We previously reported that ammonia-activated eggs undergo a form of mitosis, in which the female pronucleus chromosomes duplicate and condense, the nuclear envelope breaks down, and the chromosomes align and then segregate via unusual, anastral "mini-spindles" (Henson et al.
Confocal microscopy of sea urchin MKLP1 staining in ammonia-activated eggs indicated that this kinesin-related protein started to accumulate in the midzone region of the bipolar, anastral mini-spindles at metaphase (Fig.
Bipolar, anastral spindle development in artificially activated sea urchin eggs.
This information is important in understanding the divergence of plant lineages, and in tracing the evolution of the plant MTOC and its role in organizing the anastral plant spindle.
Mitotic spindles in mosses are anastral (Schepf, 1984; Doonan et al.