Gastroenterology

Gastroenterology

Volume 140, Issue 4, April 2011, Pages 1230-1240.e7
Gastroenterology

Basic—Alimentary Tract
Dll1- and Dll4-Mediated Notch Signaling Are Required for Homeostasis of Intestinal Stem Cells

https://doi.org/10.1053/j.gastro.2011.01.005Get rights and content

Background & Aims

Ablation of Notch signaling within the intestinal epithelium results in loss of proliferating crypt progenitors due to their conversion into postmitotic secretory cells. We aimed to confirm that Notch was active in stem cells (SCs), investigate consequences of loss of Notch signaling within the intestinal SC compartment, and identify the physiologic ligands of Notch in mouse intestine. Furthermore, we investigated whether the induction of goblet cell differentiation that results from loss of Notch requires the transcription factor Krüppel-like factor 4 (Klf4).

Methods

Transgenic mice that carried a reporter of Notch1 activation were used for lineage tracing experiments. The in vivo functions of the Notch ligands Jagged1 (Jag1), Delta-like1 (Dll1), Delta-like4 (Dll4), and the transcription factor Klf4 were assessed in mice with inducible, gut-specific gene targeting (Vil-Cre-ERT2).

Results

Notch1 signaling was found to be activated in intestinal SCs. Although deletion of Jag1 or Dll4 did not perturb the intestinal epithelium, inactivation of Dll1 resulted in a moderate increase in number of goblet cells without noticeable effects of progenitor proliferation. However, simultaneous inactivation of Dll1 and Dll4 resulted in the complete conversion of proliferating progenitors into postmitotic goblet cells, concomitant with loss of SCs (Olfm4+, Lgr5+, and Ascl2+). Klf4 inactivation did not interfere with goblet cell differentiation in adult wild-type or in Notch pathway–deficient gut.

Conclusions

Notch signaling in SCs and progenitors is activated by Dll1 and Dll4 ligands and is required for maintenance of intestinal progenitor and SCs. Klf4 is dispensable for goblet cell differentiation in intestines of adult Notch-deficient mice.

Section snippets

Animals

All animal work was conducted according to Swiss national guidelines. This study has been reviewed and approved by the Service Vétérinaire Cantonal of Etat de Vaud. All NIP1::CreERT2 study-related animals were housed in the Washington University mouse facility and were approved by the Animal Studies Committee of Washington University.

The Cre-ERT2 recombinase activity was induced by injecting 2- to 3-week-old mice with tamoxifen (10 mg/kg body weight in corn oil; Sigma-Aldrich, Buchs,

Notch1 Activation Occurs in Adult Intestinal Stem Cells

Notch signaling in the intestine plays an important role as a gatekeeper of progenitor cells and also as a regulator of the absorptive/secretory lineage.5, 6 To gain further insight whether Notch signaling might also occur at the level of adult intestinal SCs, we generated a tamoxifen-inducible Notch1 activation-dependent reporter knock-in mouse line, NIP1::CreERT2 (Figure 1A).17 The intracellular domain of the targeted Notch1 allele was replaced with a complementary DNA encoding a 6×

Discussion

It is now well established that both Wnt and Notch signaling are essential for the maintenance of the proliferative crypt compartment. Both pathways are also involved in cellular differentiation processes of the intestinal epithelium.3 Loss of Notch signaling due to genetic inactivation of the RBP-J gene, or as a consequence of using pharmacologic γ-secretase inhibitors or blocking antibodies, results in the loss of proliferating crypt progenitors, which convert into postmitotic goblet cells.5,

Acknowledgments

The authors thank C. S. Nowell for discussion and critical reading of the manuscript and the animal and histology facilities at Ecole Polytechnique Fédérale de Lausanne for their assistance.

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported by the Swiss National Science Foundation, the Swiss Cancer League, EuroSyStem, OptiStem (F.R.) and EMBO (V.R.), the National Institute of Diabetes and Digestive and Kidney Diseases (K.H.K.), Cancer Research UK (J.L.), and National Institutes of Health grant DK066408 (to Z.L., S.C., and R.K.).

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