all dead. Whereas these altered worms, they're called mutants. Mutants, because a mutant is an animal that has a change in a gene. So these DAF2 mutants are just exactly like the normal worms in all respect except one. That is that one of their particular genes they have, they have 20,000 genes in all. And one of their genes, named DAF2, is damaged. And they live twice as long. So you see at 30 days when all the normal worms are dead, most of these are still alive. And it isn't until much later that they're all dead. So it's a really remarkable, amazing result that one gene you can change and double the lifespan. The thing that I think is even more remarkable is that it's not just that they live long. It's not just that they check into the nursing home and hang on. They actually seem to age more slowly. And that I can show you here in these movies. So this is an adult that's called wild type. And that's what we use to say, that's the normal worm, the wild type, because that's what you'd find out in the wild. So here's the little worm moving around. It's about college student age in worms years. It's young. Frisky, happy, optimistic, moving along. It eats bacteria. So these little wrinkled things here are the tracks that leaves behind in the bacteria. So that's a young adult worm. Now prepare yourself. Get out your handkerchiefs. This is the same kind of worm, the normal worm, after about two weeks. Look, terrible. This worm is already dead. And this worm is clearly in the nursing home. It has its head is moving. You can see that. But otherwise, it's just lying still. Now if you take a high-power microscope and you look at the individual tissues and cells in the worm, what you find is that when they're young, all the cells and tissues look fine. They look very nice. But as they get older, there's a lot of deterioration and degeneration that seems to take place all through the body of the worm in a gradual, progressive way. And so these worms are old and they will die soon if they're not already dead. Now compare this to the mutant worms that are exactly the same age. So this is the DAF2 mutant. See? Amazing. It looks younger. It's moving. It has active interest in life. It may be, who knows, running a small business. See? And if you look with a microscope, a high-power microscope, at these worms, you see that their tissues look fine at this age. Later on, they do age and they die. But at this point, they look much younger. It's kind of as though you looked at me and I told you that I'm actually 90 years old. That's what it's like. You don't think I am because I don't look 90. I don't behave as though I'm 90. But I actually am chronologically. That's the analogy here between what this mutation does to the worms and what that would mean in human terms. OK. Now, I want to tell you something else about this gene. The name of the gene is DAF2. And this gene was already known when we discovered that it affected aging. It was already known because when you change the gene, when you make a mutation in the gene, you not only affect aging, but you affect something that happens when the animal is in childhood during the growth of the animal to the adult. And now I'm going to describe what that is. When a normal worm, first of all, they start off life as eggs. The eggs are laid by the mother. And then the animals go through various different stages that have names, L1, L2, L3, L4. Then they become adults. And then once they're adults, they start to have their own eggs, and then they age and die. Now, that's what happens if there's a lot of food around when these little worms hatch from eggs. But sometimes they hatch in an environment where there's not a lot of food. And they have a strategy for dealing with that, which is very interesting. What happens is they start down this path. But when they get about here to the L1 stage, they exit from that path here, and they go over here. And they enter another kind of state. They become what are called dowers. Now, the word dower is a German word that means enduring. And these little dowers are specialized in such a way that they can endure harsh environmental conditions, like lack of food or crowding. These animals, they look just like worms. They can move around, but they can't eat, and they can't reproduce, and they can't grow. They're just arrested. If you take a dower worm and you give it food, then it comes out of the dower state and goes right straight into this L4 state here. And then it becomes an adult, and it produces its eggs. And it actually has exactly the same lifespan that it would have if it had never gone through the dower, if it had just grown up here. OK, so now, I want to tell you that the only time these worms can enter this dower state is when their children, before they go through puberty. So it's kind of like a decision point. Basically, the animal, I think, is sort of saying, if there's enough food, then I'll do it. I'll grow up, and I'll reproduce, and I'll produce my children, because there's food for them. On the other hand, if there's not, I'll wait. I'll wait until there is food. And at that time, and only then, will I grow up and reproduce. So it's a smart strategy. If you take an adult worm and you deprive it of food, it doesn't become a dower. It's only this one period here can it become a dower. Now, the DAF2 gene affects the decision of whether to grow up to be an adult or whether to or to be a dower. OK, here, if you, instead of just damaging the gene slightly, which is what we did, if you completely destroy it so it has no function at all, then what happens is the animals hatch from these eggs, and they start down this path, and then they become dowers, even if there is food. So the normal function of this gene is to allow the worms in the presence of food to keep growing, to become adults. And the idea would be then that in the environment, when food becomes limiting, maybe this gene becomes less active somehow. So it goes toward the off state, and that allows the animals to become dowers. OK, so it had this known activity, this known function. So we were then very curious to know what was the relationship between the role that this gene had in determining whether or not the animal would become a dower during childhood and its ability to control the aging process of the adult. So what we did to address this question is we conducted an experiment in which we asked, when in the life of the worm does the daft 2 gene act to control the aging process? Obviously, it has to act soon after hatching here to determine whether or not the worm goes into dower. Does it act at that same time to control or to determine how long the animal lives as an adult? Or does it act again later in the adult? In the laboratory, we have ways of inhibiting the activities of specific genes. We can turn them down. We can essentially damage them at will whenever we want to. For those of you who are scientists, I'll just mention that the technique we use is called RNAi. And for those of you who aren't scientists, don't worry, just take it from me that we have a way of doing it. You don't really need to know how it's done to understand the result. OK, so what we did was the following. We asked, when does the daft 2 gene affect lifespan? So we could do two things. First, we could turn the gene down throughout the life of the animal. And that's the same thing that damaging the gene with a mutation does. It's down all the time. And as you would expect, these animals live long. So control here means the normal worms. And in red, again, you see what we find, the long lifespan, that animals have when we turn the gene down throughout life. And then we did an experiment where we turned gene activity down only during adulthood. So we let the worms hatch from the eggs. We let them grow up and become adults. And then only at that time do we damage the gene. Do we turn it down? And what happens is they live just as long. So the gene was perfectly fine all through childhood. It was only turned down in the adult. So that tells us that the daft 2 gene acts during adulthood to affect lifespan. You have to have the gene functioning normally in the normal adult in order for it to age at the normal rate. We did other experiments that showed us that the daft 2 gene acts exclusively during adulthood to affect the lifespan of the animal. What we did was we let the animals hatch, and then we turned the gene down while they were children. And then when they became adults, we turned the gene back up. And those worms had normal lifespans. So it doesn't matter if the gene is active or damaged or not damaged during the childhood part of the life. It's only whether it's active in the adult that matters. So the gene is acting at two different times in the life of the worm. It's acting soon after hatching to determine whether or not the worm will enter this dour state. And then it acts again in the adult independently to control the rate of aging of the worm to determine how fast it ages. So the two processes, the dour process and the aging process are distinctive. They're different. So what exactly is the daft 2 gene? Well, at the time that we made our discovery that the gene affected the aging process, many labs were already studying the role that the gene had in controlling the decision to become a dour or not during development. And one of these genes, so one of these labs, a lab of Gary Rovkin, isolated the daft 2 gene and determined what its molecular activity was. And what he found was that the daft 2 gene encodes. The word encodes means, uh-oh. I must have done something wrong. Anyway, OK. So the daft 2 gene, it encodes something called a hormone receptor. So first, I'll tell you what the word encode means. What genes do is to direct the cell to make certain kinds of proteins. They're all kinds of proteins. And the protein that the daft 2 gene directs the cell to make is called a hormone receptor. So what's that? Well, you know what hormones are. Hormones are small molecules that circulate in your blood and throughout your body that tell cells to behave in certain ways. So for example, there are sex hormones, like estrogen and testosterone. And these are functioning very, very soon in development to determine whether the fertilized egg develops as a boy or a girl. So that's one kind of hormone. There are many kinds of hormones. So what hormones do they circulate in the body? And as they do, they come in contact with the tissues of the body or the cells of the body. And what happens is that they allow the cells to respond to the hormones. And in response, the cells do something different than they would have done before. So here's a picture of a cell, one particular cell, with the hormone receptor. In this case, the daft 2 hormone receptor. And you can see that the receptor is binding to these hormones. You can think of it kind of like a baseball glove. And the hormones as a baseball. So when the baseball comes by, the glove catches it. And as a consequence, signals are sent into the inside of the cell, which tell the cell to do something different. Now, our findings showed that when the daft 2 receptor is functional, aging is speeded up. OK, remember? When we damage the worm, sorry, when we damage the gene with a mutation, the animals live longer. So that means that the normal activity of this gene is actually to speed up aging. It's kind of counterintuitive. It's like the grim reaper gene right there in the animal, making it get old faster. Yeah. So together, our results and the results from this lab demonstrated that hormones control aging. In other words, aging is controlled. It doesn't just happen. And it's controlled by hormones in these little worms. And in this case, like I said, the hormones are speeding up aging. OK, now it turns out that this hormone receptor was a very familiar one. It was very similar to two, uh-oh, now I've done it again. Sorry, OK, to two human hormone receptors, the receptors for insulin and IGF1. Now, these are two hormones that you may have heard of. The hormone insulin controls the ability of cells to take up food after a meal. So it's known to do that. The hormone IGF1 stands for insulin-like growth factor number one. And this hormone controls growth. It's less popularly known than the insulin hormone. So both of these hormones are very important. They're both essential for life. If you lack either one of them, you can't live. And so they are known to have these functions. Now, what our studies did was to raise the question, is it possible that these hormones, insulin and IGF1, have another function to control aging in people and other animals? Is this possible? Now, I told you that many biological mechanisms, like how you make a nerve cell, for example, are very similar in between worms and mammals, including people. So as soon as we had discovered that this hormone system controls the aging process in these little worms, other labs working on other animals rushed in to ask whether it was possible that changing the same genes in these other animals would increase their life spans. And we don't know the answer yet for humans. We don't know. But we do know that for many other kinds of animals, it appears that the answer is yes. So here on the left, you see the situation in the little worm. We imagine that we have these hormones, insulin and IGF1 like hormones. Then we have the DAF2 receptor that is activated when it binds to the hormones. And when it's active, the DAF2 receptor inhibits longevity. So this little arrow sign here like this, this little perpendicular line sign here, means when the DAF2 receptor is active, longevity is shortened. So two groups that work on fruit flies, the group of Linda Partridge and the group of Mark Tater, change the fruit fly version of this same gene. And what they found was that the fruit flies live longer. And fruit flies are very different from worms. You've seen them. If you leave some wine, for example, open or bananas around, you'll get these little fruit flies. They're not at all like these little worms. They're very distinct from them. So it's remarkable that the same genes, these same receptors could control aging, not just in these worms, but also in the fruit flies. And then two other labs asked, could the situation also be the same in mice? And they found that it was. Now mice, first of all, worms and flies have a single one of these DAF2 like receptor genes and proteins. Whereas mice and humans have a separate gene for the receptor for insulin, the hormone insulin, and the receptor for the other hormone, IGF1. So one group, the group of Holzenberger's, what they did was that they took mice and they, mice normally have two copies of every gene, including this gene. And what they did was they knocked out one of them. So now they had half as much, half as many genes. Instead of two genes, they had one gene. And what they found, so they have half as much activity of hormone receptor activity in their bodies. And what they found was that the mice lived longer. It was really remarkable. They lived about 30% longer than normal mice, which is a lot. Although it's not double, it's not twice as long, but they lived significantly longer. They also had normal reproduction and normal metabolism, they seemed very healthy. Another laboratory, the laboratory of Ron Kahn at Harvard, showed that if you take mice and you remove the receptor for insulin from just one tissue, the fat tissue here, the mice also live long. And these mice actually were very lucky because they were very slender and if you fed them a high-fat diet, which makes normal mice get very fat, these mice didn't get fat. So they were very lucky mice. They live long and they stayed slender. Okay, but really the big deep, profound take-home message from this is that the same set of genes is controlling aging, not just in these worms and not even just in the fruit flies, but also in mammals and were mammals. So we don't know yet whether they do affect aging in humans, but what this does suggest is that a long time ago in evolution, in a precursor animal or an ancestral animal that gave rise in evolution to these worms and the flies and the mice and also humans in those little animals, this hormone system was controlling aging. Okay, that's the most likely explanation for this and that's why it's still controlling aging now in worms and flies and mice. So either humans have lost it or not and we don't know, but it's very likely I think that these hormones are regulating the aging process in humans. Although as I say, when I say likely, I mean that's because everything else we know about that's the same in worms, flies and mice turns out to be the same in humans. We don't actually know that yet for sure, but it's a very interesting possibility. Okay, so how do hormones control aging? I mean obviously a hormone is just a little protein or a small molecule that's circulating around in the animal or the person. How could it be controlling the aging process? Well, we didn't think it was likely that, I mean it isn't likely that the hormone actually does it physically itself. Somehow it must be controlling other gene activities or activities in the cells that more directly affect the aging process. That's why we actually say that the hormones are telling us that aging is under some kind of control because they themselves can't really determine the lifespan of an animal. Now in the DNA there are many genes. Worms have 20,000 genes for example. Humans have about 30,000. And different genes do different things. So for example there are some genes that let the heart beat, for example. There are other genes that let you see. And each gene can either be active, that is telling the cell to make the protein or not active, or it can be more active or less active. So for example the genes for the heart are very active in the heart, but they're not active in the eye. And the genes that let you see are active, making proteins in the eye, but not in the heart. So see genes can be either active or inactive. So what we imagined was that the hormones were affecting aging by changing the activities of other genes in the DNA. Genes that would be more directly involved in controlling the aging process. For example genes that can repair damage to cellular components or can prevent damage to cellular components. So that was our hypothesis. And there are now, I'm just gonna have a glass of water here for a second. Okay there are now ways that molecular biologists can actually look at the activity of all the genes in the DNA. All 20,000 genes in the worm's DNA. So we use this technique. And what we found was that the DAF2 hormone receptor controls the activity of many genes. I can't touch it at all now without getting that. I don't understand why that is. Anyway, okay. If someone knows a technical person, that would be helpful to me. Anyway, okay. So the hormone receptor controls the activities of many genes. So when you turn the activity of the hormone receptor down, now the worms are gonna live long, what we find is that the activities of many genes change, some that will become more active, they make more protein, some become less active. So that's good. So the next question is, are these genes whose activity changed contributing to the changes in the lifespan of the DAF2 mutant animals? So to ask that question, what we did was we made a list of our genes whose activities changed. And we put them in order so that the ones that changed the most were at the top of the list and the ones that changed less and less were lower down on the list. And then we just marched down the list, turning down each of the individual genes, each one of these genes, one by one, using this technique I told you about for the scientists, the technique of RNAi. And then we asked, does that have an effect on lifespan? And we found that it did for most of these genes, for many of them. We found that inhibiting the activity of many genes that are more active in the long-lived mutants shortens the lifespan of the long-lived mutants. So here in black, here you see, this is the lifespan of the long-lived DAF2 mutant. And here, for comparison, is the normal worm. And all these lines here in the middle, these are the lifespans of animals that they're DAF2 mutants, so they should live this long, but we've turned down or we've inhibited the activity of, in each case, one of these genes that was turned up in the long-lived animal, who was more active in the long-lived animal. And in all of these cases, it matters. The animals don't live as long. So these genes, that tells us that their increased activities are contributing to the long life of the DAF2 mutant. And the converse was also true. We found that many genes that are less active in the long-lived mutants also affect longevity. So in this experiment, what we did was we, here in black, you see what we call the control, which these are just normal worms. So what we did was we took normal worms and then we turned these genes down one by one in the normal worms. Now remember, we find that in the worms that can live a really long time, the mutants, that these genes are less active. So these might be genes that normally inhibit longevity. So what we did is we took normal worms and we turned them down using this method. And what we found was that for many of them, we increased the lifespan of the animal here. So it was important that they be turned down. So that's really important. What that tells you is that the hormones are acting through many subordinate, or we call it, we say downstream genes, to affect lifespan. So what do the genes do, these downstream genes? They do many different things. This was really, really interesting. They fell into different groups. One set of the genes make antioxidants. You know about antioxidants. They prevent the damage of cellular proteins by reactive oxygen species. Well, there was a whole class of genes that we know already make antioxidant proteins that were more active in the long-lived mutants. And we know from our experiments that the activities of those genes were important for the long life. Because if we turned them down, the long-lived animals didn't live as long. We also found a set of genes that make proteins called chaperones. Now, these are very nice, interesting proteins. Chaperones are proteins whose function, as the name suggests, is to help other proteins. So what they do is they help other proteins fold correctly, keep them in good working order. And if another protein in the cell is damaged, these chaperones can actually chaperone them off to the garbage can of the cell to get rid of them, to make way for new proteins that are not damaged. And it turns out that a lot of chaperone genes were expressed at a higher level in, that is, they were more active in the long-lived animals. We found a whole different class of genes which we call antimicrobial genes. These are genes that direct the production of proteins that kill bacteria or other microorganisms. And it turns out worms actually die ultimately from infections. We know that because if we prevent the bacteria that they're eating from dividing, that is, we arrest the growth of the bacteria with an antibiotic, the worms can live longer. So what actually, what we think is that the worms become frail as they age. And when they become frail enough, the bacteria which are always present can penetrate into the body of the animals and kill them. That's our hypothesis. So it was really nice to see that these long-lived animals, the mutants have better protection against infection. We also found a class of metabolic genes whose activities change. One of these is really an interesting one. One of them, one class, is a set of genes whose normal function is to transport fat in the body from place to place. They're called apolipoprotein genes. And the reason that's interesting is that it converges with a completely different type of scientific exploration. As you probably know, the ability of particular people, well, the ability to become a centenarian that is to live to be 100 runs in families. There are many families in which many, many people live to be 100 or into their 90s. And other families where this is rare. So that says that there are genes then that whose activities are inherited that are predisposing certain families toward the ability to become 100. And it turns out that one of the, at least two or three of these genes turn out to be genes whose function is to transport fat around. In the centenarian families, these genes are less active and in our worms, they're less active. And if we turn them down in a normal worm, the worm lives longer. It's very interesting. So while we don't know the details of the molecular mechanisms involved, it's nice because it's a link between what we're finding in these little worms and what other people studying the same question from a very different perspective are finding. And then we also found what we call novel genes. These are genes in which we don't know what the functions are. So these will be interesting to learn more about. Okay, so when you look at the big picture, I like to think of it as being kind of like an orchestra. Oh, I should say here, before I say that, that other labs have also found other genes whose activities change in the long live mutants. And again, they fit into this general idea that many different kinds of genes act together to affect the longevity of the animal. And I like to think of the whole situation as being similar to an orchestra. Here's an orchestra. Okay, so at the top of the orchestra here, you have the orchestra conductor. That's right here. Okay. All right. And so that would be like the DAF2 receptor or the hormones. They're bringing it all together. And then you have the antioxidants, they would be like the violins, the chaperones like maybe the trumpets, the antimicrobials like the cellos. Here we have the percussion and so forth. So each of these different components of the orchestra does its own thing, does something different. But they all work together. They all weigh in. And the cumulative effect, the additive effect is enormous. And I think that's the situation that we have. Many different genes, each affecting lifespan in its own way, but all acting together under the control of the hormone system. That's what's producing these big effects on lifespan. Okay, so there's some implications for this. The first is that there is a whole control system for aging. In other words, we have the control proteins, the hormones and the hormone receptors. And then we have the downstream genes, the antimicrobial genes and so forth. Together that's a control system or a control module, if you will. It exists. Where did it come from? I think it might have evolved in evolution because of the dour state. Remember I told you earlier that if you starve young worms soon after hatching, they enter this dour state. And I told you also that the same hormones that control aging and the adult control the decision to become a dour in childhood. You can immediately see that an animal that has the ability, has evolved the ability to become a dour in harsh environmental conditions is gonna have a big advantage. You have two populations of worms and food is scarce. These guys can't become dourers, they just, they die and they don't have progeny or they have progeny and the progeny die. These can stop and wait, the ones that have the dour state. They can stop and wait. And then they can wait to have their progeny when there's food. Now it turns out that these little dour's are very resistant to all sorts of environmental stress. For example, if you heat them up, they're less sensitive. If you irradiate them, they're less sensitive, they're more resistant to that. They're what we call stress resistant. And it turns out that many of the same genes that I just told you affect the aging process are also more active in the dour's. So for example, the chaperones. I told you that the chaperone proteins help keep other proteins in good working order. Well that's important for a dour. These dour's have to be able to survive for a long time any kind of environmental hazard. So they have higher levels of the chaperones which protect the proteins. They have higher levels of the antioxidants which protect them against reactive oxygen species. And this could be very, very helpful in preventing the animals from being damaged by the environment. So the key concept here I think is that the same proteins that protect the dour from the environment can also protect the aging normal worm from the ravages of aging, okay? From damage that occurs during the aging process, from for example, the activity of the mitochondria and so forth. You see? So if you have this protective mechanism, it could have evolved. I'm sorry, the protective mechanism could have evolved because it's really gonna be helpful to the species to be able to become a dour. But once it's evolved, there it is. It's there. The genes are there. The whole network is there in place. So if it's also active in the adult, more or less active, because the same downstream genes that protect the dour from the environment can also protect an aging animal from its internal damage, the activity of that system will affect aging in the adult, you see? So you don't have to think of a reason for why aging would have evolved to be regulated. That's not necessary because there's a perfectly good reason for why the system would have evolved for the dour. There's no question that an animal that can wait and reproduce when times are good has an advantage. Okay? So I think that's pretty cool. Really interesting, it's really interesting actually. And it provides a very satisfying explanation for why how this could be. Okay. Now remember, it evolved a long time ago in a precursor of the worm and the fly in the mouse and the human. Mice don't have a dour stage. They don't have that option. But since the system was already up and running before in evolution, the worm branch split off from the mouse branch, it could still be there and maintained and it could still influence aging. Okay, so because the system is up and running, you could imagine that changes in the regulators as the control genes, like the hormone genes or the receptor genes or these downstream genes like the antioxidant genes or the metabolic genes or antimicrobial genes, any of these genes, changes in them, could have increased lifespan during evolution as our lifespans became longer and longer. So it'll be really interesting to see if animals that have longer lifespans have greater activities of these different genes. If the hormone system is wired slightly differently or if the individual downstream genes are more or less active. And I would think that probably many of these same genes determine the rate of aging in humans. If not the hormones, then I think it's really pretty likely that a lot of these individual antioxidants and so forth genes are influencing our aging. So now we have a collection of genes that we can start to investigate scientifically. Okay, now I wanna switch and talk about a very important, interesting related question. And that is what links the process of normal aging to age-related disease. As you know, there are many, many diseases would fit into the category of the so-called diseases of aging or age-related diseases. These are diseases that are more prevalent among the elderly. For example, cancer, type two diabetes, Alzheimer's disease, the different neurological protein aggregation diseases. Many of these diseases are age-related. It's not a question of how many days a person has been alive. That doesn't seem to be what makes them more susceptible. For example, mice live only two years, but when they're a year and a half old, they're very susceptible to cancer. And think about a young dog is pretty healthy and disease resistant. But as it ages, then you find more cases of cancer and kidney problems and so forth. So it's biological age that matters and not chronological age or the calendar years that go by. So what is it that makes a biologically more elderly individual more susceptible to these diseases? Well, it turns out that this very same hormone system does the insulin and IGF-1 hormone system also influences disease susceptibility. For example, you can make worms get Huntington's disease. Huntington's disease is caused by a specific gene, a mutant form of a specific gene called the Huntington's gene. And when you put that Huntington's mutant gene into the C. elegans, into the worms, then the protein forms aggregates as the worm ages. So here's a young worm here. And what you see, the protein has been put into the muscle. The gene's been activated in the muscle. So here you have the diffuse, harmless form of the protein here. But as the worms age, you get these aggregates, see the little clumps, okay? And these are what are thought to be harmful, either the aggregates themselves or something involved in the production of the aggregates. And it turns out, so this is what happens in humans who have Huntington's disease, they go along fine for a while and then they begin to get these aggregates here. And then the neurons die. So in both cases, it happens with age. What's really interesting is that the laboratory that did this, the laboratory of Rick Morimoto, showed that the aggregation of the Huntington's protein was delayed in the long-lived mutants. So it still happened, but it happened later. So isn't that interesting? So they look younger and they're also younger in the sense that they're not as susceptible to this disease. And that's not the only case. There are more and more cases of this coming up. It's really quite remarkable. Normal worms get a muscle-wasting disease that resembles human sarcopenia. And the long-lived animals come down with that disease later. In Drosophila, sorry, fruit flies, the scientific name is Drosophila. But in these flies, if you take old flies and you stress the heart, it has a high chance of failing. But in the long-lived flies, the heart doesn't fail. It's remarkable. The long-lived mice have a lower chance of getting cancer. If you change a hormone called growth hormone here, which is another hormone I haven't mentioned, but it actually controls the production of IGF-1, if you turn it down, then you make less IGF-1 and so the mice or rats live longer. And those mice have been, or rats in this case have been tested. They've been treated with chemicals that cause cancer and they've been found to be very resistant to the cancers. So lots of different kinds, very different kinds, a whole broad spectrum of diseases here seem to be influenced by this hormone pathway. Could this be the case in humans? We don't know, I'll just mention that some cancers in humans are caused by the loss of genes that normally turn these hormones down. So in other words, when you lose these genes in particular parts of the body, in particular tissues, then this hormone system becomes more active and it can potentiate the formation of cancer. So we don't know how, as I say, we know very little at this point about the role of this whole hormone system in human aging, but we do know that it has this interesting disease connection. Okay, so it looks as though, when these animals are aging more slowly, they're also really biologically younger and more disease resistant. So obviously this has potentially very powerful, is potentially powerful as a therapeutic strategy. In other words, if we could find drugs that slow down aging, maybe we could, those drugs might be efficacious for many different kinds of age related diseases all at once. There would be like a magic bullet type of drug. So it's really interesting. Okay, so we wanted to know, we wanted to go beyond this finding that the hormone system controls both aging and age related disease. We wanted to ask why or how? How does this happen? So we focused on this Huntington's disease here, that is the worms that have been modified so that they come down with Huntington's disease as they age. And we wanted to ask, what exactly is it that makes them, makes the long lived worms more resistant to Huntington's disease? Now I told you that we have this control system here, this little module that involves the hormones and it involves all the downstream genes. So what we did is we just thought, we looked among the downstream genes and we asked which of these genes might be involved in controlling the time of onset of Huntington's disease. And of course, we focused on the chaperones because what chaperones do is that they bind to damaged proteins and they actually keep them from aggregating. So we imagine that maybe the reason that the long lived worms were not getting Huntington's disease was because this altered protein that normally can clump together and form these harmful aggregates couldn't do so. And that turned out to be right. That turned out to be the case. So first I have to tell you that the chaperones were important in controlling the normal aging rate. This just says what I just told you, the chaperones keep unfolded or damaged proteins from clumping together and that they may couple this disease to normal aging. Okay, so more chaperones are made in the long lived mutants and if you inhibit them here, they don't live as long. So here we have the green shows the lifespan of the long lived mutant, the DAF2 mutant and in blue here we have the normal worms. And you can see when we inhibit any of these gene activities, the worms don't live as long. Another lab, the lab of Gordon Lithgow has actually artificially made these chaperone genes more active and he finds that that all by itself can make worms live longer. So they're clearly involved in normal aging. And then what we did was we showed that inhibiting the chaperones, again using this technique called RNAi, inhibiting the chaperones caused the aggregates to form in younger animals. So normally the animals had to reach a certain age before you saw a lot of them with the aggregates. But when we turned the genes down, the chaperone genes down, now the aggregates formed even sooner. Okay, so you see the same genes are controlling aging and the aggregation of these Huntington's proteins. And it makes sense because during the process of aging, presumably these chaperones are busy going about in the cells of the tissues preventing our own proteins from, or the worms proteins from forming aggregates or from behaving incorrectly. So the take home message is that by controlling these genes or regulating these genes, the chaperone genes, the hormone system can couple normal aging to the time of onset of this age-related disease. So it's really interesting. Now we wanna know if the chaperones can also couple normal aging to other diseases and whether there are other downstream genes that couple aging to other diseases. But I think now we're in the position where we can actually ask these questions at a molecular level. Before this work we wouldn't know where to look really, but now we have nice candidates to check. And I don't wanna give the impression that these chaperones are the whole story. They could be just a part of the story, but clearly they are at least part of the story. So now I wanna switch gears in the last few minutes and talk about the relationship between reproduction and aging. There are many people who believe that there must be a trade-off between reproduction and aging, that you can put resources either into longevity or into reproduction, but not both. And our experiments speak to that issue. So we were interested in investigating this. The long-lived worms, many of them, have fewer progeny than normal. So it looks like the DAF2 hormone system controls both aging and reproduction because both can be affected in the mutants. But what we found was that the DAF2 gene acts at different times to influence lifespan and reproduction. So it's not just one and the same. This is a timeline here and this shows you that what I already told you, that the gene acts during the adult to control aging. What we found is that it acts earlier to control reproduction. So if you come along and here in this experiment, if you take normal worms and you turn down the activity of the DAF2 gene on day one of adulthood, so they grew up to be adults with a normal gene, then you turned it down. You made it less active when they were adult. They live longer. Now if we turn it down the whole life, that would delay their reproduction and they would have fewer progeny. What we found is that if we did this experiment, they had the completely normal number of progeny here and they had them at the same time. This is the percent of the progeny that they had on the different days of adulthood. And you can see that the blue and the red lines are pretty much the same. They're almost exactly the same. So that means that lifespan can be extended without inhibiting reproduction. Actually, there's gonna be a story coming out in the journal Nature by an evolutionary biologist who has done a very interesting experiment. He's been studying guppies in the tropics and these guppies can either be in little pools that have predators or pools that don't have predators. And the guppies in the pools with predators have a very short lifespan because they get eaten. But if you, and not surprisingly, you also find that they reproduce very quickly. They start reproducing really quickly. So you might think that there would be a trade-off and these animals with the predators, even if you left them alone with no predators, they would have a shorter lifespan because they're putting all their resources into reproduction. What he found was that when he took them away from the predators and put them in aquariums in the laboratory, they had many more progeny for a longer period of time than the other ones did and they live longer. Okay, so that's really gonna affect I think this whole idea that there has to be a trade-off. These little guppies live longer and they started to reproduce earlier and they had more progeny. It's a really wonderful story from my point of view. Well, I'll just tell you personally, many evolutionary biologists think that they know everything and we find things that disagree with them and now other evolutionary biologists are disagreeing with them, which still makes me happy. It's not over till it's over. Okay, so, all right. But the thing here, so obviously this hormone system, it does control reproduction as well as aging because if you turn it down all through life, the worms have fewer progeny. So that's interesting because you can imagine that changing in this gene during evolution could change both lifespan and reproductive timing but not because there's a trade-off, one causes the other. Like it's not that the long life is caused by the lower reproduction, it's just that the same genes do more than one thing. So changing the gene in evolution might be able to help tailor the animal that's evolving to fit productively into some particular ecological niche. Now let's see, I don't have a lot of time, in fact I have no time, I have minus five minutes and I had a lot of other things to talk about so I don't quite know what to do. So I'll just hit the high points for you. I wanna tell you that the reproductive system, I'm gonna turn the whole thing on its head and tell you that the reproductive system itself controls lifespan. This is very surprising. When the worm hatches from an egg, its reproductive system only has four cells in it, it's very simple. The two blue cells in the middle give rise to the germ line. That's the sperm and the oocytes. And the green cells here give rise to the tissues that surround, the reproductive tissues that surround the germ cells like the uterus or the testes for example. Turns out that if you take a laser beam and you come in and you kill the two cells that would give rise to the germ cells when the animal hatches, it grows up and it lives long. So you might think it's a trade-off, they're not having progeny, therefore they're living long. But that's not so simple because if you come in with a laser and you kill all four cells, then they have a normal lifespan and they're still sterile, they still don't have any progeny. So instead it looks as though the germ cells are actually actively influencing the aging process somehow. I like to think that the germ cells are in charge. They're of course becoming the next generation and they're also controlling the aging of the body. So let's suppose this could be beneficial, you might imagine, during evolution. You could imagine that you could change, let's suppose there was a mutation in a gene of the worm that slowed down the development of the germ cells. Okay, so the development was delayed. Well, of course, reproduction would also be delayed. So you might worry, would the animal be too old to have progeny? And the answer would be no because you would also slow down the rate of aging of the body. So you see, you could keep the two synchronous with one another. And it wouldn't surprise me at all if some of the changes that we've seen during evolution and longevity arise from changes in the activities of the reproductive system, although that's just a hypothesis at this point. It isn't known. How do the germ cells affect lifespan? Well, it turns out they control the activity of another kind of hormone, a certain set of a hormone called a steroid hormone. And the main point is it's a different kind of hormone. So our model is that when we come along and kill the germ cells, we have more of these steroid hormones and they too affect longevity. They can increase longevity. So what I wanted to tell you is something really cool, which is if we take these animals and we do two things. First, we alter the DAF2 gene and then we also alter the reproductive system in the same animals. They live six times as long as normal, six times as long. So the average lifespan of the worms in this experiment was 20 days. And after we did these manipulations here, the average lifespan was 126 days, six times as long. And the thing that I think that is really, really interesting is that these very long-lived animals were very, very healthy. So this shows a movie of these super long-lived worms. These are two worms on day 144. So remember back to the beginning of the talk when I showed you the old worms on day 13. One was dead and one was in the nursing home. These worms are 10 times as old and they're still moving and they look very young. It's really, really, really remarkable. So it really makes you wonder just how far this could go. I should mention that during evolution, lifespan has increased much more than six-fold. The precursor to the worm and also the mouse and the fly, that common ancestor probably had a very short lifespan. So changes in genes have now been able to increase lifespan more than a thousand-fold, for example, in humans. So this isn't, compared to what evolution has done, it's not that big a deal. But still, the fact that you could make just a few changes like this and make the worms live six times as long as normal is amazing. In human terms, this would be like living to be 500 and still being active. That's not to say that we could do this in humans, we don't know, but it's really quite remarkable, changes that can be accomplished. So I just want to leave you with one real strong take-home message, which is that aging doesn't just happen. It's controlled by hormones that seems to be controlled, not just in worms or fruit flies, but also in mammals, possibly humans, but we don't know that. It's a very elaborate system. It involves a whole regulatory circuitry, a whole control module with lots of downstream genes doing different things. It involves many different kinds of hormones, at least three or so, at least two that I've told you about and some others that I haven't had time to tell you about, the steroid hormones and also these little insulin-like hormones here. And so I think this opens up a whole new way of thinking about aging, a whole new world of possibility, the idea of being able to potentially increase the quality of old age, the possibility of being able to delay many different age-related diseases all at once. And now I just want to end with a few kind of interesting philosophical points. First I want to say a few words about human longevity. Now this is a very interesting picture. Here is Jim Watson, discoverer of DNA, and Dick Clark here, look at that. Isn't that interesting? Isn't that interesting? They don't seem to be aging at the same rate. That's very interesting. So I'm sorry, I don't mean it's, yeah, it's emotional also, but it's interesting too. So like I said, changes in genes during evolution have increased lifespan by a thousand fold. So the capacity of a lifespan to increase is huge. Now I want to think a little bit about what might be possible. I think that aging, I think probably everyone believes that a big component of the aging process involves the damage of the components of the cells with time. And you can imagine two forces working against one another. One is kind of the force of entropy or damage, which is tending to probably facilitate or promote the process of aging. And the other are the repair and protective mechanisms. And in the mice, obviously, the rate of damage is much bigger than the rate of the protection. So the mice are aging really quickly. In humans, the protective mechanisms must be much stronger because we have a much longer lifespan. So you can imagine short-lived animals, protection is down here, and as you increase lifespan, it's here. What if you made the protective mechanisms really, really good? Could we live even longer? Potentially, I think you could. I mean, I can't see any hypothetical reason why that isn't possible. And remember, the germ lineage is immortal. That is, the sperm and oocytes, the germ lineage, it's been here since we evolved by definition. So it's immortal. So I think that really makes you wonder what could potentially be possible. Maybe not in our lifespans or even the lifespans of our children, but just potentially. The next thing is why do we have such long lifespans? We have very long lifespans and we're very healthy and active for a very long time. I think we probably live so long that we've evolved to have long lifespans, probably for two different reasons. One is actually because our elders are very wise, actually, and they're very helpful to a tribe or a culture. Just look around at who's running the countries of the world and who's running many of the major corporations. It's not people in their 20s, for the most part. It's people 50 to 70 or even older. It's older people. People who might lose in a boxing ring, they may not be as strong potentially, but they're clearly, obviously they have advantages or they wouldn't be running the countries and the companies. In tribes, these older people often had memories of horrible things that happened many, many years ago that probably that information was helpful if the same condition recurred. For example, there was a certain kind of pestilence. They might know that this particular leaf would be, maybe if you ate a certain kind of food or something, you could protect yourself from that. Okay, so I think the other reason is that if the grandparents are around, they can help take care of the grandchildren leaving the parents for you to go out and fight or hunt potentially. So if you have grandparents in a population, that can be beneficial for the population. For example, in my own lab, I have two postdoctoral fellows, two scientists, one of whom both have small children. One is Chinese and she had her parents come over from China and they're living with her. The other doesn't. The parents live somewhere else. Every day at five o'clock, one of them would go home and the other wouldn't. The other would stay and work. Now, this isn't a life and death situation here, but you can see, you can get the point if the grandparents are around, that person could have an advantage because they have more time to focus on other activities that could be very beneficial for survival. Okay, so I think those are the two reasons that we have such long life spans. Why don't we live even longer? Well, what would be the point of, we don't really need to live to be great grandparents, presumably. I don't think there would be that much more benefit to having great grandparents versus just grandparents around. So there might be a reason that we don't. So I think when you look at it that way, you can see why we might have these long life spans, but you could also imagine that if there were some advantage to being even longer lived, we might have evolved to have even longer life spans. We don't have any kind of role models. There aren't any primates like us, human-like animals or animals that we really think are just amazing that live to be 200. There are things like sea turtles or fish that can live to be a very old or redwood trees can live to be a thousand or more. But we don't really want to be like these fish. I think if there were animals that we really kind of wanted to emulate that had very long life spans, much longer than we do, we would already know a lot more about aging. I think the reason that we invented airplanes is because there were birds. We could tell that it was possible. Right? I think so. Are there ethical implications of this? There are. And I just want to give my particular point of view on this. And the first thing is, I think the ethical implication of being able to find drugs that can potentially improve the quality of old age and also combat a whole range of age-related diseases all at once is graded in a positive way. Could there be negative problems? Could it be that there would be just too many elderly people? Well, if you think about it, I don't think that would be the case. The kind of, I have to go. But I have to just say this. Yeah, I have to go. I'm sorry, well. But I have to say this because I started. Okay. I'm really almost done. It's my last slide. Okay. When you do things like develop techniques to cure heart disease or cancer or something, those are wonderful. It's absolutely wonderful. It's wonderful that we can do that. But the consequence is that you change the distribution of ages in the society so that you have relatively more people on a relative basis, a higher fraction of people who would have died, but didn't, so they are now older. But the kind of change that I'm talking about would be equivalent to having, that it would take you two days to age as much as you do in one day now, you see? So you would not necessarily change the age structure, the whole distribution of ages. People would remain young and productive much longer. So it's a different kind of change. Could there be overpopulation? Well, there could. But at the same time, there already could. We already have a problem. If people have large families, we're going to be overpopulated. So we already have to address that problem. We would just have to address it a little more. Not a whole lot more. Not as much more as if everyone had four instead of three children. That's a big difference, or three or four instead of two. But we would have to adjust it a little bit. Could it be that there would be no room for young people in the job market? I think this is a problem. But the thing is, I wanna just bring up what I think is that society would adapt. Society would say, look, we have a problem. We have these people, they've been CEO for this many years or they've been university professors now for a hundred years. No. And they would pass laws. They would say, okay, time's up, you have to get a new job. We can do this. We can pass laws. So society can adapt. It can adapt. And I think a lot of things that seem like they might be problems, I think society can adapt to meet the challenge. So I'm optimistic about the potential good value that comes from this kind of research. Very optimistic. And I just wanna thank the people who did the work who are my students and postdocs and they're listed here on the slide for you. And I'm sorry for going over. Thank you very much. Thank you.