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Live Cell Imaging: The Future for Discoveries
Webinar 22 May 2013
[0:00:15] Slide 1 Sean Sanders: Hello everyone and welcome to this Science/AAAS webinar. I’m Sean
Sanders, editor for custom publishing at Science. For a variety of practical reasons, cellular imaging is currently most
often performed on specimens that have been fixed and labeled. However, live cell imaging although technically more challenging is often preferred as it enables researchers to study cellular events and dynamic processes that cannot be visualized in fixed specimens allowing them to gain deeper insights into the complex mechanisms of cell biology.
In today’s webinar, we will explore the benefits of imaging live cells
and discuss how to overcome some of the technical challenges in this type of imaging modality. It’s my pleasure to introduce my guests for today’s event. To my left is Dr. Edward Campbell from Loyola University in Chicago. Next to him, we have Dr. Nick Thomas from GE Healthcare in Cardiff, Wales and finally we have Dr. Lynne Turnbull who has joined us all the way from the University of Technology in Sydney, Australia. Thank you so much for being with us. Great to have you.
Dr. Nick Thomas: Thank you Sean. Dr. Edward Campbell: Thanks. Sean Sanders: Before we get started, I have some important information for our
audience. Note that you can resize or hide any of the windows in your viewing console. The widgets at the bottom of the console control what you see. Click on these to see the speaker bios, additional information about technologies related to today's discussion, or to download a PDF of the slides.
Each of our guests will give a short presentation followed by a Q&A
session during which our panelists will address the questions
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Finally, thank you to GE Healthcare for sponsoring today's webinar. Slide 2 Now, I'd like to introduce our first speaker for today, Dr. Edward
Campbell. Dr. Campbell completed both his undergraduate and graduate studies at the University of Illinois, at the Champaign‐Urbana and Chicago campuses, respectively. Dr. Campbell is currently an assistant professor at Loyola University Stritch School of Medicine in Chicago. His research focuses on the mechanisms by which endogenous cellular proteins impact retroviral replication. In this work, Dr. Campbell has made extensive use of quantitative, live cell imaging techniques to monitor the formation of TRIM5α assemblies around HIV‐1 virions during restriction. Welcome, Dr. Campbell.
Slide 3 Dr. Edward Campbell: Thank you, Sean. I appreciate being here. So what I’d like to do is talk
to you today about some of the ways that we’ve utilized cell imaging in our research.
Slide 4 But I’d actually like to start out by laying some groundwork and
establishing or explaining to you a lot of the things that maybe new users that aren’t familiar with live cell imaging can do to enhance the likelihood that their experiment succeeds. Because live cell imaging
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as Sean mentioned is not a trivial thing and I have kind of an anecdote up here that happens all the time in my lab. When I ask a student how that live cell imaging went, he or she will say something along the lines of it was more of a dead cell imaging experiment but I learned a lot of things about apoptosis but, you know, since we study viruses, apoptosis is not very valuable to us.
Slide 5 to Slide 6 So how can we approach our experiments in a way that allows us to
image live cells? Because obviously I think we could all agree that that’s a pretty important aspect of live cell imaging. So the first thing that I want to emphasize is the importance of keeping your cells happy not just during your experiment but in the period leading up to that. A lot of these experiments can either work or not based on your relationship that you have with your cells.
Slide 7 So the foundation of that relationship, right, is tissue culture. You
know, in many ways my relationship with cells when I culture them is very much like my relationship with my wife. Maybe it’s not like every marriage but, you know, you come in on Monday and your cells got a little overgrown, they look unhappy, their media is yellow and then you passage them and the media looks better then next day and they look a little bit better and you think, oh, they’ve totally forgiven me for that, right? Well they haven’t, right. What they’re going to do is remind you of your misdeeds when you need them to perform the most.
[0:05:05] A key to keeping your cells alive during a live cell imaging experiment
is making sure that they know that you love them well in advance of that because it’s just a matter of fact that happy cells live longer. Since really our goal is to extract all of the information that we can from them before they make the ultimate sacrifice in many cases, the goal of going in with happy cells that can’t be understated.
Something else that, you know, a lot of people that use the
microscope in my lab they’ll come in with transfected cells. I also want to emphasize the importance between transfection and transduction. So you know no one has ever rained liposomes on my head right, but I can tell from looking at transfected cells that they’re fundamentally less happy than say cells that have been transduced with a retroviral vector or a lentiviral vector. Viruses have evolved for millions of years to not really let the cell know that they should be upset, right. Exploit this. If you make a stable cell line expressing
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your GFP or your Cherry proteins, by the time you get them into your experiment, they’re not going to really remember the assault if they remember it at all, right. The transient transfection you’re starting from behind the eight ball right, you know, from the beginning of the experiment.
Slide 8 So what can we do to improve viability during an experiment? So
there are many ways that one can do this. So you can see here is the microscope in my lab where we have an environmental chamber. We keep the cells at 37 degrees. We pump CO2 over them. But those things, you know, those are great if you have them. If you have the means, I highly recommend you pick up things like this. But we’ve done a lot of live cell imaging before these technologies existed and there’s a lot of alternatives to environmental chambers that you might be able to do at your university even if you don’t have access to things like this. Using things like CO2 independent media or a buffer to keep the pH of your media at an appropriate level to keep your cells happy, the importance of these things cannot be understated.
Again, humidity, evaporation is a big deal over the course of a live
cell imaging experiment. We use Kimwipe wicks. You can keep water in the environmental chambers. The humidity there is a very important thing because, you know, when you evaporate water from the media in which your cells are, the concentration of all the solutes in that media changes and those are precisely calibrated to keep your cells happy, right. So appreciate that evaporation is a big deal in live cell imaging experiments.
Also temperature, if you don’t have an environmental chamber,
which can be pretty pricey, there’s lens collars that you can at least keep that objective that you’re bringing up to your specimen at a temperature that’s more consistent with the viability of cells. These are the little things that you can do to kind of on the cheap keep your cells happy and alive through the course of your imaging experiment.
Slide 9 So the next thing I want to emphasize is the idea that especially in
live cell imaging, less is more, okay. Slide 10
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When you’re imaging a fixed cell or in fixed cell imaging, right, essentially the rules are price is right rules. You want to use the full dynamic range of your detector without going over. Live cell imaging it’s important to appreciate that quite the opposite is true, right. When you’re setting up an experiment, you don’t need that picture to look beautiful in your first frame because if you do, usually what you’re doing is you’re acquiring much more signal than you need in that frame and the consequences of that over time is going to be the graph you can see on the left. You have a great first picture but you have rapid photo bleaching. Often your cells will die, you know. But if you tolerate what you consider to be, on your monitor, an ugly first picture, what that will do is that will give you signal that’s well above background that you’d be surprised how little signal you need to be able to move forward with an experiment.
You will always going to have some element of photo bleaching. You
can see I have kind of drawn that in there. But starting out really seeing how little signal you can work with is always a better idea than working from that other end because I can tell that you that that’s an unpleasant experience.
Slide 11 to slide 12 And so finally live cell imaging is just that. It’s a dynamic relationship
and experiment where you have to monitor how things are going. Pay attention. Assess the quality of your data as it is being acquired. So sometimes, if you want to measure specific aspects of biology or in our case infection, it’s difficult to know if you had an experiment succeed when you’re acquiring it. But I could also tell you that the failures are usually quite obvious, right. The number of times I’ve come in and somebody is kind of sitting by the microscope and I can see in a moment that their cell is dead, it maybe even has floated away, right. Stop taking pictures, find a new cell.
These things seem like simple things but they’re really important to
getting the most amount of data that you can while your cells are on the stage. Then finally don’t take it so hard. If you think that live cell imaging is hard and you need an expert to do it, I think that perhaps the people on this panel really just have an excessively high tolerance for pain, right.
[0:10:17] Live cell imaging is always an iterative series of less spectacular
failures. So if your cells are dying, it’s not because you’re doing it wrong. Just change your technique or your approach slightly and try to get a little bit better. That’s something that we all go through and
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you know you shouldn’t feel bad about it or make yourself feel like it’s never going to work.
Slide 13 So from there, what I’d like to do is talk a little bit about some of the
ways we’ve used live cell imaging to approach some of the questions that we ask in my lab. So the primary focus of my lab is understanding how restriction factors, in this case TRIM5α, which is protein from rhesus macaques can inhibit HIV1 infection. So to give you a little bit of the punch line, because I really want to focus on the techniques rather than the biology of it all, is TRIM5α restricts viral infection very quickly after the virus has entered the cytoplasm. It does that by what we think is forming a hexameric lattice around the viral core. The data I’m going to show you are data that we generated well before we appreciated what these assemblies might look like.
Slide 14 But so when we’re studying this, what we had in the lab is the ability
to fluorescently label individual viral particles with a GFP‐VPR protein. So what you can see this on the red color is this red TRIM5α protein and in these cells what we’ve done is we’ve arrested restriction. We could basically phase restriction into two steps and arrest the second one by adding a proteasome inhibitor.
Slide 15 to Slide 16 In that case if you do that and you ask where did the virus end up,
the virus ends up arrested in these cytoplasmic body complexes. In this case by preventing the TRIM protein from degrading or destroying the virus, we could get these very beautiful fixed cell images of the interaction between TRIM5α and HIV. But getting a fixed cell image of this interaction in the absence of drug prove to be very difficult and that’s when we had to switch to live cell imaging approaches.
Slide 17 to Slide 18 Now here I’m going to switch colors on you here a little bit. We can
now fluorescently label our HIV virus with a Cherry‐VPR protein and we’re going to use it to infect a cell line expressing YFP TRIM5α and we can see why it was so hard for me at the time to get some fixed cell images showing these complexes.
Slide 19
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What you can see here if you focus on the larger red dot that is moving a little bit, you’ll see that separate into two red puncta. What we believe that is, is one of the viruses is escaping an endosome and what you can see is the formation of one of these cytoplasmic bodies around that virus that escapes the endosome.
Slide 20 So we can actually quantify this interaction and we can see that in
the green line that you see shoot up here, that is the formation of one of those assemblies around the individual virus. If you watch the red track, which is the fluorescent intensity of the virus, you can see there’s only a two or three‐minute window that exists between the time the TRIM5α engages the virus and the loss of the viral signal.
Slide 21 to Slide 22 Another way we’re able to quantify this in a pretty pleasing way is to
use that other virus as a control. What you can see is the virus that is not engaging the TRIM5α protein in the cell, that fluorescent intensity remains constant during the acquisition period whereas we only lose the virion signal in the one that does engage the TRIM5 protein.
Slide 23 So another dynamic interaction that we can see and measure is
demonstrated by this movie here. If you watch the virus that starts out on the far left‐hand side of the screen, what you can see is that engages a TRIM5α preexisting assembly. Then what it seems to do is it peels off and it takes with it this coat of TRIM5 protein. It kind of gets slimed in the Ghostbuster sense is what we describe it as.
Slide 24 So what we can actually do there is measure on the right side of this
plot, which you can see is when the virion leaves, it takes with it some of the fluorescent intensity that was originally with that original complex leading to two individual assemblies of smaller or less intensity.
Slide 25 So another type of approach that we’ve been using a lot lately in lab
that I’m very much in love with is the utilization of RoGFP, which is a redox sensitive form of GFP. This has two surface‐exposed cysteines positioned very close to the chromophore that allow disulfide bond formation conditionally depending on the redox state of the cell.
Slide 26
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This disulfide bond changes the fluorescent properties of these two RoGFP proteins that are available, RoGFP1 and RoGFP2, and you can therefore use that change in fluorescence to sense changes in the redox state in the cell over time.
Slide 27 [0:15:12] So what you can utilize this to do is we have a mitochondrially
targeted protein that we got from another lab, we didn’t invent it. What you can do is you can measure the redox state of these cells and then what you have to do is you have to add a strong reducing agent like DTT and then a strong oxidizing agent like aldrithiol to essentially measure the basement and the ceiling of where that cell could be. From there, you can get a sense of the relative redox state of individual cells that you’re examining.
Slide 28 We’ve used this in our studies that we just recently published about
alpha‐synuclein. I’ll go into that a little bit now. So what we’ve been doing is measuring alpha‐synuclein vesicle rupture. What we observe is that alpha‐synuclein can enter cells and rupture vesicles and to do that we used this fixed cell assay, but it’s worth talking about because I really think it’s one of my favorite things lately that’s for sure.
So galectin3 is a soluble cytoplasmic protein that has the ability to
bind carbohydrates or sugars and importantly, these carbohydrates and sugars are universally on the outer leaflet of the plasma membrane such that when you have endocytosis, they’re on the luminal side of an endocytic vesicle. Galectin3 relocalization to ruptured vesicles in the last couple of years has really been revolutionary in studying the life cycle of viruses and bacteria that enter cells using vesicle rupture.
What you can see over here on the right from our recent PloS
pathogens paper is we can do the exact same thing with alpha‐synuclein. So alpha‐synuclein is colored in green on this picture on the right and you can see it forming these arc surfaces on the periphery of these ruptured vesicles. What we think it’s doing is bending or inducing curvature of those membranes to cause cellular pathology. That cellular pathology is read out as redox stress. You know, in lysosomes and endosomes are all the digestive enzymes of the cell. When those get released out into the cytoplasm, there is real consequences for the cell such as mitochondrial dysfunction.
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Slide 29 So what we just showed and we used this system that I just
described to you using reactive oxygen species sensitive GFP to show that the addition of alpha‐synuclein increases the redox stress or the reactive oxygen species present in these cells and we don’t show it in this experiment, in a cathepsin dependent manner. You know, this is really a valuable tool because it allows us to measure the redox state of individual cells.
Slide 30 What we’re doing now is we are doing our live cell imaging
approaches and then thanks to the precision of the motors in our stage and our coordinate system then what we can go back and do is examine whether or not the cells that were feeling the most stressed had the most ruptured vesicles. This is one of I guess the combination of live cell and fixed cell imaging approaches that we’re starting to use to ask individual cells how they feel.
Slide 31 So finally, the last thing I want to talk about is a technique called
FRET, which is Fluorescent Resonance Energy Transfer. What I want to stress here, you know, I think a lot of people use FRET to really just get below the resolution limit of light microscopy to say these things are interacting directly, thank you very much. We’ve been guilty of that. We’ve used that technique in a lot of our published data to say that two molecules are indeed interacting. But what’s important here in the technique that I want to talk to you about is the idea that FRET efficiency can be used to measure dynamic and conformational changes that occur between two interacting proteins. This occurs because FRET efficiency is dictated by the physical separation of the FRET pairing fluorophores.
Slide 32 So what a colleague of mine Seth Robia is doing also at Loyola is he’s
examining the interactions between a protein called SERCA and phospholambam, which are critical in regulating intracellular calcium concentrations during cardiac muscle contraction. What you can see on the left panel is that these two proteins generally always interact. But what’s important is depending on the calcium levels of the cell and the physiology relevant to the cardiac biology, which I won’t really get deeply into today, there can be a shuttle conformational shift between the way that these two proteins are interacting.
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Slide 33 So what Seth has done is exploited this by pairing, by attaching FRET
fluorophores to the proteins of interest. Slide 34 What he can then do is he can look in individual cardiac myocytes
and measure FRET differences or differences in the FRET efficiency that occur during the beating of a heart if you will. You know, I was lucky enough to be on one of his students committees and this to me just really blew my mind. When we all think of FRET, we ask are these two molecules interacting. What Seth is doing is measuring conformational changes that are very biologically relevant and important in the context of FRET efficiency. So you know when you’re thinking about that just appreciate that FRET efficiency is much more than just showing that two things can interact.
Slide 35 [0:20:24] So I really appreciate your attention and the opportunity to talk
today. The people on the left are the people in my lab and those that did the work that I’ve showed you. So thank you very much for your attention.
Sean Sanders: Great. Thank you so much, Dr. Campbell. Slide 36 Our next speaker for today is Dr. Nick Thomas. Dr. Thomas is
principal scientist in Cell Technologies at GE Healthcare based in Cardiff, Wales. He is the inventor or co‐inventor of over 60 patents covering a wide range of technologies including microfabrication, molecular and cellular sensors, and cellular imaging. Dr. Thomas has worked on the development of cellular analysis instrumentation, software, and reagents for the past decade and has published a number of review papers and book chapters on this subject. Welcome, Dr. Thomas.
Slide 37 Dr. Nick Thomas: Thank you, Sean. It’s great to be here. So I guess my talk has a dual
purpose title. So from what to how I’m going to talk about live cell imaging in HCA, what it is and how to do it but the other way to read that is it’s one of the key aspects of why people do live cell imaging. Fixed cell imaging, which I guess for HCA that’s probably 95% of what people do and that tells you what happened. Live cell imaging comes
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in to its own when it tells you what happened or how it happened. So basically we got sort of a list.
Slide 38 What I’m looking at here is various aspects of biology. Biology is not
fixed. We choose to look at a lot of biology as if it is a fixed event because let’s be honest that’s the easiest way to do it. Fixed cell imaging is easier than live cell imaging. But if we think about biology, you know, it varies in its dynamics from things like iron flux in cardiomyocytes when they’re beating, happens very rapidly through to something like the cell cycle which will maybe take 18 to 24 hours in the typical cell through to something like the differentiation of a stem cell to a cardiomyocyte or to a hepatocyte and that will take many, many days. So all of these are dynamic processes. So when we’re using fixed cell imaging, we’re looking at a particular time point or a particular series of time points. So I think that tells us what happens. Live cell imaging has the potential to tell you how the cell actually got to the state at which you’ve observed.
Slide 39 So, you know, why do people do live cell imaging? There’s lots of
reasons. I’ve kind of summarized on this side some of the key ones. First important one is nonfixable assays. There are some things that you just can’t do as a fixed cell assay. Typical example is looking at mitochondrial membrane potential, looking at calcium fluxes and I’ll show you an example of that. Calcium flux assays whether you’re interested in cardiomyocytes perhaps or GPCR signaling again it’s a dynamic response.
Then obviously the ones I guess the people think more about when
you talk about live cell HCA is long term event, studying the cell cycle, studying as I’ll show you say a gene knockdown impact on the cell cycle. So remember important thing is fixed cell assays is what happened, live cell assay is how it actually got there. You generally need both of those to understand the complexities of cell biology pretty much whatever you’re working on.
Slide 40 So a few things to think about before we get into just showing you
some examples of live cell HCA. There are a number of key aspects and it’s really doing live cell assays as I’ve said is more complicated than fixed cell assay so you’ve always got to think, you know, there’s a certain amount of pain in doing this so what’s the gain versus that pain.
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So things to think about, environmental control, okay. Cells generally
if you’re working with mammalian cells, they like to be warm so you got to keep them warm. Are you going to keep them warm and supplied with gas for some term, depending on how long you’re going to go? You need to have flexible imaging conditions with flexible instrumentation. You don’t want to kill your cells, you don’t want to bleach them. Basically, you know, as we’ve heard already be kind to your cells. The main mantra from my point of view if you’re doing live cell imaging is don’t perturb the biology you’re trying to study by the way you look at it because then it becomes a rather pointless exercise. Imaging speed, yeah, you’re going to have to consider how fast do you need to image to capture the event you’re imaging in and you’re going to get some data out of that so you’ve got to have the appropriate software to generate your data.
Slide 41 So what I’m going to show you today are some ranges of applications
done on a range of IN Cell Analyzer instruments that we supply. Slide 42 So I’m going to start about short‐term imaging. So basically, what
I’ve done is divided this talk up into short term examples and long term examples.
Slide 43 [0:25:07] So first of all let’s look at some short term examples. So this is a
cardiotoxicity assay done in human embryonic stem cell derived cardiomyocytes and this is an example of an assay that you have to do live because you can’t fix it. Basically, it’s a multi‐parameter assay looking at mitochondrial integrity, mitochondrial membrane potential, calcium hemostasis, and vulnerability. What we do is we generate multi‐parameter data having treated the cells with drugs and then staining them with the appropriate fluids. We use this multi‐parametric profiling approach and here you can see in the bottom left, tasocitinib, that profile is invariant with dose indicating nontoxicity, and if you look top right, you can see sunitinib, which dramatically changes its profile due to impact on mitochondria and calcium homeostasis. So that’s an assay that you cannot do fixed.
Slide 44 Another thing so this is another example. It’s basically a cell health,
an apoptosis assay, a very straightforward assay to do. But
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something that you have to consider when you’re doing live cell assays is that if you are using fluids that you need to wash then washing cells generally don’t like to be washed particularly mitotic cells. They will detach and actually again this comes down to perturbing the system. If you’re trying to measure dead cells, which if you wash the cells, they’ll disappear, you’re defeating the object in doing your assay.
So this is an example of using an instrument, which has modulatable
confocality so that we don’t have to do a wash. It’s a homogenous assay and you can see in the top image there, you’re retaining dead mitotic cells, which have gone from an assay, which is done, via washing. So again something to consider when you’re setting up your assays.
Slide 45 Here’s an example of a short term assay. This is probably going back
in the history of HCA one of the most performed short‐term live cell imaging assay, a GPCR inducing calcium flux signaling. Done in population measurements a lot, great advantages of doing it in HCA that’s shown in the bottom left there is you can get individual cell data as you can see here.
Slide 46 Control image is on the left‐hand side, carbachol treated in this case
images on the right‐hand side. So the purpose of this is you’re doing an assay, which you could do on a population mode on another type of instrument, a plate read or a flipper like that the advantage here is you’re getting individual cell data.
Slide 47 Here’s a slightly longer term assay. This is actually an example of
where live cell imaging is actually used as a precursor to fixed cell imaging. So what we’re looking at here is a p38‐MAPKap GFP fusion protein in cells. P38 is a general integrator of stress responses and therefore it’s translocation that we can see in the series of images there can vary in its temporal nature depending on the stress impetus. So this experiment actually came from the precursor to running a p38 GFP translocation screen. The purpose of this experiment is to determine the optimum time in which to perform the fixed cell assay.
So you can see in the upper left panel there the change in the
subcellular localization of p38 and the arrow indicates the optimum
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time. So basically here you’re doing one live cell experiment doing that experiment very carefully and then using the data from that to set up a very large cell screen, which will be run in a fixed cell fashion.
Slide 48 Here’s a further example of that experiment. So what we actually did
was because we know that p38 can respond to a number of stressors, what we were doing was to set up in this case an IL‐1beta screen. So here as you can see in the top below the pictures here are cells stimulated with IL‐1beta but below two other types of screen, anisomycin and an osmotic shock. Again because p38 is responding to those stimuli in different way, this data allows us to set up a fixed cell assay screen that will only look at that particular type of stress response that we want to look at. So here, the live cell imaging experiment is very much the setup subsequent experiments rather than the actual endpoint.
Slide 49 So this is a couple of example of short term assays, now we’re going
to move on to some longer term ones. Slide 50 So this is quite a simple example. It’s actually looking at the mode of
action of toxicity of drugs. Again, a fairly simple assay but this time rather than doing as fixed cell assay, which tells you yes this drug is toxic and this is a result you got at the end of the assay, by doing live cell imaging, we can actually look at how things occurred.
[0:30:14] Slide 51 So what we’re looking at here is a series of stills from the assay at
zero to eight hours and you can see that with the top drug here, you’re actually getting at the beginning of the assay and at the end of the assay the images look identical. So what’s happening there is that drug is impacting our membrane integrity right at the beginning of the experiment.
Slide 52 In contrast, diclofenac the middle drug, looks different through the
assay. So it’s actually having the same effect and the eight‐hour images for both drugs look the same so the what they both killed cells, they both impacted membrane integrity. But if you actually look at the how, they actually differ very significantly in their mode of action. Similarly, at the bottom with another drug, you’re actually
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getting both a slow induction of apoptosis. So sometimes, you know, that live cell approach actually the pain of it is offset by the gain of getting additional information of how the drug is impacting on cells, which you can’t tell from just looking at the endpoint.
Slide 53 Another aspect when you get into live cell imaging over longer time,
obviously it becomes more complicated because your cells are not going to, you know, behave, sit there and just stay in the same position. They’re going to move. So collecting data from those cells means your software has to be able to track those cells. Because what you’re doing obviously is you want to have individual cell by cell data from each of your cells. If your software can’t tell is that the same cell, is that cell in the previous image, you’re just going to get lost. So you’ve got to have good software that will do cell tracking.
Slide 54 I mentioned cell cycle before. Here’s an example from and sRNA
screen that we did several years ago using live cell imaging of GFP fusion proteins that are caught on the cell cycle. Again, I come back to the point I made earlier, the whole main mantra you should have in your head is you shall not perturb the biology you’re trying to study. So what we used here is very low level of expression of those GFP fusion proteins and that allowed us to find some novel findings like the ones illustrated on the right‐hand side where we found a protein that actually are knocking that protein down has a very significant effect on the cell cycle. This is actually a retinal binding protein, something that you would not have expected to have a dramatic impact on the cell cycle and something that you can only find by live cell imaging.
Slide 55 to Slide 56 Coming back to the difference between what and how, this is an
example from looking at drug treatment of cells. This time again drug impact on impact on the cell cycle. In the middle is the data from classical fixed cell assay looking at DNA content and BrdU labeling to look at the way cells are progressing through the cell cycle. It looked like from the drug treated cells that they were going through endoreduplication and that was confirmed by the live cell imaging. So the control cells on the left‐hand side you can see they’re replicating nicely.
The hesperidin treated cells, what’s happening there is they attempt
to go through mitosis but mitosis fails and they then jump directly
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into G1. You can tell that from the subcellular localization of that GFP.
Slide 57 Another example of long term tracking, so looking at how drugs
impacting the cells and what we’re looking at here is data from our IN Cell 6000. In the upper panel, you can see images taken over a long period of control cells and the lower image drug treated cells in this case treated with colecemid. You can see I’ve put squares around the data on the right‐hand side. That data is coming directly from the video, which is analyzed. Each cell is tracked and you can see in the upper panel you’ve got proliferation of cells and in the lower panel as you would expect you’re blocking cells in mitosis and they’re dying and you can see the fall of the cell number.
Slide 60 So live cell imaging, why do it? Basically to find out, get more
information of what’s going on in your biology and get from what to how. So you can do assays that can’t be fixed, you can follow very fast dynamic events. You can understand very long and complicated cellular processes like the cell cycle. Really, the bottom line is you get to understand what’s going on in your biological system more.
Slide 61 Thank you. Sean Sanders: Fantastic. Thanks so much, Dr. Thomas. Slide 62 We’re going to move on to our final speaker for this webinar and
that is Dr. Lynne Turnbull. Dr. Turnbull is a senior research fellow at the I3 Institute at the University of Technology in Sydney, Australia. In addition to her research focus on microbial biofilms, bacterial motility, and pathogenicity, Dr. Turnbull is also the OMX Application Specialist for the Microbial Imaging Facility. In this role, she works with many collaborators to facilitate implementing superresolution microscopy into their research programs as well as developing novel techniques for microbial live cell imaging. Welcome, Dr. Turnbull.
Slide 63 [0:35:28] Dr. Lynne Turnbull: Thank you, Sean. Thank you for having me. So today, I’m just going
to talk briefly about live cell imaging of bacteria using
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superresolution microscopy and cell biology and bacteria using live imaging.
Slide 64 So for bacterial live imaging especially for cell biology, size does
actually matter. So if you look at the images on the screen on the right‐hand side you have a bone cell, a normal sort of mammalian cell and it’s quite large. You can see on the left‐hand side, there are some typical‐sized bacteria and they both have 15 micron mark on scale bars.
Slide 65 If we now adjust the scale bars to be the same size, you can see that
we’re working in a much smaller area. So when we want to look at things that are happening inside each individual cell, we’re working in a much smaller volume, about the volume of a mitochondrion. So size does matter.
Slide 66 So there are some challenges for imaging cell biology that are the
same for bacteria as for mammalian cells. But we have a few other things that happen in bacteria that we have to contend with.
Slide 67 So one of the things is actually keeping cells still and I think I mean I
by that that keeping cells the same cell over time in your field of view so that you can see what happens in that individual cell over time. So when you mount bacterial cells in a liquid medium, you might have to contain with Brownian motion and sometimes that can confound things and sometimes that it’s okay, you’re tracking software over time can cope with it. But also that many bacteria actually are actively motile through structures such as flagella and pili and you actually have to contend with them moving out of your field of view and sometimes very rapidly.
So we have some strategies to cope with that. We can change the
mounting substrate so we can try and embed them in a sloppy gel or use gel pads. We can use mutants that are no longer motile. That depends on what you’re studying. If you’re studying motility, you can’t do that of course. We can try and lower the temperature that we’re working at if you can. It all depends on your biology to try and slow them down so that you can keep them in your field of view a bit longer.
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Another thing that is coming into fashion is to use microfabricated chambers or channels to trap your cells into a much smaller area. Now again it depends on whether that fits your biological question. That’s always the first thing is am I going to change biology by doing any of these things.
Slide 68 Again, as already been iterated for bacteria, we have to try and keep
them healthy. The same as you do with eukaryotic cells and where possible we use transmitted light because it’s much healthier and helps the long term imaging. You can’t do that with superresolution unfortunately but for other live cell imaging experiments with bacteria, we definitely try to use a transmitted light channel where possible. Again media choice, keeping your cells healthy but also being aware of things like autofluorescence, you don’t want your media to be brighter than your bacteria. Again, choose low excitation when you can and short exposures. It’s more important to get information than to get the perfect image as you would with a fixed cell experiment.
We often try to use the minimal amount of z‐slices during an
experiment to get the information we need not necessarily to actually get every bacteria in the field of view or the whole bacteria if we think that the question that we’re asking doesn’t need that.
Slide 69 Again, I’m just going to reiterate, they’re small. They’re small things
up to 2 microns thick sometimes and that gives you a small focal point to work within. So what we found is that some of the automatic focal systems that come with the fancy microscopes we have today don’t necessarily always work because some of them work on a drifting where they find the coverslip by drifting slightly and coming back to the same point. If you’re working with a very, very thin specimen, sometimes that drift is enough to lose your cells. Things like using a confocal on a confocal laser‐scanning microscope with the pinhole closed, you actually can lose information because there’s not enough fluorescence being generated by the whole bacteria to actually need to cut it out using a pinhole. So we often actually open the pinhole wide up and use it as a wide field at the end of the day.
So you have to ask the questions about whether using different
styles of microscopes suit the biological question that you’re asking. Again I’ll just say conventional resolution is sometimes insufficient
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for subcellular imaging in bacteria because the volume that you’re working with, you don’t have enough resolution to see if proteins move individually or move in relationship to each other within one individual cell.
Slide 70 [0:40:14] So we’ve turned to superresolution microscopy and the one I’m
going to talk about is three‐dimensional structured illumination microscopy or 3D‐SIM. It gives you a doubling in resolution in all three dimensions and there’s been a number of reviews and this one is reviewed by Schermelleh that shows that your point spread function is actually doubled in all three dimensions.
Slide 71 The way that this technique works is you actually have a structured
light pattern that is imposed on to the sample and you’re able to extract high resolution information from the image by taking multiple images using the grid, moving the grid around at the different orientations over the course of the experiment or the course of the image. You do that for each z‐slice.
The good thing about this technique, it actually works with standard
dyes and fluorescent proteins so as long as your dyes and your proteins match the filter set and the lasers as you need to do with any fluorescent microscopy, you can use tools that are hopefully already in your toolkit. The lateral resolution is between 80 and 130 nanometers and your axial resolution 250 to 350 nanometers. It’s a widefield imaging technology and it’s well described in the literature now and the two references at the bottom are good starting points to read all about this.
Slide 72 So I’m going to just use one study that we’ve performed as an
example of why superresolution and live superresolution is actually giving us better answers or more detail than we’ve ever had before. This was published last year in PLoS Biology and you can download any of the images or movies that are involved with this study to get a better look at what I’m talking about.
So we looked at bacterial cell division and cell division in bacteria
starts with the formation of a z‐ring at midcell and then that z‐ring constricts over time to pinch off and then you have two daughter cells. Of course, it’s much more complicated than that but that’s all
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you really need to know. The z‐ring is formed of a protein called FtsZ and it acts as a scaffold for other proteins to come to the midcell division site during cell division and it’s essential for bacterial cell division.
So we studied it in two gram‐positive bacteria, Bacillus subtilis as you
can see in the left hand image there and Staph aureus, which is a well‐known bacterial pathogen.
Slide 73 So when we looked at this in conventional resolution if you look at
the top left‐hand panel, you can see that Bacillus subtilis is a big long sausage that sits flat on the coverslip. When you want to look at it in any depth, you can rotate the cell and you can see that it is actually a ring. In this image, the bottom left‐hand image is the equivalent sample done with 3D‐SIM and when you zoom out, actually you can’t really see much difference. But it’s actually when you zoom in and look at individual z‐rings that you can actually see a difference. So we can see here in the two images on the right‐hand side that with the GFP‐FtsZ fusion, you can see z‐rings in different times of constriction during the cell cycle, two very constricted ones that are probably almost about to pinch off and larger ones that haven’t started to go through the constriction cycle yet. If you turn off the GFP, you can actually see with the red membrane dye that, you know, those cells, the membrane is being pulled in ready to pinch off during cell division.
Slide 74 If you now zoom up and look at individual z‐rings more carefully,
what we can actually see is that the distribution of that protein is heterogeneous throughout the ring. This was something that wasn’t really known before we started this study because with conventional microscopy we didn’t have enough resolution to see these very small gaps. We thought that it was just a continuous structure. So by turning the ring on its side in the z dimension now going up and down in your screen, you can actually see that at the top and the bottom of the ring, there’s small gaps in fluorescence where there appears to be less protein. This was like quite exciting for us at the time.
Slide 75 The great thing about working with Staph aureus is that because it’s
a spherical cocci, you can actually catch the z‐ring lying in many different orientations just by chance because it’s a little ball. If you
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look at the panel on the left there, you can see that we’ve caught a field of view of Staph with z‐rings in all orientations. You can sort of tell by the angle tilting and also in many different times of constriction of the ring. We’ve even actually caught a couple that is sitting on their side like you see them in Bacillus subtilis. Again, if we zoom up and look at individual z‐rings as in the right‐hand panel, you can see that there’s gaps in the fluorescence again and we’ve been calling these beads on a string because that’s what it really looks like. So we can see that it’s the same in the two different species and we’re quite excited to see that it wasn’t just something that was special to bacillus.
Slide 76 [0:45:20] But 3D Structured Illumination is hard on a cell in classical terms
because you have to take 15 images in each z plane to get a reconstructed image. That’s 135 images per channel for a 1‐micron section and, you know, that repeated exposure causes higher phototoxicity for your cells. So when we try to look at how dynamic these things were over time, we found that the cells were not liking it very much and were dying very quickly. So we wanted to, you know, get something that would help us look at the dynamics of the z‐ring over time.
Slide 77 So we actually were lucky enough to become one of the first people
to get a hold of the OMX Blaze technology, which is basically fast structured illumination. It works by getting rid of the physical grid that was normally used in structured illumination and using interfering beams to create that pattern that grid pattern on to your sample in conjunction with the new shutter designs, scientific CMOS cameras, and really fast computers.
Slide 78 So combining all these things, we’ve now able to actually do 3D‐SIM
at a rate of 1 micron per second. We found that by doing this, we have shorter exposures and the cells are lasting longer and we were really happy then to be able to look at the dynamics of the z‐ring over time. What we found is that heterogeneous distribution of the FtsZ in the cell is actually maintained over time and that the gaps actually change position so that we think it’s a very dynamic process. So what you can see in these panels is an image taken every minute and it’s from a series where we went out to between 12 and 16 minutes and following the constriction of the z‐ring.
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The gaps appear in the z‐ring and change in their distribution in the
z‐ring no matter what the stage of constriction. So for big rings and also when the rings are constricted just before they’re about to split off. We were really excited because that wasn’t known either and it also helped us with the model of how constriction happens with the z‐ring. It actually provided more data about how this happens over time to build a model of how z‐rings are constricting. So the other thing that this technique allowed us to do is to look quantitatively at how that fluorescence changes over time.
Slide 79 So you can see in the panel on the right‐hand side that that’s an
image of a z‐ring taken every five seconds and for a full time of a minute and then on the left‐hand side is a measurement of the fluorescence intensity in the whole ring changing over time. You can see that the peaks and troughs in the fluorescence intensity move around in the z‐ring over time. So we were very, very excited by this and it shows that this is a very dynamic process. We also went on to show that in other proteins that were recruited to this division site during this, they’re also dynamic and move over time and that the movement of the FtsZ occurs in rings that don’t even constrict if you use mutants that don’t constrict. So this was a really nice study that wasn’t possible before the advent of superresolution and also live superresolution.
Slide 81 Again, what do we need to do in the future? So this is a sort of
where can we go from here. Well the technology delivers what the manufacturer tells us it’s going to do but of course we want faster, faster and more sensitive as always because we’re greedy.
The other thing is that we need to think about developing better
fluorophores really for fluorescent proteins and dyes. A lot of these are developed for eukaryotic cells and they work really well but again we need to develop them with microbiology in mind because bacteria and other microbes are different.
Biology versus lasers I guess what I mean here is that at the end of
the day, the lasers will always win the battle. No matter how careful you are when you put excitation energy into live cells they’re not going to like it and they’re going to die. So we need to think about better antifades and there’s been some movement in this very recently with publications coming up in the literature on adding or
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subtracting different vitamins into tissue culture media for eukaryotic cells. We need to develop these for microbiology as well. Some of the things that work in eukaryotes actually kill bacteria because we’ve tried them and you know, this is the sort of thing we need to move to.
The other thing is to increase your signal to noise ratio. So there’s a
number of ways of doing this so one of the ways is to use denoising algorithms and so you can lower your excitation energy even more than we already do. But doing things like finding better ways to increase the density of the labeling of the structures within your cells so that you actually get more signal out of each individual cell. So I think these are the future directions that live cell imaging will improve if we can move on some of these things.
Slide 82 [0:50:31] So again I would just like to thank the people who fund me and help
us purchase these things, which is the University of Technology in Sydney, the Australian Research Council, and the New South Wales Office for Science and Research that sponsors buying our equipment. And the people who worked on the study that I just showed you, Liz Harry and her very talented team of students and post docs and Cynthia Whitchurch. Thank you.
Sean Sanders: Great. Thank you so much, Dr. Turnbull, and my condolences to all
the cells that died in the making of these experiments. It sounds like there was a lot of that going on. Many thanks to all of you for the wonderful presentations. We’re going to move right on to the questions submitted by our online viewers.
Just a quick reminder to those watching us live, you can still submit
your questions. We have about ten minutes left in the webinar. Just type them into the text box and click the submit button. If you don’t see the box on your screen, click the red Q&A icon.
So the first question I’m going to put to all of you and I think I’ll start
with Dr. Campbell is one of the key issues for live cell imaging of any duration seem to be maintaining focus in Z. Do you have any tips and tricks you can share with the audience about that?
Dr. Edward Campbell: Sure. You know, I think he mentioned one of the new technologies
that’s very valuable are these laser guides systems that detect the distance between your lens and your specimen. These are invaluable
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in term of especially long duration imaging experiments. But you know, the other thing it comes back to again paying attention. You will lose focus I think to a certain degree at times if you don’t have one of these laser guided systems. If that’s the case, you can notice it and okay you lose a time point from your movie but pay attention to the data as it’s coming in. You know, you can’t really tell if an experiment is going perfectly but you can tell when you’ve lost focus right, that’s clear. And then you know often a little trick between time points, you can get right back into your focal plane and take it from there.
Sean Sanders: Uh‐hum. Dr. Thomas? Dr. Nick Thomas: Yeah, the issues HCA are kind of different from what these two guys
do. The main thing I would say here, you know, instrumentation for HCA is set up to do imaging automatically. Generally, you have hardware autofocus, the main thing is make sure that’s working properly and use the right plates. A lot of people don’t care, take so much care about selecting their plates. If you’re doing live cell imaging, it’s even more important to have the right size of plates, make sure that they’re clean and you don’t get dust in them that might throw things off and generally that it.
Sean Sanders: Uh‐hum. Dr. Turnbull? Dr. Lynne Turnbull: I guess more old school is there’s a lot of things you can do just to
help yourself whether you have automatic systems or not. We keep everything hot so we never turn off the live cell environmental chambers and we take the microscope and the objectives and the whole box at 37 or 38 degrees depending on the system all the time so that you’re not having any of the metal expanding and contracting. We keep all of that oil. All of the spare objective are all kept inside the box to keep them nice and warm. The other thing that happens is that a lot of your focal drift during experiment maybe due to evaporation so even though it changes the solute to do using something like gel pads as we do, you’re going to get change of focus because the gel pad will dehydrate. So we keep the environmental chambers full of beakers of water and soggy tissues to keep the evaporation to a minimum.
Sean Sanders: Excellent. Next question is about photo bleaching. It seems to be a
fairly popular topic. How can this be avoided? I know you’ve spoken a little bit about this but maybe you can speak in more depth. We also had a viewer who said I thought it’s an interesting question, is
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phototoxicity observable at all wavelengths? So is it possible to use different wavelengths to reduce the amount of phototoxicity. So Dr. Campbell?
Dr. Edward Campbell: So I mean I think for photo bleaching, one of the big advancements,
you know, EMCCDs really work. You know, the ability they have a function called In Chip gain, which basically allows you to collect all of the imaginable data using tricks of physics that might be outside of this conversation. The other thing, you know, is the platform you’re using. You know, we kind of talked about the difference between confocals and widefield deconvolution microscope. So there’s an article by John Murray out there who’s a real microscope wonk right and he can show that the photon capture efficiency of a deconvolution microscope is more efficient than many or these other systems. So essentially the deconvolution people think, oh, it makes my data prettier, right?
[0:55:10] Sean Sanders: Uh‐huh. Dr. Edward Campbell: Okay it does that but what it does is it restores light to where it came
from and scattered. So if you have something very small like a virus, you’re losing wavelength as it forms a cone out in your other dimensions and the ability to not only remove that, to make it prettier but to put it back where it came from means that you can get by with less exposure. Getting by with less exposure is the key to all photo bleaching.
Sean Sanders: We have agreement I guess. Dr. Edward Campbell: Yeah. Sean Sanders: Any other comments? Dr. Nick Thomas: I mean from an HCA perspective it’s yeah, cells don’t like being
baked by light. Now we would if you walked outside under an ozone hole the same thing. You know, it’s basically have the most sensitive instrument you have. That means you don’t have to have long exposure times. The thing that we do particularly on our IN Cell 6000 system, you can dial in confocality when you need it but you don’t have to have it running in all different channels. So that means you’re not blasting all of your cells in all of the channels with more light than they need to get you the data. It comes back to what I’m saying before, you know, if you have a live cell imaging experiment
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and you’re perturbing it by blasting them with photons – you’re not measuring the biology you set out to measure. It’s a rather pointless exercise.
Sean Sanders: Right. Dr. Turnbull? Dr. Lynne Turnbull: The point is less is more. Sean Sanders: Yeah. Dr. Lynne Turnbull: If you can get away with fewer time points, less Z‐slices. Do
everything you can to keep your cells healthy and you’ll get less photo bleaching but you can’t avoid it completely. It’s going to happen. You just have to make sure that you have some measurement of how healthy your cells are and stop when they’re not healthy.
Dr. Edward Campbell: And you know cells are very much like us where the light that upsets
them the most is UV to get to the viewer’s question. You know, there’s UV filters you can put to prevent the UV light from getting to your sample that will sometimes preclude the use of CFP, right. But if I had to keep my cells alive, I would generally go GFP and Cherry or YFP and Cherry because they’re just further away from that UV spectrum of light.
Sean Sanders: Right. Dr. Thomas, a quick question on HCA I believe. This viewer
says that when they’re imaging in a multiplate format, they have say 384 wells and it takes a minute to scan each well by the time they get to the end, you know, it’s a few hours since they scanned the first one.
Dr. Nick Thomas: Yeah. Sean Sanders: How do you deal with that? Dr. Nick Thomas: That brings up a whole range of very interesting things I guess we
could discuss for hours and people do discuss them for hours. It really does depend on you know, I covered very quickly a whole range of different applications, which will run over lots of times. So I guess the quick answer is if you’re doing quick imaging like calcium imaging then you generally do what we call a spit and stare. So basically, you treat each well as an individual entity. So you will add the drug, you image that for maybe 30 seconds and you’re done and you move on to the next. So you basically work your way through
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your plate. So depending on how many wells you got to do, you got to schedule it. Again, it’s all about keeping those cells happy. In this case, those cells are sitting there and you got to keep them happy until you actually use them in the experiment and then they’re done. If you’re doing long term live cell imaging or time lapse, what you’re doing there is you’re visiting a well and then you may not come back to that well until an hour later.
Sean Sanders: Uh‐hum. Dr. Nick Thomas: So each type of experiment has its own set of issues and problems to
solve. There’s no generic fix. That’s why there is more pain in doing live cell assay. But if you really want to know you know I treated my cells for 24 hours with this drug and they look like this at the end but I’m not sure what happened.
Sean Sanders: Right. Dr. Nick Thomas: You have to do that experiment to find out. Sean Sanders: Right. Can we talk a little bit about software that’s used and maybe
we’ll start with, Dr. Turnbull? This is really a question about whether there’s any standard for software or whether there’s just a number of packages and they also ask if there’s any open source software that you use.
Dr. Lynne Turnbull: Most of the microscopes that you’ll buy will come with some form of
acquisition software that will have some ability to do analysis with and some are better than others and they all have it. And there are many options for software to do analysis including people write a lot of their own stuff these days because they want to do quantitative analysis based on things like Matlab or there’s plenty of commercial things.
But one of the most powerful free software out there is ImageJ,
which is developed by or housed by the NIH. Because it’s freeware and it’s built by a lot of people who’ve asked a lot of different questions over the years and it’s maintained, almost anything you want to do there’ll be an ImageJ plug‐in for it. You just have to figure out how to use it sometimes. Once you get your head around ImageJ logic, it’s not that bad.
[1:00:12] Sean Sanders: Uh‐hum.
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Dr. Lynne Turnbull: And that’s what we get our students to do because they can do it on
their own laptop. They don’t have to sit in front of a computer. Sean Sanders: Right. Dr. Lynne Turnbull: But yeah, I think that that’s probably the most powerful freeware. Dr. Edward Campbell: And I think I totally agree and I think one of the people, a lot of
people download ImageJ and they see what it can do, right? But as she said the number of plug‐ins you can get… And I think there’s I want to say, I wouldn’t even try to come up with at name off the top of my head but there’s places you can go to install these packages and there’s a number of them that have like really a huge wealth of packages that you can install all at once if you just poke around on the internet. The amount of functionality that that adds to the basic ImageJ package is you know considerable.
Sean Sanders: Great. I’m going to stay with you, Dr. Campbell, a question about
tracking vesicles, manual tracking or automated tracking? Do you use software when you track?
Dr. Edward Campbell: So we have used manual tracking. Usually that requires a small
number of events and good time resolution. Sean Sanders: Uh‐hum. Dr. Edward Campbell: But we’ve used, you know, automated particle tracking and certainly
that makes life a good deal easier. Usually those packages are more expensive. You know, I’ve never used or tried them on ImageJ. But the software packages that we’ve used, it’s generally much more reliable because even the data that I showed where you could see the particle fluorescent intensity change over time, that was me going in with the data inspector at each time point being like 4338 plug into Excel, right?
Sean Sanders: Right. Dr. Edward Campbell: That’s great, good times. Sean Sanders: Right. [Laughs] Isn’t that what graduate students are for? Dr. Edward Campbell: Yeah, that was me, yeah.
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Sean Sanders: So any other comments? Dr. Lynne Turnbull: I guess the software packages that you can buy that have these
really good things, they cost a lot of money but the people who’ve developed them spend a lot of time doing it and they do it really well. So that’s the advantage and therefore at our end it’s a lot quicker.
Sean Sanders: Right. Dr. Lynne Turnbull: But yeah, ImageJ and things like that a lot cheaper. So you always
have to balance the resources that you have available at the time. Sean Sanders: Uh‐hum. Okay. A question about the pros and cons of fluorescent
chemical probes versus fluorescent proteins and I noticed that most of you have used proteins, fluorescent proteins but maybe, Dr. Thomas, you could start us off with this?
Dr. Nick Thomas: Yeah. I mean some of those GFP experiments that I showed you
there you know, we did ten years ago. Those techniques they work. You know, if ain’t broke, don’t fix it. You know, nowadays there are more advanced fluorescent proteins. A wider choice of colors, more stable. We won’t get into the further toxicity of GFP and others but now you can – you know, there are tagging systems where you can put a tag on to a protein and deliver fluorine to a cell. I guess you pays your money and takes your choice. I like GFP. I always have done. You know, there’s a certain essence about you’ve got all of that in the literature precedent. And generally within general increase in sensitivity of instrumentation over the years, you know, you can actually cut down on the amount of protein you express in the cell and again I don’t want to hammer the point too much but it is. You know, if you ask a cell to make 100,000 GFP fusion proteins that’s kind of distracting it from its normal business.
Sean Sanders: Right. Dr. Nick Thomas: Right? Sean Sanders: Right. Dr. Nick Thomas: If you ask it to make a thousand or two thousand, it can probably do
that.
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Dr. Edward Campbell: I think it’s relevant to think that it’s not an either/or, right? So we’ve never really found a far red fluorescent protein that we enjoy.
Sean Sanders: Uh‐hum. Dr. Edward Campbell: But a lot of these conjugatable dyes, you can utilize them and they
work very well in the Cy5 five range. So, you know, when you’re just focusing on fluorescent proteins, you’re somewhat constrained. You know, the dyes are a little bit – you know, often there’s a pretreatment and you really have to have the ability to wash things, right. So either you have to be able to wash all the things off before you go to the stage or treat something and remove the dye by dialysis. The dyes can be – they’re a little bit dicier in that regard but they’re certainly very valuable and you just have to think situationally.
Sean Sanders: Great. So we’re just over the hour but I want to squeeze in one more
question before I let you guys go and that’s just looking at some of the possible applications of the work that you’re doing. Could you talk about that in terms of healthcare, public health and you know disease research. So, Dr. Campbell, we’ll start with you.
Dr. Edward Campbell: Sure. Well I think you know, Yogi Berra said you can see a lot just by
looking right and he was right. You know, all of the down –you know, in the field of HIV, a lot of the therapies that are effective are derived from a molecular and cellular biological understanding of the events that are going on, right?
[1:05:13] Dr. Edward Campbell: And to delineate them and to, you know, what we’re doing using
jellyfish protein like that’s not going to help somebody that’s sick, right. But if you’re developing a drug or you need an understanding of a biological process to target it, to reveal intervention points, you know, I think that’s really where from my perspective live cell imaging pays the bill.
Sean Sanders: Uh‐hum. Great. Dr. Thomas? Dr. Nick Thomas: Yeah. I mean I only showed you one example there of a drug toxicity
assay but that’s something that we spend a lot of time in looking how you can use these new technologies to look both at the safety and the efficacy of drugs. You know, because I think in the past couple of years a game changer has been people recognizing the
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potential of the stem cell derived models for looking at drug toxicity and efficacy. And companies making those available on an industrial scale basically has allowed people to conceive of experiments that they couldn’t do before. So for cardiotoxicity, we use both fixed cell assays, we use live cell assays and we integrate that data from both of those types of imaging with other analytical platforms. So you get what I call a holistic surveillance of what that drug is doing to a cell. And again, you know, doing a fixed cell imaging experiment will tell you something but doing a live cell imaging will often as I actually illustrated distinguish the mode of action between two drugs that would look the same. You know, and it’s all about there’s really no such thing as a completely safe drug, we’ll probably never have completely safe drugs but what we don’t want to do is to fail drugs for reasons, which aren’t real because then you know the general population is not getting the best drugs that they could have. So that’s kind of what drives me in what I do.
Sean Sanders: Excellent. And look out for a webinar from Science on that topic in
the future. It’s going to be coming. Dr. Turnbull, last word for you. Dr. Lynne Turnbull: I guess with live cell imaging, you’re seeing the sort of the time scale
that things happen and you can understand where you might break up an infection process for us because we study bacterial infections or microbial infections. So if you can understand how the process occurs better, you could understand where the stop points are where you might be able to intervene as we enter an era where antibiotics aren’t quite as useful as they used to be so we’re coming up with different strategies. So what live cell imaging does is gives us a better understanding of the basic process and then how we might lock it or if we do have a new novel drug or something that we want to try how it works and then which part of the process that stops it which you don’t always get from fixed imaging. So yeah, I guess it’s the same answer really.
Slide 83 Sean Sanders: Fantastic. Well unfortunately, we are out of time for this webinar so
on behalf of myself and our viewing audience, I wanted to thank our speakers for being with us today, Dr. Edward Campbell from Loyola University, Dr. Nick Thomas from GE Healthcare, and Dr. Lynne Turnbull from the University of Technology in Sydney, Australia.
Slide 84 Please go to the URL now at the bottom of your slide viewer to learn
more about resources related to today’s discussion, and look out for
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