HTT and amyotrophic lateral sclerosis: Janssen et al. (2010) demonstrated that increased levels of HDAC2 and reduced HDAC11 mRNA were related to apoptotic neuronal death in human brain tissue from people diagnosed with ALS (Janssen et al., 2010). Additionally, accumulated mutant huntingtin (htt) protein in HD has also been shown to interact with the HAT domain of the CBP enzyme, decreasing HAT activity in post-mortem human brain tissue (Rouaux et al., 2004).