Cbl and Cbl-b Ubiquitin Ligases are Essential for Intestinal Epithelial Stem Cell Maintenance

Area of Science:

• Stem cell biology
• Molecular signaling pathways
• Gastrointestinal physiology

Background:

• CBL family ubiquitin ligases negatively regulate receptor tyrosine kinases (RTKs).
• Their role in intestinal stem cell (ISC) maintenance and differentiation is largely unknown.
• Previous studies show hematopoietic and mammary epithelial Cbl/Cblb knockout (KO) phenotypes.

Approach:

• Generated inducible Cbl/Cblb double-knockout (iDKO) mice targeting Lgr5+ ISCs.
• Utilized LacZ reporter lineage tracing to track cell fate.
• Performed in vitro intestinal organoid culture and single-cell RNA sequencing (scRNA-seq).
• Assessed recovery from radiation-induced intestinal injury.

Key Points:

• Cbl/Cblb iDKO resulted in rapid loss of Lgr5 Hi ISCs and increased differentiation towards enterocyte and goblet cell fates.
• iDKO impaired intestinal epithelial repair after radiation injury and prevented organoid maintenance in vitro.
• scRNA-seq identified hyperactivation of the Akt-mTOR pathway in iDKO ISCs and progeny.
• Pharmacological inhibition of Akt-mTOR rescued organoid defects.

Conclusions:

• Cbl/Cblb are essential for ISC maintenance by fine-tuning the Akt-mTOR pathway.
• This regulation balances ISC self-renewal with differentiation commitment.
• Cbl/Cblb function is critical for intestinal homeostasis and repair.