Nestin-cre was always passed through the male germline. with the TORC1-CREB interaction to repress BDNF transcription and Sirt1 rescues this defectin vitroandin vivo. These studies suggest a key role of Sirt1 in transcriptional networks in normal and HD brain and offer an opportunity for therapeutic development. Recent evidence suggests that Sirt1, a member of sirtuin family that has been implicated in aging and metabolism, plays a protective role in neurodegenerative disorders1. However, the exact nature of normal Sirt1 function in mammalian brain has yet to 4-Guanidinobutanoic acid be ascertained. To clarify the function of Sirt1 in brain and determine its contribution to neurodegeneration, we focused on Huntingtons disease (HD), an autosomal dominant disease that commonly presents in adult life with personality changes, cognitive changes, psychiatric disturbances and abnormal movements2. HD belongs to a family of polyglutamine disorders that, in addition to expanded polyglutamine repeats, share other features such as adult onset, progressive neurodegeneration, inverse correlation of numbers of repeats with age of onset and presence of polyglutamine protein-containing inclusions2. Polyglutamine diseases, including HD remain fatal as there are no effective treatments to cure the diseases or to slow their progression. The role of Sirt1 in HD has been primarily studied inDrosophila melanogasterand inC. elegans, but the results have been contradictory. For example, in worms overexpressing Sir2 (ortholog of human Sirt1),HTT-induced neurodegeneration is suppressed, whereas overexpression in fly model of HD confers no significant protection4,5. To begin testing the role of Sirt1 in HD mice, we first crossed a conditional allele of Sirt1 (Sirt1flox) to the Nestin-cre driver to 4-Guanidinobutanoic acid yield Sirt1 brain-specific knockout mice (BSKO, genotypeSirt1flox/flox; nestin-cre). These mice were born at mendelian ratios and displayed no gross defects in brain development6. To 4-Guanidinobutanoic acid determine the impact of the ablation of neuronal Sirt1 on HD, we then crossed BSKO mice to the R6/2 model of HD7. These crosses, which were carried out on an inbred C57BL/6 background, yieldedSirt1flox/floxcontrols (referred to as WT),Sirt1flox/flox; R6/2 (R6/2),Sirt1flox/flox; nestin-cre (BSKO), andSirt1flox/flox; nestin-cre-R6/2 (BSKO-R6/2). Behavioral experiments revealed significant acceleration of motor deficits in BSKO-R6/2 compared to R6/2 mice as assessed by rotarod performance (Figs. 1aandSupplementary Fig. 1a). To determine if neuropathological alterations accompanied the behavioral phenotype, an unbiased stereological analysis of brain sections was performed. Previous studies have demonstrated that R6/2 mice exhibit progressive atrophy of striatal neurons that resembles neuropathology observed in human HD8. As expected, R6/2 mice showed significant striatal atrophy compared to WT mice (Fig. 1b). BSKO mice, which are smaller than WT mice6, also had smaller striata than the WT mice. BSKO-R6/2 mice Rabbit Polyclonal to SNX3 showed significantly smaller striatal volume compared to BSKO or R6/2 mice (Fig. 1c). Moreover, when analyzing a series of sections spanning the striatum, a significant decrease in the mean neuronal volume was observed in striata of the 4-Guanidinobutanoic acid BSKO-R6/2 mice compared to R6/2 mice (Fig. 1c). To examine aggregation of mutantHTT, mean aggregate count was examined in all four genotypes. While noHTTaggregates were observed in WT or BSKO mice, the number of aggregates was significantly increased in BSKO-R6/2 animals as compared to R6/2 mice (Fig. 1d). These results demonstrate that deficiency of Sirt1 accelerates neurodegeneration in HD mice. == Figure 1. Ablation of neuronal Sirt1 exacerbates and over-expression of Sirt1 ameliorates phenotypes in R6/2 mouse. == (a) Latency to fall from accelerating rotarod at 10 weeks of age.n= 4 – 10 per group. *P< 0.05 for HD vs. BSKO-HD by ANOVA. (b) Striatal volumes at 20 weeks of age.n= 4 per group. *P< 0.01 by ANOVA. (c) Striatal neuronal volumes at 20 weeks of age.n= 4 per group. *P< 0.05 by.