A microscopic theory for chromosome congression in C. elegans mitotic spindle

The accurate separation of chromosomes during cell division is key to survival and proper development. As the nuclear envelope breaks down, the microtubules within the spindle begin to interact with chromosomes. The disordered chromosomes, then, congress and are aligned in the mid-plane of the bipolar spindle. The underlying active forces that move the chromosomes during this process are poorly understood. We utilize the data from the first full 3D tomographic reconstructions of C. elegans mitotic spindle to understand how individual microtubules interact with chromosomes and propose a microscopic theory for chromosome congression. In addition to predicting the observed length distribution of microtubules in tomography, our theory correctly predicts a mechanically stable half spindle structure, as is observed in cells with monopolar spindles. Most remarkably, we find that the shapes (curvature) of microtubules based on our micromechanical theory are in good agreement with the tomography results.