Dr. Dean's longtime interests have been to understand how nutritional status and other environmental factors stimulate cell proliferation and affect the susceptibility of vulnerable cells to degeneration. Her current interests are the determinants of endocrine mass, specifically pancreatic islet alpha cell mass. While much effort has been focused on understanding beta cell biology because of insulin's well known role in diabetes, very little is known about signals regulating other islet cells. Alpha cells secrete glucagon in response to hypoglycemia, but persons with diabetes have hyperglucagonemia contributing to hyperglycemia. Struck by the impressive alpha cell hyperplasia and hyperglucagonemia in mice with interrupted glucagon signaling, Dr. Dean sought to identify the mechanism underlying this during her postdoctoral training. She identified that unknown circulating factors stimulate alpha cell hyperplasia in mice with interrupted glucagon signaling. She then collaborated with multiple investigators at Vanderbilt and other institutions to identify that these circulating factors are amino acids defining a novel hepatic-pancreatic islet alpha cell axis. She demonstrated that this effect is conserved in human alpha cells suggesting that this axis is relevant to human biology and disease. Her current interests are 1) to define the mechanism of how amino acids are sensed by alpha cells to stimulate proliferation and glucagon secretion and 2) to investigate the role of amino acids on alpha cell dysfunction in diabetes.