Persistent repression of tau in the brain using engineered zinc finger protein transcription factors.

Neuronal tau reduction confers resilience against ß-amyloid and tau-related neurotoxicity in vitro and in vivo. Here, we introduce a novel translational approach to lower expression of the tau gene MAPT at the transcriptional level using gene-silencing zinc finger protein transcription factors (ZFP-TFs). Following a single administration of adeno-associated virus (AAV), either locally into the hippocampus or intravenously to enable whole-brain transduction, we selectively reduced tau messenger RNA and protein by 50 to 80% out to 11 months, the longest time point studied. Sustained tau lowering was achieved without detectable off-target effects, overt histopathological changes, or molecular alterations. Tau reduction with AAV ZFP-TFs was able to rescue neuronal damage around amyloid plaques in a mouse model of Alzheimer's disease (APP/PS1 line). The highly specific, durable, and controlled knockdown of endogenous tau makes AAV-delivered ZFP-TFs a promising approach for the treatment of tau-related human brain diseases.

Allele-selective transcriptional repression of mutant HTT for the treatment of Huntington's disease.

Huntington's disease (HD) is a dominantly inherited neurodegenerative disorder caused by a CAG trinucleotide expansion in the huntingtin gene (HTT), which codes for the pathologic mutant HTT (mHTT) protein. Since normal HTT is thought to be important for brain function, we engineered zinc finger protein transcription factors (ZFP-TFs) to target the pathogenic CAG repeat and selectively lower mHTT as a therapeutic strategy. Using patient-derived fibroblasts and neurons, we demonstrate that ZFP-TFs selectively repress >99% of HD-causing alleles over a wide dose range while preserving expression of >86% of normal alleles. Other CAG-containing genes are minimally affected, and virally delivered ZFP-TFs are active and well tolerated in HD neurons beyond 100 days in culture and for at least nine months in the mouse brain. Using three HD mouse models, we demonstrate improvements in a range of molecular, histopathological, electrophysiological and functional endpoints. Our findings support the continued development of an allele-selective ZFP-TF for the treatment of HD.

Overexpression of repressive cAMP response element modulators in high glucose and fatty acid-treated rat islets. A common mechanism for glucose toxicity and lipotoxicity?

The hyperlipidemia and hyperglycemia of the diabetic state accelerate beta-cell dysfunction, yet the mechanisms are not fully defined. We used rat islet-specific oligonucleotide arrays (Metabolex Rat Islet Genechips) to identify genes that are coordinately regulated by high glucose and free fatty acids (FFA). Exposure of rat islets to FFA (125 microM for 2 days) or glucose (27 mM for 4 days) reduced glucose-stimulated insulin secretion by 70 +/- 5 and 40 +/- 4%, respectively, relative to control-cultured islets. These treatments also substantially reduced the insulin content of the islets. Islet Genechips analysis revealed that the mRNA levels of cAMP response element modulator (CREM)-17X and inducible cAMP early repressor were significantly increased in both 27 mM glucose- and FFA-treated islets. Removing FFA or high glucose from the culture medium restored glucose-stimulated insulin secretion and the mRNA levels of the two CREM repressors to normal. Northern blot analysis revealed a 5-fold increase in the abundance of CREM-17X mRNA and a concomitant 50% reduction in the insulin mRNA in FFA-treated islets. Transient transfection of the insulin-secreting beta HC9 cells with CREM-17X suppressed rat insulin promoter activity by nearly 50%. Overexpression of CREM-17X in intact islets via adenovirus infection decreased islet insulin mRNA levels and insulin content and resulted in a significant decrease in glucose- or KCl-induced insulin secretion. Taken together, these data suggest that up-regulation of CREM repressors by either FFA or high glucose exacerbates beta-cell failure in type 2 diabetes by suppressing insulin gene transcription.