Aims
Self-renewal and multipotent differentiation are cardinal properties of intestinal stem cells (ISCs), mediated in part by WNT and NOTCH signaling. Although these pathways are well characterized, the molecular mechanisms that control the 'stemness' of ISCs are still not well defined. Here, we investigated the role of Krüppel-like factor 5 (KLF5) in regulating ISC functions.
Background & aims
Self-renewal and multipotent differentiation are cardinal properties of intestinal stem cells (ISCs), mediated in part by WNT and NOTCH signaling. Although these pathways are well characterized, the molecular mechanisms that control the 'stemness' of ISCs are still not well defined. Here, we investigated the role of Krüppel-like factor 5 (KLF5) in regulating ISC functions.
Conclusion
We conclude that ISC self-renewal, lineage specification, and precursor dedifferentiation require KLF5, by its ability to regulate epigenetic and transcriptional activities of ISC-specific gene sets. These findings have the potential for modulating ISC functions by targeting KLF5 in the intestinal epithelium.
Methods
We performed studies in adult Lgr5EGFP-IRES-creERT2;Rosa26LSLtdTomato (Lgr5Ctrl) and Lgr5EGFP-IRES-creERT2;Klf5fl/fl;Rosa26LSLtdTomato (Lgr5ΔKlf5) mice. Mice were injected with tamoxifen to activate Cre recombinase, which deletes Klf5 from the intestinal epithelium in Lgr5ΔKlf5 but not Lgr5Crtl mice. In experiments involving irradiation, mice were subjected to 12 Gy total body irradiation (TBI). Tissues were collected for immunofluorescence (IF) analysis and next generation sequencing. Oganoids were derived from fluoresecence activated cell sorted- (FACS-) single cells from tamoxifen-treated Lgr5ΔKlf5 or Lgr5Crtl mice and examined by immunofluorescence stain.
Results
Lgr5+ ISCs lacking KLF5 proliferate faster than control ISCs but fail to self-renew, resulting in a depleted ISC compartment. Transcriptome analysis revealed that Klf5-null Lgr5+ cells lose ISC identity and prematurely differentiate. Following irradiation injury, which depletes Lgr5+ ISCs, reserve Klf5-null progenitor cells fail to dedifferentiate and regenerate the epithelium. Absence of KLF5 inactivates numerous selected enhancer elements and direct transcriptional targets including canonical WNT- and NOTCH-responsive genes. Analysis of human intestinal tissues showed increased levels of KLF5 in the regenerating epithelium as compared to those of healthy controls.