The C-terminal PDZ-binding sequence LKV was substituted with alanines (AAA) in exon 15. Silent restriction enzyme sites were also introduced along with a loxP-flanked neomycin resistance gene upstream of exon 15. The neomycin cassette was deleted via cre-mediated recombination. Quantitative real-time PCR showed normal mRNA levels in midbrain tissue. (J:266803)