Fig. 1

Formation of the endocardium, dorsal aortae, and head vasculature. A = anterior, P = posterior, BI = blood islands, YS = yolk sac, ML = midline, ANT = anterior neural tube, All = allantois, HF = head folds, DA = dorsal aortae, VA = vitelline arteries. The subfigures show Tal1 expression in fixed uncleared embryos, imaged by light sheet microscopy. (a1–6), (b1–6), (c1–6), (d1–6): schematic representation (as in the Kaufman’s atlas of mouse development), anterior view, side view, posterior view, top view, and enlarged inset of E7.25, E7.5, E7.75, and E8 embryos. The horizontal series (a2, b2, c2, d2), (a3, b3, c3, d3), (a4, b4, c4, d4), (a5, b5, c5, d5) show, respectively, the onset of the formation of the endocardium, dorsal aortae, vitelline arteries, and head vasculature over time. (a6): enlarged inset of A3 depicting Tal1+ cells in a speckled pattern underneath the BI. (b6): enlarged inset of B3, showing prospective endothelial cells outside the YS at the anterior part of the embryo. (c6): enlarged inset of C5 showing Tal1+ cells that ingressed into the head folds and allantois. (d6): enlarged inset of D4 showing the vitelline arteries developing