ChIP-seq of PBX1, PBX2 and LEF1 in wild-type and Pbx1/Pbx2 double-knockout EpiSCs differentiated in vitro to pre-somitic mesoderm in the first 48 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). WNT signalling sustains both NMP expansion and PM differentiation, but the mechanism by which it distinguishes between these alternative fates is unknown. 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 generate the DNA-binding context that allows recruitment of the WNT-effector LEF1, and consequently promote the expression of PM genes. Here, we wanted to identify the chromatin binding pattern of PBX1, PBX2 and LEF1 during the first 48 hours of pre-somitic mesoderm (PSM) in vitro differentiation, by performing chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) at different time-points (EpiSCs, 6 hours, 12 hours, 24 hours, 48 hours). To address the impact of PBX loss on LEF1 recruitment to chromatin, we additionally performed ChIP-seq in wild-type (WT) and Pbx1/Pbx2 double-knockout (Pbx1/2-DKO) EpiSCs differentiated in vitro to PSM at different time-points (EpiSCs, 12 hours, 24 hours, 48 hours).