FY2019 Annual Report

Cell Division Dynamics Unit

Assistant Professor
Tomomi Kiyomitsu




Cell division is a very dynamic and significant process to build an organism. During the development of multicellular organisms, cells divide symmetrically or asymmetrically to create diverse tissues. Prior studies demonstrated that “spindle positioning” defines division symmetry and asymmetry. However, how spindle position and orientation are mechanically regulated in response to developmental requirements remain poorly understood.

The Cell Division Dynamics Unit studies the basic mechanisms of spindle positioning in vertebrate mitosis by combining advanced genetic, cell biological, and biochemical approaches. We are currently focusing on the following three projects, with a particular interest in how the cytoplasmic dynein motor generates forces on microtubules:

  1. Mechanisms of spindle assembly in human cells
  2. Mechanisms and roles of spindle positioning in symmetrically-dividing cells
  3. Mechanisms of symmetrical cellular patterning in Medaka early embryos

In FY2019, I joined OIST as an Adjunct Assistant Professor from August. I transferred all of my lab equipment and reagents from Nagoya University to OIST at the end of March, 2020. In addition, I recruited 4 talented members, who will join my unit in FY2020. I expect that we can start basic experiments in June 2020, and will finish lab set-up by the end of FY2020.

1. Staff

  • Dr.  Ai Kiyomitsu, Science and Technology Associate (April 2020-)
  • Ms. Makiko Ajimura, Technician (April 2020-)
  • Ms. Euikyung Yu, Technician (April 2020-)
  • Ms. Susan Boerner, Technician (June 2020-)
  • Ms. Tomomi Teruya, Research Unit Administrator (August 2019-)

2. Collaborations

2.1 Mechanisms of spindle assembly by Ran-GTP

  • Type of collaboration:  Scientific Collaboration
  • Researchers:
    • Prof. Gohta Goshima, Nagoya University
    • Mr. Kenta Tsuchiya, Nagoya University
    • Dr. Yoshikatsu Sato, Nagoya University
    • Prof. Masato Kanemaki, National Institute of Genetics

3. Activities and Findings

3.1 Lab set-up

I am currently setting up three lab spaces: Lab1C for molecular biology, Lab1A for Medaka fish culture and analysis, and Lab4F for microscopy and human cell culture. All of my lab equipment, including advanced microscopes and a fish tank system were transferred to these rooms. We will purchase other essential equipment and fully set up the lab by the end of FY2020.

3.2 Mechanisms of spindle assembly by Ran-GTP in mitotic human cells

By combining CRISPR-based genome editing, auxin-inducible degron (AID) technology, and multi-color live cell imaging, we found that Ran-GTP is non-essential to activate NuMA in contrast to the prevailing model. The paper is under review. Please see 4.1 below for details.

4. Publications

4.1 Journals

  • Kiyomitsu, T. The cortical force-generating machinery: How cortical spindle-pulling forces are generated. Curr Opin Cell Biol. 2019 Apr 4;60:1-8. Review.
  • Tsuchiya, K. Hayashi, H. Nishina, M. Okumura, M. Sato, Y. Kanemaki, M.T. Goshima, G. Kiyomitsu, T. Ran-GTP is non-essential to activate NuMA for spindle pole focusing, but dynamically polarizes HURP to control mitotic spindle length. bioRxiv 473538; doi: https://doi.org/10.1101/473538

4.3 Oral and Poster Presentations

  • Tomomi Kiyomitsu. The development of mitosis-specific rapid protein-degradation assays in human cells. EMBO/EMBL symposium, Seeing is Believing. 2019. Poster presentation.
  • Tomomi Kiyomitsu. 光操作と急速分解、二刀流でダイニンの分裂期機能に迫る. 分子モーター討論会, 2019, invited oral presentation.