Katherine Stewart

Dr. Katherine Stewart is an Investigator at the Lunenfeld-Tanenbaum Research Institute and an Assistant Professor in the Department of Molecular Genetics at the University of Toronto. 

Awards

• Canada Research Chair in Stem Cell Biology

Billions of cells in our bodies die every day as a part of normal homeostasis, with conservative estimates suggesting the loss of 41 million cells an hour. To prevent the depletion of our tissues, adult stem cells exist in these death-rich settings and serve the essential purpose of dividing to both self-renew and differentiate to replace eliminated cells.

Despite this basic tenet of stem cell biology, we know strikingly little about how stem cells experience and respond to the death of their neighbours in either healthy or diseased tissues. As a postdoc, Dr. Stewart made the exciting finding that hair follicle stem cells (HFSCs) transiently induce a phagocytic (“eating”) program of gene expression in response to signals from their dying neighbours, which results in the stem cell engulfing (“clearing”) the dying corpse. This stem cell eating behaviour serves to protect the hair follicle from aberrant immune cell infiltration and preserve homeostasis.

Using sophisticated genetics, single-cell transcriptomics, and multiplexed confocal fluorescence imaging techniques in organoids, mouse models and human patient samples, the Stewart lab’s future research directions will build upon this exciting concept to ask: (i) Why do stem cells engulf apoptotic corpses in homeostasis? (ii) How does corpse clearance contribute to tissue pathology? (iii) How does this translate to human biology?

Together, Dr. Stewart’s research develops a new concept in stem cell biology: that engulfment of dying cells directly impacts stem cell function and acts as a rheostat to return tissues to homeostasis, with dysregulation in this process directly contributing to diseases such as squamous cell carcinoma and alopecia areata (pathological hair loss). These projects will uncover fundamental mechanisms which dictate stem cell behaviours in homeostasis and tissue pathologies that may be amenable to therapeutic targeting.