Synaptic vesicles are indispensable for this biological activity, and synaptophysin, a synaptic-vesicle component, plays a key role in various neurodegenerative diseases, most likely through synaptic network abnormalities; genetically abnormal synaptophysin causes mental retardation [33], and abnormal forms of it are found in Alzheimer’s disease and Parkinson’s disease [34]. The gene discussed is SYP; the disease is early-onset autosomal dominant Alzheimer disease.