Spatio-temporal dynamics of [beta]-tubulin isotypes during the development of the sensory auditory organ in rat

There are different [beta]-tubulin isoforms in microtubules of vertebrate tissues. However, their functional significance is still largely unknown. In the present study, we investigated the localization of five [beta]-tubulin isotypes ([beta]1-5) within the hearing organ during development in rat. By using confocal microscopy, we showed that with the exception of the [beta]3-tubulin isoform that was specific to nerve fibres, all the different [beta]-tubulin isoforms were mainly present in the supporting cells. Contrary to [beta]1-4-tubulins, we also found that the [beta]5-tubulin isoform appeared only at a key stage of the post-natal development in specific cell types (pillar cells and Deiters' cells). By using transmission electron microscopy, we revealed further that this developmental stage coincided with the formation of two separate bundles of microtubules from a unique one in these supporting cells. Together, these results suggest that the [beta]5-tubulin isoform might be involved in the generation of new microtubule bundles from a pre-existing one.