Lgr5 Stem Cells in Self-Renewal and Cancer

The intestinal epithelium is the most rapidly self-renewing tissue in adult mammals. We originally defined Lgr5 as a Wnt target gene, transcribed in colon cancer cells. Two knock-in alleles revealed exclusive expression of Lgr5 in cycling, columnar cells at the crypt base. Using lineage tracing experiments in adult mice, we found that these Lgr5^+ve crypt base columnar cells generated all epithelial lineages throughout life, implying that they represent the stem cell of the small intestine and colon. Lgr5 was subsequently found to represent an exquisitely specific and almost “generic” marker for stem cells, including in hair follicles, kidney, liver, mammary gland, inner ear, tongue, and stomach epithelium. Single sorted Lgr5^+ve stem cells can initiate ever-expanding crypt-villus organoids, or so-called “mini-guts” in 3D culture. The technology is based on the observation that Lgr5 is the receptor for a potent stem cell growth factor, R-spondin. Similar 3D culture systems have been developed for the Lgr5^+ve stem cells of stomach, liver, pancreas and kidney. Using CRISPR/Cas9 technology, the cystic fibrosis transmembrane conductance regulator (CFTR) locus has been corrected in intestinal organoids of cystic fibrosis patients.