PCR for miRNAs was performed as follows: 1) denaturation at 94°C for 15 seconds, 2) annealing at 55°C for 30 seconds, and 3) extension at 70°C for 34 seconds, for a total of 40 cycles. The reverse primer for all miRNA reactions was the sequence of the universal tag present in all 12 RT primers. The forward primer for each miRNA was the mature miRNA sequence given by miRBase . PCR reactions were carried out on an ABI Step One Plus machine in 10ul volumes using SYBR Green (VWR #95072).