Identification of the genotype and IRBP gene expression. A, PCR identification of the genotypes ofIRBP+/+, IRBP+/−, andIRBP−/− mice; amplified sequences are indicated byarrows. The 530 bp marker for the targeted (pgk-neo) allele represents a region between −1273 of the IRBP gene and +592 of the pgk-neo gene. For the wild-type allele, the 403 bp marker represents a region between +211 and +613 of the IRBP gene. B, RT-PCR analysis of wild-type IRBP gene expression. Mouse β-actin was used as an internal control.