Fig. 4. Inhibition of myosin activity interferes with FMA remodeling during furrow formation. Control (A,C,E) and blebbistatin-treated (B,D,F) embryos labeled with an anti--tubulin antibody. In control embryos, the FMA forms as a parallel array of microtubules perpendicular to the furrow (A). Upon furrow maturation, FMA tubule ends closer to the furrow center appear at progressively more distal locations along the furrow, forming an oblique angle with respect to the plane of the furrow and resulting in v-shaped structures flanking the furrow (C). By the eight-cell stage (E), when the first furrow is nearly completed, the distally enriched FMA microtubules form a compact mass (arrowhead in E) that eventually disappears. The inset in E shows an intermediate stage of furrow maturation, where FMA microtubules appear enriched in the distal region of the furrow (arrowhead in inset). Treatment of embryos with blebbistatin does not interfere with the initial formation of the FMA (B), but inhibits tubule distal enrichment and tilting during furrow maturation (D), as well as the formation of the distally located residual body and the disassembly of the FMA (F). Images are animal views. Bar, 16 µm for all panels.