GRO-seq in mouse Epiblast-primed, Primitive endoderm-primed, and differentiated endoderm cells

The identification of changes in transcriptional regulation during priming and differentiation of embryonic stem (ES) cells towards the endoderm lineage. Specific populations of ES cells, either primed or committed to endoderm, were isolated and subjected to global nuclear run on sequencing (GRO-Seq). The hHex-Venus (HV) reporter ES cell line, HVJu5.1 (Canham et al., 2010) was used to isolate HV- and HV+ ES cells. Primed ES cells were identified based on the expression of the HV marker in addition to the cell surface marker of undifferentiated ES cells, SSEA-1, (the lower and upper 25% of SSEA-1+, HV expressing cells). When challenged to differentiate, HV- ES cells are primed towards an epiblast fate, while HV+ ES cells are primed towards primitive endoderm. However, these populations are considered primed, rather than committed, as they will readily interconvert when re-introduced into standard ES cell culture conditions. ES cells were grown in self-renewing conditions (GMEM, LIF, 10% FCS, plated on gelatin coated dishes). Endoderm was obtained by differentiating ES cells in medium without the cytokine LIF for 5 days. The HV+, SSEA-1- differentiated fraction was then sorted and represents an early stage in endoderm differentiation. Three subpopulations were sorted by flow cytometry from clone HVJu5.1 of the HV ES cell line as such: HV-,SSEA-1+; HV+SSEA-1+; HV+, SSEA-1-; where HV = Hex-Venus expression. Two biological replicates were collected per sample. Nuclei were isolated from each population and GRO-seq was carried out.