Lgr4 is required for Paneth cell differentiation and maintenance of intestinal stem cells

Gene inactivation of the orphan G protein-coupled receptor Lgr4, a paralog of the epithelial stem cell marker Lgr5, results in 50% decrease of epithelial cell proliferation and 80% reduction in terminal differentiation of Paneth cells in postnatal mouse intestinal crypts. When cultured ex vivo, Lgr4-deficient crypts or progenitors, but not Lgr5-deficient progenitors, die rapidly with dramatic downregulation of stem cell markers and Wnt target genes, including Lgr5. Partial rescue of this phenotype is achieved by LiCl addition to the culture medium, but not by Wnt agonists. Our results identify Lgr4 as a permissive factor of the Wnt pathway in the intestine and, as such, as a potential target for intestinal cancer therapy. Microarray hybridization was performed on LGR4 KO intestinal crypts at day 0, day 0.5 and day 1 versus wild-type crypts. The effects of LiCl treatment on LGR4 KO crypts at day1 versus control cells were investigated. After amplification and labelling, sample pairs were hybridized onto Mouse Exonic Evidence Based Oligonucleotide (MEEBO) arrays containing on average 38784 mouse 70mer oligonucleotide probes (Stanford University, US). Hybridizations were replicated with dye swap.