Expression of acetylated tubulin in the postnatal developing mouse cochlea.

Abstract

Microtubules are an essential component of the cytoskeleton of a eukaryotic cell. The post-translational tubulin modifications play an important role in regulating microtubule properties, acetylation tubulin is one of the major post-translational modifications of microtubules. Acetylation tubulin has also been shown to be expressed in the cochlea. However, the detailed expression profiles of acetylation tubulin protein during development have not yet been investigated in the postnatal mammalian cochlea. Here, we first examined the spatio-temporal expression of acetylated tubulin in the mouse cochlea during postnatal development. At postnatal day 1 (P1), acetylated tubulin was localized primarily to the auditory nerve inside the cochlea and their synaptic contacts with the inner and outer hair cells (IHCs and OHCs). In the organ of Corti, acetylated tubulin occurred first at the apex of pillar cells. At P5, acetylated tubulin first appeared in the phalangeal processes of Deiters’ cells. At P8, staining was maintained in the phalangeal processes of Deiters’ cells and neural elements. At P10, labeling in Deiters’ cells extended from the apices of OHCs to the basilar membrane, acetylated tubulin was expressed throughout the cytoplasm of inner and outer pillar cells. At P12, acetylated tubulin displayed prominent and homogeneous labeling along the full length of the pillar cells. Linear labeling was present mainly in the Deiters’ cell bodies underlying OHCs. Between P14 and P17, acetylated tubulin was strongly expressed in inner and outer pillar cells and Deiters’ cells in a similar pattern as observed in the adult, and labeling in these cells were arranged in bundles. In addition, acetylated tubulin was expressed in stria vascularis, root cell bodies, and a small number of fibrocytes of the spiral ligament until the adult. In the adult mouse cochlea, immunostaining continued to predominate in Deiters’ cells and pillar cells. In Deiters’ cells, immunolabeling formed cups securing OHCs basal portions, and continued presence of acetylated tubulin-labeled nerve terminals below IHCs was shown. Our results presented here underscored the essential role played by acetylated tubulin in postnatal cochlear development, auditory neurotransmission and cochlear mechanics.