Sequence extending from within exon 4 through a portion of 6 was replaced by an hprt minigene inserted by homologous recombination. This plasmid construct was electroporated into AB2.1 ES cells carrying a P-selectin (Selp) mutation (J:24239) and clones with the two mutations in cis were used to produce Sele/Selp double mutants. (J:33135)