Regulation of intestinal regeneration and cancer by the lysine methyltransferase Set7

Intestinal epithelial cells (IECs) form a protective covering over the small and large intestine. They are the primary interface between the body and the external environment, and  are constantly turning over, completely renewing every three to five days. This impressive turnover requires tight control of stem and progenitor cell production and variation, which is mediated by various cell signalling pathways including the Hippo and Wnt pathways.

In his study, Dr. Oudoffaims to dissect the exact role the protein-coding gene Set7 has in control of the Hippo and Wnt pathways in IEC homeostasis, regeneration, and cancer. The role of Set7 will be examined in two different in vivo intestinal regeneration models.

Systematically, his team will perform in vitro biochemical and cell biological assays to define the mechanism through which Set7 acts to regulate Hippo and Wnt pathways. In preliminary studies, Dr. Oudhoff identified that Set7 negatively regulates IEC production and turnover by regulating the Hippo pathway in vivo. Based on these results, his team tested whether the increased IEC proliferation would cause tumor development. Crossing mice lacking Set7 to mice that tended to spontaneously develop intestinal tumors, Dr. Oudhoff’s team hypothesized that mice having overactive Setd7 and overactive Wnt would develop more adenomas (benign tumors) or would develop them faster.

Ultimately, these studies will attempt to provide novel therapeutic targets to treat intestinal cancers.

Balancing immunity and inflammation in the intestine

The human gut is a unique environment, simultaneously tolerating an endless variety of food particles and billions of helpful bacteria while retaining the ability to recognize and respond to potentially dangerous infectious diseases. In the developing world, gut infections such as cholera, amoebic dysentery, and parasitic worms are the leading causes of disease and death and are a major burden on development. Gut inflammation is also involved in inflammatory bowel disease and colorectal cancer. More than 200,000 Canadians suffer from inflammatory bowel disease (one of the world's highest incidence rates) and each year more than 22,000 Canadians will be diagnosed with colorectal cancer.

Dr. Colby Zaph studies mouse models of intestinal infection and inflammation in the gut in order to identify and understand the molecules and cells that regulate the balance between immunity and inflammation. His unique approach is to study the immune responses that develop after the gut is infected with a worm parasite called whipworm (Trichuris), which infects more than 800 million people globally.

Dr. Zaph hopes that his work will aid in understanding how the body knows it is infected (sensing), how it kills the invading organisms (inflammation), and how it turns off the response to stop inflammatory diseases from developing (resolution). The results from his research will hopefully identify pathways and targets that can both promote protective immune responses and eliminate inflammatory diseases of the intestine, including infectious diseases, inflammatory bowel diseases, and colorectal cancer.

Elucidating the molecular mechanisms underlying retinoid action in chondrogenesis

Musculoskeletal diseases represent the largest burden to the healthcare system and are major contributors to long-term disability and reduced quality of life. Degenerative joint diseases, such as osteoarthritis, make up the largest proportion of musculoskeletal diseases. Osteoarthritis is characterized by a deficiency of particular cartilage, which results in a loss of joint mobility, pain, deformity and dysfunction. The research being undertaken by Helen Dranse involves characterizing the basic mechanisms that regulate the formation of cartilage, or chondrogenesis, with a particular focus on the role of vitamin A and its metabolites, the retinoids. Retinoic acid (RA) plays an essential role in cartilage formation and related functions by regulating the expression of specific RA receptor (RAR) target genes. However, the mechanisms through which the RA signalling pathway influence chondrogenesis remain poorly understood. Recently, Ms. Dranse and colleagues identified a novel direct RAR target gene. The activation of RAR target genes is controlled to a large extent by RA availability, which is influenced by a number of factors including the CYP26 enzymes. In her current research, Ms. Dranse is examining the distribution of RA in the Cyp26b1-deficient mouse limb, and how this relates to the expression of genes involved in chondrogenesis and the newly identified and other potential RAR target genes. Having gained insight into these processes, Ms. Dranse will attempt to rescue the limb defects observed in Cyp26b1-deficient mice by eliminating the expression of the newly identified RAR target gene in these animals. The information generated from her work will provide much needed insights into the role of RAR-mediated signalling in the regulatory networks that underlie cartilage formation. A better understanding of the molecular processes that regulate chondrogenesis will consequently lead to novel therapeutic targets that enhance cartilage repair and/or regeneration in adults, and assist in the development of treatment strategies for degenerative joint disease.

CD34 in development of lung inflammatory diseases

Ever since its discovery more than 20 years ago, the CD34 antigen has been widely used as a marker to identify stem cells, precursor cells that give rise to all types of specialized cells. However, the exact function of CD34 expression on hematopoietic precursors and mature cells is still not well understood. Dr. Marie-Renée Blanchet and colleagues have uncovered some fascinating details about the role of CD34 in allergy and asthma. The team recently demonstrated that CD34 is expressed on mature mast cells and eosinophils – two types of cell that respond to injury during inflammation of the body’s tissues – and that the CD34 antigen is involved in their recruitment to the lung and peritoneum. They showed that mice without the CD34 antigen are protected against development of airway hyper-responsiveness and airway inflammation, which are two major hallmarks of allergic asthma. Finally, in preliminary experiments, these mice also showed protection in hypersensitivity pneumonitis, another model of lung inflammation. Now, Blanchet is working to better understand the mechanisms behind these recent findings. Many cell types involved in asthma and hypersensitivity pneumonitis express CD34, some in which the role of this protein remains unknown (eg. fibrocytes and dendritic cells). She plans to use models to elucidate the role of CD34 expression in these cells. Ultimately, she hopes her studies will reveal potential targets for treatment of allergy and inflammation.

Microglia homeostasis and function in CNS disease

Microglia play a critical role as immune cells in the central nervous system (CNS), helping protect the nervous system in response to neural damage or inflammation. Microglia are also thought to play a role in neurodegenerative disorders such as Alzheimer’s disease, dementia, multiple sclerosis and amyotrophic lateral sclerosis (ALS). Microgliosis – the accumulation of microglia – is a common response to multiple types of damage within the CNS. However, the origin of microglia involved in this phenomenon remains elusive. It has been shown that, as a result of radiation therapy or bone marrow transplant, this increase may be due to recruitment of bone marrow-derived progenitor cells that are capable of forming microglia. In the absence of therapies that manipulate the body’s blood production system, however, this is not the case. Bahareh Ajami has observed in her previous studies that recruitment does not account for the massive increase in microglial cells that occur in two different CNS disease models: neurodegeneration and traumatic injury. Instead, microgliosis is solely the result of the expansion (division and growth) of microglia already residing in the CNS. She is now working to determine whether bone marrow-derived progenitor cells have a role in microglia accumulation in multiple sclerosis, which is an autoimmune disease of CNS. In parallel, she will also explore the effect of microglial cells on nerve cell survival in the CNS. Ajami’s results will not only contribute to the field of neuroscience, but could also provide new targets for developing gene and drug delivery systems that treat CNS disease.

The role of the CD34 family of Sialomucins in Development and Disease

Dr. Kelly McNagny studies the CD34 family of molecules: CD34, Podocalyxin, and Endoglycan. First identified solely as markers of blood stem cells and blood vessels, McNagny’s research has shown that they are also present on a variety of other cell types in the body. In particular, they are found on cells that play an important role in inflammatory diseases like asthma, allergies, arthritis, multiple sclerosis, intestinal infections and cancer.

Previously supported by MSFHR as a Scholar, McNagny’s current focus is to determine whether these molecules are important in the development or progression of inflammatory disease. Developing mice that lack each of these molecules, then testing their susceptibility to disease, has shown that mice that that lack CD34 are strikingly resistant to asthma, allergies and other lung inflammatory diseases. McNagny has also shown that these mice are more resistant to colon cancer and to bacterial infections.

Inhibiting CD34 expression may be beneficial in preventing or treating these diseases. In studies of Podocalyxin, the second member of this family, it appears that this molecule is essential for normal kidney development and for regulating normal blood pressure. McNagny has also found that this protein is ‘turned on’ in a number of high-risk cancers (those with very poor outcomes). This molecule may be a particularly good diagnostic tool for identifying those high-risk cancers. He will further clarify how these molecules work under normal and disease conditions. The research could lead to new treatments for a variety of conditions and diseases.

Identification of Positive Transcriptional Regulators of the tap-1 Gene

Worldwide in 2000, there were 10.1 million new cases of cancer, 6.2 million deaths due to cancer, and 22 million people living with the disease. The immune system plays an important role in limiting the emergence of cancers and aiding recovery from the disease. As such, researchers are looking for ways to boost the body’s own immune response as a way of improving cancer care. The immunological approach to fighting cancer involves the science of understanding and manipulating the body’s immune defenses. Our bodies already have all the tools needed to fight cancer. However, efforts to manipulate the immune system to destroy or inhibit the development of cancer cells have met with limited success. This is because the approach has been to stimulate the immune system to kill the cancer cells. The limitation of this approach is that cancer cells have ways of disguising themselves from the immune system. Jennifer Hartikainen’s approach comes from the other direction. She is working on making cancer cells recognizable to the immune system. Key pathways are depressed in cancer cells, which allows cancer to avoid immune detection and grow unchecked. Hartikainen aims to add back the components that are missing in cancer cells so the immune system can recognize and kill them, with the long-term goal of providing new therapeutic and diagnostic tools for battling cancer.

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.

Regulation of lymphocyte activation and proliferation and synthesis of pro-inflammatory cytokines by the Caprin-1/G3BP-1 heteromeric complex

To fend off infections, our immune system has evolved effective strategies. These include rapidly increasing the number of infection fighting immune cells, including cytokines that promote an inflammatory response to destroy harmful bacteria, viruses and other infectious agents. The key to the effectiveness of this strategy is striking a balance between creating an inflammatory response sufficient to destroy the infectious agents without causing severe damage to the surrounding tissues. In some cases, poorly controlled or misdirected immune responses cause long term damage and disease, including arthritis and asthma. Samuel Solomon is studying how the body regulates the immune response, in particular the role of RNA binding proteins such as Caprin-1 and G3BP-1 in the process. Caprin-1 and G3BP-1 are thought to be key players in the signaling process, which controls the action of inflammatory cytokines. Solomon is studying how they affect the production of cytokines and what are the effects when these proteins are absent or functioning abnormally. This research will contribute to our understanding of immune function, which could lead to the design of novel, better and more effective cures for infections and auto-immune diseases.

Structure-function relationship of the GTP-exchange factor smgGDS and its role in breast cancer

Ras proteins act as molecular switches that control functions including growth and movement of all cells. They also play a role in causing almost one-third of human cancers. Several families of proteins, including smgGDS, regulate Ras activity. Genetic changes leading to the production of an abnormal form of smgGDS are a characteristic of certain leukeumias. As well, too much smgGDS in cells leads to their transformation into cancer cells. Dr. Peter Schubert is determining the detailed structure of smgGDS and identifying parts of the protein that activate Ras proteins. The research should provide basic information necessary for designing drugs to block the action of smgGDS in leukemia.