RasGRP1 promotes efficient intestinal tuft cell differentiation
Intestinal stem and progenitor cells balance proliferation and lineage commitment to maintain epithelial homeostasis and adapt to environmental challenges. Tuft cells are a rare chemosensory lineage that rapidly expands in response to the cytokine IL-13 during helminth infection, yet how epithelial progenitor states influence this response remains incompletely understood. Using genetic mouse models, intestinal organoids, and single-cell approaches, we identify the Ras guanine nucleotide exchange factor RasGRP1 as an epithelial-intrinsic promoter of efficient tuft cell differentiation. Rasgrp1 is expressed in rare crypt epithelial cells distinct from Lgr5-positive stem cells. Once cells entered the tuft cell differentiation trajectory, Rasgrp1 deficiency has little impact on tuft cell maturation, including expression of the Pou2f3 tuft cell transcription factor. Instead, RasGRP1 acts at the progenitor stage, where it restrains EGFR-driven proliferation and supports a transcriptionally heterogeneous transit-amplifying state, including a subset of cells expressing Pou2f3, that is largely lost upon Rasgrp1 deficiency. Consistent with this model, EGFR inhibition restores tuft cell numbers in Rasgrp1-deficient organoids and cooperates with IL-13 to enhance tuft cell differentiation. Rasgrp1-deficient mice exhibit delayed tuft cell hyperplasia and inefficient helminth clearance. Conversely, constitutive epithelial RasGRP1 overexpression, uncoupled from its endogenous regulation, drives spontaneous tuft cell hyperplasia and accelerates parasite clearance, but alters the balance of intestinal epithelial lineages. Together, our findings identify RasGRP1 as a cell-intrinsic regulator that restrains progenitor proliferation and promotes responsiveness to IL-13, thereby coupling growth factor signaling, cell cycle control, and immune-driven epithelial lineage specification.