Degree Type


Date of Award


Degree Name

Master of Science


Theses & dissertations (Interdisciplinary)



First Advisor

Kristen M. Johansen

Second Advisor

Jorgen Johansen


The microtubule-based mitotic spindle is dynamic rather than static, as polymerization and depolymerization of microtubules occur in sequence. Motor proteins including a minus end directed Ncd are associated with the microtubule-based spindle, and have long been proposed to generate force in microtubules by crossbridging and sliding microtubules relative to adjacent microtubules.;However, the force exerted by motor proteins is only part of the force exerted in the spindle. A stationary "spindle matrix" structure has been proposed to provide a strut on which motor proteins and microtubules interact during force generation. So far at least four molecular components of the spindle matrix, Skeletor, Chromator, Megator and EAST, were characterized to be in the same complex and all localize to the fusiform spindle matrix.;Based on the distribution of spindle matrix proteins and the motor protein Ncd in the spindle, a potential interaction between Ncd and spindle matrix proteins was proposed. In this thesis, RNAi was performed to generate Ncd depleted Drosophila S2 cells. After depletion of Ncd, S2 cells displayed a range of spindle abnormalities including multipolar spindles or loss of pole focus. In addition, spindle matrix protein structure was altered. Results obtained from larval neuroblast squashes were consistent with those observed in S2 cells. In the loss-of-function mutant ncd D, the Megator-defined spindle was found to be widely extended. Moreover, immunoprecipitation experiments showed that Ncd and the spindle matrix proteins Chromator and Megator are in the same complex. These findings suggest that the motor protein Ncd interacts with the spindle matrix. My observations also support the hypothesis that the spindle matrix provides a strut for interaction of motor proteins. However, this strut might also depend on a stabilizer such as Ncd that is required for spindle matrix assembly and maintenance.



Digital Repository @ Iowa State University,

Copyright Owner

Lei Zhu



Proquest ID


OCLC Number




File Format


File Size

71 pages