• α synuclein
• Parkinson's disease
• polymorphism

α Synuclein is a presynaptic protein highly and broadly expressed in the brain but its normal function is unknown.¹ The protein is also termed non-amyloid β component precursor (NACP) because of its localisation in amyloid plaques of Alzheimer's disease.¹ However, subsequent studies failed to confirm α synuclein as a component of the amyloid plaque.¹ α Synuclein/NACP is now known to be a major component of Lewy bodies in Parkinson's disease (PD).¹ Point mutations of the α synuclein gene found in three independent PD families suggest that α synuclein may participate in the aetiology of sporadic PD.¹ To address this possibility, several groups reported case-control studies using a dinucleotide repeat polymorphism in the promoter region of the gene.² The previous Japanese study by Izumi et al³ found a tendency of a lower frequency of allele 1 in Japanese PD patients …