TubStain, a novel non-antibody tool for direct labeling of microtubules

Imaging of the microtubular network is an important strategy to define cell-cycle specific and pathological states of eukaryotic cells. Currently different experimental approaches using fluorescence microscopy are used to visualize and investigate the organization and dynamics of microtubules. Here we describe TubStain, a novel recombinant tool allowing versatile and direct labelling of microtubules in fixed cells over a broad variety of different species and tissues. TubStain consists of three modules, a (i) Microtubule-binding domain based on the sequence of human PEX14, a peroxisomal membrane protein which has been recently identified as a membrane anchor for microtubules (Bharti et al, 2011, J. Cell Science), a (ii) dimerizer and a (iii) labelling agent. Conjugation with different fluorophoretic proteins, dyes or gold-particles allows flexible, multiplexed applications in various fields of microscopy, including fluorescence microscopy and high-resolution electron microscopy. Direct microtubule visualization by TubStain is faster and more reliable than convential immunostaining techniques and could provide a suitable tool for identification and characterization of microtubule polymerizing/depolymerizing drugs. Furthermore, the smallness of TubStain in combination with the diversity of labelling agents makes TubStain an ideal tool to study microtubules by high-resolution microscopic techniques.