library_construction_protocol: RNA extraction of embryonic cholangiocytes: The supernatant was removed and RNA from cells pellets was extracted using RNAqueous™-Micro Total RNA Isolation Kit (Thermo Fisher Scientific, Waltham, MA, USA) according to the manufacturer's protocol. RNA libraries were generated using the TruSeq total stranded RNA-seq kit (Illumina, San Diego, CA, USA) according to the manufacturer's instructions.