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.

Zebrafish study provides innovative ideas for new treatment strategies

A study on zebrafish has increased our understanding of how motor neurones work and has provided potential clues for the development of future treatments for MND. The study, led by Dr Catherina Becker from University of Edinburgh, showed that a unique motor neurone repair system found in zebrafish can be enhanced if a particular signal called Notch1 is stopped. The results were published in the 29 February edition of Journal of Neuroscience.

What did they find?

Unlike us, zebrafish have the ability to regenerate motor neurones when they’re damaged. This means that zebrafish can provide scientists with an excellent tool to find out about motor neurone repair. A better understanding how zebrafish achieve neurone regeneration could provide clues to develop new treatment strategies for MND.

From their studies, Dr Becker and colleagues found that a chemical signaling pathway called Notch1 is increased when the neurones are damaged in zebrafish.

By over activating the Notch1 signal, they found that new motor neurones would not grow well, and would not grow in the same prolific numbers as normal. This means that an over active Notch1 signal can stop the regeneration of motor neurones that occurs in zebrafish.

To test whether the Notch1 signal could be counteracted, the research group treated zebrafish with an anti-Notch1 chemical to stop the Notch1 signal. This increased the generation of motor neurones.

As well as having a deeper understanding of the basic biology of how zebrafish regenerate their motor neurones, this study may help to provide new clues for the development of future treatments for MND.

This type of research is vital to lay the foundations for future studies. With a solid foundation of understanding of how motor neurones work, we can work toward identifying new and better treatments for MND.

What does this mean for people with MND?

This work is still at a very early stage of development. It unfortunately doesn’t mean that a treatment coming from this research will be available soon.

Researchers still need to identify whether developing a drug that can stop, or slow down the Notch1 signaling pathway would be a beneficial treatment strategy. To do this, researchers will need to carry out tests in a cellular, and animal models of MND. This is an important step, as it determines whether treatments are safe and effective before testing the treatment in people.

More information:

The Journal of Neuroscience, 29 February 2012, 32(9): 3245-3252; doi: 10.1523/JNEUROSCI.6398-11.2012

Official Edinburgh University news 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.

The season of the gene

“Welcome to this afternoon’s genetics session, which I hope will convey elements of hope and excitement about the season of the gene” were Professor Teepu Siddique’s (from Northwestern University, USA) opening remarks on a series of talks that really did live up to this standard. To me each talk was like being read chapters of a thriller novel, each was gripping with its own story to tell, but by the end of the session I was really buoyed up with hope, enthusiasm and an appetite for more!

Prof Siddique’s research lab have contributed two important new discoveries in MND genetics in the last few months alone (UBQLN2 and SQSTM1), so he was very well placed to begin with an overview of how recent discoveries allow us to make sense of much of what has been to date.

Prof Siddique started his talk by discussing what we can tell about MND by looking at human motor neurones down a microscope . Using some very elegant studies of the build up and removal of proteins tagged with different colour labels he demonstrated that many causes of MND (ie genetic mistakes in TDP-43, SOD1 and FUS genes, and the randomly occuring sporadic form) all have a build up of ubiquilin2. The next part of the story was to explain what this protein was doing there – what sequence of events or malfunctions in the motor neurone has caused the protein to be there. Time and again he demonstrated that at the heart of disease-causing damage in MND is the protein recycling system (see Prof Mayer’s post a month or so ago). This was summed up for delegates by playing a TV commercial of blindfolded women trying to identify different parts of an animal (a rhino this time) and only when their blindfolds were removed was the whole story revealed.

The phrase an ‘elephant in the room’ is used in reference to the presence of a huge topic that no-one is talking about. But the huge topic in genetics was most definitely getting an airing this afternoon – that of the discovery of the C9orf72 gene defect. Speakers either talked about it in light of the way that it links together a number of diseases where there is evidence of frontotemporal dementia as well as signs of motor neurone damage. Or the fact that the actual gene defect seen in C9orf72 is so different to older genetic discoveries in MND – in so much that the damage is caused by lots of extra letters included in the instruction, rather than a ’spelling mistake’ in the instruction by removing, substituting or deleting individual letters. Now that genetic researchers are tuned in to looking to genetics in a new way and looking for changes in new places, it seems that there is a huge potential to make discoveries and connections that much faster. Personally I can’t wait to read the next instalment.

Read our official press release from day two of the symposium.

Next chapter of BMAA detective story

On Thursday morning, Profs Paul Cox and Walter Bradley chaired a session titled ‘Beyond Guam: New Aspects of the BMAA Hypothesis’. This was the latest chapter in a detective story, involving botanists, epidemiologists, clinicians and biochemists that goes back 60 years….

Back in the early 1950s, American doctors started documenting a high incidence of a strange form of MND in the native Chamorro Indian population of the Pacific island of Guam. Those affected exhibited a mix of symptoms covering motor neuron degeneration, dementia and Parkinson’s disease – giving rise to the official name Amyotrophic Lateral Sclerosis-Parkinson-Dementia Complex, or ALS-PDC for short.

Early epidemiology studies linked the disease to a likely environmental exposure with a long-term incubation period, possibly a slow-acting toxin of some type. Subsequent studies linked the disease with the seeds of a member of the cycad family. Cycad seeds formed part of the islanders’ diet and these seeds contain a variety of different chemicals, including some that are toxic to nerve cells. One of these, beta-N-methylamino-L- alanine (BMAA) was a prime suspect.

But cycad seeds don’t make BMAA themselves – it is actually made by a form of cyanobacteria (blue-green algae) that live in the roots of the cycad plants. The BMAA toxin is then concentrated in the plant seeds, which were ground up as flour to make a form of bread.

In the lab, it could be shown that BMAA readily killed nerve cells, did so at concentrations that were much higher than those that would be found in the cycad bread. This led the epidemiologists to ask the question ‘What else eats cycad seeds?’ The answer was flying foxes – a type of fruit eating bat – and flying foxes in turn are considered a delicacy by the locals…

As Prof Cox explained in his introductory overview to the delegates, we have a very nice example of biomagnification. BMAA is made by algae, is concentrated in cycad seeds, is further concentrated in the bats and is finally eaten by the locals, where it presumably builds up in brain tissue over time.

This theory isn’t universally supported by researchers – for example, if a genetic factor was involved, it would likely be more prevalent in an isolated, island population such as Guam. However, the epidemiologists like to point out that the bat population has plummeted over the past 40 years (perhaps due to increased use of guns by the islanders or the introduction of an invasive tree-climbing snake) as has the incidence of ALS-PDC!

Of course, cyanobacteria are found all over the world, so it begs the question of whether BMAA might be present in very low levels in other places, perhaps acting as a subtle factor that predisposes people across the world to develop MND? Certainly, BMAA has been found to be present in water sources in various locations, in particular marine environments where, as explained by Dr Estelle Masseret (University of Montpellier) it can be further concentrated in shellfish. It has also been shown to be present in the brains of people with neurodegenerative diseases who have never been within a thousand miles of Guam.

Cyanobacteria - Dr Paul Cox

The levels of ‘free’ BMAA in the brain are relatively low, so a theory has emerged in recent years that most of the BMAA in the brain tissue is ‘protein-bound’ – not sticking randomly to proteins, but actually being unwittingly incorporated into the protein structure during the manufacturing process. This isn’t surprising, since BMAA is an amino acid and amino acids are the building blocks of every protein in our body.

The difference with BMAA is that it is an ‘unnatural’ amino acid. By this I mean that proteins are normally made from a combination of 20 amino acids. BMAA isn’t one of them, so when it gets incorporated, it can subtly alter the structure of the protein. And when protein structure is altered in neurons, it invariably leads to the aggregation of proteins, one of the classic pathological hallmarks of neurodegenerative diseases. Since our neurons have to last a lifetime, an accumulation of BMAA and misfolded proteins over many years could make neurons more susceptible to damage.

One big unanswered question is which amino acids is BMAA being mistaken for? Through some elegant experiments, Prof Ken Rogers (University of Technology, Sydney) showed  that part of the protein making ‘machinery’ is specifically mistaking BMAA for serine, the amino acid that is structurally the most similar. The ‘machinery’ is question is an enzyme called tRNA synthetase and Prof Rogers pointed out that if this process is inhibited in mice, the neurons are the first to start to show damage, indicating that they are particularly vulnerable if tRNA synthetase is not doing its job correctly.

It does raise the question of whether BMAA is incorporated more into proteins that contain the largest proportion of serine amino acids. That question has not yet been addressed, but it is interesting that the protein TDP-43, which is known to misfunction in up to 90% of cases of MND, is a protein that is made up of an unusually high number of serine amino acids,

As with many aspects of biomedical research, this session raised more questions than answers, but the really encouraging fact was that the questions were coming from scientists outside the immediate BMAA field. It will take additional expertise to definitively demonstrate whether or not BMAA is indeed a common risk factor that might prime people to develop neurodegenerative disease later in life. This session, together with a follow-up workshop organised for the end of the day, will throw up the key next steps in this field of investigation – how to strengthen the evidence in cell and animal models, how to improve the analytical methods and how to collaborate more closely together in the future, drawing in new expertise from across the world of neuroscience.

Read our official press release on day two of the symposium.

If you were a car, would you be a Ferrari or a Focus?

People at increased risk of MND might be the human equivalent of high performance cars – built for speed and agility but becoming unreliable once they reach a high mileage.

There is much anecdotal evidence amongst MND clinicians and those affected by the disease that people who develop MND tend to have been relatively physically fit before their diagnosis, often having been involved in various athletic pursuits throughout their life. This prompted MND Association-funded researcher Dr Martin Turner to ask the intriguing question: Is an athletic physique an outward sign of a subtle predisposition to MND? But how could he make a sensible measurement of ‘athletic physique’ in order to answer such a question? Or as he put it in his presentation on Thursday morning, do people with MND have motor system run to death, or is it a motor system born to run?

A pragmatic way of looking at this was to look at the history of coronary heart disease and whether this is linked to a likelihood of developing MND later in life. Dr Turner has recently published this study in the Journal of Neurology, Neurosurgery and Psychiatry). Through very careful examination of hospital medical records, he and his colleagues compared numbers of MND cases in over a hundred thousand people with a history of coronary heart disease to an even larger group with no known heart problems.

The study did reveal a slightly increased occurrence of MND in the group with healthy hearts, providing indirect evidence that MND is more likely to occur in people with greater levels of ‘fitness’. Dr Turner’s results were in fact corroborated by the findings of another more general study of lifestyle and environmental factors presented in the same session. Dr Marc Huisman’s meticulously executed and much admired questionnaire-based study of the Dutch population also suggested that people with MND were less likely to have relatives with heart disease, indicating a more genetically robust cardiovascular system, amongst many other findings.

Dr Turner’s findings are intriguing but there is still plenty more work to do and many questions are left unanswered. There are other studies that support the possibility of an increased MND risk in people with a healthy cardiovascular system and lean build but of course these two characteristics are also a result of undertaking higher levels of exercise – the question of whether exercise itself contributes to MND still won’t go away. However, Dr Turner’s work supports the concept that if you’re born with a natural leaning towards athletic prowess, you may excel at sport (or in evolutionary terms, hunting down your dinner) but your nervous system wiring may also be more vulnerable to MND as you age – a factor that’s only become problematic with the dramatic increases in life expectancy that have come about in the last couple of hundred years.

As Dr Turner put it at one our spring conferences this year, people with MND may well come from amongst the Ferraris of the human race. With clearer identification of risk factors, prevention of MND becomes a more realistic possibility. It may be that in future the Ferraris can undertake a specialised servicing schedule to ensure they have a greater chance of breaking the 100,000 mile barrier with their electrics in good working order!

Read our official press release on day two of the symposium.

Copying, transporting and creating proteins – what could possibly go wrong?

Proteins are the building blocks of our cells and have a variety of important roles within our bodies. The instructions for how to build our proteins sit within our DNA, our genetic code in the control centre of our cells (the nucleus). There are many steps to go through from reading that ‘raw’ instruction to ending up with a fully functioning protein.
However, the amount of information held within our genetic code is so huge that only small segments of it are read and transferred to the factory floor, as and when they are needed. These copies, known as messenger RNA, are small enough to be transported to the ‘factory floor’ of the cell to large machine-like entities called ribosomes where the copy is read, and used to create the resulting protein.
When I was doing my A levels and later at University (yes, that long ago!), we were taught that only 1% of the genetic code ever made it to the factory floor. This held true until a couple of years ago. However, as explained by Professor Bob Brown in his presentation at the ‘RNA and protein processing’ session this afternoon, such is the change in our knowledge in that area, we now know that 95% of our genetic code makes it through to the first step of making proteins.
This was a key piece of context in trying to understand the role that TDP43 plays in functioning cells – never mind specifically in motor neurones or in cases of the presence of damaged TDP43 in MND!
Professor Brown, University of Massachusetts Medical School, Boston, USA went on to give an enlightening review of what has been uncovered about this fascinating protein (TDP43) so far. Once the protein of TDP43 has been correctly made, its function is to go back and ensure that other proteins are correctly made too – the so called ‘reading helpers’ of the cells, or ‘editors of instructions’. Another new fact to me from this talk was that TDP43 is involved in editing or reading up to ONE THIRD of all proteins within the cell. That’s a city fat cat type of job! So how is it all related to it’s function in MND?
Some elegant experiments have shown that TDP43 regulates how many copies of it’s own protein are made. However, the regulation takes place in the control centre of the cell (see the top of this blog). If TDP43 gets stuck or waylaid on the factory floor, it can’t get back to press the stop button in time. So it’s thought that more and more protein is made, accumulating on the factory floor until that accumulation can be seen as the protein deposits so characteristic of what you see of motor neurones affected by MND down the microscope.
Part of the editing work that TDP43 does so well is known as ‘splicing’. In true ‘Blue Peter’ style, here is a description of that process that Kelly prepared before I flew out to Sydney:

Alternative protein
One gene can hold the instructions for a number of different versions or variants of a protein. These variants are created when different parts of the gene are used in alternative combinations. This is a normal process and it’s called ‘alternative splicing’. This complicates matters in terms of genetic research, as even though we have approximately 20,000 genes, we could potentially have a much higher number of functional proteins because of alternative spliced variants.

How does alternative splicing work?
The picture (below) depicts a simple version of how a gene can be alternatively spliced, given three ‘parts’. The example demonstrates that the first version of the protein is made up of parts 1, 2 and 3, whereas version two is made up of only parts 1 and 3. These resulting proteins would go on to function in our bodies in potentially different ways. It is therefore possible for a number of different proteins to be created given one set of original instructions in the genetic code.

 

 

Read our official day one symposium press release on our website.

Another recycling bounty hunter linked to MND

In the short space of three months, details of a second gene have been published linking MND to the protein recycling system in our cells.

Leading this research was Prof Teepu Siddique, eminent MND researcher from North Western University in Chicago USA. Not only was he the founder of the first MND causing gene SOD1, but he also led the group that identified faults in the UBQLN2 gene in MND in August 2011. This research was published in the November edition of the Archives of Neurology journal.

We’ve invited Prof Siddique to give a plenary talk at this year’s International Symposium in Sydney, Australia from 30 November to 2 December 2011, at which we believe he’ll be discussing these exciting new advances!

What did they do?
Instead of searching for common genetic mistakes in families with the inherited form of MND, this research group focused on a candidate gene called SQSTM1. They chose SQSTM1 as a candidate due to the prior knowledge that its protein product is associated with MND.

They then unravelled the code for this particular gene in 340 people with the rare, inherited form of the disease and 206 sporadic cases of MND. They also compared these with 738 healthy controls.

They identified 10 different mistakes in the SQSTM1 gene in 15 people and did not find any of these mistakes in the healthy controls. The research group therefore estimate that genetic mistakes in the SQSTM1 gene could account for approximately 2-3% of cases of MND.

However, it is not yet conclusively known whether these mistakes cause MND, or increase the risk of somebody developing the disease. Further studies are therefore needed to confirm this.

What does SQSTM1 do?
The gene SQSTM1, holds the instructions for a protein called P62, otherwise known as sequestosome 1. 

The P62 protein can be thought of as a ‘bounty hunter’ of proteins that need to be recycled inside motor neurones and other cells. When given instructions to find proteins waiting to be recycled, it seeks them out and delivers them to the cells recycling system.

P62 has a related role to ubiquilin 2 (UBQLN2 which we wrote about in August) as they both work in the protein recycling system within the body.

This research therefore further implicates that the protein recycling system is faulty in MND.

The next steps with this story, is for researchers to confirm whether mistakes in the SQSTM1 gene cause, or contribute to the disease in other populations around the world. They will also need to investigate how the protein recycling system can go wrong in MND to be able to develop new treatments that can target these processes to slow down, or stop the disease.

More information on the protein recycling system:
Last month, Prof John Mayer from University of Nottingham, who is the Chair of our Biomedical Research Advisory Panel, took us behind the scenes of the protein recycling system on our research blog

Read our press release.

Reference: Fecto F et al. Arch Neurol. 2011; 68(11):1-7

Chromosome 9 finally reveals its secrets

It’s taken a huge international collaboration, including 3 MND Association-funded scientists, to discover a genetic mistake that appears to cause almost 40% of cases of familial (inherited) MND – that’s nearly twice as many as are caused by mutations in the SOD1 gene and more than three times as many as are caused by TDP-43 and FUS combined. Yet despite the fact that it’s relatively common, the rogue gene proved especially difficult to find.

Digging for genes

Our genetic code is arranged into 23 pairs of subunits called chromosomes. Earlier work had homed in on an area on chromosome 9 that appeared to be significantly associated with both MND and the related neurodegenerative disease frontotemporal dementia (FTD), but nobody could drill down as far as the problem gene itself. As a result, chromosome 9 became something of an ‘archaeological dig site’ for MND researchers, with several groups using cutting edge techniques to try and excavate the elusive causative gene that they knew was lurking somewhere in the short arm of this chromosome. The successful international team, which included almost 60 scientists at 37 institutes, finally discovered the exact location and nature of the aberrant genetic code by looking in the most unlikely of places – in the stretches of DNA that do not actually provide any instructions for building proteins, otherwise known as non-coding DNA.

What did the researchers unearth?

The research team studied DNA samples from a Welsh family affected by inherited MND and FTD that was already known to be associated with chromosome 9, as well as samples from a similar Dutch family and a large number of Finnish inherited and non-inherited MND cases. In among the non-coding DNA in a chromosome 9 gene called C9ORF72, the researchers found a 6-letter genetic ‘word’ which, in healthy individuals, is consecutively repeated up to about 20 times. However, in the Welsh and Dutch families and a large proportion of the Finnish familial cases, the 6-letter word was repeated as many as 250 times. This phenomenon is known as a ‘repeat expansion’. The researchers went on to check for this repeat expansion in familial MND cases from North America, Germany and Italy, and found it cropped up in 38% of them. They even found it in a much smaller proportion of sporadic cases from Finland, suggesting that it could be an important risk factor in at least some people with the  non-inherited form of the disease.

What does the discovery mean for MND research?

Despite the fact that the repeat expansion does not directly affect the instructions for building a protein, there is good reason to believe that it can still lead to significant neuronal damage. At the moment it is not fully understood how this happens, but one possibility is that it leads to the production of excessive and consequently toxic quantities of RNA, the molecule that provides the cell with a more usable copy of DNA. Disruption to RNA processing has already been implicated as a disease mechanism in MND – this is the pathway through which faulty TDP-43 and FUS are thought to exert their effects – so C9ORF72 may provide scientists with another piece of the RNA jigsaw.

The effect of the repeat expansion is clearly open to influence. Among those people with the repeat expansion, some experienced only FTD, others showed only muscle weakness, and some had both MND and FTD.  The reasons for this variation in symptoms will be just one area that scientists will now want to look into. This overlap between MND and FTD is something that researchers are very keen to understand, and the C9ORF72 discovery may be the key to solving this puzzle. They will also want to better understand how the repeat expansion causes damage, and that will include trying to find out what C9ORF72 actually does – at the moment this is unknown. (Maybe it’ll get a more interesting name along the way!) Building on the new finding in this way could help move us closer to an effective treatment.

For now, a more tangible consequence of the discovery could be a genetic test for people already diagnosed with familial MND who want to understand more about the basis of their disease. Such a test will take a little time to develop but should become available in the UK in the next few months. When it does, it will be accessible to genetics labs across the country. Anyone interested should speak to their doctor or specialist nurse.  

Dead heat

Just as archaeologists might question whether a newly discovered artefact is the real thing, so scientists need double-checking when they claim to have made a new discovery. Fortunately, a second team hit upon C9ORF72 at exactly the same time, and their results will be published alongside the work described here, in the journal ‘Neuron’. The race to the ‘Lost Ark’ of chromosome 9 ended in a tie, but has provided the research community with a major piece of the MND puzzle on which to build future discoveries.

Article: Renton A, Majounie E, Waite A et al. A hexanucleotide repeat expansion in C9ORF72 is the cause of chromosome 9p21-linked amyotrophic lateral sclerosis-frontotemporal dementia. Neuron (2011).

Read our press release on the C9ORF72 story.

New gene finding suggests recycling is key to all forms of MND

Researchers from Northwestern University Feinburg School of Medicine in America, have identified that faulty ubiquilin 2 plays an integral role to MND.

Led by eminent researcher Prof Teepu Siddique this research group describes unique mistakes in a gene called UBQLN2, which codes for a protein called ubiquilin 2, in five families with the inherited form of ALS. This research group also found that this protein is found in both the inherited and sporadic form of MND, which suggest that this finding could be key to finding a new treatment for the disease. Their findings were published in the prestigious Journal Nature.

What did the researchers do?

The researchers started by identifying a novel genetic mistake in a gene called UBQLN2 for a family affected by the inherited form of ALS. ALS is the most common form of MND. They went on to duplicate this finding by identifying four more genetic mistakes in the same gene in four other families with inherited ALS. This verified that this finding is not simply a ‘one off’.

By examining post-mortem spinal cord samples from people with ALS within these families, faulty ubiquilin 2 was identified as being involved in forming ‘tangled lumps of proteins’ within their motor neurones. When a researcher looks down a microscope at a motor neurone with the disease this ‘tangled lump’ is a classic sign of MND.

The next question that this research group addressed was whether ubiquilin 2 could also be found in other forms of MND. Remarkably, by studying post-mortem samples of people with the randomly occurring ‘sporadic’ form, inherited form (caused by mistakes in SOD1, TDP-43, FUS or an ‘unknown’ gene) and fronto-temporal dementia – related MND, they identified ubiquilin 2 within the ‘tangled lump’ in all of the samples.

This means that ubiquilin 2 could be the ‘smoking gun’ of MND.

Never before has one single protein or gene been related to all forms of ALS. Until now.

Mistakes in this gene are very rare and as yet, we don’t know how many cases of inherited MND are caused by it. This discovery does not open up the possibility of a new genetic test to identify people who might be at risk from the disease, but it does provide a new and exciting insight into the causes of all forms of MND.

How does ubiquilin 2 cause MND?

Imagine a world where all recycling collectors are on strike. Every Wednesday at 7am you place a box of recycling on your driveway ready to be collected, but it’s still there in the evening. The next week you put out more recycling, and that isn’t collected either. After weeks of putting your recycling outside, you notice that the pile is mounting and still isn’t being collected. This doesn’t bother you too much as you can still step over it, albeit in a slightly slower manner. A few months pass and you can no longer get out of your driveway as it’s covered by recycling. Now you can’t get rid of your rubbish, you can’t get to work and you can’t even leave your house all because of the pile up of recycling. The same thing is happening to everybody all over your town. This is what happens in MND.

One of the pathological hallmarks of MND is a build-up of ‘recycling bins’ of proteins in motor neurones. Normally, these recycling bins are emptied on a regular basis by a process regulated by a family of proteins called ubiquitins – of which ubiquilin 2 is a member. This build up of recycling causes pandemonium in cells, as vital movement of nutrients around the cell cannot easily pass to where they need to get to, causing an additional burden to the motor neurones. Eventually, the motor neurones start to degenerate because of this.

What now?

These results will now need to be verified in more people with MND. However, this study could revolutionise the MND research world and provides evidence that the recycling pathway plays a crucial role in MND. Researchers now need to find out how the recycling pathway is involved with MND which could provide insights into how new treatments could be developed to target the disease.

We’ll be keeping a close eye on ubiquilin 2 in the future!

Read our press release on this news story.

Read the Scotsman article on this story.

Reference: Nature (2011) DOI:doi:10.1038/nature10353

UPDATE: Prof John Mayer from University of Nottingham takes you even further behind the scenes of this news story.