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Intracellular pH dynamics is increasingly recognized to regulate myriad cell behaviors. We report a finding that intracellular pH dynamics also regulates adult stem cell lineage specification. We identify an intracellular pH gradient in mouse small intestinal crypts, lowest in crypt stem cells and increasing along the crypt column. Disrupting this gradient by inhibiting H+ efflux by Na+/H+ exchanger 1 abolishes crypt budding and blocks differentiation of Paneth cells, which are rescued with exogenous WNT. Using single-cell RNA sequencing and lineage tracing we demonstrate that intracellular pH dynamics acts downstream of ATOH1, with increased pH promoting differentiation toward the secretory lineage. Our findings indicate that an increase in pH is required for the lineage specification that contributes to crypt maintenance, establishing a role for intracellular pH dynamics in cell fate decisions within an adult stem cell lineage.

SummaryEmerging evidence is revealing critical roles of intracellular pH (pHi) in development (1–4), but it remains unclear whether pHi regulates stem cell fate specification. We find that pHi dynamics is a key regulator of cell fate in the mouse intestinal stem cell lineage. We identify a pHi gradient along the intestinal crypt axis and find that dissipating this gradient inhibits crypt budding due to loss Paneth cell differentiation. Mechanistically, decreasing pHi biases intestinal stem cell fate toward the absorptive and away from the secretory lineage, by regulating the activity of the lineage transcription factor Atoh1. Our findings reveal a previously unrecognized role for pHi dynamics in the specification of cell fate within an adult stem cell lineage.