library_construction_protocol: RNA was extracted using the Rneasy Mini kit from Qiagen according to manufacturer's protocol The quantity and quality of RNA samples from sorted cells were analyzed using the bioanalyzer form Agilent in combination with the Agilent RNA 6000 Nano. RNA samples with RNA Integrity Number (RIN) > 7 were further used for library preparation using the 3' mRNA-Seq Library Prep Kit Protocol for Ion Torrent (QuantSeq-LEXOGEN™) according to manufacturer's instructions. The quantity and quality of libraries were assessed using the DNA High Sensitivity Kit in the bioanalyzer, according to the manufacturer's instructions (Agilent Technologies). Libraries were subsequently pooled and templated using the Ion PI IC200 Chef Kit (ThermoFisher Scientific) on an Ion Proton Chef instrument or Ion OneTouch System. Sequencing was performed using the Ion PI™ Sequencing 200 V3 Kit and Ion Proton PI™V2 chips (ThermoFisher Scientific) on an Ion Proton™System, according to the manufacturer's instructions.