library_construction_protocol: RNA was extracted from > 1M NPCs using the RNeasy kit and on-column DNAse digestion (Qiagen). RNA was quantified with Qubit RNA Broad Range assay (Invitrogen, Q10211). RNA was sent to Novogene for RNA integrity and purity quality check followed by Eukaryotic strand-specific mRNA (with PolyA-enrichment) library preparation. Libraries were then pooled and sequenced on an Illumina Novaseq 6000 platform for 2x150bp paired-end reads for 80 million reads total per sample.