All samples were collected and snap frozen following seven days of culture, then processed according to the manufacturer's instructions using the RNeasy Micro Kit (Qiagen 74004) for total RNA isolation. The sample disruption and homogenization steps were performed using QIAShredders (Qiagen 79654). Libraries were prepared at the Donnelley Centre at the University of Toronto using Takara SMART-Seq v.4 Ultra Low Input RNA kits.