Libraries, Doormen and Harry Potter

I usually travel to London two to three times a month for meetings and lab visits. If I’ve got any length of spare time, I head for what I call my ‘London office’ – aka the British Library. It’s close to Euston station, it’s free (!) it has a nice café for informal meetings and it has copies of all the latest textbooks and major research journals.

The way in which a cell turns its genetic instructions into the protein ‘building blocks’ it needs to function and survive is sometimes compared to a library.

Our ‘cellular library’ is located in the nucleus of each and every cell in our bodies. The library bookshelves are the chromosomes upon which the books containing all the important information (the DNA) is written in the language we know as the genetic code. The human genome is sometimes called ‘the book of life’ for good reason.

However, the British Library isn’t a lending library. You aren’t allowed to take the books out of the building…..and there are a couple of burly looking gentlemen by the front door to provide additional discouragement.

Instead, you have to photocopy the articles you want and carry the copied sheets out. The cell’s equivalent of these photocopied sheets of genetic instructions are the lesser known RNA molecules, which are carried out of the nucleus to the parts of the cell where the ‘protein-making factories’ are found.

There are numerous proteins that act as couriers, ferrying RNA out of the nucleus, including the RNA-binding proteins TDP-43 and FUS, both of which are known to play an important role in motor neuron health.

Once these proteins have delivered their RNA to the right part of the cell, they head back to the nucleus for their next ‘pick up’.

Which brings us back to the British Library. The other day I had a couple of hours between meetings, so decided to pop in….. but found myself at the end of a long queue snaking across the concourse outside.

There was a new exhibition: Harry Potter: A History of Magic, which was proving popular with the tourists and our aforementioned burly doormen were busy doing bag checks on everyone going in (it is a major and busy public building, so can’t be too careful these days).  But I wasn’t in particularly patient mood, so after 10 minutes of not moving, I gave up and headed for Costa Coffee instead (other coffee outlets are available).

Protein ‘mislocalisation’: what’s the FUS?

With ALS, the same problem seems to happen with TDP-43 and FUS in the motor neurons. They seem to struggle to get back into the nucleus and as a result seem to drift off to other parts of the neuron where they form clumps or ‘aggregates’. How and why this happens is not really understood.

Several presentations on the first day of the Symposium provided insight into what might be going wrong.

In the first biomedical session of the day, Prof Luc Dupuis (Strasbourg) showed that when human FUS mutations are introduced to mice, but missing a key component called the nuclear location sequence, the FUS protein mislocalises in exactly the same way as is found in human disease, leading to motor neuron death. He also found that parts of the mouse brain associated with frontotemporal dementia in humans was also affected, which may well explain some the changes in behaviour he observed in the mice.

He and his team demonstrated that the damage caused by mislocalised FUS wasn’t simply down to having less FUS protein to do the job, but was specifically linked to it being in the wrong place. This mouse model looks to be a very valuable tool in working out why this is happening and as a way of testing potential treatments.

Dr Dorothee Dormann (Munich) took us further into the mechanistic detail FUS, highlighting a particular process that seems to go wrong. She showed that another protein called ‘transportin’ which normally helps shepherd FUS back into the nucleus, struggles to do so if the FUS protein is misshapen (as happens in familial ALS cases where the FUS gene is mutated). It’s almost as if the transportin protein can’t recognise the FUS protein. Dr Dormann then went on to show that this lack of recognition and resultant aggregation of FUS protein is associated with the loss of a chemical process called arginine methylation.

Whilst FUS protein is clearly a major contributor to the disease process in the rare forms of familial ALS with FUS mutations, the importance of FUS protein in sporadic ALS is much less clear. It is a very different story with the TDP-43 protein, where cellular mis-accumulation and aggregation of the protein is a classical pathological hallmark in over 95% of all cases of ALS. It is hoped that better understanding of FUS mechanisms will improve understanding of TDP-43, given that both proteins seem to have similar roles.

C9orf72 joins the story

A number of talks discussed the detailed processes of how proteins shuttle in and out of the nucleus. Prof Ludo van den Bosch (Leuven) gave an excellent overview of what we know so far about these ‘nucleocytoplasmic transport defects’ and the stepwise order of events that seem to occur. He also introduced the most common known cause of ALS, the C9orf72 mutation, into the story, as this seems to have a powerful effect on the transport process.

Using C9orf72 models of ALS, Dr Jonathan Grima (Johns Hopkins) drilled down into the events going on at the ‘library door’.

The doorways in and out of the nucleus are structures known as nuclear pore complexes and there are around 2,000 different varieties, made up of different members of a family of proteins known as nucleoporins and – a bit like doors at Hogwarts – can move around, disappear or simply decide not to open!

Dr Grima showed that as we age, these nuclear pore complexes are not able to function quite as well as they should and this is exacerbated not only in C9orf72 ALS but also in sporadic ALS. He suggested that this may be a common defect, occurring early in the disease process.

Getting out of the library

Back at the British Library – when I was queuing to get in, I could see that the problem was being compounded by folk trying to get out of the building. Dr Grima showed some data indicating that the transport back into the nucleus might be altered by controlling the amount of transport activity going out of the nucleus.

This idea of export of molecules out of the nucleus was taken up by Dr Lydia Castelli (Sheffield) and colleagues, who wondered whether stopping the transport of C9orf72 RNA molecules out of the nucleus might limit the cellular damage. They have found that by reducing the activity of one particular protein called SRSF1, they can protect against the damaging effects caused by the C9orf72 mutation, as it seems to specifically stop the C9orf72 RNA molecules from leaving the nucleus. This work has so far only been carried out in a fruit fly model, but the team is planning to confirm this in other models.

The story continues….

There are still many unanswered questions about how (and when) nucleocytoplasmic transport deficits impact on motor neuron health and function, but given the fact that TDP-43, FUS and C9orf72 – three of the major known causes of ALS – are bound into the story, it does look like it plays an important pivotal role in the disease.

It would be tempting to talk about these as the three ‘deathly hallows’ of ALS, but that’s probably stretching the Harry Potter analogy too far…and anyway, this blog feels like it’s getting as long as the Deathly Hallows books.

Maybe I should have divided it into two parts…?

Lithium revisited: Is there a baby in the bathwater?

At last year’s Airlie House workshop to develop new ALS/MND Clinical Trial Guidelines the focus was, of course, on MND, but there was also important input and learning from outside the field.

One of the most fascinating presentations was from an oncologist who was explaining how detailed genetic analysis of tumours was leading to an understanding of why some experimental cancer drugs appeared to only work in a small subgroup of patients. The take home message from the cancer field was that there should be more effort made in future MND trials to identify and analyse smaller subgroups of patients, in case a potentially positive effect might be missed.

A new research paper, published in the journal Neurology, raises some intriguing findings from the trials of the drug lithium that were carried out several years ago. Lithium generated a lot of excitement when researchers in Italy reported a positive effect of the drug in the SOD1 mouse model of MND. Almost as an afterthought, their research paper mentioned that they had tested the drug in a small short-term trial in patients and it appeared to have some effect. Continue reading

11th Lady Edith Wolfson Clinical Fellowship awarded

We are delighted to announce that Dr Arpan Mehta has been appointed as our latest Lady Edith Wolfson Fellow, jointly funded by the MND Association and Medical Research Council.  This clinical research training fellowship will help to launch his career as an aspiring academic neurologist, providing comprehensive training in cellular, molecular and bioinformatics technologies in a world-class environment. Continue reading

Closing the door on toxic proteins – new clues in understanding a genetic form of MND

The defects in the C9orf72 gene are known to cause motor neurone disease, but researchers don’t understand why. Defective copies of this gene are passed down in some families affected by the rare, inherited form of MND. This week MND Association grantees Drs Guillaume Hautbergue, Lydia Castelli and colleagues, based at the Sheffield Institute of Translational Neuroscience have published their research study providing some important clues about the toxicity of C9orf72. Their research is published in the prestigious journal Nature Communications. Continue reading

Life of an MND researcher – part 2: PhD edition

Each year, the MND Association dedicates the month of June to raising MND awareness. This year, we focus on the eyes – in most people with MND the only part of their body they can still move and the only way left for them to communicate. Alongside the Association-wide campaign, the Research Development team selected six most-enquired about topics, which we will address through six dedicated blogs.

In our previous article we introduced four MND researchers who gave us an insight what a typical day in the life of a researcher looks like and what carrying out a research study actually involves. In this continuation article, you will get the chance to look into the lives of four PhD students, who give us an overview of their projects and their usual daily duties. Continue reading

Using stem cell technology to understand more about how MND and FTD develop

The MND Association are funding Prof Kevin Talbot, Dr Ruxandra Dafinca (née Mutihac) and colleagues at the University of Oxford, who are investigating the link between the C9orf72 and TDP-43 genes in MND. We wrote about this research earlier in the year. As we’ve recently received their first year progress report we wanted to give you an update on what they’ve achieved. Continue reading

How faulty proteins disrupt waste recycling and disposal inside nerve cells

Researchers from the Sheffield Institute for Translational Neuroscience (SITraN) at the University of Sheffield have uncovered a new function of the C9orf72 protein. A paper on their work has recently been published in the EMBO Journal.

A change or mutation to the C9orf72 gene is linked to about 40% of cases of inherited MND. We also know that changes to this gene also occur in a type of dementia called frontotemporal dementia (FTD). However, the reasons behind this link have so far been unclear.

One of the main research routes towards explaining the link between the C9orf72 gene and MND is to work out the normal function of this gene. By studying the protein the gene produces, researchers can see how alterations to this protein and the processes it is involved with result in nerve cell damage in MND. Continue reading

Transforming skin cells into nerve cells to understand MND gene mutations

In previous research Prof Kevin Talbot and colleagues at the University of Oxford began to understand more about how the C9orf72 gene defect causes human motor neurones to die. These studies were carried out using an impressive piece of lab technology, called induced pluripotent stem cell (iPSC) technology.

iPSC technology allows skin cells to be reprogrammed into stem cells, which are then directed to develop into motor neurones. Because they originated from people with MND, the newly created motor neurones will also be affected by the disease. Researchers can grow and study these cells in a dish in the laboratory. Continue reading

Investigating C9orf72 and TDP-43 proteins in a fruitfly model of MND

Background to C9orf72 toxicity

We know that damage to C9orf72 (both the gene and the protein it makes) is a crucial step in why some people get MND and why some people get frontotemporal dementia. There are three possible reasons why C9orf72 is toxic. 1) the way the gene is damaged alters how it normally works. 2) the formation of clumps of RNA – a by-product of the damage and not normally seen in cells, and 3) the formation of very short, new and unwanted proteins called ‘dipeptide repeats’ or ‘DPRs’, again these are not normally seen..

There’s evidence of all three types of toxicity within the motor neurone, but we don’t know how they work together or if one is more toxic than another. We also know that the protein TDP-43 forms clumps in motor neurones affected by the C9orf72 gene. Continue reading

Can zebrafish help us to learn more about MND?

A team at the Sheffield Institute for Translational Neuroscience are creating a zebrafish model to study the C9orf72 gene mutation in MND, and work out its role in the brain and spinal cord (our reference 864-792).

Zebrafish are a good way of modelling what happens in human MND. We know that many of the genes linked to causing MND in humans are also found in zebrafish. For example, changes to a gene called SOD-1 in humans are linked to about 20% of all cases of inherited MND, and when you genetically change the same gene in zebrafish they develop symptoms similar to MND.

A faulty or changed C9orf72 gene is associated with about 40% of all cases of the inherited form of MND. This change (or mutation) is also found in people with a form of dementia called frontotemporal dementia (FTD). FTD can alter abilities in decision-making and behaviour. Continue reading