Orchestration at the beginning: mitosis in sea urchin embryo

Abstract

Development of multicellular organisms is driven by a series of mitotic divisions after fertilization. Total cytoplasmic volume does not increase during this process, resulting in an increasing number of smaller daughter cells. Cell divisions are initially synchronous in an early embryo, but this ends at the 16-cell stage in the sea urchin. Orchesterated mitosis does, however, continue in subpopulations via the coordination of two different processes: karyokinesis and cytokinesis. Part of this asynchrony is due to the differentiation of lineages.