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Enucleation of human erythroblasts involves non-muscle myosin IIB.

ABSTRACT: Mammalian erythroblasts undergo enucleation, a process thought to be similar to cytokinesis. Although an assemblage of actin, non-muscle myosin II, and several other proteins is crucial for proper cytokinesis, the role of non-muscle myosin II in enucleation remains unclear. In this study, we investigated the effect of various cell-division inhibitors on cytokinesis and enucleation. For this purpose, we used human colony-forming unit-erythroid (CFU-E) and mature erythroblasts generated from purified CD34(+) cells as target cells for cytokinesis and enucleation assay, respectively. Here we show that the inhibition of myosin by blebbistatin, an inhibitor of non-muscle myosin II ATPase, blocks both cell division and enucleation, which suggests that non-muscle myosin II plays an essential role not only in cytokinesis but also in enucleation. When the function of non-muscle myosin heavy chain (NMHC) IIA or IIB was inhibited by an exogenous expression of myosin rod fragment, myosin IIA or IIB, each rod fragment blocked the proliferation of CFU-E but only the rod fragment for IIB inhibited the enucleation of mature erythroblasts. These data indicate that NMHC IIB among the isoforms is involved in the enucleation of human erythroblasts.

SUBMITTER: Ubukawa K

PROVIDER: S-EPMC3352306 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Enucleation of human erythroblasts involves non-muscle myosin IIB.

Ubukawa Kumi K Guo Yong-Mei YM Takahashi Masayuki M Hirokawa Makoto M Michishita Yoshihiro Y Nara Miho M Tagawa Hiroyuki H Takahashi Naoto N Komatsuda Atsushi A Nunomura Wataru W Takakuwa Yuichi Y Sawada Kenichi K

Blood 20111102 4

Mammalian erythroblasts undergo enucleation, a process thought to be similar to cytokinesis. Although an assemblage of actin, non-muscle myosin II, and several other proteins is crucial for proper cytokinesis, the role of non-muscle myosin II in enucleation remains unclear. In this study, we investigated the effect of various cell-division inhibitors on cytokinesis and enucleation. For this purpose, we used human colony-forming unit-erythroid (CFU-E) and mature erythroblasts generated from purif ...[more]

PMID: 22049517

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Project description:Myh9 and Myh10, which encode two major isoforms of non-muscle myosin II expressed in the brain, have emerged as risk factors for developmental brain disorders. Myosin II motors regulate neuronal cytoskeletal dynamics leading to optimization of synaptic plasticity and memory formation. However, the role of these motor complexes in brain development remains poorly understood. Here, we disrupted the in vivo expression of Myh9 and/or Myh10 in developing hippocampal neurons to determine how these motors contribute to circuit maturation in this brain area important for cognition. We found that Myh10 ablation in early postnatal, but not mature, CA1 pyramidal neurons reduced excitatory synaptic function in the Schaffer collateral pathway, whereas more distal inputs to CA1 neurons were relatively unaffected. Myh10 ablation in young neurons also selectively impaired the elongation of oblique dendrites that receive Schaffer collateral inputs, whereas the structure of distal dendrites was normal. We observed normal spine density and spontaneous excitatory currents in these neurons, indicating that Myh10 KO impaired proximal pathway synaptic maturation through disruptions to dendritic development rather than post-synaptic strength or spine morphogenesis. To address possible redundancy and/or compensation by other Myosin II motors expressed in neurons, we performed similar experiments in Myh9 null neurons. In contrast to findings in Myh10 mutants, evoked synaptic function in young Myh9 KO hippocampal neurons was normal. Data obtained from double Myh9/Myh10 KO neurons largely resembled the MyH10 KO synaptic phenotype. These data indicate that Myosin IIB is a key molecular factor that guides input-specific circuit maturation in the developing hippocampus. Non-muscle myosin II is an actin binding protein with three isoforms in the brain (IIA, IIB and IIC) encoded by the myh9, myh10, and myh14 genes in mice, respectively. We have studied the structure and the function of hippocampal CA1 neurons missing NMIIB and/or NMIIA proteins at different times during development. We have discovered that NMIIB is the major isoform regulating Schaffer collateral inputs, and that this regulation is restricted to early postnatal development.

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Enucleation of human erythroblasts involves non-muscle myosin IIB.

Publications

Enucleation of human erythroblasts involves non-muscle myosin IIB.

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