Mitosis is a key stage during the life of a cell. It is the stage where a bipolar spindle structure is organized to segregate duplicated chromosomes into the two daughter cells. Spindle organization and function require exquisite precision, robustness and fidelity. Defects associated with the spindle can lead to defects in chromosomal segregation, or aneuploidy, which has been correlated with some types of cancer. The spindle is a macromolecular machine made of microtubules, microtubule-associated proteins (MAPs), molecular motors and other regulatory proteins. Of intense interest have been molecular motors, which perform work such as cross-linking and sliding microtubules apart to form the bipolar spindle, or to depolymerize microtubules to maintain proper spindle lengths, or to carry chromosomes to opposite spindle poles. Surprisingly, while we have learned much about motors involved in mitosis, we still know very little about the MAPs and other regulatory proteins and how they coordinate with motors to bring about proper spindle formation. My laboratory uses the relatively simple fission yeast Schizosaccharomyces pombe and human cultured cells to address conserved mechanisms of spindle organization and function. This particular project focuses on how the initial bipolar spindle is formed at the start of mitosis, the stage termed prophase. We focus on the MAPs that contribute to spindle formation. Using fission yeast as a gene discovery tool, we have begun to define the roles of a new gene we called psr1+ (poles separation regulator 1). Our work indicates that psr1p organizes the initial bipolar spindle during prophase. Psr1-deletion leads to high frequency of monopolar spindles and subsequent chromosome segregation defects. Fission yeast psr1+ appears to have a human functional homolog. We have begun to characterize a novel human gene we called PSR1. In HeLa cells, siRNA of PSR1 also leads to high frequency of monopolar spindles and subsequent chromosome segregation defects. This proposal aims to combine modern cell and molecular biology techniques in fission yeast and human cultured cells, biochemistry, high-resolution optical live-cell imaging, and innovative microfluidic techniques to control cellular microenvironment, to reach a mechanistic understanding of bipolar spindle formation.

Public Health Relevance

Cell division is a key stage in the life of a cell, where genetic information (in the form of chromosomes) is duplicated and partitioned equally into the daughter cells. Defects in cell division can lead to cancer. Chromosome segregation is accomplished by a structure call the mitotic spindle. The spindle is a macromolecular machine composed of microtubules, motors, microtubule-associated proteins (MAPs), and other regulatory proteins. We propose to study conserved mechanisms of spindle organization and function in the genetically-tractable model system fission yeast and in human cultured cells.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
Program Officer
Deatherage, James F
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Pennsylvania
Anatomy/Cell Biology
Schools of Medicine
United States
Zip Code
Syrovatkina, Viktoriya; Tran, Phong T (2015) Loss of kinesin-14 results in aneuploidy via kinesin-5-dependent microtubule protrusions leading to chromosome cut. Nat Commun 6:7322
Scheffler, Kathleen; Minnes, Refael; Fraisier, Vincent et al. (2015) Microtubule minus end motors kinesin-14 and dynein drive nuclear congression in parallel pathways. J Cell Biol 209:47-58
Carlier-Grynkorn, Frédérique; Ji, Liang; Fraisier, Vincent et al. (2014) Fission yeast mtr1p regulates interphase microtubule cortical dwell-time. Biol Open 3:591-6
Costa, Judite; Fu, Chuanhai; Khare, V Mohini et al. (2014) csi2p modulates microtubule dynamics and organizes the bipolar spindle for chromosome segregation. Mol Biol Cell 25:3900-8
Zheng, Fan; Li, Tianpeng; Jin, Dong-Yan et al. (2014) Csi1p recruits alp7p/TACC to the spindle pole bodies for bipolar spindle formation. Mol Biol Cell 25:2750-60
Syrovatkina, Viktoriya; Fu, Chuanhai; Tran, Phong T (2013) Antagonistic spindle motors and MAPs regulate metaphase spindle length and chromosome segregation. Curr Biol 23:2423-9
Fu, Chuanhai; Jain, Deeptee; Costa, Judite et al. (2011) mmb1p binds mitochondria to dynamic microtubules. Curr Biol 21:1431-9