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.

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

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.