Episode 10: Serena Dudek, PhD

The following interview was conducted in-class, during the Spring 2021 session of Hidden Figures: Brain Science through Diversity, taught by Dr. Adema Ribic at the University of Virginia. What follows is an edited transcript of the interview, transcribed by Lucas Addis, Michael Kim, and Twindy Pham, who also drafted Dr. Dudek’s biography. The final editing was by Dr. Adema Ribic. The original recordings are available in Podcasts.

Serena M. Dudek has a Ph.D. from Brown University, where she worked with Dr. Mark Bear on long-term synaptic depression. She is currently Deputy Chief of the Neurobiology Laboratory, head of the Synaptic and Developmental Plasticity Group, and has a secondary appointment in the NIEHS Epigenetics and Stem Biology Laboratory. The Synaptic and Developmental Plasticity Group studies the regulation of synaptic effectiveness, its development in early childhood, and its lifetime effects. Using patch-clamp and extracellular recordings in brain slices, confocal microscopic imaging, and molecular and cellular techniques, the group intends to determine how the connections in the brain (synapses) change in response to neuronal activity, what regulates the critical periods of postnatal development when such plasticity is most robust, and why some brain regions are more plastic than others. This research should bring a better understanding of how environmental factors play a role in forming the circuitry of the brain so that the associated problems of brain disease caused by toxicant exposure can then begin to be addressed. Dr. Serena Dudek has a special interest in the regulation of plasticity in hippocampal CA2 and cortical layer IV.

Dr. Dudek, where do you come from?

I grew up in the shadow of Disneyland in Anaheim, California. We lived about a half an hour drive from the beach and I spent many summers going there most days. I would say it was an enriched environment and these days, I would now consider that I was quite privileged to have grown up with parents with advanced degrees. My father was an English Professor at Fullerton College and my mother was a clinical cytologist and medical technologist.

 Is your mom what initially got you interested in science?

I think yes that's what probably sparked an interest in biology. I do recall going with her to her lab a few times and poking a look at some cells. She would be looking for cancer cells- that's what a clinical cytologist does.

 Did you go to school in Anaheim?

Yes, and in high school I worked at Knott's Berry Farm, selling popcorn and ice cream. I was on the high school drill team. I also sewed a lot -maybe that was what developed my fine motor skills needed for hippocampal dissections. I liked math, but I really loved biology, and I do also recall an early interest in the brain.

 Did that help you decide where to go to college?

I do remember when I was thinking about different colleges to apply to that I did have an interest in the brain. I also recall that I was pre-med and wanting to be a doctor, but I was still interested in either fixing or working with disorders of the brain. That made my choice for college an obvious one: the University of California, Irvine was one of the first schools that had a department of psychobiology, which is what neuroscience was often called back then.

 Did you get involved with research as a student?

I was interested in Alzheimer's Disease and so I got a research position with an investigator named Tom Johnson-he worked with aging in nematodes. At the time, it was one of the few animals that people were using for genetic models of disease. In this case, they had bred worms that could live a lot longer. It turned out a lot of those had deficits in moving the pharynx and that a lot of the aging mutants were caloric restriction and so that’s why they would live long. However, my real interest was in neuroscience. It wasn’t until my junior year that I took a class in neuroscience as part of the biology core. Gary Lynch, who is a leader in the field, would teach the section on learning and memory in that class. He’d talk about synaptic plasticity as the mechanisms of learning and memory. I was just in awe. “They know that?! They know how neural synapses change with learning?!” Of course, I immediately wanted to work with Gary Lynch. He actually thought it was hilarious that my last name was Dudek, because he had had a previous postdoc, also by the name of Dudek, Ed Dudek, who has also been in the hippocampal field. Gary was a really big name in the field. But I think he thought it was funny that my last name was Dudek, so I was hired.

 How was it to work in Lynch’s lab?

That was also an enriched environment. Gary’s lab had 10-12 postdocs, 3-4 graduate students, and just a couple of us undergrads. I worked with a postdoc by the name of Pete Seubert.

 What kind of project did you work on?

We were doing biochemistry, working on the degradation of spectrin by calpains. Gary Lynch was one of the first to propose that the locus of the change for long-term potentiation was postsynaptic and that it was due to a spine shape change. Some of his work used electron microscopy to show that the spines do change and that it also involved the postsynaptic calcium. That really nailed the postsynaptic cell as an important player in the induction of long-term potentiation (LTP). We were also trying to get at how you would induce LTP pharmacologically. With Pete, I learned how to run gels, purify proteins and do large-scale calpain preps. We had a finding that calmodulin could enhance the degradation of spectrin by calpain. This was part of Gary Lynch's idea that to get LTP, you would need postsynaptic calcium, calcium would activate calpain, and these enzymes would break down the cytoskeleton to allow a spine change.

 You published a paper from this work, didn’t you?

Yes, 1987. It's always been interesting for me to follow this because just this year, there was a group that found an ataxia mutation in that exact spot where calmodulin binds that changes calpain sensitivity. This is one of the places where I'll plug basic science-a discovery that came from a lab working on learning and memory- and now we might have a mechanism for some of the ataxias in human populations. You never know where things are going to be relevant.

 Is Gary’s lab where you started doing electrophysiology?

Yes. After we wrapped up the biochemistry project, I learned hippocampal slice physiology. Gary wanted to be able to induce long-term potentiation in a slice, and then be able to run the slice (proteins) on a gel and see what biochemical changes were happening. The goal here was to be able to see if you could induce long-term potentiation with N-methyl-D-aspartate (NMDA) application. What I kept getting was long-term depression (LTD). We were pretty convinced that we were killing the slices though; we weren't thinking long-term depression at the time. But then, another postbac found that if they put in glycine and spermine, which also act on the NMDA receptors, they got this fast depression or loss of synaptic response, that then came back bigger. It was my role in the preliminary data generation that got me on that paper, and I was very happy to get credit for that.

 You went to graduate school immediately after that, right?

I went to graduate school at Brown and I joined the lab of Mark Bear. There were a number of papers we published and a part of those was being persistent but not being stupid about it.

 Can you elaborate on that?

At the time, we were working on trying to get a method to induce long-term depression -no one thought that LTD existed in the hippocampus. There was some evidence at the time that long-term depression could be induced in the cerebellum, but everybody just thought that the cerebellum is weird. At the same time, the theorists were saying, “No, no, no, if you're going to strengthen synapses, you have to be able to weaken them for the networks to behave”. It was really the neural network theorists that kept pushing on this (depression). Mark and I were working with Leon Cooper, who actually had a Nobel Prize for the theory of superconductivity, but had turned to neural network theory. They had a theory that would be explaining ocular dominance plasticity.

 Was this your foray into vision?

When I started in Mark's lab, using biochemistry we found that phosphoinositide turnover peaked at right about the same time that ocular dominance plasticity peaked. This didn't even have really a name at the time, but now we know that it was metabotropic glutamate receptor (mGluR) signaling. Those receptors didn't have any names yet. In fact, we had proposed a few that didn’t stick. It made perfect sense for us to think that would be a great mechanism for making LTD. In our heads, we were thinking: “Okay, yes, NMDA receptors, make LTP. mGluRs, you don't have the postsynaptic depolarization.” mGluR signaling would be highest at the peak of the critical period, which also made perfect sense because that is when a lot of synapse pruning takes place.

 We now know that idea didn’t pan out-what happened?

What I had to do to find a good way of inducing LTD in the hippocampus at that time. As I said, we didn't know if it existed or not, but Mark and I were really pretty sure it existed at least in the visual cortex. What we found then after many, many-well, after over a year of trying different methods-we found a way that you could decrease the size of the synaptic responses and it would stay down. We found that you could get LTD with a 15-minute long stimulation at one hertz, two hertz, or three hertz. When you started getting into five and 10 hertz, then it was much more likely to flip one way or the other. LTD was input specific and it was not a global reduction in synaptic transmission. It was also NMDA receptor dependent-it was both a disappointment and a relief when amino-5-phosphonovaleric acid (APV) blocked this phenomenon. Disappointing, because the title of my thesis was going to be on mGluRs and we were convinced that it would be dependent on mGluR’s.

 Was the length of the stimulation the reason you were worried that you were killing the slices initially?

Yes, and APV block meant that LTD wasn't an artifact of the electrical stimulation, or that at least I wasn't burning the slices because the stimulation was 15 minutes long. In fact, we had joint lab meetings with Leon Cooper's and his people were asking: “well, why didn't you match the time and change the frequency?” And I'm like: “yeah, I'm not going to do 15 minutes at 100 hertz.” You literally could fry the tissue. You'd pull your electrode up and the slice would stick to it, or you'd see bubbles coming at the end of the electrode. Even though we were working together with the theorists, there were things that you couldn't actually do: one would be negative numbers of action potentials. I couldn't pull that one off.

 Was this the data that supported the BCM theory?

Yes, we had varied the stimulation frequency, but kept the same number of pulses and got the data that supported their theory, the BCM theory.

 What did you do after graduation?

I continued having this interest in both ocular dominance plasticity and biochemistry, and I took a postdoc at the University of Alabama in Birmingham (UAB) because Mike Friedlander was there and he was a big name in the field of ocular dominance plasticity and visual thalamus. Gail Johnson was an assistant professor that worked with microtubule associate proteins. My hope was to do a joint postdoc with the two of them, but I wasn't quite able to put the two projects together. Gail and I were working on crosslinking of Tau by transaminases and in Mike’s lab we were looking at developmental downregulation of LTD in Layer IV. I also learned sharp intracellular recordings in his lab. Being in two labs is not something I’d advise to do on a regular basis-it can stretch you pretty thin.

 Did you go on the job market after that?

Yes, I was interviewing for jobs, but I had very little experience in public speaking. I think I went to a lot of my job interviews with my voice was shaking. I wasn't able to land a faculty position right out of my first postdoc. Mike was encouraging me at the time to go learn some new stuff.

 Did you do anything special to improve your public speaking?

I would recommend Toastmasters. It helped me a lot and I had the opportunity at NIH to do that.

 Where did you go after UAB?

Doug Fields was one of the few people working on synapse pruning at the neuromuscular junction. In his lab, I was trying to do paired recordings in culture and see if I can induce LTD to then look at synapses. I started to realize it was not working very well and I was going to need a different approach. At that time, I started getting interested in activity-dependent gene regulation. Richard Morris published their work supporting the idea of synaptic tagging, and I thought we might be able to actually test whether synapse to nucleus signals were required for the late phase of LTP. Right about this time, my LTP stopped working.

 You couldn’t induce it any more??

It's always funny when until it happens to you, but it was probably the water-it was so sad, very sad. This is my advice to you: work hard when things are going well in the lab, but also have a side project that works when other things are not going well. I was going crazy at the time, and that’s how I got interested in using immunocytochemistry to stain slices after they'd been stimulated. Using that, we were able to conclude that you don't really need a synapse to nucleus signal and that the action potentials were sufficient to drive this type of activity-dependent gene expression.

 Did you stay at the NIH as an independent investigator after that?

Yes, I started my own lab at the National Institute of Environmental Health Sciences in North Carolina. When I started my lab, I wanted to ask these questions: does LTD leads to synapse pruning, do you need a synapse to nucleus signal for the late phase of LTP, and, finally, what is controlling the critical period for plasticity? It turned out these are really very distinct projects that I’d love to go back to, but the CA2 has taken over the lab!

 How did you start working on CA2?

Always go to your departmental seminars. You never know where your good ideas are gonna come from. I was in a seminar where Doug Bayliss a slide with TREK1 potassium channel expression data. I saw this little bit of TREK1 in CA2 in that slide. We knew at the time that CA1 has plasticity throughout life, and that Layer IV in the visual cortex has plasticity limited to the critical period. Plasticity in CA1 is probably important for learning and memory. But what about CA2? Was it going to be more like Layer IV? Or was it more like CA1?

 What did you find?

We found that you can't induce LTP in CA1 in the way that you would induce LTP in CA1. It seems there are multiple redundant mechanisms regulating the synaptic plasticity in CA2, including the extracellular matrix, like what is going on in the visual cortex as well. CA2 also has a critical period that takes place around P9 to 11, and there's a lot more mGluR-dependent LTD in CA2 than CA1.

 What would you like to see changed about the field of neuroscience? Do you think the field is moving to recognize the contributions of women and minority scientists?

I would (overall) like to see the journals having less impact on what gets published. There is a big push for that now in that folks are posting their work on pre-print servers like BioRxiv.

I think we're moving in the direction of recognizing contributions from diverse groups. Obviously, this class is one, but I would add that I have been on the admissions committee at the University of North Carolina and I'm really pleased with the attention to wanting to see more about the person. This means going beyond grades and test scores. Now that we are paying attention to those things, we really have a great diverse group of students that are being admitted this year into the UNC graduate program. Getting more people in the pipeline is helps, but obviously, when you see that most of the graduate students are women and you're still not seeing the recognition, you realize it’s insufficient.

 Did you face any barriers in your research or throughout your scientific career, simply based on the fact that you are a woman?

 I would say that I've had every advantage, but I think that my recognition is just not what some of my peers get. We all have to consider how much of it is me, and how much of it is the field. Then you think, “well, how many groundbreaking studies do I have to do before I get credit? Is it 1 or 2, 3, 4, 5?”

Do I think this (lack of recognition) has impeded my career? I think in some ways, but my brother said it best. He said: “You have a lab? You're doing the research you want? What are you complaining about?”.  It’s so hard to tell though.

 Did you ever feel the need to adjust what you wanted to research or you felt that your funding kind of constricted you to a specific research line?

Overall, it seems like the people with the most freedom are the ones with the most grants, like the Howard Hughes labs. Trying new ideas requires having enough money to try some things on the side or enough personnel that you can put this person on this project that might not be on the main specific aims. I’m in the NIH intramural program and that program is really something (special). I think the Intramural program is more honest in its accounting: it’s like “ okay, you're good enough, we're gonna give you money, tell us every four years what you did with it”. We do have to propose a rough plan, but we have a lot of a lot more freedom to do what we want.

 So do you think you would want to go back to your pre-CA2 research sometime if you could?

It depends on who walks in the door. If I had an amazing postdoc candidate who had a lot of experience looking at synapse pruning, or very specific ideas on how they wanted to do something different, then I would be open to it.

 Would you consider your studies of CA2 your favorite?

I think CA2 has turned into my favorite. It's not every day you get to discover a new brain area that had been sitting unstudied for most of history.

 Are there any things that you're specifically emulating from your old mentors?

What I got from Gary Lynch is approaching things from different levels. It's not necessarily the best approach, it's just one that feels comfortable to be in. From Mark Bear I learned you can be successful and nice-you don't have to be a jerk. What I appreciated about Mike Friedlander was that he left me alone. If I have a good fellow with independent ideas, I just tell them to go ahead. My preference is not to hold people’s hand. If somebody has to open a manual, I prefer that it not be me, it’s going to be you. I have high expectations for my people. You don’t want me telling you what to do, because independence is something you should be wanting to learn.  

Drs Serena Dudek and Mark Bear in 1992

 This interview was conducted during the Spring Session of UVA’s Hidden Figures class in 2021. Class roster:

Addis, Lucas; Ahmed, Anushey; Akram, Amman; Alam, Maisha; Anderson, Sydney; Bhatia, Rhianna; Bonagiri, Paavan; Booth, Morgan; Clarke, Casey; Fisher, Grayson; Gandhi, Shreyal; Hossain, Mohammed; Rayan; Jensen, Kate; Kim, Michael; Lahham, Zina; Lea-Smith, Kori; Leffler, Schuyler; Leventhal, Emily; Mehfoud, Matthew; Morrisroe, Erin; Pham, Twindy; Sajonia, Isabelle; Sisk, Emma; Suram, Ananya; Wang, Jessica Beth; Webster, Tessa; Wilson, Gina. TA: McDonald, Amalia. Instructor: Ribic, Adema, PhD.