RNA-seq of wild-type, Pbx1/Pbx2 double-knockout and pMsgn1-mut EpiSCs differentiated in vitro to pre-somitic mesoderm in the first 24 hours of differentiation.

In vertebrates, body axis elongation is fuelled by bipotent neuromesodermal progenitors (NMPs), which support the development of both spinal cord and paraxial mesoderm (PM). HOX transcription factors have been historically implicated in axial elongation, with their sequential activation playing a fundamental role in timing PM development. PBX1 and PBX2 are obligate anterior HOX cofactors, and therefore they represent prominent candidates for controlling the distinct response to individual HOX factors. In our work, we have demonstrated that PBX proteins play a fundamental role in promoting the expression of PM genes, including the master regulator Mesogenin1 (Msgn1). To address the role of PBX proteins in PM differentiation, RNA-seq was performed on wild-type (WT) and Pbx1/Pbx2 double-knockout (Pbx1/2-DKO) EpiSCs differentiated in vitro to pre-somitic mesoderm (PSM) at different time-points (12 hours and 24 hours). To establish the direct transcriptional regulation of Msgn1 by PBX/HOX, we employed the CRISPR/Cas9 technology to generate lines carrying base-pair substitutions on the Msgn1 promoter (pMsgn1-mut) that abrogate the recruitment of PBX/HOX complexes, and we performed RNA-seq of pMsgn1-mut EpiSCs differentiated in vitro to PSM at 24 hours. All differentiation experiments were performed in biological triplicates with WT and Pbx1/2-DKO lines, and in biological duplicates with pMsgn1-mut lines.