We replaced the IgH 3′ enhancer (3′EH) region with a neomycin resistance gene in ES cells and generated chimeric mice in which all mature lymphocytes were either heterozygous (3′EH+/-) or homozygous (3′EH-/-) for the mutation. In vitro activated 3′EH-/- B cells responded similarly to 3′EH+/- B cells with respect to proliferation and secretion of IgM and IgG1 but were specifically deficient in IgG2a, IgG2b, IgG3, and IgE secretion. These isotype deficiencies correlated with a deficiency in accumulation of transcripts from and class switching to affected CH genes. In vivo, chimeric mice containing only 3′EH-/- B cells were deficient in serum IgG2a and IgG3. We propose that the 3′EH-/- mutation disrupts the activity of a regulatory region that influences heavy chain class switching to several different CH genes that lie as far as 100 kb upstream of the mutation.
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)