Isotypes of α-tubulin are differentially regulated during neuronal maturation

Abstract

The mRNAs for two isotypes of α-tubulin, termed Tα1 and T26, are known to be expressed in the rat nervous system. We have compared the expression of these two α-tubulin mRNAs during neural development, using RNA blotting and in situ hybridization techniques with probes directed against unique sequences of each mRNA. Tα1 mRNA is highly enriched in the embryonic nervous system but is markedly less abundant in the adult brain; T26 mRNA is expressed in many embryonic tissues with little change in abundance during development. Within the nervous system, Tα1 mRNA is enriched in regions with neurons actively undergoing neurite extension, such as the cortical plate, whereas T26 mRNA is relatively homogeneous in distribution, with some enrichment in proliferative zones. Expression of Tα1 mRNA is also increased in PC12 cells induced to differentiate and extend neurite processes by nerve growth factor. Taken together, the data indicate that Tα1-tubulin mRNA is expressed at high levels during the extension of neuronal processes. The abundant expression of Tα1-tubulin mRNA may therefore reflect either a means to increase the available pool of α-tubulin or a specific requirement for the Tα1 isotype for neurite extension.