CASK and Huntington disease: To find out whether the proteins making up the cytomatrix of the active zones are affected by mutant huntingtin, we studied the expression levels of four of the active zone proteins (Bassoon, ERC, RIM1 and Munc 13–1) and two associated proteins (CASK and Mint 1; Fig. 1a) in the R6/1 mouse model at the late stage of HD (40 weeks old) and WT mice as control.