Fig. 4. Myosin localization in RhoGEF2 mutant embryos. (A-F) Localization of myosin (white) to the cellularization front of Ore and RhoGEF2 mutant embryos (arrow in A,D). The cellularization front of RhoGEF2 mutant embryos is irregular at mid cellularization (E). (G-L) Localization of myosin during gastrulation. For precise staging, embryos were viewed under oil and individually fixed at the onset of gastrulation. Within this range of ages, 41% (n=39) of Ore embryos accumulate myosin on the apical side of ventral furrow cells (asterisk in H), but in RhoGEF2 mutant embryos collected in the same way (n=30), myosin never accumulates apically above background levels (asterisk in K), whereas basal loss of myosin proceeds normally (arrow).