Polarized Myosin Produces Unequal-Size Daughters During Asymmetric Cell Division

Abstract

Daughter Diversity Asymmetric cell division generates cell diversity and maintains tissue homeostasis. In early Caenorhabditis elegans embryos, the mitotic spindle is pulled toward one side of the cell by the molecular motor, dynein, and the cell divides into two unequally sized daughters. However, other types of asymmetric cell divisions (for example, in Drosophila neuroblasts) start with a centrally localized spindle. In this latter case, the mechanism by which two differently sized daughters are created is not understood. Ou et al. (p. 677 , published online 30 September; see the Perspective by Grill ) studied asymmetric cell divisions in the Q neuroblast lineage during C. elegans development and found that when the spindle was centred, myosin II accumulated at higher levels on the side of what will become the smaller daughter cell, giving rise to asymmetric myosin-based contractile forces acting on the membrane.