Total RNA was extracted using Trizol (Invitrogen) and assessed for quantity and purity with a Bioanalyzer 2100 and RNA 6000 Nano LabChip kit (Agilent),  with all samples having RNA integrity numbers (RIN) above 7.0. Approximately 10 μg of RNA was purified by isolating poly (A) mRNA with poly-T magnetic beads (Invitrogen) and fragmented using divalent cations at elevated temperatures. Fragmented RNA was reverse transcribed into cDNA with the mRNA-Seq Sample Preparation Kit (Illumina),  generating libraries with an average insert size of 300 bp (±50 bp).