library_construction_protocol: RNA was extracted using TRIzol Reagent (Thermo Fisher Scientific). RNA libraries were prepared with QuantSeq 3' mRNA-Seq Library Prep Kit FWD V1 for Illumina (Lexogen), using 20.25 ng of input RNA. Input was 4.5 ul input RNA plus 0.5 ul of ERCC RNA Spike-In Mix (Thermo Fisher Scientific) pre-diluted 1:10,000 in water. Samples were multiplexed for sequencing, using i7 indices 7023 (CACACT, anterior rep 1), 7025 (TTTATG, anterior rep 2), 7022 (GGAGGT, posterior rep 1), 7024 (CCGCAA, posterior rep 2) and 7026 (AACGCC, posterior rep 3).