DIVISION OF MOLECULAR MEDICINE

RESEARCH ESSAYS

The Division of Molecular Medicine is comprised of several groups and laboratories that pursue fundamental research into cellular, molecular and genetic processes of relevance to medicine. Common medical problems investigated by members of the Division include cancer, diabetes, cardiovascular disease and mental illness. Several of the groups with overlapping interests have formed collaborative research programs within and between the separate Divisions. These programs focus on specific areas and generate synergies that could not be achieved independently. For example, the Integrative Genetics Program is pooling the expertise of several groups in order to address fundamental questions regarding the biological and clinical significance of genetic diversity. These studies have implications for understanding of the genotype / environmental interactions that appear to have a role in many disorders such as common forms of mental illness that are characterized by anxiety and depression, Parkinson's disease and different forms of cancer.

Another major program in the Division is focused on the development and regulation of the immune system and the molecular and physiological analysis of autoimmunity and its contribution to the pathogenesis of diseases such as diabetes and multiple sclerosis.

The research carried out within the Division and its associated programs has been enhanced recently by the establishment of the Medical Genome Centre. The mutant mice generated in the Centre will provide a range of animal models for the detailed study of the many biological processes under investigation within the Division.

The groups within the Division continuously review their research findings to identify those aspects with potential clinical applications. Many of the groups have well established collaborations with hospital based researchers to facilitate the transfer, to the clinic, of advances made in fundamental research.

Professor Philip Board, Head of Division

CANCER GENETICS LABORATORY

Leader: Dr Maija Kohonen-Corish

The Cancer Genetics Laboratory studies the genetic basis of bowel cancer using blood and tumour samples from patients who have a strong family history of these tumours. Bowel cancer is the most common form of malignancy in non-smokers. The majority of patients have no family history of bowel tumours, but in about 5% of cases there is a clear hereditary predisposition. One of these inherited cancer syndromes is known as Hereditary Nonpolyposis Colorectal Cancer (HNPCC). Since 1993 six different susceptibility genes have been identified for HNPCC. If a person is found to have inherited a defect in one of the genes, regular surveillance can detect tumours at an early and relatively harmless stage. A research project is being conducted involving 60 families in Melbourne, Sydney and Canberra, who suffer from HNPCC. The project involves taking blood from one or two patients in each family, determining the specific defect involved and then referring the rest of the family to genetic counselling and DNA testing. The development and testing of improved mutation detection methods, such as Enzymatic Mutation Detection™ (EMD™) is the central theme of this research.

A mouse model of bowel cancer is also studied. The Msh2 deficient mice are susceptible to cancers because they have a defect in a gene whose normal function is to repair DNA replication errors. We use these mice to determine how experimentally induced inflammation can trigger tumour development. The experiments are designed to address the question why chronic ulcerative colitis, a type of inflammatory bowel disease, is associated with an increased risk of bowel cancer in humans. The development of new and innovative treatments depends upon a better understanding of the disease process in a suitable animal model.

CARDIOVASCULAR DISEASE GROUP

Leader: Dr Neville Ardlie

Coronary heart disease is an epidemic of our time and it is becoming more common in nations previously impoverished by history or recent circumstance, as living standards improve. The villain of the piece in coronary heart disease is coronary atheroma, which can rupture, causing clotting and culminating in a heart attack. Previous research by the Group, in collaboration with the Department of Cardiology at The Canberra Hospital has shown that premature coronary heart disease is associated with increased clotting. The Group has also obtained evidence linking stress to coronary heart disease.

An elevated LDL (low density lipoprotein) is at the core of atherogenesis, but the mechanisms whereby LDL initiates and promotes atherosclerosis remain unknown. Furthermore, the measurement of LDL cholesterol alone is generally useless for predicting risk of CHD. This stems from the fact that the standard measurement of LDL cholesterol comprises a number of separate components which are not atherogenic. The number of small dense LDL particles is much more predictive of CHD risk than are levels of total cholesterol. This finding is being exploited to obtain a greater understanding of atherogenesis, and to develop new diagnostic tests for detection of coronary disease.

The Group is also involved in a national and international collaboration linked to Utah (USA) to promote early diagnosis and family screening in familial hypercholesterolemia, one of the commonest inherited metabolic disorders, affecting one in 500 Australians. People with this condition have up to a 40-fold increased risk of premature coronary heart disease, and, if untreated, their life expectancy is reduced by 20 to 30 years.

In summary, major aims are to identify and characterise modified LDL particles involved in atheroma development, investigate metabolic factors linked to LDL modification, determine how LDL particles cause atheroma, and develop new diagnostic approaches to CHD.

DEVELOPMENTAL PHYSIOLOGY GROUP

Leader: Dr Peter McCullagh

A distinctive feature of the research of the Developmental Physiology Group is the breadth of the topics under investigation. We believe that, in any study of development of the fetus, it is necessary to remain constantly aware of the potential that exists for interaction between different organ systems. Whilst inter-system interaction is, of course, a feature of any aspect of physiology it assumes its major importance during fetal life. The fetal lambs on which our research is based are undergoing a continuous process of maturation and growth during which events that happen in one system of organs are likely to be influenced on a continuing basis by occurrences in other systems.

The major investigations that are currently underway include projects examining the immune system, the gastrointestinal system, the endocrine system and the lungs.

Despite the superficial diversity of these topics, there exist a variety of interfaces between them and a fundamental objective of our research is to attempt the integration of results obtained in any individual project into an overall description of fetal development. A second objective underlying our research is to relate processes which operate during normal fetal development to disease processes that subsequently arise in the postnatal life of animals and humans. In relation to this objective, the responsibilities of the immune system and the endocrine system are of particular interest. Susceptibility to disease after birth can be heavily influenced by events which occur in these systems during fetal life. The specific problems that our research addresses may be grouped under several headings.

How does the normal wide range of capacities to produce antibodies develop?

By the time of birth, a lamb, or a baby, must be able to form protective antibodies against an enormous number of dangerous micro-organisms. This can only occur if a process of diversification of the types of antibodies that can be produced has already occurred in the white blood cells during fetal life. However, this process of diversification requires the precursors of cells which are to produce antibodies to populate, and multiply in, a few specific locations in the fetal body. To understand more accurately what steps are required to achieve the process of diversification, a technique has been developed for the formation of small organs from isolated cells in tissue culture. Examination of these artificial small organs by biochemical and electron microscopic techniques is revealing some of the details about processes that could previously only occur within the fetal animal.

Why are newborn animals and humans particularly vulnerable to gut infections?

A substantial proportion of illness and death in the perinatal period is attributable to infection of the gut by pathogenic bacteria and viruses. The reasons for this susceptibility are not well understood. One of our research projects is seeking to discover why the gut is so susceptible to infection for some time after birth. Fetal lambs have been exposed to pathogens in order to define the protective processes available to resist infection.

How does function of the thyroid gland during fetal development differ from its function after birth?

Whereas the manner in which the thyroid gland of adult animals and humans is controlled by the pituitary gland and, in its turn, controls function in many tissues throughout the body is well established, the nature of these relationships in the fetus is poorly understood. Indeed, research within the Group strongly suggests that some of the central features of thyroid function in the fetus, as currently described in medical textbooks, are incorrect. It now appears highly likely that the thyroid hormone, or chemical messenger, responsible for regulating maturation in the fetus is not the same as the hormone which performs this function after birth.

How does the fetus learn to avoid mounting autoimmune responses against itself?

In the course of acquiring the capacity to produce white blood cells with a diverse range of antibody-forming ability, it is inevitable that many cells capable of attacking the tissues of the fetus itself will also be generated. We have been examining the manner in which the fetus avoids the developmental complication of autoimmunity. Our earlier research discovered cells in normal fetuses that are able to suppress autoimmunity. More recently we have used microsurgical removal of different parts of the fetal immune system in an attempt to find out details of a process called apoptosis in which specific cells of the fetal immune system are programed to die. As a result of apoptosis, white blood cells that are likely to attack the body and produce autoimmune disease are eliminated before birth.

Can the existing prevention and treatment strategies for respiratory distress syndrome in premature infants be improved?

Respiratory distress syndrome, in which the lungs of a prematurely born infant fail to function adequately, is responsible for much disability, death and expense to the health care system. Research originally undertaken on fetal lambs by a New Zealand group several decades ago established that infants at risk of respiratory distress syndrome because of lung immaturity could be greatly assisted by cortisone administration. Nevertheless, the measures available for prevention and treatment of this syndrome still leave much to be desired. Thyroid hormones have been proposed as therapeutic agents to treat respiratory distress syndrome but have failed to gain general acceptance. The Group has undertaken the most thorough study to date of the interactions between thyroid hormones and developing lung tissue. We conclude that thyroid hormones are likely, together with cortisone, to be valuable in managing the respiratory distress syndrome. Our future research will concentrate on translating the information that has been gained in fetal lambs into a therapeutic model.

AUTOIMMUNITY/GENETIC MANIPULATION LABORATORY

Leader: Dr Brett Charlton

Autoimmunity and mechanisms of disease development in insulin dependent diabetes mellitus and multiple sclerosis

Our lab is studying the processes of autoimmune disease with a focus on type I diabetes and multiple sclerosis. To analyze the immunological and pathological process we use animal models of the disease, including transgenic and knockout mice, to isolate particular processes. We aim to understand what is abnormal in autoimmunity and determine new means of counteracting these abnormalities. Particular areas of study include the role of nitric oxide in autoimmunity, the role of Fas and fas ligand in diabetes and the role of the MHC in diabetes.

TRANSPLANTATION IMMUNOBIOLOGY LABORATORY

Leader: Dr Charmaine Simeonovic

Insulin-dependent or Type 1 diabetes in humans results from an autoimmune disease which selectively destroys insulin-producing beta cells of the islets of Langerhans. Islets are normally found in large numbers, scattered throughout the pancreas. The transplantation of pancreatic islet tissue represents a treatment which would restore physiological control of blood sugar levels thereby preventing the secondary microvascular complications associated with current insulin therapy. Islet tissue transplants, however, are faced with destruction via two possible mechanisms: rejection and autoimmune disease which returns to attack the transplanted tissue. From a practical viewpoint, there is a vast shortage of human pancreases available for transplantation. Use of a non-primate animal species (e.g. pig) for pancreas donation would offer the bonus of an abundant supply of islets for replacement therapy. However, ethical concerns have been raised about the possible transmission of pig viruses (e.g. endogenous retrovirus) from the transplant tissue to diabetic human recipients. This cross-species transmission is known as "xenozoonoses".

Although immunosuppressive drugs are currently used to prevent the immunological rejection of life-saving organ transplants e.g. kidney and heart, such therapy can severely compromise the body's immune defenses and render patients susceptible to fatal infections. This potential risk cannot be justified in patients with Type 1 diabetes because the immunosuppressive treatment could lead to far worse health problems. For this reason, the laboratory's research focusses on identifying the immune mechanisms responsible for the destruction of pig pancreatic islet tissue following transplantation to a different recipient animal species (i.e."xeno"- grafts). This information is being used to develop a safe, non-toxic strategy for preventing transplant destruction i.e. thereby eliminating the need for systemic or toxic immunosuppression. Approaches currently under investigation include: gene therapy using viral (Avipox) vectors and cellular co-transplants engineered to express protective proteins (e.g. cytokines) in the local vicinity of the islet transplant; peptide therapy to inhibit activation of the immune system, and non-specific antigen stimulation (Q fever antigen vaccination) to generate a protective or regulatory immune response. The latter treatment (a single injection prior to transplantation) has been shown to prolong the survival of pig pancreatic islet transplants in mice; this protective mechanism is dependent on the cytokine interferon-gamma. Ultimately the safety of pig islet tissue transplantation needs to be established for it to be recognised as an improved treatment for Type 1 diabetes. Bioinformatic research is being used to assess the potential for transmission of pathogens, e.g. viruses, from transplanted pig islet tissue to recipient tissues (xenozoonoses); this information will be used to develop clinically relevant diagnostic procedures (e.g. oligonucleotide micro-arrays) to ensure quality control via analysis of porcine viral gene sequences in donor and transplant recipient tissues.

MEDICAL GENOME CENTRE

Director: Professor Chris Goodnow

Many of the health problems we face today - cancer, autoimmune diseases, allergy, cardiovascular disease, osteoporosis, - stem from a discordance between genetics and environment. Our genetic code was selected to survive for a shorter period of time in a very different world, and it is inevitably out of step with the lifestyles we lead today. In some cases we know what to do to fix this imbalance, like putting on a hat and sunscreen to offset genetic susceptibility to the sun. For many cancers and numerous other diseases such as rheumatoid arthritis, diabetes, osteoporosis or obesity, the solutions are not so straightforward.

Rapid advances in gene technology are bringing us to the point of visualizing the imbalance between our genetic code and lifestyle/environment. A worldwide effort has already given us a map and a "dictionary" of many of our genes -- collectively referred to as our genome. The epic challenge for the next decade is to decipher what these gene words mean. How are they combined into the genetic language that guides the cells in our body and determines how well we cope with different environmental stresses? Which gene products are good targets for new drugs to prevent or cure common diseases? Differences in the spelling of those gene words underly differences in susceptibility to modern diseases, and in response to particular therapies, and it is likely that technology will soon allow a list of spelling differences to be rapidly compiled from each person's unique genetic dictionary.

The Medical Genome Centre was officially opened in 1997 to promote research into the function of genes that underpin human health. To decipher the functional meaning of genes and their contextual interactions, laboratory mice represent a crucial Rosetta stone. Almost all of the genes in mice match a human counterpart with only small changes in their spelling. While surprising given the large differences in external appearance, the mouse and human genetic languages are in fact no more different than Chaucer's english and modern english. This underlying similarity makes it possible to define the function of human health genes in the mouse in a way that is impossible in humans.

The strategy being followed is genome-wide mutagenesis in the mouse at an unparalleled scale. In the last year, the Medical Genome Centre has successfully screened the first of a series of libraries of laboratory mice in which single letters in the spelling of many of the genes in the mouse genetic dictionary have been changed by random chemical mutagenesis. The 1999 library comprised 200 pedigrees of ENU mutagenised mice, bred 3 generations to yield at least 25 potentially recessive homozyogous offspring in each pedigree. Collectively, we estimate that this library scans 20,000 genes for loss of function consequences. By visual inspection and high-throughput screening of blood, this library has yielded many new mutant mouse models to discover and understand genes controlling obesity, cardiovascular disease, limb and spine abnormalities, eye function, melanocyte function, coordination, seizures, dermatitis, colitis, and disorders of lymphocyte development such as autoimmunity, immunodeficiency, and leukemia/lymphoma. Collaborative screening projects are underway with several other groups: with the Garvan Institute in Sydney using the library to discover genes affecting bone density and breast cancer; with the Walter and Eliza Hall Institute to discover genes controlling platelet and neutrophil function; with the University of California San Francisco to illuminate genes controlling lymphocyte migration; and with the Novartis Institute of Functional Genomics in San Diego to illuminate genes controlling brain functions.

This "forward genetics" resource is being used by collaborating research groups to identify and study genes that are important in susceptibility, resistance or prevention of particular disease processes, by looking for subtle changes in the behaviour of cells and tissues, by transgenesis, and through DNA chip technology. State-of-the-art facilities for transgenic mouse production, sperm freezing, and database tracking of genetic and phenotypic data have been developed to support this resource and provide a service to researchers.

A parallel, collaborative effort with the JCSMR Human Genetics Group led by Dr Simon Easteal and other members of the Integrative Genetics Programme is developing a new "reverse genetics" resource using a different method of genome-wide mutagenesis. Human genetics advances and gene expression profiling on DNA chips are driving the search for higher-throughput ways to study specific genes in the mouse, where information can be more clearly obtained about how individual gene products link together into coordinated molecular pathways guiding the behaviour of cells. To accelerate the process of deriving mouse strains with mutations in specific genes of interest, a library of mice with heterozygous gene deletions on half of the chromosomes has been constructed. The deletion library is being archived as frozen sperm, DNA and RNA, and screened by gene-specific tests to identify individuals carrying deletions in these genes. To facilitate these tests, a large set of single nucleotide polymorphisms (SNPs) between several inbred strains has been identified by resequencing cDNA.

AUSTRALIAN CANCER RESEARCH FOUNDATION GENETICS LABORATORY

A one million dollar grant from the Australian Cancer Research Foundation in 1997 made possible the establishment of the ACRF Genetics Laboratory in the Medical Genome Centre. The laboratory's focus is on developing genome-wide mutagenesis resources for studying candidate human cancer genes and novel laboratory mouse models to accelerate cancer research at both the basic and clinical ends of the spectrum.

Three new mouse strains to illuminate cancer genes have been obtained from the 1999 forward genetics library. One of these strains carries a single dominant gene defect that results in acute T cell leukemia, and Dr Peter Papathanasiou is currently mapping this gene. The other two strains carry recessive mutations that cause acute myeloid or lymphocytic leukemia or lymphoma. In one of these strains, parents that carry only a single copy of the mutation develop solid tumours of the bone/cartilage in middle age, possibly indicating that the remaining functional copy of a tumour suppressor gene has been lost in rare bone or cartilage precursor cells. At least ten new mouse strains that have recessive gene defects in lymphocyte development and growth regulation have also been obtained, and it is likely that these represent important leads on new targets for cancer vaccination and anti-lymphoma drugs.

A separate discovery project has begun, aimed at illuminating genes regulating solid tumours of the skin and cervix. This project involves a consortium with Dr Douglas Hanahan at the University of California in San Francisco, who has developed a sensitized mouse strain for skin and cervical cancer research, and Dr Simon Foote at the Walter and Eliza Hall Institute. The project is mapping cancer inhibitory genes between two inbred mouse strains, C57BL/6 and FVB, and conducting genome-wide mutagenesis to illuminate dominant and recessive cancer inhibitory genes.

Genes and functions discovered by these efforts will be available to the research community to help in three key areas: 1. primary prevention, where illuminating patterns of inherited susceptibility will help to resolve environmental risk factors and target preventive measures; 2. early diagnosis, where alterations in gene spelling and expression pattern will help to distinguish cancer cells early and predict the best course for treatment; 3. therapy and prevention of secondary tumours, where the genes identified will provide new targets for drugs and new avenues for chemotherapeutic or immunological intervention.

GOODNOW LABORATORY

Leader: Professor Chris Goodnow

Our research aims to understand how immune cells make a fundamental decision: either to fight or to disarm. The process of deciding which immune cells should fight and which should disarm is key to our ability to resist infection and parasitism. Mistakes in this process result in autoimmune diseases, allergy, lymphoma, and leukemia. Moreover, drugs and other ways to alter fight or disarm decisions are sorely needed to improve the success of organ transplantation and treatment of autoimmune diseases and metastatic cancer.

The immune system is made up of billions of immune cells called lymphocytes. By a remarkable gene shuffling process akin to a poker machine, each lymphocyte carries a unique receptor, enabling every lymphocyte to detect a different set of molecules termed antigens. Some lymphocytes have receptors for foreign antigens that are unique parts of the molecular makeup of different infectious organisms. When these rare lymphocytes bind a foreign antigen during an infection, they receive a signal to fight. The lymphocyte first multiplies to make many clones of itself, and then the cells elaborate destructive compounds that neutralize the infectious antigen.

By chance, other lymphocytes carry receptors for self antigens, ie. parts of our own normal tissues and body fluids. When a lymphocyte binds a self antigen it normally receives a signal to disarm. Instead of multiplying and producing destructive compounds, the lymphocyte either commits cell suicide by apoptosis or the cell disarms itself by becoming functionally tolerant, ie. less responsive to antigens and less able to multiply or produce destructive compounds.

For a long time it was not possible to see how self-reactive lymphocytes disarm themselves. Our laboratory has developed ways to visualize this process in genetically modified laboratory mice called transgenic mice. By studying cells in the transgenic mice, we have discovered that each immune cell must run through a complex series of fight or disarm checkpoints before it can be fully launched into an immune response. In some ways, the process resembles the sequence of fight/disarm decisions in a military missile launch, which serve a similar purpose of preventing friendly fire.

Members of the laboratory are deciphering different fight/disarm checkpoint processes, using a combination of biochemistry, cellular immunology, genetic analysis, and transgenesis. At each of these checkpoints, we are focussing much of our work on elucidating how it is that antigen receptors on lymphocytes can trigger several different cell fates ranging from cell proliferation to cell death. Progress on this goal in the last year is summarized below.

Role of receptor crosslinking in determining lymphocyte fate

As part of her PhD studies, Jane Rayner has been analysing a new transgenic model to explore how intracellular signaling by a single class of antigen receptors on immature B cells promotes three alternative fates: survival in some cells, survival with diminished responsiveness in others (anergy), and inhibition of maturation and survival in other cells. We previously found that monomeric HEL antigen, when present in the blood as a self antigen, engaged the receptors on immature B cells in the bone marrow in a way that could trigger anergy responses in the cells, but was unable to abort the cells' development and survival. By studying a new set of transgenic mice where HEL is present in the blood as a covalent dimer, Jane has found that this single change in the the antigen switches its effects so that it now aborts the cells in the bone marrow. The proportion of receptors engaged by the monomer and dimer antigens are the same, yet the responses elicited are strikingly different, indicating that small differences in the extent of receptor clustering play a key role in determining the cellular outcome. Using this model, we hope to illuminate the biochemical signaling pathways that underpin these different ways of controlling self-reactive lymphocytes.

Role of receptor location in determining lymphocyte fate

In B cells that have been made functionally tolerant (anergic) to self antigen, all of the known signaling molecules are present but the antigen receptor is somehow desensitized from triggering them (eg to activate NFkB and JNK) to promote cell growth and division. Interestingly, other signaling pathways (eg. ERK activation and NFATc/p nuclear translocation) are still activated efficiently. Our previous work identified a tyrosine phosphatase, SHP-1/PTP1C, as a key negative regulator of signaling by B cell antigen receptors, but biochemical studies of whole cell extracts have not revealed any change in SHP-1 activity that might account for the signaling block in anergic B cells. Studies by Dr Bennett Weintraub in the last year have revealed a novel, early step in signaling by B cell antigen receptors that appears to hold the key to how the receptor can be selectively uncoupled from mitogenic signaling pathways in anergic cells. He has found that when antigen binds, the receptor quickly moves into specialized domains on the cell surface that appear to correspond to cholesterol and src-kinase-rich rafts. Most of the induced receptor phosphorylation and downstream kinase activation appears to occur after the receptor moves into these domains. In anergic B cells, movement into the signaling domains is suppressed, presumably accounting for the uncoupling of key signaling pathways.

Gene expression changes underpinning different lymphocyte fates

To search for gene expression differences that bring about different cell fates in lymphocytes responding to antigen, Dr Richard Glynne has been illuminating genes whose expression patterns collectively provide a signature and molecular explanation for lymphocyte activation, self-tolerance, or immunosuppression in mature B cells. Using Gene Chip arrays at Affymetrix, Inc to probe mRNA abundance for 6500 mouse genes, he has identified a small set of 19 gene expression changes that underly the B tolerance/anergy response, many of which are negative regulators of signaling. Cell proliferation is blocked in tolerant B cells by preventing responses by a large set of B cell activation genes, including essential anti-cell death genes (A1), stasis-promoting genes (LKLF) and growth-promoting oncogenes (c-myc and LSIRF/IRF4/MUM4). The immunosuppressive drug, FK506, also blocks B lymphocyte proliferation but does an inadequate job establishing tolerance in vivo. Using the same DNA chip strategy, Richard showed that the drug inhibited a subset of the tolerance response genes and an unexpectedly small fraction of activation genes, providing a rational strategy to screen for better immunosuppressive and anti-proliferative drugs.

T cell tolerance and destruction of pancreatic islets

The cellular and molecular processes regulating CD4 T cell responses to self antigens that are restricted to specific organs (organ-specific tolerance and autoimmunity) are being investigated through an NIH-funded project involving a unique transgenic mouse model. The core of this model is a "TCR-transgenic" mouse where most CD4 T cells react with a model antigen, and where the model antigen is made by pancreatic islet beta cells. In the last year, Dr Suzanne Hartley and staff in the Medical Genome Centre have established that the T cells in this mice are balanced on the brink of damaging the islets and causing diabetes, but normally regulated by a mechanism under active study. This balance is broken by one or more genes from the NOD strain, allowing the T cells to reorganize the invading cells within the islets to promote antibody formation, islet destruction and diabetes. Because the T cells and antigen are well defined, and balanced on the edge of autoimmune disease, we believe this model makes it possible to illuminate the underlying regulatory mechanisms and genes in a way that is difficult in conventional mouse models or in humans.

HUMAN GENETICS GROUP

 Leader: Dr Simon Easteal

Research in the Human Genetics Group is aimed at understanding the nature of genetic variation in humans and how it relates to disease. We take a broad view, recognising the importance of the evolutionary forces that have shaped the structure of the human genome and the nature of human genetic diversity. Accordingly, our investigations can be divided into two areas: Mechanisms of gene and genome evolution, and The nature of human genetic and genomic variation.

Gene and genome evolution

 In mammals genetic novelty may arise through a diversity of genetic and evolutionary processes, such as mutation, gene duplication, gene conversion, genetic drift and natural selection, occurring in large and structurally complex genomes. Information relating to genome and protein function, the processes by which functional novelty has arisen and patterns of species evolution are contained within DNA and protein sequences. We use a comparative approach to the interpretation of this information, investigating differences in genomes, genes and the proteins they encode, among related species, particularly humans and other primates. Work is focussed on the mitochondrial genome, the MHC complex and a number of other multigene families.

Human genetic and genomic variation

 Medical genetics has largely been focussed in recent years on understanding single gene defects. Less attention has been given to genetic disorders that have a polygenic basis, such as mental illness, cardiovascular disease and diabetes. Although these are more important from a public health point of view, they are technically more difficult to investigate. This situation is changing largely through the technological advances of the human genome project. Associated with this change is an increased recognition of the importance of the normal range of human genetic variation, and its importance in relation to disease prevention. Furthermore, understanding the relationship between molecular genotypes and disease phenotypes becomes more dependent on population-based rather than family-based investigations and an understanding of the genetic structure of human populations is needed. Our research is directed at understanding the basis of a number of genetic disorders, and of the patterns of normal genetic variation in human populations.

One particular focus is the genetic basis of personality variation, which is associated with a predisposition to common forms of mental illness involving depression and anxiety. This work is done in collaboration with the NH&MRC Social Psychiatry Research Unit. We also investigate the pattern of genetic variation among human groups particularly in relation to HLA loci, mitochondrial genes, and microsatellite loci. Our work on HLA variation includes analysis of structure and function and, in addition to its significance to medical genetics, it has important implications with respect to organ transplant programs and to the rational design of peptide-based vaccines. Variation at mitochondrial genes and microsatellite loci have important forensic implications and the work has an overall goal of understanding the origin and evolution of humans and of human groups.

MOLECULAR GENETICS GROUP

Leader: Professor Philip Board

Because human beings are constantly exposed to a variety of environmentally derived chemicals that effect the normal function of our cells, tissues and organs, we have evolved a complex group of enzymes that detoxify these compounds and provide an important layer of protection against their deleterious effects. It is now very clear that an individual's genetically determined compliment of detoxication enzymes has a significant influence on their response to a variety of therapeutic drugs and environmentally derived toxins. The work of the Molecular Genetics Group is aimed at gaining a fundamental understanding of the molecular and biochemical mechanisms that underlie individual responses to such compounds. One of the major research interests of the Molecular Genetics Group is the role played by the glutathione linked enzymes such as the glutathione transferases (GSTs) in the metabolism and detoxification of therapeutic drugs and environmentally derived carcinogens and toxins.

The GSTs are a large family of enzymes and previous studies have shown that they can be subdivided into a number of different classes that have characteristic structural variations, substrate preferences and sites of expression. The GSTs function by conjugating glutathione to the target chemical thereby making it more water soluble and making it recognisable by an export pump that expels glutathione conjugates from cells.

Genetically determined deficiency in the expression of some GSTs can be a risk factor for lung, stomach and skin cancer. In contrast, over expression of GSTs has been associated with resistance to cancer chemotherapy. Genetic variations that cause subtle changes in GST function can be clinically important. For example, we recently found that a variant form of glutathione transferase GSTP1 that works with different substrates was associated with the occurrence of Parkinson's disease in patients who had been exposed to pesticides.

To gain a comprehensive understanding of the genetic diversity in response to environmental toxins and therapeutic drugs it will be necessary to identify all the enzymes involved in detoxication processes and to identify the common genetic variants of these enzymes that contribute to functional differences. The recent expansion of the Expressed Sequence Tag database (EST) to include more than a million DNA sequences encoding copies of most active human genes has provided a remarkable resource for the identification of new genes and polymorphisms. We have developed novel screening strategies that have successfully identified several new glutathione transferase gene families and a number of novel polymorphisms. The new enzymes discovered by this data mining approach have been shown to catalyse unique detoxification reactions and to participate in metabolic pathways not previously attributed to the action of glutathione transferases.

The strategies we have developed for screening the EST database can be readily applied to other genes and gene families and will be of great value in the identification of new genes and polymorphic variants of pharmacogenetic interest.

UBIQUITIN LABORATORY

Leader: Dr Rohan Baker

Critical steps in the control of complex processes such as cell growth, development, and gene expression, are controlled by proteins that are only required transiently and must be rapidly destroyed to control their activity. This is accomplished by attaching multiple ubiquitin proteins to the target, which "marks" it for destruction by a large proteolytic complex called the proteasome. Most of our research focuses on a family of enzymes called ubiquitin-specific proteases (USPs), that have the ability to cleave ubiquitin from such marked proteins, and thus slow or prevent their destruction. In this context, some USPs can be considered "proof-reading" components of the system, safeguarding a target from inappropriate ubiquitination (and thus destruction), and imposing a further level of regulation on the pathway.

We study USP enzymes using yeast as a model system, both because it is very amenable to genetic and biochemical studies, and also because the ubiquitin system is so highly conserved between yeast and humans, that insights we gain in yeast can be applied to our studies on mouse and human enzymes. Our current work centres on three of the family of 16 USPs in yeast, Ubp2, Ubp6 and Ubp15. We have shown that all three of these enzymes can control the degradation of other proteins, both positively and negatively. We are currently seeking to find proteins that these three Ubps interact with, to identify proteins whose degradation they can control. Initial results with Ubp15 suggest a role in the turnover of multi-drug resistance proteins, and thus Ubp15 can regulate drug sensitivity of cells. Mouse/human relatives of both Ubp6 and Ubp15 have been identified, and we will extend our work to these species.

We also use mice as a model organism to study human disease. We have previously identified a USP that functions as an oncogene in mice; that is, it causes cancer when overproduced. Others have linked the human version of this USP with certain types of lung cancer. We and our collaborators have shown that this USP interacts with the Retinoblastoma protein, which functions to prevent cell growth by keeping transcription factors (proteins that control gene expression) in check. We have also recently identified a very close relative of this oncogenic USP in both mouse and human cells, and it is also predicted to interact with the Retinoblastoma protein. Our current efforts are aimed at determining the functional significance of these interactions; if the closely-related USP is also an oncogene; and if the interaction with the Retinoblastoma protein is the basis of their role in cancer.

Our results show that USPs can play important roles in regulating the ubiquitin pathway, and through this, processes such as cell growth. Aberrations in these USPs may lead to cancer and disease.

STAFF - DIVISION OF MOLECULAR MEDICINE

Professor and Head:
PG Board, BSc. (Hons), PhD (UNE)
School Technical Manager:
J Bateman, BSc (Syd)
Divisional Administrator:
M Goodisson
Administrative Assistants:
G Noble, M Tankosic
 
Cancer Genetics Laboratory
 Research Fellow and Leader:
M Kohonen-Corish, MSc, MSc (Helsinki ) PhD
Visiting Fellows:
M L Bassett, MB ChB (Otago), MD (Qld), FRACP
G Buffinton, BSc (Hons), PhD
WM Burch, MSc (Melb), PhD (Lond), MIE (Aust)
J Cavanaugh, BSc, MS (North Carolina State University), PhD
P B Herdson, BMedSci, MB, BS, PhD, FRCPA
F Lomas, MB, BS (Hons) (Syd), FRACP, DDU, FRACR
P Pavli, MB, BS (Hons) (Syd), PhD, FRACP
Y Wang, MS (Nanjing), PhD
Senior Technical Officer:
J Hornby, BSc (Hons) (Queens, Belfast) (until August)
Laboratory Technician:
A Janssen, BSc (until January)
K Kugathas, AssDipAppSC (CIT) Canberra (until July)
 
Cardiovascular Disease Group
 Senior Fellow and Leader:
NG Ardlie, MB BS MD (Adel), PhD (McMaster) FRACP (until 31 December)
Postdoctoral Fellow:
I A Popov, MD, BSc, PhD (Crimean Medical University, Simferepol, Ukraine)
 Visiting Fellows:
JE Dahlstrom, MB BS(Hons) (Syd), PhD, FRCPA
DP Dhall, MB ChB (Manchester), PhD (Aberdeen), MIBiol, MRCS, LRCP, FRACS
DA McGill, BSc(Hons) (UNSW) BS&M (UNSW), PhD FRACP, DipDU.(ASUM)
CH Nair, BSc (Hons) (Aberdeen), PhD
SG Nogrady, MB BS (Syd), FRACP
Laboratory Technician:
M Yang (until May)
 
Developmental Physiology Group
 Senior Fellow and Leader:
PJ McCullagh, MD BS (Melb), DPhil (Oxon), MRCP
School Visitors:
W Whitten, BVSc DSc (Syd), FAA
M Peek, MB, BS BSc (Med) (Hons) PhD, FRACOG, MRCOG
HA McKenzie, MSc PhD (Syd) FRACI
Technical Officers:
B Barancewicz, BRTC, AIST
K King, BAppSc, MedLabSci (Canberra)
 
Goodnow Laboratory
Professor and Leader:
CC Goodnow, BVSc (Hons) Syd, BScVet (Hons) Syd, PhD (Syd)
Postdoctoral Fellows (externally funded):
B Weintraub, BS (MIT), PhD (UCSD) (until 30 July)
S Townsend, BS (Cornell), PhD (UC Berkeley) (until 30 April)
SB Hartley, BSc (Hons) ANU, PhD (Syd) (until 21 May)
J Blasioli, BSc (Hons) (Melb), PhD (Melb) (commenced 5 July)
A Fahrer, BSc. (Hons) (Melb), PhD (Melb) (commenced 11 October)
S Lesage, PhD (McGill) (commenced 8 November)
Laboratory Technicians:
L Wilson, DipBiolSc (CIT)
C White (part time) (until 31 October)
A Murtagh, DipBiol Science (CIT)
J Hardy, BSc (Biomed) (UTS) (commenced 23 August)
 
Medical Genome Centre
 Professor and Leader:
CC Goodnow, BVSc (Hons) Syd, BScVet (Hons) Syd, PhD (Syd)
Facility Manager:
A McKenzie, BSc (Hons) Monash
Coordinator/Animal Technician:
K Sullivan, AssocDipAppSc (Animal Science), AdvCertVetNursing
Animal Technicians:
J Carter, City & Guilds 244 Marine Craft Fitter (BCA, UK)
S Chaudhry, AssocDipAppSci (Animal Science)
L De Wit, Animal Care Certificate Course, (CIT)
S Ewing, Biological Research Techicians's Certificate, (CIT)
L Miosge, BSc (Hons)
I Whiting, BSc (in progress)
J Wilson, Assoc.Dip.App.Sci. (Animal Science) (CIT)
Material Support Technicians:
J Webster
A Wright (until January)
D Smith (from February)
 
Autoimmunity/Genetic Manipulation Laboratory
Fellow:
B Charlton, MB BS, PhD (UNSW)
Technical Officer:
K Currie, BSc (Until February)
Laboratory Technician:
J Kofler DipApplAnimal Sc
 
Transplantation Immunology Laboratory
 Fellow:
CJ Simeonovic, BSc (Hons), PhD
Visiting Fellow:
JD Wilson, BSc (Hons), MB BCh, BAO (Hons), MD (Queens, Belfast), MRCP (UK), FRACP
Senior Technical Officer :
MJ Townsend, AssDipAppPath (Bruce TAFE)
DA Mann, BSc (Hons) (ANU) (from November)
Techincal Officer:
KUS McKenzie, AssDipAppSc, Animal Sc (Bruce TAFE) (until October)
Laboratory Technicians :
JC Zarb
K M Debono
S K Popp, AssDipAppSc, Biol (CIT)
R McMurray (Part-time)
S Meharg (Part-time) (from December)
 
Human Genetics Group
 Senior Fellow and Leader:
S Easteal, BSc (St Andrews), PhD (Griffith)
 Research Fellows:
G Chelvanayagam, BSc (UWA), PhD (UWA/EMBL)
 Postdoctoral Fellows:
G Huttley, BSc (Hons I) (Macquarie), PhD (Univ California, Riverside, USA)
C Wise, BSc (Hons) (Monash), PhD (from April)
Visiting Fellows:
LS Jermiin, Cand. Scient. (Århus), PhD (LaTrobe)
N Saha, BSc (Calcutta), MBBS (Calcutta), MD (Punjab), PhD (Med) (Calcutta)
 Senior Technical Officer:
X Tan, BSc, (Shandong University, Jinan), MSc (China Pharmaceutical Univ, Nanjing)
 Technical Officers:
B Whittle, BSc (Hons)
Y Zhang, MSc (Xinjing, China)
G Herbert, BSc (Hons) (Leics UK) (until July)
A Mettenmeyer, BSc (Hons) (from February)
 
Molecular Genetics Group
 Professor and Leader:
PG Board, B.Sc (Hons), PhD (UNE)
Post Doctoral Fellows:
A Blackburn, BSc (Hons) (UNSW), PhD (until September)
Visiting Fellows:
D Liu, PhD (Syd)
M Webb, MB BS, FRACP (UWA), FRCPA
D Le Couteur, MB BS (Hons) (Syd), FRACP, PhD (UQLD)
Senior Technical Officer:
MA Coggan, BSc (Hons)
Laboratory Technicians:
L Langton, AssDipSc (Pathology) (CIT)
Research Assistant:
M Taylor, BSc (until May)
 
Ubiquitin Laboratory
Fellow (RFT) and Leader:
RT Baker, BSc (Hons) (UNSW), PhD
 Post Doctoral Fellow:
G McGurk, BSc (Hons), PhD (Edinburgh)
Technical Officer:
X-W. Wang, BSc (Fudan, Shanghai, China), MSc (Melb)