elsewhere (Jones et al., 1992). RNA was prepared from 80-100 mg of frozen tissue samples, with Omni Prep Multi-Sample Homogenizer (Omni International, Kennesaw, GA). Total RNA isolation was performed with TRIZOL™ reagent (Invitrogen, Carlsbad, CA), following the manufacturer's instructions. RNA was quantified by OD260/280 with a UV spectrophotometer and treated with RNase-free DNase using the RNeasy MinElute columns (Qiagen, Valencia, CA). The quality of the total RNA was finally evaluated using the Agilent 2100 Bioanalyser RNA Chip (Santa Clara, CA). Genomic DNA was extracted from tissues using the DNeasy Blood & Tissue Kits (Qiagen), following the manufacturer's instructions.
