Cftr Modulates Wnt/β-Catenin Signaling and Stem Cell Proliferation in Murine Intestine

Area of Science:

• Gastroenterology
• Molecular Biology
• Cell Biology

Background:

• Cystic fibrosis (CF) is linked to a higher risk of gastrointestinal tumors.
• CF mouse models exhibit increased intestinal proliferation and an altered intestinal environment.
• The role of the cystic fibrosis transmembrane conductance regulator (Cftr) in intestinal stem cell (ISC) regulation and Wnt/β-catenin signaling is not fully understood.

Purpose of the Study:

• To investigate the function of Cftr in intestinal stem cells (ISCs).
• To examine the impact of Cftr on Wnt/β-catenin signaling and ISC proliferation.
• To determine if altered intracellular pH (pHi) in CF ISCs facilitates Wnt/β-catenin signaling.

Main Methods:

• Comparison of crypt epithelia and intestinal organoids from wild-type (WT) and CF mice.
• Assessment of Cftr expression in ISCs (Sox9+ cells).
• Measurement of intracellular pH (pHi) regulation in ISCs (Lgr5+ cells) using confocal microfluorimetry.
• Analysis of Wnt transducer Dishevelled 2 (Dvl2) plasma membrane association via fluorescence imaging.

Main Results:

• CF intestinal crypts displayed a ~30% increase in epithelial and ISC proliferation compared to WT.
• Loss of Cftr resulted in an alkaline pHi in ISCs and increased Wnt/β-catenin signaling.
• Increased plasma membrane association of Dvl2 was observed in CF crypt-base columnar cells, a process dependent on pH and charge.

Conclusions:

• CF intestine exhibits elevated ISC proliferation and Wnt/β-catenin signaling.
• Loss of Cftr leads to increased pHi in ISCs, stabilizing Dvl association and promoting Wnt/β-catenin signaling.
• The absence of Cftr-mediated suppression of ISC proliferation in CF may contribute to the heightened risk of intestinal tumors.