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Fig. 7. Summary of myosin-dependent processes during zebrafish cytokinesis. A-C and A'-C' represent animal views of embryos centered on the first furrow, immediately after furrow initiation (A-C) and towards furrow completion (A'-C'). (A,A') During early furrow formation, the contractile ring apparatus is formed at the center of the furrow, as well as f-actin enrichments in pericleavage regions of the furrow (A). Upon furrow maturation, pericleavage f-actin forms lamella-like structures that converge towards a septum at the center of the furrow (A'). (B,B') Cortical ß-catenin aggregates appear distributed in a broad band centered on the initiating furrow (B), and these aggregates are recruited to the furrow during furrow maturation (B'). (C,C') FMA microtubules are recruited to the forming furrow as a parallel array perpendicular to the furrow (red lines in C), and the germ plasm components become recruited to the furrow as rod-like aggregates (blue rectangles in C) that are in physical contact with FMA tubule ends. Upon furrow maturation, FMA tubule ends closest to the center of the furrow become enriched at the distal end of the furrow, exhibiting a characteristic tilting of the microtubules (red lines in C'), and the germ plasm aggregate becomes compacted at the distal end of the furrow (blue triangle in C'). Events that occur during furrow maturation and completion (A'-C') are myosin dependent. Analysis of blebbistatin-treated embryos also reveals a ladder-like f-actin arrangement of the contractile ring towards furrow completion (not shown in this figure, see Fig. 2P), which is consistent with a role for myosin in contractile ring disassembly. See text for details.
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