The mitochondrion-dependent pathway was predominant in SCA-, SCA-S1-, and SCA-S2-induced apoptosis of A-549 cells as evidenced by the analyses of mitochondrial membrane potential (MMP), cytochrome c release, Bcl-2 expression, activation of caspase-3, and DNA fragmentation. Here, BCL2 is linked to autosomal dominant cerebellar ataxia.