Single-cell RNA-seq of heart from mouse-rat chimeric embryos
By combining  Nkx2.5-Cre x diphtheria toxin ablation (DTA) and interspecies blastocyst complementation we have generated rat hearts into mouse embryos at E10.5.  These hearts have been compared by single cell-RNA sequencing with the hearts of stage matched E11.5 rat embryo. All heart specific cell types were found in complemented chimeras, and they showed high correlation with the control. This suggests that the mechanisms of formation of the heart are compatible between mouse and rat, and that all cardiac cell types are specified correctly in the rat-to-mouse chimeras. However, global gene expression comparison identified some genes differentially expressed between complemented chimeras and control. Notably, the most relevant transcriptomic differences between rPSCs-derived hearts and rat embryonic hearts were associated with metabolism, specifically, with a decrease in oxidative phosphorylation and an increase in glycolysis processes in the rPSCs-derived cells of chimeras. Additionally, vascular endothelial cells of the complemented chimeras augmented the expression of genes related to vasculogenesis and vascular development. These changes are suggestive of a low level of oxygen in the embryo. Overall design: Single-cell RNAseq of the heart region of rat-mouse heart complemented embryos and comparison with a stage matched rat heart region