Arx is required for normal enteroendocrine cell development in mice and humans

► Arx is expressed in GI endocrine progenitors and in hormone producing cells. ► Ablation of Arx in mice results in changes in enteroendocrine subtypes. ► Arx acts as a cell fate determinant in endocrine progenitors. ► Ileal lipid droplet accumulation observed in the Arx-deficient mice. ► Human intestinal endocrine cell development requires ARX.