[i] The relative expression, determined by Northern blot analysis of different tissues, is indicated for a particular gene but cannot be compared here between genes: α-synuclein (Ueda et al. 1993, 1994); β-synuclein (Jakes et al. 1994; E. Leroy. pers. comm.); γ-synuclein (Lavedan et al. 1998b).