Figure 4. Wnt ligands cannot augment Lgr5+ ISC number or substitute for Rspo but are required to prime ISCs for Rspo action.
a, scFv-DKK1c does not induce Lgr5+ ISCs by itself or in combination with Rspo despite synergistic induction of villus proliferation. Top, Lgr5-eGFP-IRES-CreER reporter. Bottom, Ki67 IF. D7 post-adenovirus, jejunum. b, Wnt ligand augmentation by Ad scFv-DKK1c does not alter Lgr5+ ISC lineage tracing either by itself or in combination with Rspo1. Jejunum of Lgr5-eGFP-IRES-CreER; tdTomato mice, d4 following simultaneous administration of adenovirus and tamoxifen. c, Rspo1 treatment cannot rescue Lgr5+ ISC loss after Fzd8 ECD-mediated Wnt sequestration. d–e, scFv-DKK1c cannot rescue loss of Lgr5+ ISC or crypts after (d) dual Rspo blockade via LGR5 ECD + Znrf3 ECD or (e) single Rspo blockade via LGR5 ECD. c-e are d4 post-adenovirus, jejunum, Lgr5-eGFP-IRES-CreER mice. Bars = 50 μm. All experiments used n=3 mice per condition and were repeated at least twice.