Feature: Wellcome-Beit Fellowships
22 March 2012. By Chrissie Giles
Defining moments in your career can be hard to recognise without donning the lab specs of hindsight. For Dr Eva Frickel, Wellcome Trust Research Career Development Fellow, National Institute for Medical Research, such a moment came in 2005. "I was a postdoc, and we were looking for a big infectious agent that we could colour and manipulate in the cell." A biochemist and biophysicist by training, Eva's first encounter with the chosen parasite - Toxoplasma gondii - was low-key. But now she's leading her own lab to study how this parasite interacts with our immune system.
As a parasite, Toxoplasma is no small fry: in some parts of the world, as many as 90 per cent of people are infected. Rates of infection are particularly high in South America, France and Germany, possibly because of dietary habits, gardening methods and high numbers of cats - the ultimate host for Toxoplasma.
As the parasite reproduces sexually in cats, its intermediate hosts include things that felines eat: mice and birds. And, although cats don't tend to eat humans, Toxoplasma can live in us too, having evolved the ability to persist chronically in the brain.
As unpleasant as that sounds, Toxoplasma infection passes by unnoticed for most people. The real problems come if people have suppressed immune systems - for example, through HIV infection. In these cases, severe, often fatal, inflammation of the brain can occur. If you become infected during pregnancy, the outcome can also be grave, including miscarriage or progressive blindness of your child.
For Eva, the fascination of Toxoplasma is in the molecular machinations it employs to evade the immune system and persist in the brain. If the parasite gets into our cells, it creates a hiding place called a vacuole. Human proteins recognise and react to this by breaking up the parasite and presenting fragments of it to CD8 T cells. These immune cells keep the parasite in check in the brain.
One thing Eva is tackling is finding out which host proteins are sent to recognise the vacuole. Among the suspects is a family of enzymes called large GTPases. Their regularly sized counterparts play roles in cell signalling, trafficking, division and more, yet the large GTPases' raison d'être remains unclear. There are hints, however, that they are involved in the immune response to Toxoplasma.
Describing her first parasitology conferences as an "eye-opener", Eva experienced a gulf between her past and future research fields. "People were looking very broadly at parasites using methods that were behind the times compared to my previous biochemistry research - I hadn't even studied them." Now, she and her team are bringing their experience in microscopy and biochemistry to work out where host proteins go in the cell, and which other proteins they interact with.
Without Wellcome Trust funding, her move to establish a lab at the National Institute for Medical Research (NIMR) in London would not have been possible, Eva says. "At the time I was thinking about where to go, I was looking at the whole world. NIMR didn’t have a position, but said that they would take me if I got the Fellowship. Without it, I could have ended up somewhere without the crucial expertise and equipment."
As for the Wellcome-Beit Prize Fellowship itself, she was "very, very happy" to receive it. "It's a bit daunting to start a young lab but the £25 000 extra will make that a bit more worry-free."
Unravelling nerve degeneration
It was an encounter with a patient that spurred Rhys Roberts, a medical doctor and PhD, back into the lab. "Working as a Specialist Registrar in Neurology, I met one patient who really struck me. She had been attending the clinic for over 25 years when we found out that she was carrying a mutation in one of the 40 or so known genes implicated in Charcot-Marie-Tooth disease."
Charcot-Marie-Tooth disease (CMT) is one of the commonest inherited neuromuscular disorders. A progressive illness, it affects the nerves in the arms and legs to cause weakness, numbness, and hand and foot deformities. There are two main forms: axonal and demyelinating. In the latter, the insulating myelin sheath - which, like the plastic coating of an electrical cable, is vital for effective conduction of the nerve signal - is disrupted.
Rhys's patient had a form of demyelinating CMT called type 4C. The mutated gene results in a mutated form of a protein called SH3TC2. Nothing was known about the function of this protein, so having identified the gene involved meant very little for the patient’s treatment or quality of life. Struck by this and keen to return to the lab, Rhys completed a year of preliminary work at the Cambridge Institute for Medical Research (CIMR), funded by the Wellcome Trust. It is here that he is now working as Wellcome Trust Intermediate Clinical Research Fellow.
"In all cells, proteins and lipid are constantly being moved to different parts of the cell. Making sure that they end up and stay in the place they should be is crucial for the health of the cell," says Rhys. "Schwann cells need to produce and mobilise a huge amount of membrane to form the myelin sheath. Presumably, the regulation of proteins in and next to that sheath is essential to nerve health."
Rhys was able to show that the protein SH3TC2 is part of the cell's delivery network - the endocytic pathway, which brings molecules into the cell from the outside, to be sorted and sent to their particular destination or fate. He found that SH3TC2 associates with another protein called Rab 11, which oversees the redirection of protein and membrane back to the cell membrane for recycling.
When the mutant version of SH3TC2 was added to a cell, its affinity for Rab 11 disappeared, along with its involvement in recycling membrane receptors. Now, with his Fellowship, Rhys is trying to find out more about what this protein does.
"The hypothesis is that this protein is binding to lots of other proteins, and probably recruiting them to recycle. I want to find out what these protein complexes are and how they're regulated."
With a Trust-funded summer studentship as an undergrad, an MB-PhD and time in Denmark learning mass spectrometry, Rhys's CV is not that of a typical clinician but that of someone bringing personal experience of working with patients to the Western blots, cell cultures and microscopy stains of the membrane trafficking lab.
Aptly enough, he was on the wards when the call about his Fellowship came through. "I was thrilled to get the award, and the Wellcome-Beit Prize will be very helpful. It's a great time for clinicians to be working in basic science, and I'm very fortunate to be surrounded by such a concentration of experts at CIMR."
Rewinding brain cells
Dr Steven Pollard was one of the final researchers to gain a Beit Memorial Research Fellowship - the forerunners of the Wellcome-Beit Prize Fellowships - which allowed him to turn an interesting side project into a whole new direction of research.
"I was a developmental biologist working at the NIMR [National Institute for Medical Research]," he explains. "I wanted to move into mouse development, using embryonic stem cells, so went to work with Professor Austin Smith in Edinburgh and subsequently Cambridge, at the new Wellcome Trust Centre for Stem Cell Research. Now, nine years later, I'm talking about a clinical trial for a brain cancer drug."
Supported by the Fellowship, Steven was investigating adult neural stem cells in the forebrain. A side project he started during this time, on a highly lethal type of brain cancer called glioblastoma, has since become a major area of interest. Historically, glioblastoma was seen as a relatively simple disease and, perhaps for that reason, had suffered from a lack of basic research. "The view up until recently was that glioblastoma is driven by a cell called an astrocyte that proliferates out of control," he says. Now, rather than just a proliferating ball of astrocytes, the tumour is seen more as a tissue, a mixture of cells including those with characteristics of neural stem cells.
However, it's not clear from which cells the cancer begins. Is an astrocyte 'rewinding' its development to acquire stem-cell-like abilities, or are neural stem cells themselves behind these devastating malignancies? "Understanding how normal neural stem cell biology relates to glioblastoma is really the core interest of our lab," says Steven.
To grow neural stem cells in the lab, many researchers use a suspension culture technique, in which the cells are free to float around. Steven and colleagues developed a way to grow them on flat plates and keep them growing indefinitely in the lab. "You can work with them like normal cell lines," he says. This had made it much easier to use the cells. For example, his team have run imaging screens using automated microscopy and software tools to track the behaviour of individual cells.
Using these techniques, Steven has been able to compare neural stem cells grown from glioblastomas with normal neural stem cells. He screened the cells with 160 kinase inhibitors - molecules that block the activity of a type of enzyme. "We reasoned that if we found something that made any of the tumour-derived cells differentiate, stop dividing or die - but not the normal cells - then that may be a good drug target. That has led us to a [cellular] pathway and kinase inhibitor that could be pushed forward to clinical trials."
The Beit Fellowship allowed Steven to become semi-independent, covering his salary and some laboratory consumables, and giving him the chance to try the cancer project alongside his primary project. Now a Team Leader at the Samantha Dickson Brain Cancer Unit within the UCL Cancer Institute, supported by a grant from Cancer Research UK, he is following up promising compounds highlighted by the screening.
"The translational work was never my intention, but there are opportunities to do things quite quickly that could have an impact," Steven says.
This feature also appears in issue 70 of ‘Wellcome News’.
Top image: Schwann cells myelinating axons in the peripheral nervous system. Rhys Roberts is exploring the proteins in and around the myelin sheath. Credit: Dr David Furness, Wellcome Images.