Interferon-responsive intestinal BEST4/CA7⁺ cells are targets of bacterial diarrheal toxins

BEST4/CA7⁺ cells of the human intestine were recently identified by single-cell RNA sequencing. While their gene expression profile predicts a role in electrolyte balance, BEST4/CA7⁺ cell function has not been explored experimentally owing to the absence of BEST4/CA7⁺ cells in mice and the paucity of human in vitro models. Here, we establish a protocol that allows the emergence of BEST4/CA7⁺ cells in human intestinal organoids. Differentiation of BEST4/CA7⁺ cells requires activation of Notch signaling and the transcription factor SPIB. BEST4/CA7⁺ cell numbers strongly increase in response to the cytokine interferon-γ, supporting a role in immunity. Indeed, we demonstrate that BEST4/CA7⁺ cells generate robust CFTR-mediated fluid efflux when stimulated with bacterial diarrhea-causing toxins and find the norepinephrine-ADRA2A axis as a potential mechanism in blocking BEST4/CA7⁺ cell-mediated fluid secretion. Our observations identify a central role of BEST4/CA7⁺ cells in fluid homeostasis in response to bacterial infections.