of mice and men: a multidisciplinary approach to the pre-clinical … · 2018. 5. 8. · of mice...

Alzheimer’s Research UK Oxford Network Open Day – March 2018

Of mice and men: a multidisciplinary approach to the pre-clinical study of dementia

Dr Francesco Tamagnini, University of Reading

Hello everyone, how are you? Thank you for being here on a Saturday morning. Heroes. Thank you

very much for coming. Thank you very much for inviting me here today.

Today I will talk to you about my work and how I investigate dementia from a preclinical view. How I

try to understand what causes dementia, in a system that is controlled, and that is standardised, and

that is before the patient. How I try to use animal models and mathematical models to understand

what causes dementia. My talk will be divided into 3 parts.


The first part will be dedicated to how the brain works through electricity. I hope I will convince you,

that as the scientist, we the scientist don't use the combination between the brain and electricity to

create the monster, Frankenstein. No monster of Frankenstein in our lab.

Yet.

The second part will be about memory and dementia. Here, I've brought 2 examples that, to me,

represent what memory is and what dissolution of memory is. On the left you see the persistence of

memory by Salvador Dali. Which is now at the Museum of Modern Art in New York. You've got solid

shapes, and a landscape, and a figure that sleeps, and melting clocks, which represent how time is not


absolute. How time is fluid. On one of these watches there are the ants, these bugs that in Dali's

symbolic representation represented the progressive dissolution of memory.

At a distance of 20 years, Dali represents The Disintegration of the Persistence of Memory. As you can

see, information is still there, but somehow the components of the information are breaking down.

The more you go down to the horizon, the more information you lose.

Finally, I will talk about how the mechanisms in memory, and the loss of the same and

electrophysiology can be combined to better understand dementia and Alzheimer’s Disease.


Briefly about me, I come from the Republic of San Merino where I grew up. Then I did my PhD in

Neuroscience at the University of Bologna. Then I moved to Bristol, where I worked with Professor

Zafar Bashir. Then I got a job with Andy Randall to study neuronal correlates of memory and learning.

Trying to understand what happens in the single neuron cells in mouse models overexpressing certain

genes involved in the pathogenesis of Alzheimer's Disease. I then moved to the University of Exeter,

where I got my fellowship with the Alzheimer's Society I recently have been appointed lecturer at the

University of Reading.

Basically, what I've been doing in the last 10 years, was to stick electrodes into slices of brains to

understand the electrical activity. How the electrical activity works when it underlies the encoding of

new memory? How the electrical activity in the brain of mouse models with Alzheimer's Disease is

altered? If we can use this information to harness electrical properties that we used for developing

new therapies.


First of all, some questions. Something that's always fascinated me, was how this mass of disgusting

flesh, that is the brain, can generate something so beautiful like poetry, like mathematics, like art, like

our memories, the memories of our lifetime and the emotional content connected to that. The answer

is, we don't really know how that happens. But we are on the way to understanding it.

Even though the mind and the physiology have always been seen historically as two separate things.

Neuroscience does the opposite, Neuroscience tries to understand what are the pathological

processes that underlie the workings of the mind? Including memory. Memory is something that's

encoded by a specific set of operations at a neuronal level. The loss of memory, the progressive

cognitive decline can be related to a specific biological mechanism that we can identify, and possibly,

fix.


Everything has to start with a functional unit. Traditionally, the functional unit of the brain is the

neuron. The neuron is a very complicated machine itself. Without even considering the brain, the

neuron itself is a very complicated machine. I will not enter into the details of how a neuron works.

Probably, I don't even know how a neuron works completely. I will speak to it's surface. The plasma

membrane. As an electrophysiologist, a person that studies the electrical activity of the brain. I mainly

focus on this layer of fat that determines the surface of the neural brain. It's not just a layer of fat that

works as a border, to define a border. It also works as an electrical circuit.


I'm pretty sure most of you have seen the movie "The Matrix", right? As a matter of fact, our neurons

work like batteries. If you see the accumulation of positive and negative charges between the 2 sides

of the plasma membrane of the neurons. You see that actually the electrostatic potential is higher

than the electrostatic potential between the clouds and the ground during a thunderstorm. It contains

a lot of energy. This energy can be harnessed by artificial intelligence to overtake humanity, hopefully

not. Or it could be used by us to study the operations of the brain.

This electrostatic potential, as I will show you, is not static at all. It's something that fluctuates. The

fluctuations in this potential are used by the neuron as a way to process information, and even to

store information.


The first guy that had the idea, was another Italian from Bologna region, Luigi Galvani. Who noticed

that if you applied an electrical current to the legs of a frog, the legs would contract. There was a

coupling between electricity and a function. It's going to take 300 years, to understand that between

these experiments and the function of the neurons. we can identify specific mechanisms that underlie

the functioning of the brain.

In 1949, Hodgkin & Huxley, in Plymouth, by working on the squid. Just because, in Plymouth, at the

Centre for Marine Biology they had loads of them. A good scientist knows how to optimise their

resources. There were loads of squids. Squids are pretty cool because they've got these big axons.

These big neuronal processes that you can see under a microscope. What they did was to characterise


the electrical activity, the action potentials. These electrical spikes that you can see in the axons of the

squid.

How is this relevant for Alzheimer’s Disease and memory repair? Well it is, because in the brain the

neurons are connected to each other into networks. In a network, for the function to arise there’s

always a balance between excitation of electrical activity and inhibition of electrical activity. If

everything works fine, it's like in an orchestra. The inhibitor, the Maestro, orchestrates the excitement

of the neurons. If everything goes well, what you have is music. The workings of the mind. However,

if you give too many coffees to the instrumentalists, or a couple of bottles of chianti to the maestro

before the execution. In other words, if you excite the excitation or you inhibit the inhibition or both

things at the same time. What you have is a mess.

This is the electrical activity from a slice of brain treated with a drug, picrotoxin, that inhibits the

inhibition. What you have is epileptic like behaviour.


That leads us to chapter 2, how we understood the relationship between the different parts of the

brain and memory and learning. Wilder Penfield ran a series of experiments showing that by

stimulating electrically different parts of the brain, you could evolve different methods. He started to

hypothesise that there were single neurons that encoded for different memories.

For example, if the patient was remembering the grandmother when part of the brain was electrically

stimulated, he hypothesised that there was a "grandmother neuron". We do know that it's not like

that nowadays.


We do know that, thanks to the curious case of patient H.M. Patient H.M. had a rare case of bilateral,

drug resistant epilepsy. He had to have removal of both hippocampi. When he woke up from the

surgery he was perfectly fine. He remembered everything. However, he could not consolidate new

memory for the long term. The Dr had to introduce himself, or the nurses had to introduce themselves

every time, every day. But the patient was getting better in, for example, doing crosswords or doing

logic tests.

So they understood there were 2 kinds of memories. There was a memory of facts and events. He lost

the ability to consolidate that memory. There was also the memory of procedures, like playing an

instrument, or going on a bike. that was maintained.

This is very important because it inspired some nice movies. Also because it gives us alot to work on,

in terms of studying dementia.


I will not discuss in detail what dementia is, and how it is a great healthcare priority. Both for the

economical, and the human cost it has worldwide, and for the reason that there is no cure. There is

not a disease changing treatment, there is only a set of symptomatic treatments. This has been already

discussed in detail.

I would just like to talk briefly about Alzheimer's Disease, which is the main cause of dementia. I was

talking with some of you during the break, and someone asked me what the difference was between

familial and sporadic Alzheimer’s Disease.


Familial is the genetic form. What you inherit is a gene that almost certainly will give you the disease.

It's normally early onset. The sporadic form is sporadic because we don't really know what causes it.

When scientists don't know what causes it we call it sporadic. What we do know though, is that there

are genetic and environmental factors that increase the risk of getting Alzheimer's Disease. We still

don't know clearly what is the cause of the dementia. The link between these risk factors and the

disease itself.


Also, we do know from postmortem studies that there are 2 specific hallmarks. The accumulation of

beta amyloid plaques and intracellular tau tangles in the brain of people with Alzheimer's Disease.

This becomes important because by putting together different signs we also do know that epilepsy is

increased in people with Alzheimer's Disease. There is an increased proclivity of epilepsy with age in

people with Alzheimer’s Disease.

The question that I, as an electrophysiologist ask myself, is can I study the electrical properties of

neuronal cells in Alzheimer's Disease? Can these help me to cure Alzheimer’s Disease? Is this epilepsy

phenotype just a symptom, or something I can harness to actually cure the disease?


That leads us to chapter 3, where we're going to talk about how to use electrophysiology for studying

Alzheimer's Disease. Lots of people ask me, do you need animals, do you need mice? Can't you use

Electroencephalography?

We surely can. You can get a lot of information from Electroencephalography. There is only a problem

that the electrical activity is in the brain. Between the brain and your instrument there is the skull.

The skull doesn't completely shield the electrical activity, but it's like looking at a person through a

subtle glass. You can still see something. You can say about the height. This person is probably reading

a book and talking to a phone. Probably a male from the way he dresses, but you can't be sure. You

already see that you're unsure about certain details, If I ask you if that person has a mole on the left

side of his or her upper lip, there's no way you can get that level of detail of information through the

glass. There's only 1 way to get information, which is to break the glass. Which is to break the skull.

Which you can't do on a patient of course. That's the reason why we use animals in dementia research.


Basically what I do is to source genetically modified rodents that express dementia, Express genes

associated with human dementia. This is how they look in real life. Not like in teenage mutant ninja

turtles. What the brain looks like, is like this. They show hallmarks of Alzheimer's Disease. such as

amyloid plaques or neurofibrillary tangles.

What I do in my lab, is to humanely sacrifice these animals, remove the brain, cut slices and keep the

slices alive. The slices are perfused with a liquid that reproduces the liquid in which the brain is

suspended in the skull. Then with a very small electrode, and with a very small micropipette, I

approach the single cell and I break the patch of membrane between the pipette and the cell. That


allows me, not only to be in contact with the inside of the cell but also to measure the electrical activity

of the whole cell.

As we said, cells are like electrical circuits. If someone here likes to play around with electrical circuits,

we'll see that, as a matter of fact the neuron is like a simplified circuit. There is a capacitance

component there is a resistive component, the channels, and there are other channels that can open

and close depending on the electrical protection.

This is important because the properties of these cells can be represented mathematically and they

can be simulated in computers. With these experiments I can push the cell to fire those electrical


spikes which are necessary to encode information and memory. I can measure quantitatively, the

waveform properties of this electrical activity. I can see differences between mice that are "normal",

that are healthy, and mice that express genes associated with Alzheimer's Disease.

I've been working on this for the last 6 years of my life I've been working on different genetically

modified mice. What I persistently observed was this reduction in width of the electrical spikes. This

is not trivial. Because this means 2 things. That these animals can fire more of these spikes, because

these spikes are narrower. If they can fire more, it means that this could be a correlate of that epilepsy

that we observe in patients.


This is also interesting, because what generates the narrowing of the width of the action potential is

a specific protein of the plasma membrane which is the voltage gates potassium channel. It doesn't

matter if you remember the name, what matters is that it's a new target for a potential drug to rectify

this alteration, and possibly rectify the cognitive decline observed in people with Alzheimer’s Disease.

To sum up. Epilepsy is more frequent in people with Alzheimer’s Disease Epilepsy is caused by single

neuron altered excitability. We have consistently found changes in the action potential shape in the

neurons from Alzheimer's genetically modified mice.


The answers to the questions I asked at the beginning. Can we study the electrical properties of

neuronal cells in Alzheimer's Disease? Yes, with patch-clamp. The only condition. We need to do it in

animals. Can this help me to cure Alzheimer's Disease? Well, we certainly think so. If you want to know

more details that I can't give for time reasons I'm more than happy to answer your questions later on.

In the meanwhile, thank you very much for listening.

of mice and men: a multidisciplinary approach to the pre-clinical … · 2018. 5. 8. · of mice...

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