The neurodegenerative disease Machado Joseph disease (MJD, also known as spinocerebellar ataxia-3) is a fatal disease that impairs control and co-ordination of movement. MJD is caused by expansion of a trinucleotide (CAG) repeat region within the ATXN3 gene, encoding a long polyglutamine (polyQ) region within the ataxin-3 protein. As transcription regulation is one of the functions of the ataxin-3 protein, weWe aimed to examine whether zebrafish expressing polyQ expanded ataxin-3 had altered levels of histone acetylation, and to establish test whether treatment with the histone deacetylase (HDAC) inhibitor sodium valproate was protective for the the first transgenic zebrafish.