Dr. Nathalie Rivard

The intestinal epithelium is under constant renewal (4 to 5 days). Taking its origin from stem cells confined to the base of the crypts, this cell population quickly loses its ability to proliferate and engages its differentiation program while migrating to the top of the glands. Once located on the villus axis, only then are these cells fully differentiated and complete their absorptive and digestive functions. Our knowledge as to the intracellular signaling mechanisms modulating cell cycle division and the subsequent establishment of differentiation is only partially understood. The focus of Dr. Nathalie Rivard’s research is precisely the identification and analysis of the intracellular signaling transduction mechanisms that control and coordinate the renewal and differentiation of the intestinal epithelium. A dysregulation of these intracellular signaling control mechanisms can lead to the development of colorectal cancer. In Canada, one out of eight individuals will be diagnosed with colorectal cancer during their lifetime, the second leading cause of death due to cancer (after lung cancer). Since the ensemble of the intestinal tissue is in perpetual renewal, it involves a massive number of cell divisions and hence the non-negligible risk of genetic alterations. This rapid rate of intestinal tissue renewal as well as exposure to toxic substances, notably through food ingestion, could explain the high frequency of colorectal cancer. Cell cycle defects in tumors are in fact not intrinsic to cell cycle enzymes but rather to defects in the regulation of these enzymes. Indeed, cancer cells obviously require that their cell division machinery is in perfect working order. Key events in the cell cycle are the phases of DNA synthesis (S) and mitosis (M). These phases are separated by intermediary phases designated G1 (before S) and G2 (before M). The most important regulation occurs during the initiation of new cell division cycles, the G1/S transition phase. Indeed, there exists a critical point in the G1 phase called “restriction point”. Prior to this restriction point, a cell synthesizes all that it needs to create two healthy daughter cells. Passed this point, the cell attempts to finalize its division cycle without interruption. A defective regulation of this restriction point, notably through the loss of certain signaling pathways, is one of the universal causes of cancer.

Nathalie Rivard completed her undergraduate studies in microbiology and holds a doctorate degree in biology (University of Sherbrooke, Canada, 1994). She pursued a post-doctorate fellowship in the laboratory of Dr. Jacques Pouysségur, an internationally renowned investigator in the field of intracellular signaling (University of Nice, France, 1994-1997) upon receiving a Centennial Fellowship from the Medical Research Council of Canada (now CIHR). In 1997, she joined the department of Anatomy and Cell Biology at the Faculty of Medicine of the University of Sherbrooke as an assistant professor. Devoting her research to intestinal epithelial cell signal transduction since 1997, Dr. Rivard is a member of the CIHR research group on the functional development and pathophysiology of the digestive tract, one of the most active research groups in the field, both nationally and internationally. Promoted to associate professor in 2002, she was also awarded a Canada Research Chair in Intracellular Signalling and Digestive Physiopathology in 2002. Dr. Rivard is actively involved as a member of peer review committees for both the CIHR and the FRSQ. Dr. Rivard also regularly reviews submitted articles for scientific journals, notably The Journal of Biological Chemistry, Gastroenterology and The Journal of Cellular Physiology.

Dr. Rivard’s research is funded by the CHIR, the Cancer Research Society, NSERC and the Canada Research Chairs Program.

For further information, please contact Dr. Nathalie Rivard using the Email contact form or by phone at 819 820-6868 ext 15431