Total RNA was extracted from the sorted cells using miRNeasy Micro Kit (Qiagen, 217084). The RNA purity was tested with a Nanodrop spectrophotometer (Thermo Scientific). RNA-seq libraries were prepared with SMART-Seq Stranded Kit (Takara, 634442) and SMARTer RNA Unique Dual Index Kit (Takara, 634451) using 1ng purified total RNA according to the manufacturer's instructions.