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 We are interested in intracellular dynamics, particularly those regulated by microtubules. The mitotic spindle is a research subject, and we have adopted multiple methodologies to understand the mechanism of spindle formation, most notably high-resolution live cell microscopy, high-throughput RNAi screening, quantitative image analysis, and computer simulation (Fig. 1).
Fig. 1: Spindle defects observed after mitotic gene RNAi in Drosophila S2 cells
 Augmin and microtubule amplification
 Microtubules are nucleated at centrosomes, pre-existing microtubules and near chromosomes. The importance of these pathways has been shown recently in several cell types, yet it is largely unknown how they are achieved at a molecular level. Our genome-wide RNAi screen and extensive follow-up analyses identified an 8-subunit protein complex, “augmin”, that is required for microtubule-dependent microtubule generation within the mitotic spindle. We anticipate that comprehensive analysis of this protein complex will help to build a global molecular picture of microtubule generation pathways (Fig. 2).

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Model for the augmin- and γ-TuRC
Fig. 2: Model for the augmin- and γ-TuRC (γ-tubulin ring complex)-dependent microtubule amplification within the mitotic spindle
 Microtubule dynamics in Drosophila cells
 We identified a protein ‘Sentin’ that is localised at the growing end of microtubules via binding to EB1 protein (Fig. 3). Sentin depletion in Drosophila S2 cells, similar to EB1 depletion, resulted in the increase in microtubule pausing and led to the formation of shorter spindles, without displacing EB1 from growing microtubules. We showed in vitro that Sentin promotes microtubule catastrophe and, together with the microtubule polymerase XMAP215/Msps, accelerates microtubule growth. We wish to understand the molecular mechanism underlying regulation of microtubule plus ends by EB1, Sentin, XMAP215, and other associated proteins.
sentin
Fig.3: Sentin, a critical regulator of microtubule dynamics

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 Moss P. patens for plant cell biology
 We are interested in molecular basis of intracellular dynamics of plant cells. Is it similar or different to animals? We have introduced the moss Physcomitrella patens as a model land plant system (Fig. 4).
moss physcomitrella patens
Fig.4: Moss Physcomitrella patens

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●Kiyomitsu group
 This group was founded in August 2013. Based on my postdoctoral work (Kiyomitsu and Cheeseman, Cell 2013, Nat. Cell Biol. 2012), our group is interested in studying the mechanisms of equal-sized cell division in vertebrate mitosis and the biological significance of cell size symmetry during organismal development. We combine advanced live cell imaging with novel technologies such as optogenetics and genome editing.
Original research papers
Kiyomitsu and Cheeseman, Nature Cell Biology 2012
Kiyomitsu and Cheeseman, Cell 2013
Review
Kiyomitsu, Trends in Cell Biology 2015
Link
Cell 40 under 40
>>http://www.cell.com/40/tomomi-kiyomitsu
PRESTO, Design and Control of Cellular Functions
>>http://www.jst.go.jp/presto/synbio/en/member/researcher3.html#_researcher4
 
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