Polymorphism at codon 66 of the brain-derived neurotrophic factor gene is not associated with sporadic Alzheimer's disease.

Memory acquisition and consolidation are associated with an increase in brain-derived neurotrophic factor (BDNF) in synapses, particularly those innervating the hippocampus and cerebral cortex. A polymorphism producing an amino acid substitution (valine to methionine) at codon 66 of the BDNF gene could affect intracellular processing and secretion of BDNF and lead to impairments in hippocampal function. Preliminary evidence in an Italian population indicates that this polymorphism is a predisposing factor for sporadic Alzheimer's disease (AD). A case-control study utilizing a clinically well-defined group of 237 sporadic AD patients and 218 control subjects was performed to test this association. The current study does not demonstrate any significant difference in Val66Met BDNF genotype or allele frequencies between AD patients and controls. Our study in the Spanish population argues against the hypothesis that this polymorphism is causally related to AD.