“When I first heard that seminar describing GFP, and realised, ‘I work on this transparent animal, this is going to be terrific! I’ll be able to see the cells within the living animal.'”
Transcript of the telephone interview with Martin Chalfie following the announcement of the 2008 Nobel Prize in Chemistry, 8 October 2008. The interviewer is Adam Smith, Editor-in-Chief of Nobelprize.org.
[Martin Chalfie] Hi.
[Adam Smith] Hello, this is Adam Smith.
[MC] Hi Adam.
[AS] Hi. Thank you very much indeed for making time for this. It must be a very busy day. I’ve read on the news wires that you didn’t actually receive a call from Stockholm this morning?
[MC] I did not. Well, I did. I didn’t answer it because I slept through it.
[AS] Reasonable enough – I guess it was early in the morning.
[MC] Well, it also has to do with the fact that the normal ring on my home phone had been changed inadvertently a couple of days ago and I never took the time to change it back to the regular ring, so it was actually quite faint. So when I actually did finally wake up I actually heard something ringing, and I thought, “Ah, that must be somewhere else.” Another apartment!
[AS] Well I guess that in itself says that you weren’t expecting the news, so there you go.
[MC] Well, I … you know. You know that when October runs around that there are people that are considered for things, and you wonder, and especially when people come to you and say “Oh, you know, do you think this might happen?” So, it’s not that it comes out as a bolt from the blue, but it certainly is, you know, it’s not something you expect but it’s also, you know, you don’t really anticipate it’s going to happen so it’s always a surprise. But, on the other hand, it’s also not something completely new either.
[AS] How did you actually found out that you had …?
[MC] Ah. This is a sort of ridiculous situation, but sort of funny. I woke up at ten after six, and I realised that they must have given the Prize in Chemistry, so I simply said, “Okay, who’s the schnook that got the Prize this time?” And so I opened up my laptop, and I got to the Nobel Prize site and I found out I was the schnook! This was very funny to find. Now the other two guys are really terrific scientists, but I … so this is a very big and very nice surprise.
[AS] What a lovely way to hear. And, yes, I imagine you’re pretty much losing control of your life now as everybody’s …
[MC] For the day I think, yes.
[AS] Yes, yes.
[MC] So, how are you connected with the Nobel Prize organization?
[AS] So, we are the web site that you looked up. We are Nobelprize.org.
[MC] Ah, okay. Terrific.
[AS] If we just turn to the work for which you were awarded, you had the idea of using green fluorescent protein in species other than the jellyfish in which it was found, to label the expression of specific proteins, or indeed label specific cell types.
[MC] That’s correct.
[AS] And it was Doug Prasher who cloned it, and then you had the idea of taking it from him and expressing it in your systems, in C. elegans?
[MC] Yeah, I would put it slightly … I would use the wording slightly differently. I had heard about GFP in a seminar that I was listening to in about early 1989. I can’t remember the exact date. But I … and I tried to find out who was studying this and whether we could work on it, and I talked to Doug, and he had ideas that this would work as well, and he was wondering about it, and that was certainly the motivation he had in cloning this gene. And so we worked, we had a very excited, about a one-hour, conversation on the phone, and the upshot of that was that we were going to collaborate, and see if this would work in C. elegans. And through a couple of mishaps, it took us a couple of years to actually get back in touch with one another, but in 2002 we did. Not 2002, 1992 we did. And we got the clones from Douglas, and a very good graduate student, Ghia Euskirchen, put this in E. coli, and we had green fluorescent E. coli within a month.
[AS] Yes, yes. So, you mentioned that there was a couple of years delay in there, and given how incredibly powerful this technique has become, on reflection was it quite lucky that nobody else picked up on the idea while that was taking time?
[MC] You know, some people did. This is an interesting thing. I’ve subsequently found that at least three different people tried to get GFP to work, and had actually … See, Douglas … I’ll tell you a little bit about the intervening time. The intervening time after Douglas and I talked, I got married, and the woman I married was a Professor at the University of Utah. Her name is Tulle Hazelrigg. Now she’s here at Columbia. And, when I married Tulle, I decided to take my sabbatical working with her, so we could be together. And it was during the 9 months that I had of my sabbatical, in Utah, that Douglas finished the cloning. When he finished the cloning, he got in touch with me, or he tried to. He called my lab here at Columbia University and they said I wasn’t here, but I think they gave him the phone number for the University of Utah lab. But someone must have answered the phone at the University of Utah and said something to the effect of “Marty Chalfie, never heard of him.” And so Douglas Prasher got the idea that I had dropped out of science. And so, he didn’t tell me because he didn’t think I was interested anymore. So, it wasn’t until 2002, that …
[AS] Or 1992?
[MC] I’m sorry, I keep saying 2002, you’re right, thank you. It’s been an interesting day! … In 1992, that in September I had a new graduate student come and join my lab, Ghia Euskirchen. And Ghia and I talked; she had had some previous Masters degree work in which she had looked at fluorescence. And I said, “Well, I have this wonderful idea, or I hope it’s a wonderful idea, about using a fluorescent protein in cells. But the person I was supposed to collaborate with never got back to me, never called me back. So maybe we’ll have to look at something else. But the University now has just put Medline, the Medline database, on our computers. Let’s go look and see if they have anything about fluorescent proteins.” And what came up was Douglas Prasher’s paper about the cloning of the cDNA for green fluorescent protein.
[AS] Perfect timing.
[MC] And I said, “I wonder why he didn’t get in touch with me?” I subsequently learned he thought I was out of science. Anyway, we immediately ran downstairs to the library, got the article that he had published, and got in touch with him, and that’s what started our work. But other people also saw that article, and were also … You know, this is an idea that I’m sure has occurred to many people. And so, when these other people got it, there was one other thing that needed to be done, and no one would have really predicted this ahead of time. It was a stroke of luck on our part. And that is, that people in the field that were studying fluorescent proteins, particularly GFP, had the knowledge that the GFP fluorescence was made because of a rearrangement of the backbone of the protein; the peptide backbone. And they didn’t know how that peptide rearrangement – the peptide backbone rearrangement – took place. And so they said, “We don’t know, it might take one more enzyme to do this, or two or four, or 100. We don’t know how this is made.” But the thought was, that it would not work on its own. Well that was the bet that we were hoping to … So if you have sort of the weight of the field saying to you, “This should not work on its own”, and you do an experiment, and it doesn’t work, you, I think could be allowed to say “Hmm, maybe it doesn’t work. Maybe it does need something else.” And so, the three other cases of people that I know that tried this, tried it, and it did not work. And we …
[AS] So they thought they were missing some auxiliary factor.
[MC] They could have interpreted it like that. But what it turned out is the way they made the construct. And what they did is they had taken Doug Prasher’s clone, and cut out the appropriate-sized fragment from the DNA. But that fragment had extra little bits of sequence on either end. And apparently, it’s those sequences that were poison, so it never got made. So the extra DNA interfered with the protein production.
[AS] And you couldn’t have known that really.
[MC] And you couldn’t have known that. But we did it a different way. We simply amplified exactly the coding sequence from the clone, and didn’t have any of the extra DNA. So when we put our things in bacteria, it worked.
[AS] Right. It fluoresced.
[MC] So it was just great good fortune that we, that the procedure that I chose us to follow, was the one that happened to allow it to work. And the other three that I know of found it going in the other direction, or not being expressed.
[AS] A classic case of lucky experimental hands, but …
[AS] … some people have them. And, it’s such a powerful technology. Are there any particular favourite applications that spring to mind?
[MC] You know, I have, there have been many wonderful applications, and there continue to be other applications. I, what I can tell you is not so much what are my favourites, but certainly the things that we have used in my lab that have been really of great help in the studies that we’ve done. Mainly I study the sense of touch, and what the molecules are that transduce touch. And I use mutants in the nematode Caenorhabditis elegans to look at that problem. And so, we have used GFP to ask in which cells genes are turned on. We’ve asked the question of, when we have a gene turned on and a protein is made, where does the protein go in the cell, and we’ve found some interesting patterns. We’ve used GFP to label the cell so we could then mutate the animals and look for defects in the development or growth of the nerve cells, whether they branch inappropriately. And other people have used it to ask questions of whether they make synapses inappropriately or not. We’ve also used GFP to label cells for electrophysiology. This animal is extremely tiny, and so it’s very hard to get an electrode to record electrically from a nerve cell. But there are methods that have been worked out, that one can look at this, one can be able to record from the cells, but only if you know what the cell is, and you can see it. And the way we see it is through GFP.
[AS] Right, and …
[MC] And then finally, we’ve been able to use GFP to label the cells, so that we could then take apart the embryo, and isolate the fluorescent cells away from all the other ones, so you can have just a pure collection of the cells we’re interested in to ask something about the nature of these cells and what they’re doing.
[AS] All quite amazing. And the worm you study is actually transparent, so that you can label cells and then see them in the living world.
[MC] Oh, absolutely. And in fact, I have said for many years now that the only reason that I worked on GFP is that for several years before I worked on GFP, I said that one of the great things about working on C. elegans was the fact that it was transparent, and so when I first heard that seminar describing GFP, and realised, “I work on this transparent animal, this is going to be terrific! I’ll be able to see the cells within the living animal.” That was really great. That really was the motivation.
[AS] Right, right. And so, given the explosion of interest in the field, for those who were now thinking of coming into it, what advice would you give?
[MC] Which field do you mean? The field of fluorescent proteins, or …?
[AS] I mean the field of using fluorescent proteins to label cells and proteins.
[MC] So GFP has now become an almost universally used tool. So, as … But I believe that there’s probably – and I’m not really the best person to talk about the future of the chemistry of this molecule and manipulations of it. But I’m always astonished that just about every year someone has come up with a new variant or a new idea where they use GFP. So people’s ingenuity always outstrips mine in terms of what can be done. And people have made remarkable discoveries about it. I think that the important thing is people should know is that it’s a tool that has been manipulated in a variety of ways to be an even more useful tool, and then to think about how that works, and what they want to do with it. I think that, as people see the examples of work, for example, that Roger Tsien has done, to make these really wonderful derivatives of GFP, or that use GFP. These tools he has made like the chameleons, for example. These are wonderful tools, and it’s by the ingenuity of using a fluorescent protein, coupled with another idea. And several people have had these wonderful ideas that have enlarged the usefulness of the molecule. So people, if they get interested in it, I think it’s up to their imagination of what they want to do, as it is in any aspect of biology, chemistry or physics.
[AS] That’s a nice thought. Okay, well, when you come to Stockholm in December, we get the chance to record a video interview with you, and so hopefully we’ll be able to speak for longer then.
[MC] That’s wonderful. I look forward to it.
[AS] I look forward to it too. And just one last question. Do you have any thought about how you might celebrate once you get off the phone with people like me?
[MC] Well, we had a nice reception here already in the department, and we’re going to have some friends over this evening, and I’ll try to wake up tomorrow and say that it wasn’t a dream! I think that’ll be the celebration. I think, I guess I could say that the real celebration I’m going to do is I have to write a grant by the end of the month, so I think I’m going to have to start getting to work on that grant application.
[AS] Yes, I’ve heard from previous Laureates that they’ve sometimes asked for delays given what’s just happened to them, and the authorities have said “No way!” So…
[MC] Yes, I’m not even anticipating asking, I know I just have to get the thing written. I don’t think they care!
[AS] Okay, best of luck.
[MC] Thank you very much. Nice talking with you.
[AS] Thank you so much. Bye.
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