For example, Complexin II – a protein involved in neurotransmitter release (Rizo and Südhof, 2002), is decreased in HD patients (Morton and Edwardson, 2001), R6/2 transgenic mice (Morton et al., 2001) and neuronal cell model of HD (Edwardson et al., 2003). This evidence concerns the gene CPLX2 and Huntington disease.