Whole ventricles were dissected and frozen in TriZOL (Invitrogen) immediately after dissection. Tissue was homogenized at 30 kHz for 2 min using the TissueLyserII (Qiagen). Bead-homogenized samples were centrifuged to pellet insoluble tissue. DNA-free RNA was isolated using the Direct-zol™ RNA MiniPrep kit (Zymo Research). Poly(A) mRNA was isolated from 1 ug of total RNA of adult heart using NEBNext Poly(A) Magnetic Isolation Module (New England Biolabs). mRNA was used to prepare RNA-seq libraries using the NEBNext Ultra™ II RNA Library Prep Kit for Illumina (New England Biolabs).