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Smaller hippocampal volumes and decreased memory function have been associated with a polymorphism on the gene for brain-derived neurotrophic factor (BDNF). This allele — specifically, the substitution of methionine for valine at codon 66 — occurs in approximately 30% of humans. To expand upon this research, investigators examined the effect of the methionine allele in mice.
The researchers compared brain structure, hippocampus-dependent memory, and anxiety behaviors in wild-type mice (with two valine alleles) and in mice engineered to be homozygous for methionine (met/met), heterozygous (val/met), or heterozygous knockout (val/-). Each transgenic group had significantly smaller hippocampal volumes and less dendritic branching than did the w…