library_construction_protocol: Mice hearts were dissected at 6 months of age, followed by total RNA isolation using an RNA isolation kit (Qiagen, cat# 763134), according to the manufacturer's instructions. Total RNA concentration and quality (A260/280 ratio ≥2.0) were evaluated using a Nanodrop spectrophotometer (ThermoFisher Scientific). The quality of total RNA was further measured using the Agilent 2100 Bioanalyzer (Agilent, Santa Clara, CA). After Sample QC was by qubit and Agilent Bioanalyzer, a certain amount of RNA samples were denatured at suitable temperatures to open-up their secondary structure, and mRNA is enriched by oligo (dT) -attached magnetic beads followed by mRNA fragmentation and cDNA Synthesis. The double-stranded cDNA fragments were subjected to end-repair, the addition of a single 'A' nucleotide to the 3' ends of the blunt fragments and ligated to adaptors before amplification.