Fig. 10. nud-1 RNAi in C. elegans: cleavage-furrow regression. Selected Nomarski images from digital time-lapse video recordings of live C. elegans embryos progressing through the two-cell stage in a wild-type (A-D) and a nud-1 RNAi embryo (E-L). Each image displays the time elapsed (minute:second) since initiating sequence capture, approximately 20 minutes after fertilization. Embryos are aligned with the anterior to the left, as determined by the presence of the polar body and denoted by asterisks (some polar bodies are out of the focal plane). (A,E) In wild-type and nud-1 RNAi embryos, the pronuclei have fused and the spindle is beginning to elongate. (B,F) Spindle elongation is not affected in nud-1 RNAi embryos. (C,G) The first cleavage furrow has been initiated. (D,H) Telophase is completed in the wild-type embryo. However, the cleavage furrow is incomplete in the nud-1 RNAi embryo (arrow). An `x' is used to label each nucleus. (I-L) The furrow in the nud-1 RNAi embryo quickly regresses and the nuclei aggregate in the center of the embryo. Bar, 5 µm in all panels. Digital time-lapse videos of these embryos are available online (http://jcs.biologists.org/supplemental).