Msi RNA-binding proteins control reserve intestinal stem cell quiescence

Area of Science:

• Stem Cell Biology
• Gastrointestinal Physiology
• Molecular Oncology

Background:

• Intestinal epithelium regeneration relies on distinct intestinal stem cell (ISC) populations.
• Active Wnt^high ISCs drive homeostasis, while reserve Wnt^low/off ISCs are quiescent but can activate.
• The role of Msi oncoproteins in ISC function and intestinal regeneration remains unclear.

Purpose of the Study:

• To investigate the function of Msi proteins within the intestinal stem cell compartment.
• To determine the necessity of Msi proteins for intestinal regeneration following injury.

Main Methods:

• Analysis of Msi protein expression in active and reserve ISCs.
• Genetic ablation of Msi activity specifically in reserve ISCs.
• Assessment of intestinal epithelial regeneration capacity after injury in Msi-ablated models.

Main Results:

• Msi proteins are dispensable for active ISC homeostasis and self-renewal, despite high expression.
• Msi proteins are essential and sufficient for activating quiescent reserve ISCs, promoting cell cycle entry.
• Ablation of Msi in reserve ISCs prevents intestinal regeneration after injury that eliminates active ISCs.

Conclusions:

• Msi proteins act as critical regulators of reserve ISC activation, controlling exit from quiescence.
• This pathway highlights a key molecular mechanism governing reserve ISC function in intestinal repair.
• Reserve ISCs, regulated by Msi, are vital for intestinal regeneration, particularly after severe injury.