Organization of the constant-region gene family of the mouse immunoglobulin heavy chain

We cloned overlapping DNA segments that encompass the region from the immunoglobulin JH segments to the C gamma 3 gene of BALB/c mouse. We have now cloned the entire region (about 200 kilobases) of the constant-region gene family of the immunoglobulin heavy chain, the organization of which is 5'-JH-6.5 kb-C mu-4.5 kb-C delta-55 kb-C gamma 3-34 kb-C gamma 1-21 kb-C gamma 2b-15 kb-C gamma 2a-14 kb-C epsilon-12 kb-C alpha-3'. Using these cloned DNAs, we have characterized several structural features of the constant-region gene loci. There are no other J region segments except for those at the 5' side of the C mu gene. The S region is 5' to each CH gene except for the C delta gene, and the nucleotide sequences of the S region share some homology. There is no reasonably conserved pseudogene. There are at least two species of reiterated sequences scattered in these loci. Cloning and Southern blot hybridization analyses indicate that the general organizations of the heavy-chain gene loci of BALB/c and C57BL/6 mice, which have many different serological markers, are fundamentally similar but different in the lengths of S regions. Restriction enzyme cleavage maps of the whole constant-region gene loci were constructed with respect to eight restriction endonucleases.