Crosslinkers and Motors Organize Dynamic Microtubules to Form Stable Bipolar Arrays in Fission Yeast

Janson M, Loughlin R, Loiodice I, Fu C, Brunner D, Nedelec F, Tran P
Cell 128, 357-68, Jan 2007.



Microtubule (MT) nucleation not only occurs from centrosomes, but also in large part from dispersed nucleation sites. The subsequent sorting of short MTs into networks like the mitotic spindle requires molecular motors that laterally slide overlapping MTs and bundling proteins that statically connect MTs. How bundling proteins interfere with MT sliding is unclear. In bipolar MT bundles in fission yeast, we found that the bundler ase1p localized all along the length of antiparallel MTs, whereas the motor klp2p (kinesin-14) accumulated only at MT plus ends. Consequently, sliding forces could only overcome resistant bundling forces for short, newly nucleated MTs, which were transported to their correct position within bundles. Ase1p thus regulated sliding forces based on polarity and overlap length, and computer simulations showed these mechanisms to be sufficient to generate stable bipolar bundles. By combining motor and bundling proteins, cells can thus dynamically organize stable regions ofoverlap between cytoskeletal filaments.

Simulations by Rose Loughlin:

Simulated kymograph - model 1: (36 MB)
Simulated kymograph - model 2: (22 MB)
Simulated kymograph - model 3: (26 MB)
Simulation - unbundled model: (7 MB)

More Simulation Movies:

Model 1 - full cell (17MB)
Model 1 - aligned bundle (17MB)

Simulation executable and parameter files:

Windows 32 (23 MB)
Mac OS X: (9 MB)