Whole Sox7-/- embryos and their wild-type littermates were isolated at E8.5. The Ambion RNAqueous-micro Kit; was used for isolating total RNA from three Sox7-/- embryos and three wild-type controls, according to manufacturer's instructions. Libraries were prepared using the TruSeq RNA Sample Preparation v2 Kit, Low Throughput (LT) Protocol, Illumina Inc, San Diego CA. This process purifies the poly-A containing mRNA using poly-T oligo-attached magnetic beads. Following purification, the mRNA was fragmented and primed for cDNA synthesis. The cDNA fragments were subjected to an end repair process, the addition of a single 'A' base, and then ligation of the adapters. Post ligation cleanup was performed using AMpure XP beads (Agencourt, Beverly, MA, USA).  The products then enriched with PCR to create final cDNA library. The quality of the amplified libraries was checked on an BioRad Experion Bioanalyzer System (BioRad, Hercules CA, USA) using the BioRad DNA 1K Analysis Kit. The libraries were normalized to 2nM and pooled in equal volumes and sequenced using 50 bp reads on the Illumina HiSeq 2000 platform (Illumina Inc., San Diego, CA, USA).