Observational study of the dynamic emergence of Ng2-DsRed+ cells before vasculogenesis in a murine embryonic stem cell model of blood vessel development.

Time-lapse images of double-reporter embryonic stem cell (DR-ESC) differentiation over ≈30 h. Magenta arrowheads (vii and ix) denote emergence of endothelial cells (ECs; x and xii). Dashed magenta circles are precursor Flk-1-eGFP-low (enhanced green fluorescent protein) mesoderm (i, iv, and vii; green in iii, vi, and ix). Dashed purple boxes indicated EC coalescence into primitive vessels (x). Cyan arrows are Ng2-DsRed+ cells (ii, v, viii, and xii; red in iii, vi, ix, and xiii) arising before Flk-1-eGFP+ signals. Dashed cyan ovals note Ng2-DsRed+ cell and Flk-1-eGFP+ mesoderm interactions (vi, ix, and xii). Dashed yellow ovals note Ng2-DsRed+ cells interacting with ECs undergoing organization (xii). Time (hh:mm:ss).