Generation of a transgenic zebrafish model of Tauopathy using a novel promoter element derived from the zebrafish eno2 gene

The aim of this study was to isolate cis-acting regulatory elements for the generation of transgenic zebrafish models of neurodegeneration. Zebrafish enolase-2 (eno2) showed neuronal expression increasing from 24 to 72 h post-fertilization (hpf) and persisting through adulthood. A 12 kb eno2 genomic fragment, extending from 8 kb upstream of exon 1 to exon 2, encompassing intron 1, was sufficient to drive neuronal reporter gene expression in vivo over a similar time course. Five independent lines of stable Tg(eno2 : GFP) zebrafish expressed GFP widely in neurons, including populations with relevance to neurodegeneration, such as cholinergic neurons, dopaminergic neurons and cerebellar Purkinje cells. We replaced the exon 2-GFP fusion gene with a cDNA encoding the 4-repeat isoform of the human microtubule-associated protein Tau. The first intron of eno2 was spliced with high fidelity and efficiency from the chimeric eno2-Tau transcript. Tau was expressed at approximately 8-fold higher levels in Tg(eno2 : Tau) zebrafish brain than normal human brain, and localized to axons, neuropil and ectopic neuronal somatic accumulations resembling neurofibrillary tangles. The 12 kb eno2 promoter drives high-level transgene expression in differentiated neurons throughout the CNS of stable transgenic zebrafish. This regulatory element will be useful for the construction of transgenic zebrafish models of neurodegeneration.