In particular, mRNA levels of complexin II, a key player in the mechanisms underlying cognitive processes (Reim et al, 2001; Glynn et al, 2003), are reduced in R6/2 mice and in human HD striatum and cortex (Morton & Edwardson, 2001; Freeman & Morton, 2004) and complexin II knockout mice show selective cognitive deficits that reflect those seen in R6/2 mice (Glynn et al, 2003). The gene discussed is CPLX2; the disease is Huntington disease.