Fig. 8. Aberrant morphogenesis of dorsal clones in sqt^-/-; cyc^+/- embryos. Morphogenesis and resulting fates of dorsal marginal clones (A,B) and ventrolateral marginal clones (C,D) in wild-type (A,C), and in sqt^-/-; cyc^+/- embryos (B,D) were examined during the time periods indicated. Tracings of the behavior of individual cells within each clone are shown (A'-D'). Dorsal marginal cells migrate towards the vegetal pole with the movements of epiboly, and begin to involute at the onset of gastrulation at 50% epiboly (A). Some cells do not involute and contribute to the tail (asterisk in A'). In sqt^-/-; cyc^+/- embryos (B), dorsal marginal cells fail to involute (B'). Whereas the dorsal marginal cells became hatching gland, pharyngeal endoderm and endothelium near the eye in wild type (A'', blue circle), these cells became floorplate in sqt^-/-; cyc^+/- embryos (B'', blue circles). Arrows in A'' and B'' mark labeled notochord cells. In many sqt^-/-; cyc^+/- embryos, a region devoid of cells is created at the dorsal midline, possibly generated by the abnormal movements of dorsal marginal cells. By contrast, morphogenetic movements of ventrolateral marginal cells in wild-type (C,C') and sqt^-/-; cyc^+/- embryos (D,D') are indistinguishable, each undergoing the normal movements of epiboly, involution and convergence (Warga and Kimmel, 1990). Labeled cells formed heart endothelium (C'',D''; yellow circles), pronephric duct (C'',D''; white circles), fin bud (C'',D''; green circles), and muscle (C'',D''; black circles) in both wild-type and mutant clones. Other labeled cells (red) are in the EVL. The genotypes of all embryos shown were determined by PCR after photography.