Deletion of Icam4 gene. Targeting strategy for homologous recombination in ES cells. Restriction map of wild-type Icam4 allele (top), targeting vector (middle), and targeted allele (bottom). In the wild-type Icam4 allele the black boxes represent the 3 exons. In the targeting vector, hGh-N indicates human growth hormone-N gene; PGK, phosphoglycerate kinase; Neo, bacterial neomycin resistance gene.