Competence of failed endocrine progenitors to give rise to acinar but not ductal cells is restricted to early pancreas development

► Neurog3+ cells differentiate into hormone-expressing cells in 10 hours. ► Neurog3 is necessary for cell cycle exit and delamination. ► Failed endocrine progenitors differentiate into acinar cells only prior E12.5. ► Islet progenitors arise from bipotent duct/endocrine precursors after E12.5. ► Plasticity of Neurog3-induced cells varies during pancreas development.