Genotyping (long range PCR and genomic sequencing) for this allele revealed that the 5' half of intron 3-lacZ-neo-intron 3 construct inserted into Gria4 intron 3 resulting in truncation of most of the lacZ gene and some of intron 3, instead of the intended homologous replacement of Gria4 exon 3 with a lacZ-neo cassette. No Gria4 RNA was detected in the brain by RT-PCR.