The endogenous 3' UTR was replaced with a bovine growth hormone 3' UTR. The bovine sequence contains an identical polyadenylation hexanucleotide but lacks a dendritic localization signal. In situ hybridization of mutant brain sections indicated that dendritic localization was disrupted. Quantification of the hybridization results showed reduced expression levels in hippocampal cell bodies (approximately 85.3% of wild-type).