Campylobacter jejuni (Cj) is the leading cause of bacterial food poisoning in the world. Each year about 300,000 Canadians are infected by these highly invasive bacteria through ingestion of undercooked meats or dairy products. An acute infection causes diarrhea, fever, vomiting, and, occasionally, death. Cj infection may also lead to Guillain-Barré Syndrome, an autoimmune disease that causes weakness or tingling in the legs and arms. In some cases, symptoms can become so severe that the patient is almost totally paralyzed. Most people recover, although some continue to have some degree of weakness. Ann Lin is researching how Cj bacteria cause disease in the gastrointestinal tract. Cj is predominantly found in the first and last sections of the small intestine and the colon. The bacteria penetrate layers of cells in the intestine and infect underlying tissues. Lin is examining whether this process disrupts the intercellular junctions that provide integrity for host epithelial cells. Disrupting this barrier is believed to contribute to diarrhea, but the molecular process is not well understood. Lin will determine whether Cj causes gastrointestinal disease by damaging the barrier. Ultimately, her findings could lead to the development of new methods of preventing Cj infection.
Research Pillar: Biomedical
Characterization of a kinase implicated in kinetochore function during S phase
Chromosomes, which are a compacted form of DNA, must be accurately duplicated and separated into two new daughter cells during each cell cycle. Genetic instability arises when chromosomes are separated improperly. This error is the source of many diseases, such as cancer and Downâs syndrome. Accurate chromosome separation relies on machinery assembled on each chromosome called the kinetochore. The regulation of the kinteochore is essential for cellular fitness and prevention of genetic instability. Understanding the mechanism by which the kinetochore is regulated will lead to a better view of cellular division and will provide insight into the treatment of diseases such as cancer. Because chromosome separation is a fundamental cellular process in all types of cells, Jennifer McQueen is using budding yeast as a model to study chromosome segregation. She is using many genetic and biochemical tools to examine the involvement of the Mck1 kinase in chromosome separation. Her project aims to discover a new role for the Mck1 kinase in kinetochore function and to produce a new model of kinteochore regulation that is applicable to human health.
The biological role of bone marrow-derived keratinocyte precursor cells in wound healing
Skin, which is the most extensive organ in the human body, performs multiple vital functions. Wounds to this organ, whether chronic or acute, are a serious threat because they leave the body open to infection. Thatâs why burns are a major cause of infection-associated deaths and why early replacement of burned tissues is so critically important. There is an urgent need to engineer skin substitutes for patients with extensive burns who do not have enough skin available for harvesting as grafts to close wounds. However, relatively little is known about how to establish a large-scale production of skin substitutes and how to control the healing process when such material is used. Bone marrow-derived stem cells may be a potential source for the preparation of skin substitutes due to their capacity to be reprogrammed to produce a variety of cell types. Abelardo Medina is studying whether bone marrow-derived stem cells can be used in this fashion both to close wounds and to improve wound healing. Findings from his research may also lead to a better understanding of the healing process and the treatment of chronic non-healing ulcers that develop in elderly people, diabetic and immuno-compromised patients. It also may contribute to a better understanding of the processes associated with over-healing wounds such as those that result in thick burn scars.
Use of a recombinant fusion protein to expand hematopoietic stem cells in vitro and to elucidate mechanisms that determine the expansion and self-renewal potential of mouse fetal liver and adult stem âŠ
Bone marrow is the tissue that fills most bone cavities and is the source of red blood cells and many white blood cells. Disorders that require bone marrow transplantation include aplastic anemia (inadequate blood cell formation by bone marrow), immune disorders, and many types of blood cancers. Current bone marrow transplantation therapies are limited by the number of blood-forming hematopoietic stem cells (HSC) that can be isolated from the patient or donor and transplanted to the patient. Typically, bone marrow or peripheral blood, as closely matched as possible to the patient, is transplanted into the patient. As this match is rarely perfect, patients will often develop a condition of varying severity known as graft-versus-host disease, which causes the patientâs immune system to destroy donor cells. Michelle Miller aims to generate in the laboratory a non-viral method of expanding HSC in the aim of avoiding certain complications that can arise from gene therapy or allogenic bone marrow transplantation.. Michelle (or Ms. Miller) is in the process of testing a fusion protein, which in viral form, has proven to lead to significant HSC expansion and generation of functional mature cells without leading to malignancy. She is also investigating whether there are pathways in common between the self-renewal capacity of mouse fetal liver HSC and those found in the adult as these cells perform better in transplantation tests when compared to HSC from adults. Ms. Miller (or Michelle â see above)hopes her research will lead to increased knowledge about hematopoietic stem cells, and to safer, more effective stem cell therapies.
Modulation of Cav3.2 T-type calcium channels through neuronal nitric oxide synthase activity
Normal brain activity involves the controlled transmission of electrical impulses across networks of neurons (nerve cells). Occasionally, undesired electrical activity occurs within cellular networks and a response is necessary to suppress this outburst. Kirk Mulatz is investigating a negative feedback mechanism that allows neurons to inhibit this atypical electrical activity. He is focusing on the role of T-type calcium ion channels in generating this aberrant electrical activity, and exploring the effectiveness of inhibiting characteristics of the channels to inhibit the activity. Investigations into negative feedback mechanisms both increase understanding of normal brain activity and how cells respond to abnormal activity. A number of neuronal disorders such as epilepsies, mood disorders and chronic pain are associated with atypical brain activity, and the feedback mechanism that Mulatz is researching may contribute to restoring normal activity across cellular networks.
Identification of Enterohaemorrhagic Escherichia coli (EHEC) effector protein binding partners in host intestinal epithelial cells
Certain strains of Escherichia coli (E. coli) bacteria can be harmful and cause disease; other strains are harmless and live harmoniously with their host. In fact, harmless strains of E. coli colonize the human intestine shortly after birth and survive there. In contrast, the disease-causing strains produce a wide variety of infections, including meningitis, urinary tract infections and intestinal infections. Enterohaemorrhagic E. coli (EHEC) colonizes the small intestine and induces severe bloody diarrhea. It is a significant cause of illness and death worldwide. EHEC attaches to the surface of cells lining the intestinal walls. These epithelial cells have microvilli, which are small finger-like projections that increase the surface area available to absorb water and nutrients. EHEC causes flattening of microvilli, which enables the bacteria to bind tightly to the intestinal cells and inject effector proteins into the interior of the host cell where they disrupt normal host cell processes and cause disease. Seven novel EHEC effector proteins have been identified and the mechanisms of their function are unknown. In her research, Stephanie Shames is working to identify host proteins in epithelial cells that are targeted by the seven novel EHEC effector proteins and to describe the interaction that occurs between these host and bacterial proteins. This research may provide important insights into how EHEC causes diarrhea which, in turn, could lead to the development of better methods of treatment and prevention, with world-wide benefits.
The role of CD34 in muscle regeneration
Exercise damages muscle, which the body subsequently repairs. In the repair process, satellite cells (also called muscle stem cells) that are normally at rest, get switched on to replicate, and fuse to, existing muscle fibers. As few as seven satellite cells can generate over 100 new muscle fibers to replace damaged tissue. Consequently, these cells are ideal candidates for treating severe muscle degenerative diseases such as Duchenne muscular dystrophy (the most common form of MD), which cause rapidly progressive muscle weakness and atrophy, and is eventually fatal. Leslie So is assessing the role of a protein called CD34 in muscle regeneration. A short form of CD34 is present on resting satellite cells. Once the cells are activated and recruited for muscle repair, a longer form of CD34 quickly replaces the short form. During the last steps in muscle regeneration, CD34 is no longer present. Leslie is investigating whether the protein maintains satellite cells in their resting state, or helps these cells switch on. To date, efforts to grow and inject satellite cells to treat damaged muscle have been disappointing. In previous work, she developed methods to isolate satellite cells, and therefore hopes that further research will enable scientists to grow cells able to repair damaged muscles, providing a new treatment, and possibly a cure, for muscle degenerative diseases.
Mechanism of Histone Variant H2A.Z Deposition by SWR1-Com
DNA, which is packaged into highly condensed structures in the cell, carries genetic information that is passed from one generation to the next. Chromatin is the first level of DNA packaging that eventually results in the formation of chromosomes â threadlike parts of a cell that carry hereditary information in the form of genes. Many debilitating and life-threatening diseases, such as cancer, neurodegenerative diseases including Alzheimer’s and Huntington’s, and inherited childhood syndromes, result not only from changes in the basic DNA sequence, but also from changes in the structure of chromatin. DNA is condensed into chromatin with the help of DNA-packaging proteins called histones. DNA wraps around eight core histones â two each of H2A, H2B, H3, and H4 â to assemble into chromatin. H2A.Z is a variant of the core histone H2A that is conserved through evolution. Structurally, H2A.Z is different toward the end of the protein. A large protein complex called SWR1-Com, which binds to H2A.Z but doesnât bind H2A, deposits H2A.Z into chromatin. Alice Wang is researching the differences between the way H2A.Z and H2A are deposited into chromatin. She is specifically investigating whether the difference between H2A and H2A.Z lies in their different binding capabilities to SWR1-Com. The findings will help increase understanding of H2A.Z biology and how chromosomal neighbourhoods containing H2A.Z are made. Wangâs ultimate aims for the research is to contribute to development of therapies for diseases that result from changes in chromatin structure.
Identifying the Pro-Survival Actions of Glucose-Dependent Insulinotropic Polypeptide on the Pancreatic Beta Cell
Diabetes is a rapidly growing worldwide epidemic. Itâs estimated that by 2030, more than 366 million people will have the disease, many of whom will acquire additional conditions such as neurological dysfunction, kidney failure and cardiovascular disease. Between 90 and 95 per cent of diabetics have type II diabetes mellitus. This results in hyperglycemia and hyperlipidemia (high glucose and fat in the blood), which causes cell death in the beta cells that produce insulin. This further reduces insulin output, accelerating other conditions associated with diabetes. However, by increasing insulin secretion and promoting survival of beta cells, it should be possible to reduce or prevent the conditions associated with type II diabetes. Glucose-dependent insulinotropic polypeptide (GIP) is a gut-derived peptide hormone whose stimulatory actions enhance insulin secretion and inhibit beta cell death. However, the mechanisms by which GIP protects beta cells are unknown. Scott Widenmaier is studying the possibility that GIP prevents beta cell death by relieving the stress placed on the mitochondria, the cellâs energy producing machine. It is expected that this protective mechanism of GIP will provide key information regarding the effects of chronically-high glucose and lipids on beta cells in type II diabetics. This could lead to a novel class of therapeutics to prevent beta cell death, contributing to better health outcomes for type II diabetics.
The Role of Ubiquitin/Proteasome System in Heart Failure
Heart failure is a disorder in which the heart loses its ability to pump blood efficiently. Despite recent advances in treatment, heart failure remains the leading cause of death in Canada. One in four Canadians suffers from heart disease, and more than 70,000 Canadians die from heart diseases each year. Treatment of heart failure is a major economic and social burden. The proteasome is a large multiprotein complex found in all cells, which breaks down unwanted or damaged proteins that have been âtaggedâ for elimination with a small protein called ubiquitin. The ubiquitin/proteasome system contributes to many cellular functions, including cell division, quality control of newly-produced proteins, and immune defense. Impairment of this system has been linked to several diseases, including cancer, Alzheimerâs and Parkinsonâs diseases. It may also play a role in the development of heart failure. Tse Yuan Wongâs research is exploring the contribution of the ubiquitin/proteasome system to heart failure. This involves examining the functional changes of this system in heart failure and determining how it is regulated. He will also explore how disturbed proteasome function affects the progression of heart failure. This study will provide valuable insights into the mechanisms of heart failure, which could lead to novel therapeutic strategies that could have a huge impact on health care in Canada.