Dual states of murine Bmi1-expressing intestinal stem cells drive epithelial development utilizing non-canonical Wnt signaling.

Intestinal epithelial development and homeostasis critically rely upon balanced stem cell proliferation, involving slow-cycling/label-retaining and active-cycling/canonical Wnt-dependent intestinal stem cell (ISC) subtypes. ISC regulation during development remains poorly understood but has important implications for establishing key mechanisms governing tissue maintenance. Herein, we identify Bmi1+ cells as functional stem cells present in early murine intestinal development, prior to Lgr5-expressing ISCs. Lineage tracing and single-cell RNA sequencing identify that Bmi1+ ISCs can trace to Lgr5+ ISCs and other differentiated lineages. Initially highly proliferative, Bmi1+ ISCs transition to slow-cycling states as Lgr5+ ISCs emerge. Non-canonical Wnt signaling regulates the proliferative Bmi1+ cell state. These findings highlight the dynamic interplay between stem cell populations and the opposing Wnt pathways that govern proliferation-ultimately having implications for tissue development, homeostasis, regeneration, and tumorigenesis. Understanding these fundamental developmental mechanisms is critical for understanding adult intestinal maintenance.