library_construction_protocol: After expansion, total RNA was isolated using the Direct-zolTM RNA MiniPrep kit (Zymo Research) following the manufacturer's instruction. Ribo-RNA depletion with Low Input RiboMinus Eukaryote System v2 (Thermo Fisher Scientific). Ribo-RNA-depleted samples were then used for cDNA synthesis with Ovation® RNA-Seq System V2 (Nugen) following the manufacturer's protocol. Following cDNA fragmentation and size selection, libraries were prepared using Illumina TruSeq ChIP Library Preparation Kit (Illumina) according to manufacturer's protocol.