Ectopic Recombination within Homologous Immunoglobulin µ Gene Constant Regions in a Mouse Hybridoma Cell Line

Abstract

We have transferred a pSV2neo vector containing the wild-type constant region of the immunoglobulin µ gene (Cµ) into the mutant hybridoma igm482, which bears a 2-bp deletion in the third constant-region exon of its haploid chromosomal µ gene (Cµ3). Independent igm482 transformants contain the wild-type immunoglobulin Cµ region stably integrated in ectopic chromosomal positions. We report here that the wild-type immunoglobulin Cµ region can function as the donor sequence in a gene conversion event which corrects the 2-bp deletion in the mutant igm482 chromosomal Cµ3 exon. The homologous recombination event restores normal immunoglobulin M production in the mutant cell.