Leucine-Rich Repeat-Containing G-Protein-Coupled Receptors as Markers of Adult Stem Cells

Molecular markers are used to characterize and track adult stem cells. Colon cancer research has led to the identification of 2 related receptors, leucine-rich repeat–containing, G-protein–coupled receptors (Lgr)5 and Lgr6, that are expressed by small populations of cells in a variety of adult organs. Genetic mouse models have allowed the visualization, isolation, and genetic marking of Lgr5^+ve and Lgr6^+ve cells and provided evidence that they are stem cells. The Lgr5^+ve cells were found to occupy locations not commonly associated with stem cells in the stomach, small intestine, colon, and hair follicles. A multipotent population of skin stem cells express Lgr6. Single Lgr5^+ve stem cells from the small intestine and the stomach can be cultured into long-lived organoids. Further studies of these markers might reveal adult stem cell populations in additional tissues. Identification of the ligands for Lgr5 and 6 will help elucidate stem cell functions and modes of intracellular signaling.

Keywords: Lgr5, Lgr6, Stem Cell Marker, GPCR

Abbreviations used in this paper: Ascl2, Achaete scute–like 2, CBC, crypt base columnar, FSH, follicle-stimulating hormone, GFP, green fluorescent protein, Lgr, leucine-rich repeat–containing, G-protein–coupled receptor, LH, leutinizing hormone, 7TM, 7-transmembrane, TSH, thyroid-stimulating hormone