title: Intact function of Lgr5 receptor-expressing intestinal stem cells in the absence of Paneth cells.
abstract: Lifelong self-renewal of the adult intestinal epithelium requires the activity of stem cells located in mucosal crypts. Lgr5 and Bmi1 are two molecular markers of crypt-cell populations that replenish all lineages over time and hence function as stem cells. Intestinal stem cells require Wnt signaling, but the understanding of their cellular niche is incomplete. Lgr5-expressing crypt base columnar cells (CBCs) reside deep in the crypt, mingled among mature Paneth cells that are well positioned for short-range signaling. Partial lineage ablation previously had implied that Paneth cells are nonessential constituents of the stem-cell niche, but recently their absence was reported to interfere with Lgr5(+) CBCs, resurrecting an appealing idea. However, previous mouse models failed to remove Paneth cells completely or permanently; defining the intestinal stem-cell niche requires clarity with respect to the Paneth cell role. We find that Lgr5(+) cells with stem-cell activity cluster in future crypts early in life, before Paneth cells develop. We also crossed conditional Atoh1(-/-) mice, which lack Paneth cells entirely, with Lgr5(GFP) mice to visualize Lgr5(+) CBCs and to track their stem-cell function. In the sustained absence of Paneth cells, Lgr5(+) CBCs occupied the full crypt base, proliferated briskly, and generated differentiated progeny over many months. Gene expression in fluorescence-sorted Lgr5(+) CBCs reflected intact Wnt signaling despite the loss of Paneth cells. Thus, Paneth cells are dispensable for survival, proliferation, and stem-cell activity of CBCs, and direct contact with Lgr5-nonexpressing cells is not essential for CBC function.
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
authors.forename: Tae-Hee
authors.initials: TH
authors.lastname: Kim
authors.forename: Silvia
authors.initials: S
authors.lastname: Escudero
authors.forename: Ramesh A
authors.initials: RA
authors.lastname: Shivdasani
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D049109:Cell Proliferation; D003433:Crosses, Genetic; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology; D019394:Ki-67 Antigen / Q000096:biosynthesis; D051379:Mice; D008822:Mice, Transgenic; D008840:Microfilament Proteins / Q000378:metabolism; D019879:Paneth Cells / Q000166:cytology*; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D049452:Green Fluorescent Proteins; D019394:Ki-67 Antigen; D008840:Microfilament Proteins; D043562:Receptors, G-Protein-Coupled; C500943:Atoh1 protein, mouse; C493597:Lgr5 protein, mouse; C026615:villin