The major cause of HD is the cytotoxicity of the mutant Htt protein (mHtt) (Rubinsztein and Carmichael, 2003), which is expressed throughout the brain and peripheral tissues, but elicits selective neurodegeneration of the corpus striatum and lesser damage to the cerebral cortex in HD patients (Cowan and Raymond, 2006). This evidence concerns the gene HTT and Huntington disease.