Fig. 4

Appearance of live embryos after over-expression of eFGF. (A-D) Lateral views of embryos at 50% epiboly, (E-H) lateral views of late gastrulation stages, dorsal to the right, anterior at the top, (I) 18 hpf. (A) In the normal embryo the germ ring (gr) is barely visible and the yolk syncytial layer (YSL, arrowhead) is just below the margin of the epiblast. A similar view of an injected embryo (B) with a greatly enlarged germ ring. The distance between the cells of the YSL (arrow) and the epiblast margin is greater than normal, and the YSL has migrated further toward the vegetal pole. When viewed with Nomarski optics, it is clear that the enlargement is in the hypoblast (compare arrowed structures in C, a normal embryo, with D, an injected embryo). (E) Normal embryo at 90% epiboly; the shield cells have migrated to the animal pole (ap). In the injected embryo (F) these cells have failed to reach this position and an abnormal accumulation of cells is forming (asterisk). Note the increased thickness of the ventral hypoblast (arrowheads). (G) Normal embryo at 10 hpf (arrowhead = tail bud). (H) An injected embryo at the same stage showing an abnormal accumulation of cells at the top of the embryo (asterisk) and more than one thickening in the region of the tail-bud (arrowheads). (I) Embryos at 18 hpf showing a range of abnormal morphologies. The central embryo has a large accumulation of tissue on top of the yolk cell, whereas the left and right embryos have belts of tissue constricting the yolk cell. A variable number of axis-like extensions (arrowheads) have formed.