Gene expression data from cortex of 9w old WT, R6/2, HDAC4het and R6/2::HDAC4het mice

Histone deacetylase (HDAC) 4 is a transcriptional repressor that contains a glutamine rich domain. We hypothesised that it may be involved in the molecular pathogenesis of Huntington’s disease (HD), a protein folding neurodegenerative disorder caused by an aggregation-prone polyglutamine expansion and transcriptional dysregulation. We found that HDAC4 interacts with huntingtin in a polyglutamine-length dependent manner and co-localises with cytoplasmic inclusions. We show that HDAC4 reduction delayed cytoplasmic aggregate formation, restored Bdnf transcript levels and rescued neuronal and cortico-striatal synaptic function in HD mouse models. This was accompanied by an improvement in motor co-ordination, neurological phenotypes and increased lifespan. Surprisingly, HDAC4 reduction had no effect on global transcriptional dysfunction and did not modulate nuclear huntingtin aggregation. Our results define a crucial role for cytoplasmic aggregation in the molecular pathology of HD. HDAC4 reduction presents a novel strategy for targeting huntingtin aggregation which may be amenable to small molecule therapeutics. mRNA expression analysis was performed by microarray in 9 weeks old WT (n=9), R6/2 (n=9), HDAC4het (n=9) and Double R6/2::HDAC4het (n=10) mice. Microarray quality control was performed using the software package provided on RACE (http://race.unil.ch).