Differential synthesis of β-tubulin isotypes in gerbil nasal epithelia

Compartmentalization of β-tubulin isotypes within cells according to function was examined in gerbil olfactory and respiratory epithelia by using specific antibodies to four β-tubulin isotypes (β_I, β_II, β_III, and β_IV). Isotype synthesis was cell-type-specific, but the localization of the isotypes was not compartmentalized. All four isotypes were found in the cilia, dendrites, somata, and axons of olfactory neurons. Only two isotypes (β_I and β_IV) were present in the cilia of nasal respiratory epithelial cells. The β_IV isotype, thought to be an essential component of cilia, was present in olfactory neurons and respiratory epithelial cells, which are ciliated, but was not found in basal cells (the stem cells of olfactory sensory neurons, which have no cilia). Olfactory neurons therefore do not synthesize β_IV-tubulin until they mature, when functioning cilia are also elaborated. The failure to observe compartmentalization of β-tubulin isotypes in olfactory neurons sheds new light on potential functions of the β-tubulin isotypes.