FY2020 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 assembly and positioning in vertebrate mitosis by combining advanced 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 FY2020 (April 2020- March 2021), our unit formally started with 5 members as described below. We set up several key equipment including a spinning-disc confocal microscope, a liquid chromatography system, and aquarium systems with water recirculation. We also accepted two students as described below. Most importantly, we published a research paper in Current Biology which is highlighted on the OIST website: https://www.oist.jp/news-center/news/2021/2/5/cell-division-research-explores-questions-core-life. In parallel, we started collaboration with Prof. Tanaka & Dr. Nishimura (Nagoya Univ.) and Dr. Ansai (Tohoku Univ.) regarding Medaka projects. T. Kiyomitsu got an external grant, KAKENHI Basic Research B.


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. Students     

  • Mr. Junichi Enomoto, an intern student (October 2020 -December 2020)
  • Ms. Shannon Hayashi, a rotation student (January 2021- April 2021)


3. Collaborations

 3.1 Mechanisms of spindle assembly by Ran-GTP

  • Prof. Gohta Goshima, Nagoya University
  • Mr. Kenta Tsuchiya, Nagoya University
  • Dr. Yoshikatsu Sato, Nagoya University
  • Prof. Masato Kanemaki, National Institute of Genetics

 3.2 Mechanisms of spindle positioning in Medaka early embryos

  • Dr. Minoru Tanaka, Nagoya University
  • Prof. Toshiya Nishimura, Nagoya University (currently Hokkaido University)
  • Prof. Satoshi Ansai, Tohoku University
  • Prof. Masato Kanemaki, National Institute of Genetics


4. Activities and Findings

     4.1 Lab set-up

We set up three lab spaces: Lab1C for molecular biology and biochemistry, Lab1A for Medaka fish culture and analysis, and Lab4F for microscopy and human cell culture.

     4.2 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 established rapid mitotic depletion assays for the Ran pathway. We found that the Ran pathway is non-essential to activate NuMA for spindle-pole focusing, but maintains HURP’s polarized spindle localization during metaphase. The study was published in Current Biology as described below.


5. Publications

     5.1 Journals

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 near chromosomes. Current Biology Jan 11;31(1):115-127.e3. doi: 10.1016/j.cub.2020.09.091. Epub 2020 Nov 12.

     5.2 Books and other one-time publications

        Nothing to report

     5.3 Oral Presentations

  • Tomomi Kiyomitsu, A brief introduction to the Cell Division Dynamics Unit. OIST Internal Seminar Series, October 2nd, 2020
  • Tomomi Kiyomitsu, 急速タンパク分解で見えてきたRan依存的な紡錘体形成の仕組み 第55回HiHA Webinar, October 13th, 2020
  • Tomomi Kiyomitsu, How dynein motor complexes control cell division symmetry and asymmetry? OIST Faculty Lunch Seminar, October 27th, 2020
  • Tomomi Kiyomitsu, Mechanisms of Ran-based mitotic spindle assembly revealed by auxin-mediated rapid protein knock-down. The annual meeting of Molecular Biology Society of Japan, December 2nd, 2020
  • Tomomi Kiyomitsu, Faculty talk (Biology), Science Challenge 2021 at OIST, March 16th, 2021.


6. Intellectual Property Rights and Other Specific Achievements

Nothing to report

7. Meetings and Events

Nothing to report

8. Other

Nothing to report