Animal research FRIEDRICH SAURER / SCIENCE PHOTO LIBRARY LIBRARY PHOTO SCIENCE / SAURER FRIEDRICH

42 | Chemistry World | April 2011 www.chemistryworld.org Of mice and men 2009 marked the first year that more genetically modified animals were used in UK scientific procedures than animals deemed ‘genetically normal’. Katrina Megget investigates the benefits and pitfalls of the GM revolution

The year 2000 wasn’t just the Understanding Animal Research. medical problems we now face’. start of a new millennium. It also Establishing and maintaining a In short Whether it’s a ‘knockout’ model ushered in a new scientific battle new genetic alteration in an animal  GM animals have – deleting or silencing – understanding the molecular population takes several breeding overtaken ‘normal’ – purposely mutating a , roles of the 20–25 000 genes that procedures. They then need to be animals in research or introducing foreign genetic comprise the genome. Fast continuously bred to provide subject  Most of that number material, the premise is that more forward almost a decade after the animals for experiments. is down to breeding. can be understood about a disease, draft human genetic blueprint was According to the UK Home Office, Each line takes multiple its physiological pathway and published and this battle is in full animals are used in six areas of breeding procedures to progression when investigated swing. Indeed, genetic research research and testing. In 2009, 42 per establish and maintain at this molecular level. It’s an has become so pivotal in science cent were used for breeding, 32 per  Appropriate GM advantage non-modified animals that 2009 marked the first year that cent for fundamental biological and animals could reduce can’t provide. more genetically modified animals medical research, 22 per cent for numbers of higher And with up to 25 000 genes in were used in scientific procedures developing new disease treatments, like primates the to decipher, than animals deemed ‘genetically 2 per cent for safety testing non- being used in research that’s a lot to understand. But just normal’ – of the more than 3.6 million medical products, less than 2 per  Some researchers understanding the genes is no procedures, just 48 per cent involved cent in developing new methods of think we are focusing longer enough. Now GM animals animals with a normal genome. diagnosis, and less than 1 per cent too strongly on are increasingly being engineered It’s not a complete surprise – use for education and training. For rather than other factors as ‘models’ of human disease of GM animals has been on the rise genetically modified animals, the in disease states. There are currently more since 2000 when the initial results bulk of the increase seen in 2009 than 500 genetically modified of the Human Genome Project saw was down to breeding, which was 10 mouse models of human diseases the focus of disease really tune in per cent up on 2008 levels. according to animalresearch.info to the molecular level. For many in – an information website run by an the area, it was only a matter of time Why bother? international team of researchers before GM animals overtook their GM animals aren’t bred just for to present current consensus on unadulterated counterparts. And the sake of it. And they aren’t animal research. similar shifts are being seen outside used because they are cheap or For some in this area, this the UK. But what has the engineered convenient – one GM mouse can science signals a move to more version got that the untampered cost anywhere between £30 and targeted therapies that revolve form hasn’t? And why is the GM £100, while a genetically normal around a gene’s role in disease – variety seemingly becoming the mouse comes in at just £3. The such as the breast drug, version of choice? point most scientists make is that, Herceptin (trastuzumab) – and For starters, there is a numerical with GM animals, it’s all about the in turn, more effective drugs in misconception in how animals in genes and the insights they can the future. Already advances are scientific procedures are counted; provide. Animal research in general being seen, says Festing. ‘GM the vast majority are used for has made a major contribution mouse technology has been used breeding. ‘Just breeding a GM to advances in medicine, and recently to: create a new model animal – even if it is not used in any continues to do so. But Festing of Parkinson’s disease, which other regulated procedures – is says genetic modification now may replace some research using counted as an animal procedure provides a whole new playing field. monkeys; study a new compound in UK legislation’, explains ‘GM animals have an important that may halt Alzheimer’s disease; Simon Festing, chief executive role to play in understanding discover genetic similarities of pro-research organisation and treating the more complex between prostate cancer and www.chemistryworld.org Chemistry World | April 2011 | 43 Animal research

hereditary ; reveal used this to create four different processes that limit excessive genetically modified pig models scarring and could be used to that develop the symptoms of type 2 prevent it; and develop a new gene diabetes. The GIPdn pig – based therapy to treat the most severe on the receptor for the incretin type of muscular dystrophy.’ hormone GIP (glucose-dependent Drug giant GlaxoSmithKline, insulin-releasing polypeptide) and for example, is using genetically the only model of the four so far modified mice in obesity published – has a partially defective CHRIS KNAPTON / SCIENCE PHOTO LIBRARY LIBRARY PHOTO SCIENCE / KNAPTON CHRIS research. The company has receptor, causing a weak response to produced a transgenic mouse the hormone. This pig is currently that overexpresses the human being used for metabolomic studies mitochondrial transporter protein and for treatment studies with ‘uncoupling protein-3’ (UCP-3) in incretin hormone GLP-1 (glucagon- skeletal muscle. Research found like peptide 1) receptor agonists. that the transgenic mice ate more Eckhard Wolf from the Gene than the wild-type counterparts, Center at LMU says animal models of yet remained leaner and lighter. diabetes are vital for understanding They also showed lower glucose the disease and for developing new and insulin levels and increased therapies. ‘It has been possible glucose clearance rate. It is hoped without genetic modification, since that from this research compounds there are diabetes models originating that regulate the expression of by spontaneous ,’ he UCP-3 might potentially treat says. ‘The advantage of genetic obesity in the future. modification is that the approach is Meanwhile, researchers in more targeted and is also suitable to Canada and Brazil have used mimic human disease mechanisms at genetically modified mice to the molecular level. We believe that reveal a previously unidentified the pig, and especially the tailored mechanism contributing to pig produced by GM, will represent heart failure. The mouse line an important link between the had originally been engineered in a statement. Already the team Pigs’ metabolism and findings in rodent models and their with a decreased secretion of is looking at possibilities of how physiology are simliar to translation into human therapies.’ neurotransmitter acetylcholine to to treat the disease by increasing ’, making them Andy Greenfield, from the study neuronal function, but over acetylcholine levels. useful disease models Medical Research Council’s time the mice developed symptoms Mammalian Genetics Unit in similar to heart failure in humans. Diabetic pigs Harwell, UK, says that now, with ‘There are other mouse and rat It’s not just mice that are being the technologies and infrastructure models of heart failure, but what used to model and research available, ‘this [genetic research] we haven’t had before is a model human disease. Pigs have a similar is a logical progression of study where we specifically target this metabolism and physiology with an obvious biomedical chemical messenger acetylcholine,’ to humans, and in Germany, a objective’. Indeed, GlaxoSmithKline Marco Prado from the University team from Ludwig Maximilian’s says on its website: ‘Without of Western Ontario, Canada, said University (LMU) in Munich has [genetically modified animals], the pharmaceutical industry’s ability to Genetic modification in a nutshell discover new treatments would be significantly reduced.’ British scientist used for research – called set the genetic modification transgenic and ‘knockout’ A blinkered view? ball rolling in 1981 when he mice. Transgenic mice contain Greenfield’s statement is all very genetically altered embryonic foreign DNA, which could be well considering the world faces

CARDIFF UNIVERSITY CARDIFF stem cells from mouse . human or from another animal. an population and hefty These produced mice that Generally the foreign DNA will chronic disease burden, but are we passed on altered genes to produce a new protein, but it becoming fixated by genetically their progeny. By the 1990s this may also prevent production modified animals? One person who technique was being employed of a particular protein or believes so is Helen Wallace, director to produce knockout mice to interfere with a biochemical of GeneWatch UK, a not-for-profit study physiology. The next wave pathway. A common example group that monitors genetic science of genetic research occurred in of a transgenic mouse is the and technologies. She says science 2002 when the mouse genome , which has an has become ‘genocentric’: ‘One big was published. About 99 per inactivated oncogene making problem with using GM animals cent of human genes have a Martin Evans was one of the first it predisposed to cancer. is the underlying assumption that mouse equivalent, there are people to breed knockout mice Knockout mice have a particular the causes of disease are primarily similarities in gene expression gene removed or inactivated to biological and that understanding and mice suffer from many of the research, and proved to be help determine function of that the genetics of complex disease is same diseases. This has meant useful models of human disease. gene. The gene is usually altered the solution to a diverse range of that mice have quickly become There are two main kinds by replacing it with a similar but problems: cancer, heart disease, the favoured animal for genetic of genetically modified mice mutated sequence. deafness, obesity and so on.’ Sebastien Farnaud, science 44 | Chemistry World | April 2011 www.chemistryworld.org of the genome – not mistaking mice for humans,’ says Greenfield. ‘Certainly we are studying distant relatives – and that must be borne in mind – but the data we generate on GM mice are less like a detailed map of the human genome and more like a ruler, compass, dictionary and torch that guide our understanding of what we are looking at when we examine the human genome.’ GM animals don’t tell us exactly how things work in humans, he notes, but they give us a pretty good idea of where to start looking. ‘It’s about using animal models to generate not just the answers, but the right questions.’

Where to from here? Consensus is that the increasing trend in GM animal use will continue and the research will become more sophisticated. As Festing says, ‘scientists are continually looking for new and better ways of advancing knowledge and understanding’. Indeed, there are already new molecular genetic techniques being developed that can turn a gene on or off at director at the Dr Hadwen Trust – a Indeed, much research is already ‘GM mice are less like different times in adult mice. This non-animal research charity – agrees, progressing into what has been a detailed map of the ‘reversibility’ feature aims to control saying ‘many within the scientific dubbed the ‘envirotype’ (factors human genome and more the resulting phenotype. Next community, and also the public, are external to the organism that affect like a ruler, compass, generation models are also likely too eager to see its observable characteristics, or dictionary and torch that to take into account the genetic as tomorrow’s universal response to phenotype) and incorporating this guide our understanding ’ variation in humans and other every problem of mankind.’ This, he into study design when modelling genetic interactions. says, is a consequence of the ‘gene human disease. For example, the While the proportion of craze’ that started a few decades German Mouse Clinic at LMU is procedures using GM animals ago, where genes were believed to be exploring the relationship between might have increased, in 2009 responsible for practically all ills. genes, environment and physical the absolute number of animal However, as Wallace notes, many characteristics by analysing procedures actually decreased by diseases can not be defined purely phenotype through five environment 1 per cent. Festing says it is possible by their genes – environmental platforms that have been identified that developments that provide aspects such as socio-economic as risk factors in human disease – better animal models of disease may status, pollution, diet and lifestyle diet, air quality, stress, exercise and mean that fewer animals, or fewer are all contributing factors towards immunity. higher animals such as primates, are the risk of disease. The danger, she needed in the future. ‘For instance,’ says, is that ‘scientists are led down Beyond just genes he says, ‘a triple transgenic a dead end because the decision to Including envirotypes into mouse can be a better model for focus studies on genetics excludes genetic research is one example Alzheimer’s than an ageing primate. a much wider range of questions of how this area is becoming more Using genetically modified mice from research’. sophisticated, but there is still the instead of primates to test polio Festing disagrees. Even though argument that genetically modified vaccine potency is another example diseases have an environmental animal models will never be ‘human of partial replacement’. component, it is important to enough’ to provide the research Genetic science is heralding new understand the genetic basis of the insights needed. The mouse model understandings, and GM animals disease as well. And GM animals, he for cystic fibrosis, generated in are the gateway to that. In 2007, says, enable scientists to separate the the early 1990s, is often cited as ‘A triple the Nobel prize in physiology influence of genes from other disease an example of this. Characterised or medicine was awarded to the factors. ‘It is possible, in an animal, by lung and pancreatic problems transgenic creators of the first . to alter one or two genes against a in humans, cystic fibrosis in mice mouse can be In the words of the Nobel Assembly stable genetic background, while manifests itself in the gut. in awarding the prize: ‘Its benefits to controlling other factors such as diet But what this highlights is a better model mankind will continue to increase and environment. This means you the complexity of genes. And for Alzheimer’s over many years to come’. can understand the role of specific understanding this complexity can genes in multifactorial disease and in only come through further research. than an ageing Katrina Megget is a freelance science the internal environment.’ ‘We are learning about the principles primate’ writer based in London, UK www.chemistryworld.org Chemistry World | April 2011 | 45