  The dynamic architecture of the microtubule cytoskeleton is crucial for cell
division, motility and morphogenesis. The dynamic properties of microtubules -
growth, shrinkage, nucleation and severing - are regulated by an arsenal of
microtubule-associated proteins (MAPs). The activities of many of these MAPs
have been reconstituted in vitro using microscope assays. As an alternative to
fluorescence microscopy, interference-reflection microscopy (IRM) has been
introduced as an easy-to-use, wide-field imaging technique that allows
label-free visualization of microtubules with high contrast and speed. IRM
circumvents several problems associated with fluorescence microscopy including
the high concentrations of tubulin required for fluorescent labeling, the
potential perturbation of function caused by the fluorophores, and the risks of
photodamage. IRM can be implemented on a standard epifluorescence microscope at
low cost and can be combined with fluorescence techniques like
total-internal-reflection-fluorescence (TIRF) microscopy. Here we describe the
experimental procedure to image microtubule dynamics and severing using IRM,
providing practical tips and guidelines to resolve possible experimental
hurdles.
