Fig. 2

Comparison of the expression patterns of hemoglobin and seven different genes involved in hematopoiesis and/or vasculogenesis in developing zebrafish embryos. Whole-mount in situ hybridization staining of wild-type zebrafish embryos with lmo2 (A, I, Q, Y); gata2 (B, J, R, Z); gata1 (C, K, S, AA); c-myb (D, L, T, BB); fli1 (F, N, V, DD); flk1 (G, O, W, EE); flt4 (H, P, X, FF). Hemoglobin revealed by o-dianisidine staining of embryos (E, M, U, CC). Ages of embryos are 12 h (A–H), 18 h (I–P), 24 h (Q–X), and 48 h (Y–FF). Embryos shown in A–H are viewed dorsally with anterior to the left. At 12 h lmo2 (A), gata2 (B), and fli1 (F) are expressed in cells located in two strips of ventral mesoderm. Embryos in I–FF are viewed laterally with either the anterior to the left (I–X) or at the top (Y–FF). By 18 h, the ventral mesodermal cells are converging to form the ICM. All seven genes are expressed in converging cells at this time. Just prior to circulation, around 24 h, ICM cells expressing the seven genes and hemoglobin (U) are located at the midline between the gut and the notochord (arrow in Q–X). In addition cells in the tail express lmo2 (Q), gata2 (R), fli1 (V), flk1 (W), and flt4 (X), but not gata1 (S), c-myb (T), or hemoglobin (U) (arrowhead, Q–X). At this time, lateral cells in the trunk region around the pronephric primordia and dorsal aorta express lmo2 (asterisk in Q). In 48-h-old embryos, the embryonic red blood cells are in circulation and putative definitive blood cell progenitors that express c-myb (arrow in BB) are developing in the dorsal aorta. At 48 h lmo2 (Y), gata2 (Z), and flt4 (FF) are not expressed in hematopoietic cells, while gata1 (AA) expression is decreasing, and fli1 (DD), flk1 (EE), and hemoglobin (CC) continue to be highly expressed. All embryos, except in U are in 70% glycerol/PBS. U is in BB/BA.