Case study: Dr John Parrington

Research: Finding a treatment for a type of infertility in men, and understanding fundamental cell biology that could have an impact on diabetes, heart disease and immune problems.

Animals used: Sea urchins, mice and hamsters

‘Egg activation is really the thing that sets life going. When a sperm fuses with an egg and fertilises it, the sperm introduces a specific protein which sets off a series of calcium oscillations. The protein triggers the release of calcium from stores inside the egg cell in a series of pulses, activating the egg and setting it off on a path towards a new life. It’s a signal that’s essential for life to begin.

‘Some men are infertile because their sperm fail to activate eggs – the calcium oscillations don’t happen. The sperm lack a proper functioning version of the protein involved called PLCzeta and there’s nothing that can be done.

‘One gauge of how many people are affected comes from couples in IVF treatment where a procedure known as intracytoplasmic sperm injection, or ISCI, is used. Here, the sperm is injected into the egg. Two to three per cent of the men will show this type of infertility. ISCI was used in 47% of all IVF treatments in the UK in 2006, or over 20,800 cases. So that’s potentially around 600 couples a year just in this country who find that they can’t have children in this way.

‘Our aim is to make an artificial version of the protein as a treatment. Although we are still at a preliminary stage, we are beginning to work with IVF clinics. As well as a fertility treatment, we could also use our work to try and come up with a contraceptive as an alternative to the pill. It wouldn’t have side effects like the pill, which alters a woman’s hormone balance.

‘Our research began with sperm from mice and hamsters so that we could identify and then purify the protein involved from large sperm extracts. We wouldn’t have discovered PLCzeta otherwise.

‘We’ve since moved on to human sperm and clinical samples. Using antibodies, we’ve been able to detect where the PLCzeta protein is in the sperm. We also have some preliminary data from a patient that may allow us to determine the mutations involved in infertility.

‘We use mouse eggs in all this work on egg activation because they are much more accessible. Human eggs are very precious. Not only must ethical approval be obtained as it a very invasive procedure to obtain eggs, but also those eggs obtained are generally used in IVF to make babies. The fertilised egg never develops after we have injected it with sperm. We only let it go as far as the calcium oscillations we are looking for.

‘Calcium signalling is also involved in controlling insulin secretion, heart contraction, body weight, the immune system, nerve connections, many different processes in the body. In another area of our research, along with others in Oxford, we study the mechanisms that lead to calcium release. If this goes wrong in some way or is imbalanced, it can lead to conditions like diabetes, heart disease, and obesity.

‘There are three different pathways that mediate calcium release in the cells of the body. One of these is well worked out, but the other two are much less well known. We have gone some way to identifying all the enzymes in cells involved in these two pathways and their mechanisms of action.

‘By determining the enzymes involved in these processes, we can get a lot of specific information about the mechanisms of these diseases, perhaps find better ways of diagnosing them, and come up with new ways of treating them. It is very difficult to design and develop good drugs to manipulate these pathways if we don’t know the enzymes involved. It is a necessary first step.

‘We use sea urchins as a model organism for these studies on calcium signalling because their eggs are very large single cells and so are easy to work with. While sea urchin eggs are a fantastic tool, it is still important to study something that is much closer to human physiology and the mouse is an obvious example. We breed “knockout” mice (mice with a single gene removed) with defects in enzymes involved in the signalling pathways. This is essential for modelling human disease.

‘There is no doubt that the Biomedical Sciences Building is better for animal welfare. The cleaner environment for the animals makes a major difference to the animals’ health and the success of our studies. Knockout mice are very sensitive to their environment and need to be free of disease. If you’re studying a model of a disease the last thing you want is animals getting an infection. With the filtered cages in the new building there is less exposure to infection.

‘It is also important for human welfare. Researchers working with animals over a long period of time can develop allergies. Since the mice are in filter boxes, this will protect the people working with them too. This is incredibly important. Occupational health is a major concern too.

‘We do all we can to use as few animals as possible. We use recombinant proteins in bacteria, culture human cells in the lab and test them, and model the structure of proteins like PLCzeta or drug targets on the computer. But to understand processes at the level of a whole organism, it is still necessary to use animals and test predictions in an animal system.’