MUTUAL HOMOLOGY OF MOUSE IMMUNOGLOBULIN GAMMA-CHAIN GENE SEQUENCES

We have assessed the relative homology of mouse immunoglobulin heavy-chain gene sequences using complementary DNAs (cDNAs) synthesized against 7-chain mRNAs (γ1, γ2a, γ2b, and γ3) purified from mouse myelomas. cDNAs complementary to the γ-chain mRNAs did not cross-hybridize with the µ-and a-chain mRNAs, whereas they cross-hybridized to significant extents (22-66%) with the γ-chain mRNAs of other subclasses. The heterologous hybrids formed, however, melt at 5-13 °C lower temperatures as compared to the homologous hybrids, indicating that significant portions of the heterologous hybrids are mismatched. The rates of the cross-hybridization reactions are 2-to 17-fold slower than those of the homologous hybridization reactions. Therefore, the γ-chain gene sequences of four subclasses share a part of homology with each other, but they are different enough to be measured separately. Cross-hybridization analyses indicate that the γ2a and 72b genes are the most closely related, while the γ1 and γ3 genes are the least related among the γ subclass genes. © 1979, American Chemical Society. All rights reserved.