Conserved organization of the murine immunoglobulin epsilon gene region: restriction endonuclease maps and switch-region nucleotide sequence.

Various inbred mouse strains showed remarkable conservation of organization in the epsilon germline region as determined by restriction mapping. Restriction fragment length polymorphisms (RFLP) were seen in the epsilon gene region for only two of eight restriction enzymes tested. Furthermore, the RFLP did not correlate with the IgE-response phenotype for the murine strains SJL, SJA, C57BL/6, BALB/c, A/ST, and A/J. The IgE class-switch region (S epsilon) DNA from an SJL genomic clone was sequenced and was compared with S epsilon sequences from BALB/c mice. These S epsilon sequences were at least 95% homologous. Most of the S epsilon sequence differences observed between the two strains were single base pair substitutions, deletions, or insertions. The largest difference between the S epsilon sequences resulted from an insertion of seven contiguous bases seen in the SJL S epsilon region.