The synuclein family members, including Alpha-synuclein (also designated NACP for non-Beta-Amyloid component) and Beta-synuclein, are predominantly expressed in the brain and are speculated to be involved in synaptic regulation and neuronal plasticity. Alpha-synuclein is localized to neuronal cell bodies and synapses. Alpha-synuclein was first identified as a component of Alzheimer’s disease amyloid plaques. Abnormal platelet function in Alzheimer’s disease has been demonstrated. During megakaryocytic differentiation Alpha-synuclein has been found to be upregulated, while Beta-synuclein is downregulated, indicating that coordinate expression of synucleins may be important during hematopoetic cell differentiation. A mutant form of Alpha-synuclein has been found in patients with early onset Parkinson’s disease.