Total RNAs were extracted using a TRIzol plus RNA Purification kit (12183555, Invitrogen) following manufacturer's instructions. An aliquot was collected for every sample and analyzed with an RNA 6000 Pico Kit (5067-1513, Agilent) on an Agilent 2100 Bioanalyzer (Agilent, CA). All RNA samples produced a RIN > 8.0 while those entering next step had a RIN ³ 8.5. Illumina Stranded mRNA Prep and Ligation Kit