This allele is a derivative of Eportm1.3Jtp in which cre-mediated recombination in vivo removed the PGK-neo cassette in the germline. The resulting allele, Eportm1.4Jtp, contains human sequence carrying a C5964G transversion mutation in exon 8. RT-PCR analysis of bone marrow detected truncated human transcript in homozygous mutant mice.