16-cell purple urchin embryo expressing three tandem GFPs fused to the ensconsin microtubule-binding domain (EMTB-3G; Faire et al., 1999). The embryo was treated with 40 µM trichostatin A (TSA), an inhibitor of HDAC6 (a tubulin deacetylase) that selectively disrupts dynamic microtubules in mammalian cells, at time 00:00. All four cells entered anaphase, but extremely reduced spindle length with a very small midzone gap suggests minimal chromatid separation. Virtually no astral microtubules survived, and some centrosomes separated from the spindle (bright dots in the 13:00 frame). Nonetheless, all cells initiated furrows at the right place (arrowheads, 13:00), only one of which regressed (open arrowheads), whereas the other three of the four completed (19:00). Embryos were imaged with a laser scanning confocal microscope (Radiance 2000; Bio-Rad Laboratories) mounted on a compound microscope (E800; Nikon) using a 40× 1.3 NA Plan-Fluor oil lens. Room temperature was maintained at 14–17°C. Corresponds to Video 4 segment 3 and Figure S4 in J Cell Biol. 2009 Dec 14;187(6):831-45.