library_construction_protocol: RNA was extracted from the sorted cells using a RNeasy Mini Kit (Qiagen). Reverse transcription into cDNA was performed based on polyA tail. For library construction, PCR products were purified and selected with the Agencourt AMPure XP-Medium kit. The single strand circle DNA (ssCirDNA) were formatted as the final library. The library was amplified to make DNA nanoball (DNB) which had more than 300 copies of one molecular. The DNBs were loaded into the patterned nanoarray and single end 50 bases reads were generated in the way of sequenced by combinatorial Probe-Anchor Synthesis (cPAS).