The C9orf72 mystery begins to unravel even more of its secrets

The C9orf72 mystery begins to unravel even more of its secrets

In 2011 an international team of scientists, including three MND Association-funded researchers, identified the elusive C9orf72 gene located on Chromosome 9. Since this ground-breaking discovery, researchers from around the world have been trying to find a way to open-up and reveal more about this MND-causing gene.

Determined to get inside and unravel the secrets behind C9orf72, the Association is funding a number of new and exciting research projects to help solve the mystery. These projects look at, not one, but a number of different aspects to try and understand more about C9orf72.

In order to solve this mystery our C9orf72 researchers are following the clues using zebrafish, mice, flies and DNA samples.

How the C9orf72 MND mystery began

We each contain copies of 23 pairs of chromosomes, including the X and Y sex chromosomes. These chromosomes contain thousands of genes that portray our characteristics such as hair and eye colour. These genes are made up of DNA which can either be ‘coding’ to make a protein, or ‘non-coding’. For details of how genes make a protein see our earlier blog post.

Before C9orf72 was identified researchers had focused on an area on Chromosome 9 that appeared to be connected with both the rare inherited form of MND and the related neurodegenerative disease frontotemporal dementia (FTD).

Using a number of cutting-edge techniques the international team isolated the C9orf72 gene expanded GGGGCC hexanucleotide repeat as being a crucial player in both inherited MND and FTD. Not only did the researchers find a link between MND and FTD, they also found that C9orf72 was found in approximately 40% of cases of inherited MND (where there is a strong family history). This means that we now know 70% of the genes that cause the rare inherited form of MND. For more details on C9orf72 see our earlier blog post.

For more information on inherited MND please see our website.

So, researchers found C9orf72. The next question was ‘What does it do? Is the gene defect repeat itself, or the protein it makes responsible for causing MND? And what goes wrong in MND?’

Following the clues to solve C9orf72

Two recent research clues

Since 2011 researchers have been trying to answer these questions and find out more about C9orf72. This has led to a dramatic increase in research, including two papers published in February and March this year!

Prof Christian Haass (Munich Centre for Neurosciences, Germany), who recently presented at our 23rd International Symposium on ALS/MND in December 2012, published a paper on the 7 February in the journal Science. The second paper lead by Prof Leonard Petrucelli (Mayo Clinic, USA) was published open access in the journal Neuron on the 20 February.

In a big surprise, both researchers found that the presumed ‘non-coding’ C9orf72 GGGGCC repeat expansion actually made a protein. Normally these ‘non-coding’ regions do not make proteins so this was a very big surprise indeed!

The researchers found that these proteins formed large clumps in the brains, and throughout the central nervous system (CNS), of people with C9orf72 MND and/or FTD. Importantly, they did not find these clumps in healthy individuals or those with other neurological disorders.

It is currently unknown as to whether these protein clumps are involved in MND and/or FTD, but they may be a potential biomarker or a therapeutic target in this most common type of MND. The next step is for the researchers to find out whether these proteins actually cause MND and/or FTD.

Finding more evidence to piece together the clues

In addition to these two papers looking into the mystery behind C9orf72, the Association is funding some exciting new research projects, each looking at different things, to further understand more about this gene.

Dr Johnathan Cooper-Knock, MRC/MND Association Lady Edith Wolfson Clinical Research Fellow

Dr Johnathan Cooper-Knock (Sheffield Institute for Translational Neuroscience, UK) is already trying to identify how C9orf72 causes MND by utilising a genetic technique known as gene expression profiling. He is using samples from the Association’s DNA bank which are positive for the C9orf72 genetic mistake. Gene expression profiling is a technique which allows researchers to understand how the activity of genes contributes towards causing MND. (Traditional genetic studies are designed to look at which genes are affected, rather than their activity – ie when and how). Read more about Johnathan’s project here.

Developing new disease models enables us to understand the causes of MND and to test new therapies. One way to understand the function of C9orf72 and how this goes wrong in MND is to create a model. Our current research projects are developing new C9orf72 models in flies, mice and zebrafish.

Dr Frank Hirth (Kings College London, UK) will be producing a fly model, Dr Javier Alegre Abarrategui (University of Oxford) will be making a mouse model and Dr Andrew Grierson (University of Sheffield, UK) will be creating a zebrafish model.

All of these models aim to understand the function of C9orf72 and what goes wrong. The researchers hope to study what happens in MND and how this occurs by looking at behaviour and what happens when C9orf72 is ‘switched’ on and off. For more information about these exciting research projects please see our website.

Solving the mystery

All of our C9orf72 Association-funded research projects are using different approaches to look at C9orf72 in different ways as we are still unsure whether the protein or the repeat is the problem. From mice to flies all of these research projects together are helping to solve the mystery of C9orf72 and MND.

With the proteins formed by C9orf72 likely to be a potential biomarker or therapeutic target the two recent papers are adding to the growing number of clues, pointing researchers in the right direction to unravelling and solving the secrets of C9orf72.

References:

Mori, K. et al. The C9orf72 GGGGCC Repeat Is Translated into Aggregating Dipeptide-Repeat Proteins in FTLD/ALS. Science. 339(6125): 1335-1338. 2013 DOI: 10.1126/science.1232927

Ash, P. E. A. et al. Unconventional Translation of C9ORF72 GGGGCC Expansion Generates Insoluble Polypeptides Specific to c9FTD/ALS. Neuron. 77(4): 639-646. 2013 DOI: 10.1016/j.neuron.2013.02.004

MND stem cell study identifies TDP-43 astrocytes as not toxic to motor neurones

Funded by the MND Association, international researchers have used stem cell technology to learn more about the relationship between motor neurones and their support cells.

These findings highlight the potential of stem cell technology as a tool to create new human ‘in a dish’ cellular models of disease to learn more about the causes of MND.

The research group included MND Association funded researchers Prof Siddharthan Chandran and Sir Prof Ian Wilmut from University of Edinburgh, Prof Chris Shaw from King’s College London and Prof Tom Maniatis from Columbia University in America.

This important finding was published in the scientific journal PNAS on 11 February 2013. This new finding follows on from previous work published by this research group in 2012 where they demonstrated the proof of principle of creating human motor neurones with MND in a dish.

Why we need an astrocyte model of MND

Astrocytes, so called because of their star-like appearance, normally act as neurone support cells to nourish and protect motor neurones. They act with motor neurones to ensure that they can continue to function.

From previous studies, we know that when these cells begin to dysfunction, they can become toxic to motor neurones to contribute to MND. Finding out why astrocytes can cause motor neurones to degenerate is an issue of ongoing debate – we recently gave an update on this from the International Symposium.

Being able to grow human astrocytes in a laboratory dish is of importance to be able to learn more about the relationship between astrocytes and motor neurones in MND.

Creating human astrocytes in a dish

Using cutting-edge stem cell technology, the research group reprogrammed skin cells into astrocytes in a laboratory dish. The skin cells were donated by people with MND who have a family history of the disease caused by known mistakes in a gene called TDP-43.

Led by Prof Chandran and colleagues, the research group aimed to identify whether these cells would develop the ‘hallmarks’ of MND in a laboratory dish.

By studying the characteristics of these human astrocytes with faults in the TDP-43 gene, the research group identified that they shared the same qualities as cells affected by MND. The astrocytes had increased levels of TDP-43 found in areas where it isn’t usually found – outside of the control centre of the cell. They also found that the astrocytes didn’t survive as long as astrocytes created from skin cells of people that didn’t have MND.

This means that the human astrocytes created by Prof Chandran and colleagues using stem cell technology develop MND-like characteristics. This new model can be used to study how motor neurones develop the disease in a system that is directly relevant to people living with MND.

Answering whether faulty astrocytes affect healthy motor neurones

The next question that this research group wanted to answer was whether these faulty astrocytes had an effect on healthy motor neurones.

By growing faulty TDP-43 astrocytes with healthy motor neurones, the research group identified that the survival of motor neurones was not adversely affected.

This was surprising as other research groups have shown that when astrocytes have faults in the SOD1 gene (which cause one in five cases of MND with a family history) that motor neurones are compromised, even if the motor neurones were originally healthy.

TDP-43 is found within tangled lumps in over 90% of cases of MND (irrespective of whether it was caused by an inherited genetic mistake). However, when MND is caused by SOD1, TDP-43 is not found in these tangled lumps. This important difference could be leading to the key difference in whether astrocytes become toxic to contribute to causing MND.

These findings will of course need to be verified by an independent research group to determine that they are valid, but the results suggests that SOD1 and TDP-43 could be causing havoc in motor neurones in slightly different ways, both avenues leading to MND.

Our Director of Research Development, Dr Brian Dickie comments: “From a therapeutic perspective this is important because it means that specific treatments targeted at astrocytes may only be relevant and effective, in specific subsets of patients who will have to be carefully selected for drug trials.”

References:

Our news release on this finding.

March 2012 finding: Association-funded stem cell study achieves milestone

Serio A et al. Astrocyte pathology and the absence of non-cell autonomy in an induced pluripotent stem cell model of TDP-43 proteinopathy. PNAS 2013

Zebrafish show that ‘connector neurons’ are the key in early stages of MND

A recent study by Motor Neurone Disease Association-funded researcher Dr Tennore Ramesh from the Sheffield Institute for Translational Neuroscience (SITraN) has shown that even before the symptoms of MND occur, at the earliest stages of the disease, ‘connector neurones’ known as interneurons are already becoming damaged in the zebrafish.

Dr Tennore Ramesh

Zebrafish are ideal models for helping scientists understand what happens in MND. Unlike mice and fly models, zebrafish have transparent embryos which enable scientists to get a unique view of the developing neurones under a microscope! Scientists can also look at disease progression in adult zebrafish by looking at muscle strength and measuring their progress swimming against a current.

Not only are zebrafish useful for helping scientists understand what happens in MND, they are also an ideal drug screening model. Zebrafish and humans are more similar than you may think (see Kelly’s post) and potential new MND drugs can be screened quickly. Looking at how MND progresses in the zebrafish, before symptoms appear, can help us gain a better understanding of what causes the disease.

Motorways, dual carriage ways and slip roads

No, I’m not writing about travel alerts or the latest roads disruptions due to flooding or snow. In fact, these road systems happen to be a perfect example of what interneurons are, how they relate to motor neurones and what goes wrong in MND.

Our body consists of two types of motor neurones, which are known as upper and lower motor neurones. The upper motor neurones are found in the motor region of our brain and connect to the spinal cord. The lower motor neurones are found between the upper motor neurones in the spinal cord and connect to the muscles (e.g. in the arms and legs). Interneurons are the vital connections between the upper and lower motor neurones.

Interneurons are the ‘slip roads’ between upper and lower motor neurons

When a signal is sent from our brain to bend an arm it starts by travelling down an upper motor neurone. The signal then travels to a lower motor neurone via an interneuron. When the signal from the lower motor neurone reaches the muscle in our arm it causes the muscle to contract and bend.

In MND these upper and lower motor neurones become damaged and they are unable to transport the nerve signal from the brain to the muscle in our arm. This means we are unable to contract and bend, even though the brain is telling it to.

­­­In our road system scenario the upper motor neurones are the motorways (e.g. the M1), and the lower motor neurones are the dual carriageways that link the motorways to nearby towns (e.g. the A38). In order for an upper motor neurone to send a signal (e.g. a car) to a lower motor neurone it needs to go via an interneuron, which in our road system scenario is a ‘slip road’ – making these interneurons vital connections between motor neurones.

This study has given us a better understanding of what happens in MND at the early stages of the disease (before symptoms occur). The researchers found that interneurons became damaged before the motor neurones themselves. Therefore this shows that interneurons are important in the early stages of the disease and scientists can begin to look at ways of preventing interneuron damage to see whether this has an effect on MND.

Adding more evidence to the puzzle

This study showed that, in zebrafish, interneurons are involved in the early stages of MND, which adds further evidence to previous work by another MND Association-funded researcher. Dr. Martin Turner (Oxford) also found damaged interneurons at the early stages of the disease before symptoms of MND occur in humans, with other studies showing interneuron damage in SOD1 mice models.

The next step would be to look at ways of preventing these interneurons from becoming damaged, to see whether this has any effect on the progression of MND.

This research is the first article we have paid to be made available Open Access, so that it is freely accessible to all. The article was published online in the prestigious journal ANNALS of Neurology on the 31 December 2012.

Paper reference:

McGown, A. et al. Early Interneuron Dysfunction in ALS: Insights from a mutant sod1 Zebrafish Model. ANNALS of Neurology 2012 DOI: 10.1002/ana.23780 http://onlinelibrary.wiley.com/doi/10.1002/ana.23780/abstract

Mastering Pac-Man

Growing up in a seaside town in the 1980s led to me spending a lot of my “formative years” in the local amusement arcades, playing iconic video games like Space Invaders (at which I was average) and Asteroids  (I was the kid to beat!). One game I never got the hang of was Pac Man, where you had to guide a munching yellow ball around a maze eating up lots of dots. I even bought a book ‘Mastering Pac Man’ which didn’t help much – I was just plain rubbish!

Dr Brian Dickie and Pac Man

Talking about rubbish, fast forward 30 years and Prof Anne Simondsen from The University of Oslo is on the platform in Chicago describing the ways in which neurones deal with their cellular rubbish, such as poorly manufactured or damaged proteins.

Much as the dots are gobbled up by Pac Man, so cells employ a couple of basic ways to dispose of and recycle damaged proteins. One is a process called proteasomal degradation, which has been discussed on this website before by one of our guest bloggers, Prof John Mayer. However, some proteins, especially protein aggregates, are a bit too large and tough to be broken down by the proteasome, but they can be degraded by another process called autophagy – which can literally be translated as ‘self-eating’.

Prof Simondsen explained how aggregated proteins and even larger cellular structures can be packaged up for destruction by being encapsulated within membranes, forming structures called autophagosomes. These in turn seek out a structure called the lysosome, which contains digestive enzymes which break down the protein rubbish and keep the cell ‘spick and span’.

Using studies involving fruit fly models (a favourite model for cell biologists) she showed that the autophagy process declines with age, which is unfortunate because protein damage tends to increase with age. It was therefore no surprise that the level of autophagy in the brain was directly associated with the accumulation of protein ‘inclusions’, the health of neurones and the life expectancy of the flies.

Much of the evidence supporting a role for autophagy in neurodegeneration comes from the field of Huntington’s disease. Prof Simondsen explained how a particular mutated protein – called huntingdin – accumulates in the dying neurones and is a classic pathological hallmark of the disease. She demonstrated that autophagy normally plays a central role in the disposal of damaged huntingdin, but the system simply cannot cope with the amount of damaged protein, which starts to accumulate and literally ‘gunge up’ the cell. However, by stimulating the manufacture of additional autophagy machinery, the amount of aggregated protein can be reduced, helping to protect the neurones. This has so far only been shown in simple lab models of Huntington’s disease, but the encouraging results mean that further development to try and develop a treatment is underway.

So, could a similar approach be useful in other neurodegenerative diseases such as MND? Certainly, for some types of MND, such as those linked to a rare gene mutation called CHMP2B, it appears that a component of the autophagic machinery is impaired, which leads to protein build-up in cell models.

Dr Eiichi Tokada (Umea University, Sweden) provided further evidence that autophagy plays a role in disease progression in the SOD1 form of MND. By switching off a crucial component of the autophagy machinery, the disease progression in SOD1 mice was accelerated and their lifespan shortened. In addition, when he examined the spinal cords of the mice, he saw an increased presence of the characteristic SOD1 protein aggregates – a pathological hallmark of the disease.

Dr Faisal Fecto (Northwestern University, USA) provided evidence from a third genetic cause of MND. He showed how mutations in the Ubiquilin 2 gene disrupt the autophagy pathway by stopping the autophagosomes from linking up with the lysosomes.

So, it certainly seems that autophagy has a role to play in some of the rarer familial froms of MND. It remains to be seen to what extent it is involved in MND more generally, but it may mean that the potential treatment strategies being developed for Huntington’s disease may offer future opportunities for MND as well.

Our International Symposium website news stories:

International Symposium closes in Chicago

International Symposium focuses on clinical trials

International Symposium focuses on carer and family support

International Symposium begins in Chicago

Researchers unite at our International Symposium on MND

After you’ve finished reading the symposium articles that interest you, we’d be grateful if you could spare a few minutes to fill in our short online survey on our symposium reporting. Your comments really are useful and allow us to continually improve our symposium reporting. surveymonkey.com/s/alssymp

Of yeast and men: reducing toxic effects of TDP-43 as a potential treatment for MND

A collaborative American research group, led by Prof Aaron Gitler from Stanford University School of Medicine in California, has identified a potential therapeutic target for MND using yeast.

The toxic activity of the MND-linked protein TDP-43 was suppressed when a gene called DBR1 was deleted from yeast and mammal cells.

The study marks the first steps in the identification of a treatment that can target TDP-43, which is found to clump together in over 90% of cases of MND.

The study was published in the prestigious journal Nature Genetics.

Toxic tangle of TDP-43

To develop effective treatments for MND, we need to find ways of targeting the systems that go wrong to cause the disease.

One hallmark of MND is the accumulation of tangled lumps of protein – including TDP-43.

For years, researchers didn’t know whether the clumps of TDP-43 they could see was a by-product of MND, or a cause of the disease. That was of course, until researchers identified that mistakes in the TDP-43 gene can cause inherited MND in 2008. Since then, researchers have been busy creating new disease models to learn more about how TDP-43 can cause MND.

So far, at least 400 studies have been published to better understand TDP-43 in MND (search terms ALS, FTD, variations of TDP-43 on Pubmed).

Yet we still don’t know whether TDP-43 is doing harm by being over active or under active. We do however know that it’s found in the ‘factory floor’ of the cell, called the cytoplasm, when it’s normally found in the control centre. Using this information, it’s possible to focus on therapies that decrease the toxic effect of TDP-43 rather than to increase or decrease the amount of TDP-43.

This is exactly what a collaborative American research group, led by Prof Aaron Gitler has done.

Using yeast, Prof Gitler and colleagues performed two unbiased genetic screens in different laboratories using different techniques. By doing this, they verified a list of genes that can modify the effects of TDP-43 when deleted – by either enhancing the toxic effect or suppressing it.

Out of the list of resulting modifiers, the research group chose to investigate a suppressor of TDP-43 toxicity, a gene called DBR1.

DBR1

Far from a classic Aston Martin sports racing car (also named DBR1), DBR1 in biological terms is an ‘RNA lariat de-branching enzyme’. It plays an important role in recycling genetic ‘junk’.

Our genes are split into segments within our genetic code, separated by what’s often referred to as ‘junk’ DNA. These sections of junk, known as introns, don’t code for anything, but often perform other important roles.

When a gene is copied into its intermediate form of RNA (before these instructions are used to create a functional protein), it needs to be edited to remove the introns, leaving the vital instructions intact. This involves the introns forming loops of RNA – called lariats – which cut away from the rest of the copy. This leaves only the instructions for the gene product. These lariats then move away from the control centre of the cell (the nucleus) to be recycled.

DBR1’s role normally cuts these lariats open into strings, which can then be recycled. When in a lariat form, RNA is resilient to being recycled. DBR1 therefore plays an important role in recycling intronic RNA in the cell.

What happens when DBR1 is deleted?

When the research group deleted DBR1, intronic lariats accumulated in the factory floor of the cell (the cytoplasm). These lariats then competed to bind to TDP-43, acting as a decoy. This stopped TDP-43 from performing its dastardly deeds when faulty – chopping up essential RNAs within the cell –which could be contributing to the cause of MND.

By deleting DBR1 in yeast and in rat neurones grown in a dish, the research group identified that it increased the chance of neurone survival by nearly 20%.

This means that identifying a therapy that can decrease the amount of DBR1 could be a potential treatment for MND.

Reliability

Prof Gitler and colleagues independently verified their results from the genetic screen in yeast using different laboratories and different methods.

This is significant in terms of its reliability, as this often has huge repercussions for future research.

This topic was recently discussed in the popular science magazine New Scientist in an article called ‘Is medical science built on shaky foundations?’ In the article, the writer explains that a number of pharmaceutical companies have recently announced their failure to replicate a large number of promising results of potential drug targets from published studies.

It’s vital that if we are to identify a treatment for MND that works, that the evidence that led it to be tested in humans is solid. Gaining evidence to suggest the effectiveness of a treatment means replicating the results using independent researchers and using different methods to put an idea through its paces. This ensures that the original results aren’t identified as a coincidence and can be relied upon.

The decision by Prof Aaron Gitler’s group to reproduce their genetic screen independently, using different methods should be applauded. It means their findings are unlikely to be added to the heap of potential targets that cannot be reproduced in other studies.

Being thorough to identify potential targets may take more time, but it’s likely to produce more fruitful results in the long haul.

Looking forward

There are many steps left to climb with the development of a treatment that targets TDP-43. For example, the research group will need to determine whether stopping DBR1 could itself be toxic due to side effects. They also need to determine where the ‘therapeutic window’ is with this therapy – where it’s both effective and safe.

This study also identified many other modifying factors for TDP-43, which can begin to be investigated by other research groups for their potential as a therapy for MND.

As this is the beginning of the story of TDP-43 specific treatments for MND, it will inevitably be a long journey to answer these questions and to bring treatments to the doctor’s prescription pad.

Hopefully, the beacon of rigor and scientific righteousness that this study symbolises will continue and we will see the first TDP-43 therapy being developed for MND in the coming years.

References:

Maria Armakola et al Inhibition of RNA lariat debranching enzyme suppresses TDP-43 toxicity in ALS disease models. Nature Genetics 2012; doi:10.1038/ng.2434

http://www.newscientist.com/article/mg21528826.000-is-medical-science-built-on-shaky-foundations.html

EPHA4 gene influences survival in MND

An international research group spanning seven countries and including 23 researchers has identified a gene that modifies survival in MND. The gene, called EPHA4 was identified through a zebrafish genetic screening project and verified in rodents and humans with MND. The study was led by Prof Wim Robberecht, who has previously been funded by the MND Association and who is the Chair of our International Symposium on ALS/MND. The findings were published in the prestigious journal Nature Medicine this week.

What did the research group find?

By screening zebrafish for genetic factors that can modify the progression of MND, the research group identified EPHA4. By stopping, or slowing down the activity of EPHA4, they identified that MND zebrafish can be rescued and rodents (mice and rats) can live longer.

They also identified that MND vulnerable motor neurones have a higher level of EPHA4 than those at a lesser risk of developing the disease. This also means that a low level of EPHA4 confers to a lower risk of MND.

The research group then looked to humans to see if anybody with MND had mistakes in the EPHA4 gene that resulted in a change in survival. The group found two people with MND with genetic differences in the EPHA4 gene. These two people lived with MND for an exceptionally long time. As these genetic differences result in a lower level of EPHA4, this suggests that EPHA4 could be a valid therapeutic target for MND.

What does EPHA4 do?

Ephrin type-A receptor 4 (EPHA4 for short), plays a vital role in the development of our nervous system, in maintaining the shape of the neurone and in preventing regeneration after injury.

As our motor neurones grow, the projecting length of the neurone (the axon) needs to be guided to grow toward the right areas to connect to its respective muscle. To do this, a complex ephrin negative signalling system is used to guide the growing neurone in the right direction.

In real life terms, this signalling pathway can be thought of as somebody blindfolded, navigating a traffic cone maze. This person (the neurone) doesn’t want to move into an area cornered off by traffic cones (the corresponding ephrin signal). As the neurone can’t see where it’s going, it feels its way around using Eph receptors like EPHA4. The neurone moves away from ephrin signals as it ‘feels’ them. This eventually leads to the neurone reaching its target destination (the muscle).

To physically make the neurone move, when an ephrin signal connects to the ephrin receptor, the inner workings of the neurone are called into action. To find out more information on this, please read our previous article about Profilin1, which was found to be a cause of MND last month.

As EPHA4 plays an integral role in stopping neurone growth, it isn’t surprising that it also plays a role in stopping regeneration of neurones after injury. For example, in mice that have spinal cord injury (this was a study unrelated to MND), by genetically stopping the EPHA4 signal, new axon growth can be seen. With mice that have spinal cord injury that have a normal level of EPHA4 signal, growth cannot be seen.

The above non-MND study, along with the current EPHA4 finding further suggests that a lower level of EPHA4 can result in a longer survival because of its inability to perform its usual function to its usual extent. This incompetance seemingly allows the protection of neurones from degenerating at it’s normal pace.

As an additional note, you may be thinking that it seems counterintuitive that humans have additional signals that stop processes like regeneration when less complex animals like frogs still have this ability. Unfortunately, it’s a bi-product of mammalian evolution that continues to baffle scientists!

What does this mean for people with MND?

This finding unfortunately does not mean that a new genetic test will become available for EPHA4.

This discovery does however, offer another target for research institutes to look into and develop therapies that could slow down disease progression by lowering the amount of EPHA4.

Although this research is likely to take years to develop toward a clinical trial* in humans, it’s promising to see yet another exciting genetic advance that could have an impact on finding a better treatment for MND in the future.

*It’s important to point out that therapeutically lowering the EPHA4 signal in humans would not necessarily mean that neurones could regenerate as seen in the zebrafish. Many different signals other than EPHA4 prevent a human motor neurone from regenerating and from finding its target muscle. However, finding a way to lower the EPHA4 signal may still slow down progression, as seen in mice in this study.

What does this mean for the future of MND research?

Further studies are needed to verify and expand on these exciting results.

This finding means that researchers can explore this pathway in more detail as it, in conjunction with the recent Profilin 1 finding, suggests that this guidance/growth system of motor neurones may play an important role in the development of MND.

References:
Van Hoecke et al. Nature Medicine 2012 doi:10.1038/nm.2901

Munro et al. PLoS One 2012 10.1371/journal.pone.0037635

Our blog article on Profilin1

Discussing MND in Dublin

Delegates to last weekend’s ENCALS (European Network for the Cure of ALS) meeting in Dublin were met with uncharacteristic hot and sunny weather – enjoyed by the numerous Stag and Hen parties wandering the city centre, but not by the 200 people ensconced in the impressive, new Biomedical Sciences Institute at Trinity College, from 8am to 7pm, for a packed programme of presentations and debate.

ENCALS was established to help develop the standards of clinical and biomedical MND research across Europe and create a more collaborative environment for researchers, industry, funding agencies and Patient Associations. However, the meeting had a very transatlantic flavour, thanks to the participation of several of the leading researchers from North America.

With around 40 speakers, as well as numerous poster presentations, there is too much to cover in a few hundred words, so I’ll focus on just a few of the key themes that were covered. I also apologise for the quite technical language, which may make for hard reading, but is a positive in that it reflects the increasing complexity and sophistication of MND research.

Can we block the ‘molecular funnel’?

The opening speaker, Prof Teepu Siddique, from Northwestern University in Chicago, spoke on The molecular funnel of neurodegeneration. His view of MND is that it may have a large number of different causes, but the way a motor neurone dies will probably be similar, no matter what the original cause. We’re currently finding lots of new genetic factors involved in the disease, but we don’t understand how many of these genes work in health, much less how they malfunction in disease. So, the mouth of our funnel is getting wider.

Prof Siddique’s view is that by focusing on the cellular changes that are common to all forms of the disease, it gives us possible therapeutic targets that could be relevant to all forms of MND. It’s easier to block the funnel at its narrowest point.

He discussed how the degradation of incorrectly formed or damaged proteins is a classic hallmark of all forms of MND. While the way in which the proteins are damaged may differ from one form of MND to the next, it’s the cell’s inability to correctly deal with these proteins that may be a good target. If we can normalise or improve this process, it may keep the motor neurones functioning for longer.

Prof Orla Hardiman, the meeting organiser from Dublin, discussed the need for much larger and more detailed study of large numbers of patients, to attempt to unpick the environmental influences that undoubtedly exist.

A question that many people often ask is whether MND is occuring more often in younger people that in the past. Intriguingly, Prof Hardiman’s ‘population-based’ research using the Irish MND Register suggests the opposite – the average age of symptom onset is getting older. She suggests that continued improvement in medicine and diet means that the population in general is healthier, so our ‘biological age’ is slowing. If age-related diseases such as MND are linked to ‘biological age’ rather than ‘actual age’, it would explain this surprising trend.

Good Genes/Bad Genes

While factors that cause or predispose towards MND are clearly the subject of intensive research, there is of course also interest in factors that might prevent or slow the disease. Some of these potentially ‘good’ genetic variants are being explored:

• Prof Wim Robberecht’s group (University of Leuven) is examining the function of a gene called ephA4, which appears to correlate with longer survival in humans. This work is supported by studies in zebrafish and mouse models of MND.
• Prof Kevin Talbot (University of Oxford) showed data that suggests that by increasing activity of a gene called smn1 might be beneficial to motor neurones. This is a strategy that is being followed for a predominately childhood motor neurone disease called Spinal Muscular Atrophy, so if these approaches work in this particular condition, they might be of benefit in other, adult onset motor neurone diseases.
• Prof Robert Brown (University of Massachusetts) presented early data from a study of a variant in a gene called sarn1, which appears to protect motor neurones from damage….at least in fruit flies and mice. Work is ongoing to see whether it also has relevance in humans.

In contrast, Dr Andrea Calvo (University of Torino) provided information from Italian patients confirming studies in other populations that a variation in the unc13A gene can speed up disease progression.  However, the important issue about these disease-modifying genes – and it doesn’t matter whether they speed up or slow down MND – is that they all represent potential therapeutic targets.

Not just about the motor neurones!

We know that motor neurones do not die alone. Other parts of the brain and spine can be affected, but it’s the motor neurones that ‘bear the brunt’. 

Dr Sharon Abrahams (University of Edinburgh) provided an excellent overview of the range of cognitive and behavioural changes that can occur in the disease, indicating damage to other part of the brain, in particular the frontal lobe. Thankfully, the ‘real world’ effects of frontal lobe changes are usually subtle, but the fact that they can be picked up by psychological tests and MRI scans will help in defining specific ‘subtypes’ of MND which may require additional approaches to managing the disease.

Dr Martin Turner (University of Oxford) outlined evidence from a number of clinical research studies, including his own that nerve cells, called interneurones, might be involved early in the disease. These particular neurones usually play a role in calming down motor neurones, so if they are damaged or lost, the motor neurones themselves become over-excited and stressed, which leads ultimately to their degeneration.

Dr Turner’s evidence comes mainly from clinical imaging and electrophysiology studies in MND patients, but his theory was supported by a presentation from Dr Tennore Ramesh (University of Sheffield) who works with zebrafish models of MND. He showed results using zebrafish that carry a human SOD1 gene known to cause MND. The fish develop a form of MND in adulthood, but the very earliest signs of nerve damage actually occurs in specific types of interneurones that connect with the motor neurones, with the motor neurone damage occurring much later, closer to the onset of symptoms.

Presentations also covered the role of non-neuronal support cells, such as microglia and astrocytes, both of which have been the subject of extensive research in recent years, as they appear to play a role in the speed of progression of the disease. Prof Jeff Rothstein (Johns Hopkins University) introduced a new cellular player to the MND field, called the oligodendrocyte. These specialised cells have been known for many years to play a role in helping neurones to carry electrical signals, as well as helping them to maintain energy levels. Although they are known to be involved in multiple sclerosis, they hadn’t attracted much attention in MND.

Prof Rothstein showed that in human post mortem MND brain tissue, there is evidence that the brain has been making oligodenrocytes. This is certainly very clear in SOD1 mice, where  a massive production of new oligodendrocytes occurs. However the total number of these cells was not increased in the mice, suggesting that older oligodendrocytes were being killed and getting replaced.

He suggested that the new ‘immature’ oligodendrocytes are not nearly as efficient in their supporting role, especially when it comes to supporting motor neurones in maintaining their energy balance. This provides two possible treatment approaches – either try to keep the existing oligodendrocytes healthier or find a way of making sure that their replacements reach their full functional maturity.

I’ve no doubt we’ll be hearing a lot more about these cells in the future.

Sharing and networking in Liverpool

From Sunday morning to Tuesday evening last week, there was a lot of talk of MND research going on in Liverpool. The reason for this ‘hotspot’ of discussions was due to the annual meeting of an international consortium of MND researchers taking place at the University of Liverpool. The 10th International Consortium on SOD1 and ALS (ICOSA) meeting took place last weekend (4 – 5 March).

In 2001, five laboratories came together to form ICOSA, where the aim was to share knowledge to design better-informed experiments to understand the rare, inherited SOD1 form of MND. MND Association grantee, Prof Samar Hasnain was one of its founding members. Success of this philosophy of sharing knowledge prior to publication has resulted in several leading groups joining the effort, looking at other causes of inherited MND too.

A tradition of ICOSA meetings is to hold an open meeting for sharing latest results with a wider audience, following their closed meeting. Thus, on Tuesday 6 March, an open meeting was held to allow the exchange of the latest results and ideas between ICOSA members and the UK MND research community.

I attended this one day meeting in Liverpool and I’ve written a mini report on the meeting below, including a couple of highlights.

The first few presenters demonstrated the truly international nature of this collaboration – they had travelled from the snowy landscape of northern Sweden, the sweltering heat (at least in August!) of mid-state Florida and from RIKEN, the large natural sciences research centre, in Japan .

The researchers represented were a mixture of physicists, biochemists and neurologists – an unusually broad spectrum of knowledge and speciality for an MND research meeting. Essentially, their core, joint interest was in understanding how the structure of a protein has such a marked change leading to MND developing or the disease progressing.

The structure of a protein is essentially about folding. The correct folding will mean that the protein can do its job. Folded incorrectly the protein won’t be able to work. An example of incorrectly folded protein is the protein clumps or ‘aggregates’ seen within motor neurones in MND. There is a whole chain of events that lead the appearance of these clumps of protein – and researchers at the meeting discussed every step along the way.

How do proteins fold and why is it important?

When the instructions for making a protein (ie genes) are read and edited by DNA and RNA respectively, they are reading or editing instructions to arrange a set of building blocks in a particular order – there are 20 different types of building block – our amino acids. ALL of our proteins within our bodies are made from specific arrangements of this core set of 20 building blocks. The arrangement of the building blocks determines where the protein folds, in which direction and the shape it makes. There are many possible folding arrangements a protein could make, but it will always try and fold itself into the lowest energy shape (a good way to think about this is the shape where the protein is ‘most comfortable’).

Geneticists know a lot about the beginning of the process (what the sequence of building blocks will be) and biochemists and pathologists know a lot about the end of this process (what the protein does and a what it looks like in the cell when it clumps together) – but the physicists of the MND research world are working on the bit in the middle (precisely where which building block is, in the folded protein).

A change to the sequence of the building blocks, as seen in the proteins made from mutated genes that cause MND, will lead to unusual folding, and damage to the cell – due to the loss of normal function or a trigger for toxicity. So having a complete picture of a protein ‘lifespan’ is really important in understanding what goes wrong in MND and how to fix it.

Unravelling questions about SOD1

People with the SOD1 form of the rare, inherited type of MND have a mistake in the assembly of one building block in the instruction to make the SOD1 protein. Over 160 different, single building block mistakes have been found in this form of MND so far. All of them lead to the development of MND. So that means 160 damaging variations in the folding of the SOD1 protein.

Over 70 other delegates and I heard the latest on how mimicking the effects of these mutations (by changing building blocks of the protein) in SOD1 mouse models tells us more about this cause of MND. It’s even possible to study the different effects of the toxic protein on different cell types essential for motor neurone function. (Although motor neurones carry the messages, they are supported by groups of ‘glia’ cells around them).

Where (the) ‘FUS’ is

Prof Larry Hayward presented his research on a protein called ‘FUS’; mutations in this gene causes another form of the rare inherited MND. The damaged ‘FUS’ protein is found in a completely different place in motor neurones than usual. Images of motor neurones where the FUS is in the centre of motor neurones, as usual, looked a bit like fried eggs; but the location of the damaged FUS in the outside of the cell reminded me of ring donuts! By stressing motor neurones, he showed a video of the proteins moving from the centre to the outside of the cell; and back to the centre when the stress was removed. This all happens very quickly, in a matter of minutes!

C9orf72 – a hot topic

Another highlight of the meeting was the presentation by MND Association grantee Prof Huw Morris on both how the C9orf72 gene mistake was found last year, and also on what’s happened since the results of this finding were announced. In the five and a half months since the 21 September announcement, another 26 reports have been published in this area of MND research. That’s slightly more than one report a week! (To put this in context there are roughly 36 MND reports published a week, total, across a broad range of topics). He commented that one factor that kept him focussed in the long search for this gene defect was the people with MND in his care.

Drug scaffolding to correct damaged folding

Above I mentioned that the physicists work out the precise folding of proteins, knowing where each of the building blocks is within its final shape. They do this by isolating the protein they want to study and placing it in increasingly high concentrations of salt solution to remove literally every molecule of water, until the protein itself comes out of solution and forms crystals. These crystals are then analysed by x-ray crystallography and other analytical chemistry techniques.

For a protein made from a mutated SOD1 gene, x-ray crystallography studies found a hole in the protein folding that may explain why it forms clumps within motor neurones. MND Association funded researcher Dr Neil Kershaw from the University of Liverpool presented the latest results from his research in designing a drug that will ‘prop up’ incorrectly folded SOD1, in the hope that this will remove its damaging effects.

I hope that this report demonstrates that in between the ‘big news’ stories about MND research, steady progress continues to be made in understanding MND and searching for treatments for it.

Cogane produces encouraging results in MND Association-funded study

Prof Linda Greensmith

Thanks to funding and some strategic ‘match-making’ by the MND Association, a new drug may have taken one step closer to beginning clinical trials in MND after producing promising results in an animal model of the disease.

The drug, known as Cogane, was developed by the biotechnology company Phytopharm. It had already demonstrated in laboratory tests that it could help to protect neurones by promoting the production of natural, nerve nourishing substances called neurotrophic factors and early animal testing had hinted at its potential beneficial effects in MND. However, its journey towards clinical testing in MND had hit a road block because it hadn’t been extensively put through its paces in large numbers of the most widely used animal model of the disease, the SOD1 mouse. Without robust data from this model, there would have been little to encourage further investment in Cogane’s development.

So up stepped the Association to introduce Phytopharm to Professor Linda Greensmith at University College London, a leading MND researcher with considerable expertise in SOD1 mouse testing. With funding from the Association, Prof Greensmith and her team were able to conduct a rigorous study of the effects of Cogane, administered to the mice after they had developed MND-like symptoms.

The drug produced some significant improvements in muscle strength and motor neurone survival and managed to produce positive effects even in mice that had reached the later stages of the disease. To give more substance to these preliminary but very encouraging results, the research team will now go on to the painstaking work of examining more closely Cogane’s effects on the motor neurones and other key cells that play a critical role in the progression of MND. 

After the disappointment of the Trophos trial results, it’s great to be able to share some positive news on the drug development front. We know from long experience that it’s wise to limit our excitement over positive results from the mouse model – after all, plenty of drugs have shown promise at this stage and have then gone on to fail in clinical trials. However, Prof Greensmith’s experience and expertise mean that Cogane will have been tested with the utmost rigor. As she herself commented, the results indicate that “Cogane has significant potential as a therapy for ALS and merits further evaluation”.  We don’t yet know what Phytopharm’s next steps will be – these may become clearer once the more detailed data from Prof Greensmith’s work have been published, which could take the best part of a year. Let’s hope that we have a given Cogane enough of a boost to push it out of the drug development ‘doldrums’.

Read the Phytopharm press release.

Promising news for keeping the motor neurone neighbourhood safe

There was standing room only in the first of the dedicated scientific sessions of the Symposium last week. All had gathered to hear Prof Stan Appel inform them of the latest chapter of this story on the role of inflammation in MND.

Listening to his presentation I got the gist of the overall positive message – a real step forward in MND research – but to report in any more detail of how and why was a step too far for my brain when I was in Sydney! Reading through my notes when I got back to the office, I was determined to get to the bottom of this science. It helped me to write a non-technical summary of it as I went. It’s perhaps a bit more technical than our normal blog posts – but I couldn’t resist the opportunity to (try and) share my new found knowledge. So here goes:

Inflammation is one response of the immune system. The immune system is a community of cells that exist within your body to protect it from damage and to maintain its status quo. Given its important function, it is perhaps reassuring to know that how it works is mind-blowingly complex!

In the brain and spinal cord, a slightly different defence system exists in comparison to the rest of the body. It is now common knowledge that motor neurones are surrounded by cells that support their function – known as glial cells. Within the community of these glial cells there are ‘police’ cells called microglia. Prof Appel’s lab has contributed many elegant studies to a consensus of research showing that in MND these police cells operate a delicate balance between protecting the environment around motor neurones and triggering a toxic atmosphere. Gradually the toxic atmosphere prevails.

In Sydney, Prof Appel discussed another component of this defence system, ‘regulator T-cells’. Continuing the police analogy, T-cells patrol the blood, rather than the brain and spinal cord tissue of microglia. As their name suggests, regulator T cells regulate the response rate of removing toxins and maintaining a healthy environment, in particular they regulate microglia by sending out specific chemical signals.

Prof Appel wanted to know how the interaction of T-cells with microglia is affected in MND. He found that a large ‘police presence’ (or high numbers) of regulator T-cells influence microglia to maintain their protection of motor neurones. In other words, large numbers of regulator T-cells kept motor neurone death at low level, showing itself as a slower phase of disease progression. As the levels of regulator T-cells get lower, the microglia turn toxic and the rate of progression of the disease speeds up. These conclusions were based on studies in mice models of MND and in patients at different stages of MND – by analysing blood samples for the presence of regulator T-cells and comparing this with what they knew of their symptoms.

This information presents two opportunities to MND researchers – firstly if therapies can be developed to maintain the levels of these regulator T-cells they may slow down the disease; and in the meantime, chemical markers in the blood, used in these studies, may be a valuable biomarker to measure the rate of progression.