Targeted expression of human CuZn superoxide dismutase gene in mouse central nervous system

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.

Induced overexpression of mitochondrial Mn-superoxide dismutase extends the life span of adult Drosophila melanogaster

A transgenic system ("FLP-out") based on yeast FLP recombinase allowed induced overexpression of MnSOD enzyme in adult Drosophila melanogaster. With FLP-out a brief heat pulse (HP) of young, adult flies triggered the rearrangement and subsequent expression of a MnSOD transgene throughout the adult life span. Control (no HP) and overexpressing (HP) flies had identical genetic backgrounds. The amount of MnSOD enzyme overexpression achieved varied among six independent transgenic lines, with increases up to 75%. Life span was increased in proportion to the increase in enzyme. Mean life span was increased by an average of 16%, with some lines showing 30-33% increases. Maximum life span was increased by an average of 15%, with one line showing as much as 37% increase. Simultaneous overexpression of catalase with MnSOD had no added benefit, consistent with previous observations that catalase is present in excess in the adult fly with regard to life span. Cu/ZnSOD overexpression also increases mean and maximum life span. For both MnSOD and Cu/ZnSOD lines, increased life span was not associated with decreased metabolic activity, as measured by O2 consumption.

Targeted neuronal gene expression and longevity in Drosophila

Earlier studies from this laboratory have shown that in the insect, Drosophila melanogaster, the motorneuron is an important cellular nexus between the metabolism of reactive oxygen species (ROS) and adult lifespan. This was demonstrated by experiments in which expression of CuZn SOD (SOD1) specifically in motorneurons was shown to extend the mean and maximum adult lifespans to 140% of normal, and to rescue the majority of deliterious phenotypes displayed by SOD1-null mutants. We have interpreted these results to mean either that the lifespan of the organism is normally limited by the functional lifespan of this post-mitotic cell type, or that ROS metabolism in motorneurons affects organismic lifespan via a systemic, perhaps neuroendocrine, signaling mechanism. We have now extended these studies to ask: (i) whether expression of catalase (CAT) or of the mitochondrially-localized Mn SOD (SOD2) in motorneurons, either singly or in combination with SOD1, have similar effects on lifespan; (ii) if expression of SOD2 can rescue SOD1-null mutant phenotypes; and (iii) if ROS metabolism in cell types other than motorneurons has significant impact on aging and lifespan determination.