Differential contributions of nonmuscle myosin IIA and IIB to cytokinesis in human immortalized fibroblasts

Abstract

Nonmuscle myosin II (NMII) plays an important role in cytokinesis by constricting a contractile ring. However, it is unknown how NMII isoforms contribute to cytokinesis in mammalian cells. Here, we investigated the roles of the two major NMII isoforms, NMIIA and NMIIB, in cytokinesis using a WI-38 VA13 cell line (human immortalized fibroblast). In this cell line, NMIIB tended to localize to the contractile ring more than NMIIA. The expression level of NMIIA affected the localization of NMIIB and vice versa. Most NMIIB accumulated at the cleavage furrow in NMIIA-knockout (KO) cells, and most NMIIA was displaced from this location in exogenous NMIIB-expressing cells, indicating that NMIIB preferentially localizes to the contractile ring. Specific KO of each isoform elicited opposite effects. The rate of furrow ingression was decreased and increased in NMIIA-KO and NMIIB-KO cells, respectively. Meanwhile, the length of NMII-filament stacks in the contractile ring was increased and decreased in NMIIA-KO and NMIIB-KO cells, respectively. Moreover, NMIIA helped to maintain cortical stiffness during cytokinesis. These findings suggest that appropriate level of NMIIA and NMIIB in the contractile ring is important for proper cytokinesis in specific cell types. In addition, two-photon excitation spinning-disk confocal microscopy enabled us to image constriction of the contractile ring in live cells in a three-dimensional manner.

Comparative Analysis of the Roles of Non-muscle Myosin-IIs in Cytokinesis in Budding Yeast, Fission Yeast, and Mammalian Cells

“…Several recent studies indicate that IIA generates cortical tension and drives furrow ingression during cytokinesis, whereas IIB controls cortical stability and cytokinetic fidelity, perhaps by attenuating the IIA-dependent rate of rapid ingression (Yamamoto et al, 2019;Taneja et al, 2020). These observations are consistent with the distinct biochemical properties of IIA and IIB, i.e., IIA is "designed" for rapid motility whereas IIB is best for maintaining static tension (Golomb et al, 2004;Kovacs et al, 2007;Zhang et al, 2017;Melli et al, 2018).…”

Multiscale analysis of single and double maternal-zygotic Myh9 and Myh10 mutants during mouse preimplantation development

“…On the other hand, we did observe reverting cleavages in maternal Myh9 mutants (Figure 2-Video 3), effectively reducing cell number at the blastocyst stage. Loss of MYH9 is likely to cause difficulties during cytokinesis (Taneja et al, 2020;Yamamoto et al, 2019), which could in turn impact cell cycle progression (Figure 2B) and explain the significant reduction in cell number in mzMyh9 embryos. As for mzMyh10 embryos, we do not observe any cell cycle delay and count blastocysts with the correct cell number (Figure 2B and Figure 3B), indicating that MYH9 is the primary NMHC powering cytokinesis during mouse preimplantation development.…”

“…However, several in vitro studies point to specific roles of NMHC paralogs. For example, MYH9 plays a key role in setting the speed of furrow ingression during cytokinesis (Taneja et al, 2020;Yamamoto et al, 2019) and is essential to drive bleb retraction (Taneja and Burnette, 2019). During cell-cell contact formation, MYH9 was found essential for cadherin adhesion molecule clustering and setting contact size while MYH10 would be involved in force transmissions across the junction and would influence contact rearrangements (Heuzé et al, 2019;Smutny et al, 2010).…”

Multiscale analysis of single and double maternal-zygotic Myh9 and Myh10 mutants during mouse preimplantation development

“…Reduced cell number could also result from the occasional cytokinesis defects observed in maternal Myh9 mutants such as cleavages that reverse back shortly after (Movie 3). Loss of Myh9 is likely to cause difficulties during cytokinesis [27,28], which could in turn impact cell cycle progression (Fig 1B) and explain the significant reduction in cell number in mzMyh9−/− embryos. On the other hand, mzMyh10−/− embryos do not show cell cycle delay and make blastocysts with the correct cell number (Fig 1B and 2B), indicating that Myh9 is the primary NMHC powering cytokinesis during mouse preimplantation development.…”

“…However, several in vitro studies point to specific roles of NMHC paralogs. For example, Myh9 plays a key role in setting the speed of furrow ingression during cytokinesis [27,28] and is essential to drive bleb retraction [29]. During cell-cell contact formation, Myh9 was found essential for cadherin adhesion molecule clustering and setting contact size while Myh10 would be involved in force transmissions across the junction and would influence contact rearrangements [30,31].…”