Speaker 1: Welcome to the Salk Institute’s “Where Cures Begin” podcast, where scientists talk about breakthrough discoveries with your hosts, Allie Akmal and Brittany Fair.

Brittany Fair: Dr. Allen investigates how the brain normally forms and functions and goes awry in different diseases such as autism and Alzheimer’s disease.

Brittany Fair: Most research on the brain focuses on neurons, but Dr. Allen takes a unique approach by asking how non-neuronal cells in the brain called astrocytes regulate brain function.

Brittany Fair: Dr. Allen, can you tell us a little bit about what you study here at Salk?

Nicola Allen: So, in my lab, we really want to understand your brain, and when we’re thinking about the brain, we want to understand how it is that this amazing organ forms during development, how it functions throughout life, and how it can go wrong in many different diseases. So, if you think about your brain, you have billions of neurons. These are electrically excitable cells that communicate with each other.

Brittany Fair: Wow, billions.

Nicola Allen: Billions, yep, and they’re encoding all your thoughts and actions. And the way they communicate is they make special connections with each other called synapses, and actually, your human brain has trillions of synapses. So, billions of neurons and trillions of connections. Imagine when the brain is forming, how it manages for the right neuron to find the right partner, so your brain can function properly throughout life is a really complex question.

Brittany Fair: It’s like each neuron is reaching its arms out, searching for other neurons to hold hands and make connections.

Brittany Fair: What approach are you taking to study neurodevelopment?

Nicola Allen: We know we have billions of neurons, but what most people don’t realize is that in addition to these neurons, there’s another type of cells called glia, and there’s actually an equal number of glial cells in your brain as there are neurons. So, in my lab we work on one of these types of glial cells called an astrocyte. They’re called astrocytes because of their shape. They look like stars. They have many, many processes that go out and touch the neurons, and we’ve shown that actually that these astrocytes are talking to the neurons and telling them how to connect with each other, and then also instructing how the connections function.

Brittany Fair: What is one of the main differences between an astrocyte and a neuron?

Nicola Allen: So neurons, these are the cells that use electrical activity to communicate with each other. So they’re the cells that, when you have a thought or you want to do something or perform an action, these are the cells that are carrying out that function, but they can’t do it on their own. So, the astrocytes they interact with, they don’t have this electrical activity, this electrical signaling, but they do share the same chemical signaling that neurons use. So actually when neurons signal to each other using chemicals such as neuro-transmitters, the astrocytes also sense and respond to this, and then they can talk back to the neurons and really control on a more global level how the neurons are functioning.

Brittany Fair: And I know that one of the things that your lab has found is that different proteins are also being secreted and used for communication either between astrocytes. Or, is it astrocyte to neuron communication?

Nicola Allen: Right. So, most of the work we’ve done so far is looking at astrocyte to neuron communication, but you can imagine in the future, thinking how these cells signal to each other will be just as important.

Nicola Allen: We found one signal, a protein called glypican 4 that in the young brain is really instructing neurons to make the first connections.

Brittany Fair: Glypican 4 is a protein that may play a role in the control of cell division and growth regulation in the central nervous system.

Nicola Allen: So, when the neurons are just forming and looking to find the right partner, this is a signal from astrocytes that’s telling them now’s the right place and the right time, and you should start communicating.

Nicola Allen: Then recently, we identified a second protein, something that comes on in the adult brain, called Chrdl1, and this is doing something different. So, this is acting, once these connections already exist, it’s making them stable and mature and saying, okay, you’re in the right place, so now you’re going to stay here and be a functioning connection throughout life.

Brittany Fair: Chrdl1 basically acts to tell the brain that it has become an adult and to stop acting like an adolescent.

Nicola Allen: So, we’re excited by this because actually on the flip side, what happens is by stabilizing that connection, what you’ve actually done is then inhibited plasticity.

Brittany Fair: What she means by plasticity is that the brain isn’t static and as you age, the brain has this incredible ability to continue to create new neurons and new connections between those neurons.

Nicola Allen: So, you are now stopping the neuron from remodeling even if it might want to. And what we actually found is if you get rid of this signal in the brain, then you now have plasticity present throughout life. So we’re very interested in thinking in future, how we can use this knowledge of specific signals that either induce a new synapse or stabilize a synapse, how we could think about using those as potential therapies in different disorders where synapses don’t work properly.

Brittany Fair: The protein Chrdl1 could be responsible for some of these disorders?

Nicola Allen: Sí.

Brittany Fair: So how do you study something like protein signaling in astrocytes in the brain?

Nicola Allen: So, we simplify things. We put neurons and astrocytes in a dish. We can grow them outside the body. And then we can look at what’s the function of these neurons on their own or these astrocytes on their own. So, with the astrocytes, we can grow them on their own, and what we actually do is we can collect everything that they release into the media that they’re growing in. We call that the secretome. Then actually working here with our mass spectrometry colleagues in the core, we can then actually analyze and detect every single protein that’s being released.

Brittany Fair: To better understand how the Allen Lab grows astrocytes, we met up with one of Dr. Allen’s postdoctoral fellows, Dr. Elena Blanco Suárez for a tour of the lab.

Elena Blanco Suárez: Welcome to the Allen Lab. So, we can go into the electrophysiology room. This is quite specific to neuroscience labs like ours, and basically what they do here is to study the electrical features of neurons. Neurons can communicate through electrical signals, so sometimes we want to measure that.

Brittany Fair: And how does this electrophysiology setup help inform scientists about how neurons communicate with one another?

Elena Blanco Suárez: So, then electrophysiologist can read all the signals that they get from their neurons. So, they can measure current, voltage, they measure the amplitude of the signal, the frequency of those signals, and depending on the conditions that these neurons are under in your experiment, those different characteristics will vary.

Brittany Fair: So, now we’re coming into Dr. Blanco Suárez’s office and we’re going to look at some of the pictures she’s taken of the astrocytes that she studies.

Elena Blanco Suárez: So, this image, this is all the layers from the cortex, from the visual cortex. So, what I was trying to do was to find a nice marker for astrocytes. So, we’ve been testing different labels here, different tags, and that makes our astrocytes fluorescent.

Brittany Fair: This literally looks like a picture of a galaxy of stars and you’ve just put on tiny little X’s on the stars. Did you manually put these on?

Elena Blanco Suárez: Yes. These particular experiments been manual. So it requires a lot of patience.

Brittany Fair: What does this tell you? Why do you want to have this information?

Elena Blanco Suárez: Because at the moment we don’t have any grade markers for astrocytes and people are trying to work towards finding the best ones. I can show you where we took these images in the microscope room.

Brittany Fair: Oh, fantastic!

Elena Blanco Suárez: This is our epifluorescence microscope. We put these labels on the brain slides to tag different proteins in the cells. We do this with fluorescent markers. We can see on the screen there’s one image just taken from this brain slice.

Brittany Fair: It looks like a bunch of sex to me.

Elena Blanco Suárez: Those are neurons, body of the neurons, so that’s why you only see the [inaudible 00:08:44] and not all the dendrites or axons coming out, because it only tags protein that’s in mainly in the neuronal body.

Brittany Fair: By the time you’re coming into the room to use the microscope and actually look at this brain slice, this is typically at the end of the experiment, right?

Elena Blanco Suárez: Sí.

Brittany Fair: Are you excited to come into this room and see what you have?

Elena Blanco Suárez: Yeah, but it can be also very frustrating because you can come and nothing is in there and there are so many different steps that could have failed and you have to try and figure it out. You have to go back and think, okay, what went wrong that now looking at this brain slice and it’s not fluorescent. I cannot see anything. What happened?

Brittany Fair: On the tour we also met with Isabelle Salas. She’s a postdoctoral researcher in the Allen Lab. Dr. Salas was examining an image of a brain on a computer screen.

Isabelle Salas: So, this is the hippocampus. That is a region in the brain that is important for learning and memory and is very early affected in Alzheimer’s disease. And then we’re going to sequence these RNA to see their changes in the expression of the genes in an Alzheimer’s model versus the controls.

Brittany Fair: Dr. Salas hopes to uncover new pathways and genes that are affected in Alzheimer’s.

Brittany Fair: Well thank you so much for the tour of the Allen Lab Dr. Blanco Suárez.

Elena Blanco Suárez: Gracias.

Brittany Fair: An absolute pleasure and super interesting to see where all this work is conducted.

Brittany Fair: Neurodegeneration is one of the main focuses of the Allen Lab.

Nicola Allen: Yeah, so looking at the role of astrocytes and Alzheimer’s and aging in a few different ways. In the aging brain, astrocytes are changing and they’re actually turning on pathways that in the young brain would cause the loss of synapses. So, we think they’re partly responsible for the loss of synaptic function that seen just in normal aging. So, based on this we’re now already interested in asking, well is this also happening in neurodegeneration? Is this something that’s also happening in Alzheimer’s disease? So, we’re really asking are these kind of changes in astrocytes with age, part of what allows dementia to progress in aging? Are they active players in synapse loss? Can we do something useful with that in aging or neurogeneration? So, could we reverse or prevent some of this synapse loss?

Brittany Fair: Alzheimer’s disease affects nearly 3 million people in the United States each year. And that number is growing.

Brittany Fair: Normally when we think about Alzheimer’s disease, you think about amyloid beta or tau, so this astrocyte perspective or angle seems very novel.

Nicola Allen: Some of the genetic risk is, for Alzheimer’s disease, has actually been showing that, not just astrocytes, but also microglia or another glial cell type present in the brain could really be some of the cells underpinning. Some of the changes that are going on. So, I think it’s an exciting time to be in this research area because people are realizing, obviously, the amyloid beta and tau is important, but perhaps there are other pathways we could try and target to try and have some help in this disease.

Brittany Fair: And it’s also interesting because when you, when you just think about the brain, I think a word that comes to mind first is probably neuron. So if we have equal amounts of glia cells, namely astrocytes in this research, why have glial cells been ignored?

Nicola Allen: So, I think one of the reasons is just, I mean neurons are exciting. They’re great to study. You can actually record their activity in real time. So, it’s really amazing. You can really see what’s going on. They’re a direct readout of the function of the brain. So, part of it, I think, has been our inability to measure those same things in astrocytes.

Nicola Allen: So, the lack of tools that are available for us to really monitor what these cells were doing because they don’t have this electrical activity. It looked like they weren’t doing anything but it turns out when you start looking at them, one of our colleagues, Axel Nimmerjahn, here at Salk, he can monitor the activity of astrocytes in real time by looking at another signal, the increase in calcium levels. So, the work from labs like his is now showing actually these cells are involved in these ongoing neuronal activity processes. It’s just on a slower scale. So I think once we begin to think of them as separate cell types, as they are, and come up with tools to actually monitor them specifically, then we’re going to be getting a lot more information about what they’re doing in the brain. There’s a lot to be explored and I think Salk’s a great place for it because we have a number of different groups who are working in this area.

Brittany Fair: Beyond your research, I just wanted to learn a little bit more about you and your career to becoming a neuroscientist.

Brittany Fair: So, did you always know you wanted to be a neuroscientist?

Nicola Allen: I always liked biology. Not necessarily neuroscience, but I always enjoyed biology in high school. And then at university, same thing, biology, and then I became very interested in neuroscience and immunology just as, I think, two of the areas that still have a lot to be learned, essentially, so that’s what I focused on.

Nicola Allen: I think my favorite part of being a scientist in general is just the discovery. So, that you can come up with ideas, have a hypothesis, go in and test it, then get an answer. And every now and then you’ve got a big breakthrough and it’s very exciting.

Nicola Allen: When we first discovered the glypican protein having an effect on synapses, that was after years of work. But when you actually finally get that breakthrough, then that’s a great day and it then leads on to many, many findings.

Brittany Fair: Do you have any advice for aspiring young scientists?

Nicola Allen: I think you have to make sure you’re doing something you enjoy. You just talked about part of the thing that keeps you going as a scientist is the excitement because it can take a long time before you have a breakthrough. So, I think perseverance is important and also having that, always having that bigger goal in mind. So think about why you’re doing this, what drives you, and making sure it motivates you.

Brittany Fair: So, how long does one of your typical research projects take from thinking about the idea to actually publishing an article?

Nicola Allen: So, each paper in the lab it probably takes four or five years from the beginning to the final publication. So yeah, you do have to persevere because within that there are a few moments of Eureka and a breakthrough, but then a lot of the rest of it is just making sure you’re right.

Brittany Fair: When you come across one of these more exciting findings, do you find yourself experiencing awe in that moment?

Nicola Allen: I don’t know about awe it, but definitely “hurray!”.

Brittany Fair: And you talked a little bit about the future of your work, but what’s a more broad overall future for astrocyte research?

Nicola Allen: I think it’s a great time to be in this area because more and more neuroscientists are realizing that if you’re going to understand the brain fully, be it in development or an adult function or in disease, then you’ve got to think about the whole brain. So, all the cells that the neurons interact with. So, I think for us it’s exciting to be in this area looking at astrocytes because now we’re just really thinking about how we can use these cells therapeutically is going to be really important.

Brittany Fair: Thanks for joining us today, Dr. Allen. It was a pleasure having you. It was great to be here. Join us next time for more cutting edge Salk science.
At Salk, world renowned scientists work together to explore big, bold ideas from cancer to Alzheimer’s, aging to climate change. “Where Cures Begin” is a production of the Salk Institute’s Office of Communications.