Meiotic telomere clustering is inhibited by colchicine but does not require cytoplasmic microtubules.

Telomere clustering, the defining feature of the bouquet, is an almost universal feature of meiotic prophase, yet its mechanism remains unknown. The microtubule-depolymerizing agent colchicine was found to inhibit bouquet formation. Telomeres in colchicine-treated cells remained scattered in the nuclear periphery, whereas untreated cells exhibited a prominent telomere cluster. Colchicine administered after the bouquet had formed did not affect telomere dispersal. The effect of colchicine on bouquet formation appeared to be separable from its effect on cytoplasmic microtubules; amiprophos methyl, a highly effective plant microtubule-depolymerizing drug, did not affect telomere clustering. Inhibition of bouquet formation was limited to colchicine and the related drug podophyllotoxin out of the variety of microtubule-depolymerizing drugs tested, suggesting that the target involved in bouquet formation has a structural specificity.