Samples were homogenised in 1 mL of Trizol reagent (Thermofisher Scientific, Waltham, MA) and total RNA was extracted using the Life Technologies min-RNA purification kit (Qiagen, Valencia, CA) according to the manufacturer's protocol. Libraries were constructed using the 3'QuantSeq kit (Lexogen) with the following modifications. To enable the removal of PCR duplications, a custom oligo-dT primer was designed using a 12-bp unique molecular identifier.