Induction of alpha1-tubulin gene expression during development and regeneration of the fish central nervous system.

The alpha1- and alpha2-tubulin encoding genes were cloned from a goldfish genomic DNA library. alpha1- and alpha2-tubulin RNA expression was examined in developing and adult retinas. These studies demonstrated increased alpha1-tubulin RNA in presumptive ganglion cells that grow axons early in retinal development and in adult retinal ganglion cells whose optic axons had been damaged. The alpha2-tubulin RNA was undetectable in developing retina and constitutively expressed in adult retinal ganglion cells regardless of optic nerve crush. To determine if these changes in alpha1-tubulin RNA reflected changes in alpha1-tubulin promoter activity, we introduced into zebrafish embryos and adult goldfish retinal explants expression vectors harboring the alpha1-tubulin gene's promoter. These studies showed that the alpha1-tubulin promoter confers a developmentally regulated, neuron-restricted pattern of reporter gene expression in vivo and its activity is increased in adult retinal neurons induced to regenerate their axons. Promoter deletions defined regions of alpha1-tubulin DNA necessary for this pattern of expression. These results suggest that DNA sequences necessary for alpha1-tubulin gene induction during central nervous system development and regeneration are contained within the alpha1-tubulin gene's 5'-flanking DNA and that this promoter will be useful for identifying these elements and their DNA binding proteins.