Enucleation of cultured mouse fetal erythroblasts requires Rac GTPases and mDia2

Nat Cell Biol. 2008 Mar;10(3):314-21. doi: 10.1038/ncb1693. Epub 2008 Feb 10.


Mammalian erythroid cells undergo enucleation, an asymmetric cell division involving extrusion of a pycnotic nucleus enveloped by the plasma membrane. The mechanisms that power and regulate the enucleation process have remained obscure. Here, we show that deregulation of Rac GTPase during a late stage of erythropoiesis completely blocks enucleation of cultured mouse fetal erythroblasts without affecting their proliferation or differentiation. Formation of the contractile actin ring (CAR) on the plasma membrane of enucleating erythroblasts was disrupted by inhibition of Rac GTPases. Furthermore, we demonstrate that mDia2, a downstream effector of Rho GTPases and a formin protein required for nucleation of unbranched actin filaments, is also required for enucleation of mouse fetal erythroblasts. We show that Rac1 and Rac2 bind to mDia2 in a GTP-dependent manner and that downregulation of mDia2, but not mDia1, by small interfering RNA (siRNA) during the late stages of erythropoiesis blocked both CAR formation and erythroblast enucleation. Additionally, overexpression of a constitutively active mutant of mDia2 rescued the enucleation defects induced by the inhibition of Rac GTPases. These results reveal important roles for Rac GTPases and their effector mDia2 in enucleation of mammalian erythroblasts.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Culture Techniques / methods*
  • Cell Differentiation
  • Cell Line
  • Cell Proliferation
  • Erythroblasts / cytology*
  • Erythroblasts / metabolism
  • Flow Cytometry
  • Gene Expression Regulation*
  • Guanosine Triphosphate / metabolism
  • Humans
  • Mice
  • Microtubule-Associated Proteins
  • Models, Biological
  • Mutation
  • NADPH Dehydrogenase / metabolism*
  • rac GTP-Binding Proteins / metabolism*


  • Microtubule-Associated Proteins
  • Guanosine Triphosphate
  • Dia2 protein, mouse
  • NADPH Dehydrogenase
  • rac GTP-Binding Proteins