In the last decade, the ability to have genetic targeting of cell types in mice and to be able to manipulate specific cell types, work out their connectivity, has really provided huge insights into the way the brain works. And there's going to come a day, it might be 30 years or 50 years from now, where there will be gene therapy in the human brain targeting cell types and manipulating circuits that are defective in brain disorders.
The human brain is the most complex structure in the known universe and we are in the middle of a scientific revolution to understand its inner workings. Join us for a conversation with world-renowned neuroscientists as they visit Rochester. I am Dr. John Foxe, Director of the Del Monte Institute for Neuroscience at the University of Rochester, and you are listening to Neuroscience Perspectives.
So Ed Calvi, we never met in person before, that's why it's really, I mean, having read your papers over the years, it's really great to have you here in Rochester. And wanted to introduce you to our community and ask you a few questions about your science and how you ended up where you're at in the world. So you're at the Salk Institute and have you spent your entire career on the west coast?
Well my first faculty position for three years I was in Colorado at the Health Sciences Center in Denver and then moved to, in 1995, to Salk Institute. So it's been 24 years there now. Excellent, excellent. Well let's dive into your science. I actually, you know, of course I was reading beforehand trying to get ready to meet with you and I got very struck by something that was on one of the sets of materials and it was describing the brain as a veritable bowl of spaghetti.
And so a lot of your work has been about untangling the mysteries of the circuitry of the brain and that. And would you like to tell us a little bit about how you think about brain circuitry and this massive neurons and interconnectivity? Well there are two levels of different ways you can entangle that. And the one that I think is the most tractable right now and where the field is really moving is cell types, right?
Because even though it's a big tangle, if we can, you know, label one of those pieces of spaghetti and follow it, or it's maybe not just a big piece of spaghetti, it's got some penne pasta and rigatoni and different kind of things in it, but, you know, without having the ability to target and see that that's all in there and each of those is different. It's pretty clear to us now that cell types matter. Each cell type is connected in a different way, mediates brain function in different ways.
And in the last decade, the ability to have genetic targeting of cell types in mice and to be able to manipulate specific cell types, work out their connectivity has really provided huge insights into the way the brain works. And there's going to come a day, it might be 30 years or 50 years from now, where there will be gene therapy in the human brain targeting cell types and manipulating circuits that are defective in brain disorders.
Is it the idea then that there may be disorders that are allied to specific deficits in specific cell types? That's why we need to know that. Yeah, and there's evidence for that. So for example, post-mortem tissue from schizophrenic patients, there's a particular cell type called chandelier cells. They make a particular kind of synapse on pyramidal cell axon terminals, beautiful chandelier-like axons. That's how they got their name from the old days when you've, Golgi labeling of neurons.
It turns out in schizophrenic patients, they have fewer than normal number of these axon terminals on the pyramidal neurons. So that's just a clue that there might be something wrong there. But there now exist mouse lines that you can target gene expression to just the chandelier cells. And you can inactivate and activate them and see what their role is in the function of a mouse brain.
And within a couple of years, there will be ways to target chandelier cells in a monkey brain, which is much closer to a human brain in its function and where you can study higher level cognitive functions and manipulate them and look at them in that context of something. So you're talking about looking at these cells and of course, people... Yeah, I'm sort of looking in a figurative sense. Yeah, I know, right? So we do look at them. Exactly.
And in some ways, that's where your lab has really become famous around that. So there are ways to stain these neurons, but you brought new technologies using a virus, right? A very famous virus to bear in terms of our ability to really paint these pictures. Would you want to talk about that? Yeah, sure.
So for many years, we wanted to have a way of...if all these cell types are mixed together and you want to entangle the connectivity, you'd like to know where are all the cells in the brain that connect to a particular cell type in a particular place that starts in a particular place in the brain. And back, I guess it's been about 2007 now, about 12 years ago, we first developed this method working very closely with Ian Wickersham, who was a graduate student in the lab.
We modified rabies virus, which has natural abilities to spread very selectively only across connected neurons. But it doesn't have a property where you'd inject it in the brain, it would only infect the cell type. And it doesn't have the property where it would spread one step and stop, so you could unambiguously say, those are the cells connected. It would just keep spreading.
And in fact, in animals that are infected, like bats, they'll eventually change their behavior and they'll spread to other bats and they die. But we modified the virus in ways that allowed us to target its infection to specific cell types, and so that it would only spread one synaptic step and label the direct inputs to those cells. Then you can look across the entire brain and look at those. And you can even do functional studies.
You have people here in Rochester that are taking advantage of this virus to express optogenetic constructs, which allow you to turn those cells that are connected in specific ways on and off to look at their roles in function in the intact brain. And 15 years ago, if somebody had said to you, it would be possible to switch on and off cells with light that are transfected with the rabies virus. Would you have laughed at them or did you see it coming?
I mean, optogenetics has been around, probably is it getting close to 15 years? I'm not sure. And we worked on other methods to inactivate that were chemical, because we did want to be able to target cell types in brains of animals like monkeys. We're only just now getting the ability to target cell types in monkeys very selectively. And it's something we imagined 15 years ago.
I think the first experiments that got us thinking about tracing connections in cell type specific ways were ones that used a different virus called PRV. It's in the herpes family of viruses, like chickenpox viruses and things like that. And Jeff Friedman and Lynn Enquist made a version of that that could label the inputs to a specific cell type, but it kept spreading multiple synaptic contacts. And we actually worked with that for a couple of years trying to get a way to make it stop.
But all those things didn't work, and it was those failures that led us to the properties of rabies virus as one that we would be able to engineer in a way that would work. That was more than 15 years ago. They published that paper in 2001 showing that tracing. So all this work, it led to quite an honor for you just this past year, right? I believe you were inducted into the National Academy of Sciences, which is our most prestigious scientific society. How did you find out?
Did you get a phone call? Did they send you a letter? Well, that's how it usually works, apparently, is they have this thing of...especially if you're on the West Coast and it's early in the morning, it must have...well, to me early, I sleep late, eight in the morning. But I actually found out from my daughter, strangely, because I had my...I go silence my cell phone when I go to bed and I had gotten up and was in the shower and I didn't notice that people had called and left messages.
And then I opened my computer to check traffic in the morning, to have a look at my emails and see all these sort of congratulations messages. And I was like, oh, what's that for, I wonder? And then next thing I know, my phone's ringing and it's my daughter telling me. So yeah. And then, of course, I called and talked to the... Yeah. Tell us, how did it feel? Were you surprised or was it... Well, yeah, because I mean, it's not something I was really on my radar thinking about.
They do have a meeting every year at a certain time. I didn't know this was the time when the meeting was happening and they would be doing this voting. And of course, you have a sense that you're being nominated because the people nominating you have to ask for materials. They can't tell you they're nominating you, but you can tell from the format of it. It's a nice honor and really mostly a reflection of all the stuff that people in my lab over the years have done.
So here you are, a National Academy member. But let's go back in time and track...how do you end up as a National Academy member? Tell us about the academic trajectory. When did you figure out you wanted to be a neuroscientist? Was this something when you were 10 years of age or was that later? Well, I mean, I've always...even since when I was a kid, fascinated with how things work and sort of would take apart mechanical things like to work on bikes and cars and things like that.
And like to build things, which helps a lot with neuroscience because you have to, especially longer ago, build all of your own things. But just really a fascination with how things work. But it wasn't until I was in college, I knew I was interested in biology and was dabbling with the idea of medical school.
But during my sophomore year in college is when I first started the first biology lectures, first years you take chemistry, physics, math, and learned about neurons and that they have this electrical activity and action potentials. These beautiful lectures that Corey Goodman gave, he was assistant professor at Stanford at the time, that's like 30 years ago. And that was when it just hit me, this is what makes me who I am.
Everything about me and how I work and think and feel is because of these neurons in the brain and their activity together. How does that work? And what would give me...could be more fascinating. So I just started at that time signing up for every neuroscience class I could find and found a lab to work in with Jack McMahon and studied neuromuscular development and got interested in nervous system development. Now, I happen to know you and I have something in common.
I don't think you know this because I think we both started out life as dumb jocks. Did you end up as university... I hope I wasn't dumb. Stanford has some academic standards, but I do think they are a little relaxed if you're a fast runner because I might not have gotten in if I wasn't a fast runner, but that led to all kinds of opportunities. It kind of goes with being a scientist.
Distance runners are a bit obsessive and you have to just run a long time for what might be a reward that may or may not happen later to win. But I was very competitive and so it's a sport where hard work pays off.
And I think that's true of science too and I think I learned a lot of lessons through that and also being an athlete in college, you have to be very efficient with how you use your time because you're taking a full course load and you've got to work out every day and all your friends are out laying on the lawn in the sun or playing volleyball or something for fun and you're out working hard running and come back tired and still have to go to the library and study.
So I think it taught a lot of self-discipline. And I love just the camaraderie of that and that's something that the lab also does for you, right? That you have this group of people that you work with every day. That are almost family because of the closeness and intensity of it, the engagement. And the graduate students in post-docs, they're putting their career in your hands and you got to look out for them.
So I didn't mention that before but I came to the United States on the track and field scholarship. Oh really? And I also believe that there's this sort of obsessional aspect to folks in the sciences and you find out when you dig a little deeply that they've run track and field at a high level or they've played a musical instrument at a high level or they're a very fine artist as well and there's a little bit of the manage...
Musicians are great to work in the lab because they do the same thing over and over and practice and practice. Exactly. And the delayed gratification, the part where you need to stay applied to something for hours and hours and hours with very little return but the long-term goal. Very good. You have three children and I was fascinated by this some more from a human interest perspective because they've grown up in a household where their dad is a very, very prominent scientist.
Are any of them following in your footsteps or they steering care of it? One of them is, I mean mostly they have remained...it's good to be kind of oblivious to exactly everything we're doing. I mean you're just their dad. What's the difference as a scientist? So I have my three children and the oldest is a computer science engineering guy and of course works in the Bay Area and does very well in that.
My older daughter is in grad school at Berkeley in immunology, virology and she was the one who paid the most attention especially during the early rabies days and I gave talks at her school about rabies virus stuff and maybe that influenced her interest in virology and diseases. She's childhood malaria in a lab at UC San Francisco and through a graduate program at Berkeley and then my youngest daughter is applying to law school this year and working in the public defender's office in Oakland.
So they're all doing great things. Very proud of all of them. So what about work-life balance and all through the years when you're raising children, I think people are often think about scientists and the quantity of hours that have to be put in the lab and I think it's a reality of the world.
And especially in the earlier years I spent a lot more time in the lab and I'm very fortunate with my wife who's very supportive of that and I also travel more than I do now at times and that's really helpful to have a partner who helps you to manage all that and tolerates it to a certain degree too because there were times when we did all night experiments and things.
I do think you have to be able to turn it off at times too and when you're done at the end of the day to be able to come home and that was when the kids were younger, one of my favorite things was it was time to go home, give everybody a bath and read and I would read them books.
And what about some advice, so young graduate student thinking about life as a scientist today, 2019 going forward, the challenges of it, the young graduate student thinking about having a family in this field and in this business, do you have any pearls of wisdom? Yeah, I mean it's nothing that's not common sense, you have to make the choice that works for you.
I mean when I was in grad school I was very focused, I probably was in the lab 12 to 16 hours a day and didn't really have a lot of balance but didn't have any kids yet either. And so, and I consciously, my wife and I discussed that we should wait until I'm a postdoc to have our first kid. But then our first kid, our son was born while I was a postdoc and that worked out just fine. Everything's hard, no matter where you do it there's no easy time.
But if you believe in what you're doing and you like it, it's difficult but it's not hard in the sense that you're enjoying what you're doing. Is there a difference for youngsters these days, when maybe you and I were coming up through the system, you became an expert in a very specific domain and today you really have to start to work across disciplines? Yeah, it's harder for sure.
And in neuroscience now in particular, because what you could possibly do with the range of tools that has emerged, the expectation for a high profile paper is that it's going to have a little bit of everything and how could you do all that? So I think it becomes more important to work as a team and to have different people in the group that you see more co-first author or even three co-all gave the same amount of effort to the paper going on.
But it's also good to learn from the other people that you're working with because eventually you do need to go start your own lab and it's good to have learned multiple skills and bring that and to be able to train the people that are coming in. Well, can I lean on that? Eventually you have to go start your own lab. Are our models correct today? You don't have to. You get the opportunity.
So would it be fair, you can push back on this, would it be fair to say that the way we do business today with a new investigator gets a job in a lab at a university, opens up their lab and starts, it hasn't changed much over the last 40 or 50 years. We still operate under the same basic model. Is that the right way to do science these days? If you were shaking it up, would you approach it in a different way? Perhaps.
I think it probably depends on the kinds of institution and other, I mean a lot of institutions have a really important emphasis on teaching as well and other things that need to be done. A really good model of doing it a different way is the Allen Brain Institute, right? And they have a very different structure where they bring in people, they actually pay people at postdoc level a lot more than our postdocs get paid. We should pay our postdocs a lot more.
But I mean that's dictated largely by government levels that are set. So what's the model there for our audience? Much more a team kind of science. And so they do have people who are more specialized and have careers that are doing science. And some of those people move through the ranks and become the people who are more interested in asking big questions and directing programs. Other people would rather stay in what they're doing, but they can get paid a good wage.
I mean often better than what some starting assistant professors do and have a career in that program. As a career scientist as part of a... Working as somebody who does bioinformatics or somebody who does slice physiology or does calcium imaging in vivo or does electron microscopy and all these different things. Because that's one of the real inefficiencies in the way that things work now is that I have somebody who comes as a postdoc.
And just as they get really good at what they're doing, they leave and I have to replace them with somebody else that's going to come in and start over. We do often have career research assistants who stay in the lab, but the system is much more designed to have funding for postdocs and grad students through fellowships and different kind of things. So we rely on that labor I think more than we should.
There are other models in other countries where they give you a budget and say, hey, this is for technicians and then here's the budget for these people, but here it works differently. So I think that it's kind of like how things are in the US. It's not the perfect system, but it works well and we do well with it. You could design a better system, but then if you try to impose things, then you have unintended consequences at times too. So look into the future.
Now you mentioned specific cell type targeting and genetic manipulation of specific cell types as ways to get after disease. But looking at 10 years, 15 years from now, what's on the horizon? What do you see as the really exciting areas that we should be? In terms of targeting cell types, I think that the field is just now in the last, it's probably been in the last year, but what I'm seeing in publications and there's more and more of a trend of people to publish preprints on bio archive.
And just in the last six months, there have been what people call enhancers, cell type specific regulatory elements in the genome that are responsible for the normal mechanisms that give rise to the differences between cell types. Cell types are different not because they have different genes in them. They all have the same genetic material, but it's which genes get turned on and which genes turned off during development and the specification of a cell to a type.
And there are marks of that in the genome and there are analyses that can be done called epigenetic analysis that can look at those marks in the genome and find out where are these elements that might be enhancer elements in the genome that might be responsible for the difference between this cell and this cell and this cell. And there are some of these publications now that are coming out showing that you can use that analysis to predict enhancers.
You can put them in a viral vector, the same viruses that are used now for gene therapy in humans. And you can then, in fact, even human tissue in one case from the Allen Institute where they have tissue from people that are having tumor surgery or epilepsy surgeries and those patients donate some of their brain that can then be cultured and you can test those viruses.
And they've shown that you can get the targeting to the cell type that was intended based on their epigenetic analysis of these marks. And I think that in the next just couple years there's going to be a huge explosion in our ability to target gene expression to cell types, not just in mice where we have to genetically engineer the genome of the mouse, but where we can go into any species including humans and target a cell type for therapeutic purposes.
A great future and it's on the horizon here. It's not a million miles away at all. And I don't think it's overhyped at all. Now, how long is it going to be until you actually do gene therapy in a human? You're going to have to have...that would require a cell type targeting. There will probably be types of diseases that are more tractable and the cost benefit kind of equations where, you know, if maybe somebody who has epilepsy, the treatment now is to remove that part of the brain.
So there is not a huge cost to saying, well, we have a potential gene therapy. We can try this first before we take it out. Yeah. We can do something where we would express a gene, a transgene only in a cell type that would then if you activated that cell type would suppress the activity. And then if you detected a seizure coming, you could maybe do that.
Or if you had a drug, the transgene is affected by a drug that the person takes that's targeted only to those cells rather than the drug that would have all kinds of side effects for the epilepsy drug somebody might be taking now. You've now targeted to just that part of the brain where they have the epileptic focus and you can just regulate with the dose of this drug, which doesn't have any side effects because there are no receptors for it in the brain.
So that's something that you could imagine coming along. And you start small with something that's cost benefit is big. Because if it doesn't work or something goes wrong, you're just going to cut that tissue out anyway. But then building to things that are more sophisticated over the years. I think the basic research is necessary to identify how the normal circuit mechanisms work and then to be able to say there is a target, there is a treatment that you might try.
And there's going to have to be a translation across species. You're not going to go straight from mice to humans. It's very clear now that you can find homologous cell types, 100 cell types in the cerebral cortex of people and mice. And you can find nearly all of them are homologous. But the genes that are expressed in the primate cell types in monkeys and chimps and humans, that's highly conserved, but it's different in mice.
So the way we're going to target those cell types and the genes and how they relate to genetic disorders and genetic prevalence for disorders is going to be different between mice and monkeys. You need a transitional species to work with to do that. So we're getting close on our time. I wanted to ask you, at the end of the day, I assume these days you're not running cross country to wind down. How do you switch off? What's your thing? Well the last few months haven't been as diligent.
But I do still try to run a few days a week, go for a five or six mile run. Like going hiking, I like going fishing. Do you find, like I do, when you're running that there's a clarity, it's a really good time to think about science actually? Usually when you're not thinking about it, yeah. That happens sometimes. You just have a chance to go back and clear your head. That neurotransmitter milieu that allows for that kind of clarity when you're on a night. Now they're not all nights.
Sometimes it's just a slog. But when the mind clears and we're on and all the rest of the world falls away, sometimes I have some of my best thoughts about experiments. It's such a pleasure to have you here in Rochester. Thank you. I really appreciate you coming in. Excellent. Thank you.