Igh-8^{tm2(Ighg1)Aak}

The Igh-8 gene segment contains an upstream Igamma3 noncoding exon implicated in class switch recombination. A 2 kb PmeI-EcoRV fragment containing the Igamma3 promoter and the proximal part of the exon was replaced with 500 bp of the Igamma1 enhancer/promoter region of Ighg1. The remaining 368 bp portion of the Igamma3 exon contains the canonical splice donator site necessary for class switch recombination. A loxP site flanked neomycin resistance gene cassette was inserted upstream of the targeted region. The neo cassette was removed through subsequent cre-mediated recombination Germline transcripts containing the shortened sequence of the targeted Igamma 3 exon were detected by RT-PCR of RNA from activated splenocytes of homozygous mice. (J:130574)