Cells, genes and molecules

PROFILE: A new line of attack on migraine

MRC Clinician Scientist Dr Zam Cader has found the first gene to be directly linked with a typical form of migraine, which points the way to effective new treatments for the condition.

As an MRC Clinician Scientist, Zam divides his time between being a Consultant Neurologist at the John Radcliffe Hospital in Oxford and doing research on the genetics of neurological disorders at the MRC Functional Genomics Unit. It’s a balance that works well for him:

“If you have an academic turn of mind then there’s nothing better than being able to see the patients for whom you’re doing the research. It gives you an immense sense of satisfaction that you’re directly addressing some of the problems that they talk about, especially when there aren’t good treatments available. You’re right there at the frontier.”

Zam’s research aims to discover genetic changes that cause nerve conditions, find out why they are causing the condition and investigate ways of intervening in this process to develop new treatments. In particular, he looks at the genetic basis of migraine.

“Migraine is perhaps one of the most dismissed disorders,” explains Zam, “people think that it’s just a headache, but it affects 14 per cent of people worldwide, so it’s a huge health burden. It’s a severe, pounding, type of headache that can last for a couple of days and quite often beyond that, and sometimes you get warning signs with it, things like flashing lights and zig-zag lines, which is what we call migraine with aura.”

Until recently, the genetic causes of migraine were unknown. But in 2010, Zam struck gold by discovering a direct link between migraine and a mutation in the gene responsible for making a protein called TRESK. He says:

“Before our study, scientists had been looking really hard but they hadn’t actually pinpointed a gene linked with migraine, they had only found migraine-associated genetic markers. Often these markers were located in areas of DNA between genes – and understanding how these non-gene regions increase susceptibility to getting migraine was always going to be a challenge. So finding a damaging mutation directly in the TRESK gene was a real breakthrough.”

The TRESK gene is responsible for making a type of ion channel. Ion channels are pores in the membranes of nerve cells which let electrically charged particles in. The movement of electrically charged particles allows nerve cells to generate electrical impulses and send signals to other nerve cells. Through studies in frog eggs and human brain tissue samples, Zam and his team showed that the TRESK ion channel can control the excitability, or electrical activity, of nerve cells in a part of the brain called the trigeminal ganglia. This has long been known to be the central place in the brain which is activated during a migraine headache.

The scientists found the TRESK mutation by looking for ion channel gene mutations in a migraine sufferer with a strong family history of migraine with aura, which is a type of migraine known to have genetic causes. When they looked at all the other members of the person’s family, they found that those who had the TRESK mutation suffered from migraine and those without the mutation did not – strong evidence of the gene’s involvement.

“The discovery was a major step forward in understanding what migraine is. We found out that patients who have a TRESK mutation have certain neurons that become more excitable, more prone to be triggered, and thereby set off a migraine headache attack,” says Zam.

“It’s getting very exciting now because the discovery of the TRESK mutation, and the heightened nerve excitability allows us to immediately start thinking of ways of tackling migraine by bringing the excitability back down again.”

And the new knowledge stemming from this discovery has the potential to help all migraine sufferers, not only those who have the TRESK mutation, Zam explains: “The trigeminal ganglia are very much at the centre of the migraine headache, whatever the cause. So if we can reduce the excitability of that area of the brain, we can potentially improve the symptoms or even prevent all types of migraine.”

Zam’s team is now working with MRC Technology, the company which commercialises MRC-funded discoveries. They are about to begin a drug discovery programme to find small molecules which can alter the effects of TRESK and reduce the excitability of the neurones which cause migraine, ultimately leading to new drugs for the condition.

Of the progress he has made, Zam says: “One of the reasons why I went into neurology is because when I started - and to still a large extent now - it’s a big black box of unknowns, with patients who are hard to treat. If my research ultimately makes a difference to the patients that I see, to bridge some of that gap between what they want from their doctor and what neuroscience can provide, I think that’d be great.”

Achievements

Genetic cause for extreme dwarfism uncovered

Primordial dwarfism is a group of rare growth disorders which significantly limit growth at every stage of life, from before birth to adulthood. Those affected by it are among the smallest people in the world.

Research involving three MRC teams, one in Edinburgh and two in Brighton, has found five new genes, collectively called the ‘pre-replication complex’, which are involved in these growth disorders. The work has important implications for improving the diagnosis of primordial dwarfism.

Dr Andrew Jackson led the team at the MRC Human Genetics Unit in Edinburgh, working in collaboration with colleagues at the Radboud University Nijmegen Medical Centre in the Netherlands. He commented: “This is the first time we’ve been able to find a link between genes controlling the basic process which copies our DNA in cells and an extreme form of dwarfism. We’re very excited that these discoveries not only help us understand what causes primordial dwarfism but could also offer us a general insight into how these genes may more widely influence human height and body size.”

Professor Penny Jeggo and Dr Mark O’Driscoll, who led the teams at the MRC Centre for Genome Damage and Stability at the University of Sussex, added: “It’s fascinating to discover that DNA replication has such a significant impact on growth development. This is a clear example showing that investment in understanding basic mechanisms underlying cell growth and replication is critical for understanding development of organisms and disorders of human health.”

A pancreas-protecting protein

New treatments to reduce the chances of people developing pancreatic cancer could be closer thanks to the findings of an MRC-funded group at Cardiff University. Professor Ole Petersen and his colleagues at the University’s School of Biosciences have discovered a protein that provides protection against the effects of alcohol in the pancreas.

The protein, calmodulin, is present in all human cells. The study revealed that in cells from the pancreas which have been genetically modified so that they have no calmodulin, alcohol has a much greater toxic effect; it speeds up a chain reaction that causes cells to self-destruct. This can lead to inflammation (pancreatitis), which in the long-term significantly increases the risk of developing pancreatic cancer. Pancreatic cancer is the fifth most common cause of death through cancer, and only three per cent of patients survive beyond five years after diagnosis.

Professor Petersen found that calmodulin protects pancreatic cells against alcohol’s toxic effects, particularly when it is activated by another small protein, CALP-3. He said: “There is a strong correlation between alcohol intake and incidence of pancreatitis, and we hope that our new findings will eventually lead to the development of drugs to combat this. This is a key step forward.”

Decoding the causes of cleft lip and palate

Cleft lip and cleft palate are common birth defects and can lead to significant difficulties with the infant’s swallowing and speech, as well as life-long psychological problems resulting from low self-image.

Clefts result when small parts of the face fail to fuse together in the developing embryo. At Newcastle University, Dr Heiko Peters aims to define risks that exist even though there is no apparent family history of the problem.

He explained: “We carried out studies in mice to investigate the connections between genetic mutations and the environment of the womb, such as drugs that pregnant mothers may take.”

By modelling these interactions, Dr Peters has revealed that three genes, Pax9, Msx1 and Bmp4, are critical for correct development. “Some medical drugs appear to interact highly selectively with these genes, suggesting that specific patient groups who use these are at a greater risk of having children with cleft lip or palate. We now have a promising tool to investigate how humans can be predisposed to clefts, and we hope to bring improved advice to parents who are at risk for the problem.”

The clock that keeps all living things on time An MRC-supported study at the University of Cambridge’s Institute of Metabolic Science has found the mechanism underlying the internal 24-hour clock found in all forms of life, from humans to algae, known as circadian rhythms.

Circadian rhythms have always been assumed to be linked to our DNA - but rhythms have now been shown to be present in red blood cells, which do not have DNA.

The researchers incubated purified human red blood cells in darkness and at body temperature, and then sampled them at regular intervals for several days. They examined levels of biochemical markers called peroxiredoxins in the cells, which are found in virtually all known organisms, and discovered that they underwent a 24-hour cycle.

A second study, by scientists at the Universities of Edinburgh and Cambridge, and the Observatoire Oceanologique in Banyuls, France, found a similar 24-hour cycle in marine algae, indicating that our internal body clocks share common ground with ancient forms of life on our planet.

Steve O’Rahilly, Director of the MRC Centre for Obesity and Related Metabolic Diseases at the University of Cambridge, which hosted the study said: “By furthering knowledge of how the cell’s 24-hour clock works, scientists are now better placed to explore how these processes go awry in disorders ranging from insomnia to metabolic diseases such as diabetes.”

Sex development disorders linked to faulty gene

The future sex of an embryo depends on a complex set of interacting genes which trigger whether the embryo develops testes or ovaries. An international team of researchers, including scientists from the MRC Mammalian Genetics Unit in Harwell, have found that a mutation in a gene called MAP3K1 plays a key role in such disorders. The mutation can cause someone with a Y chromosome, predicted to develop as a male, to instead develop as a female, or as a male with some female characteristics.

The researchers studied two families affected by a heritable form of sex development disorder that can cause problems such as ambiguous genitalia and issues with gender assignment. They tracked down the defective gene to an area on chromosome 5. At the MRC Mammalian Genetics Unit, Dr Andy Greenfield led research using mice - which share 90 per cent of their genes with humans - to investigate further and found a gene called MAP3K1 to be the likely culprit. They went on to show that the affected individuals had a mutation in this gene.

Screening for this gene, along with others known to influence sexual development disorders, could help doctors to intervene earlier with treatments to enable healthy puberty and fertility in later life.

Dr Greenfield said: “Other research has shown that infertility and tumours in reproductive disorders are more common in people with disorders of sexual development similar to those described in this study, so unravelling the building blocks of how our sex is determined in the womb could help shed light on these diseases.”

Gene therapy to fight prostate cancer

With funding from the MRC, Dr Emilio Porfiri from the University of Birmingham and his team have been working on a new gene-based treatment for prostate cancer, the most common cancer in men.

The team has modified the common cold virus by adding a gene which boosts our immune response against tumours, and a second gene, NTR, which activates a drug precursor. The virus is injected into the tumour and the drug precursor, or prodrug, is given to the patient separately, turning into a powerful anti-cancer drug when it is activated by the gene carried in the virus.

Dr Porfiri explained: “The two genes work together to maximise the killing of cancer cells. We plan to use this modified virus in a new gene therapy trial in prostate cancer patients and we hope the results will match the encouraging observations in the laboratory that have led us to this stage.”

Prostate cancer patients often need to have radio- and chemotherapy which damages healthy cells as well as cancer cells. But the treatment Dr Porfiri is developing specifically targets the tumour cells, thus minimising the risk of side-effects: “Our modified viruses are injected into the cancer, then the prodrug is administered intravenously. Only the prodrug that reaches the cancer is activated, which would keep side-effects to a minimum.”

Better diagnosis for rare disorder

Carpenter syndrome is an inherited disorder in which the skull bones of babies fuse together abnormally early. It causes deformities of the cranium and face, as well as other problems with fingers, toes, and sometimes the heart. It is caused by mutations to a gene called RAB23 and is inherited when both parents carry and pass on a copy of the defective gene. The syndrome is rare, with around 100 cases reported worldwide to date, but can be devastating to patients and their families.

Professor Andrew Wilkie at the MRC Weatherall Institute of Molecular Medicine in Oxford has been using MRC funding to investigate the functions of RAB23 and explore ways to improve diagnostic methods for identifying Carpenter syndrome. He and his team have studied over 40 individuals in whom doctors have suggested the diagnosis, to find out which features predict a positive RAB23 test result.

He explains: “About 60 per cent of Carpenter syndrome patients turn out to have RAB23 mutations and we can give these families better information, helping them to plan whether to have further children. The negative cases fuel the next phase of our research to try to piece together other causes of this condition.”

This diagnostic tool has now been approved for clinical use by the UK Genetic Testing Network and is used in the Oxford NHS Genetics laboratory. It has been used to diagnose patients both prenatally and clinically.

DNA repair ‘scissors’ discovered

Researchers from the MRC Protein Phosphorylation Unit at the University of Dundee say they have unlocked a key part of the puzzle of how DNA repairs itself.

The research team have discovered a protein, known as FAN1, which plays a vital role in maintaining healthy DNA. They discovered that during the natural DNA repair process, DNA ‘flaps’ are produced that need to be trimmed if the repair is to be completed. These leftover pieces of DNA can get in the way during the repair process, so they must be removed. FAN1 carries out this task, acting like a pair of molecular ‘scissors’. Cells that do not have FAN1 are unable to repair DNA breaks and their DNA becomes irreversibly damaged, ultimately leading to death of the cell – this underlines the fundamental importance of FAN1.

Lead scientists Dr John Rouse, explained: “Now that we have identified FAN1 and the role it plays in repairing DNA we can start to develop drugs that inhibit it. This may have a significant effect in cancer, primarily in helping to greatly enhance the efficacy of drugs used in chemotherapy treatments.”

The clock that keeps all living things on time

An MRC-supported study at the University of Cambridge’s Institute of Metabolic Science has found the mechanism underlying the internal 24-hour clock found in all forms of life, from humans to algae, known as circadian rhythms.

Circadian rhythms have always been assumed to be linked to our DNA - but rhythms have now been shown to be present in red blood cells, which do not have DNA.

The researchers incubated purified human red blood cells in darkness and at body temperature, and then sampled them at regular intervals for several days. They examined levels of biochemical markers called peroxiredoxins in the cells, which are found in virtually all known organisms, and discovered that they underwent a 24-hour cycle.

A second study, by scientists at the Universities of Edinburgh and Cambridge, and the Observatoire Oceanologique in Banyuls, France, found a similar 24-hour cycle in marine algae, indicating that our internal body clocks share common ground with ancient forms of life on our planet.

Steve O’Rahilly, Director of the MRC Centre for Obesity and Related Metabolic Diseases at the University of Cambridge, which hosted the study said: “By furthering knowledge of how the cell’s 24-hour clock works, scientists are now better placed to explore how these processes go awry in disorders ranging from insomnia to metabolic diseases such as diabetes.”