Fluorescence-activated cell sorting (FACS)

Embryonic pancreas was dissociated using 0.05% trypsin in PBS incubated at 37°C. Samples were resuspended in 1 mL FACS buffer (2% FBS and 2mM EDTA in PBS) and transferred to a round-bottomed tube with cell strainer cap (Corning). TdTomato⁺ cells were isolated using a BD FACSAria III Cell Sorter and RNA extraction was performed as described above.