Allelic polymorphism of mouse Igh-J locus, which encodes immunoglobulin heavy chain joining (JH) segments

The mouse genome contains four functional JH genes, which encode immunoglobulin heavy chain joining segments. The JH gene cluster is located a few kilobases 5' from the constant region genes (C genes) on chromosome 12. The polymerase chain reaction (PCR)-technique was used to amplify DNA stretches from mouse genome of approximately 1,340 nucleotides in length containing all four JH genes (Igh-J locus). PCR products were directly used as templates in Sanger's dideoxy-sequencing, and sequences were determined. Twelve inbred mouse strains belonging to ten different Igh-C haplotypes were studied. The strains were: BALB/c, C58/J, RIII, DBA/2, CE, RF, CBA, NZB/J, AKR, C57BL/10, SJL, and A/J. Five allelic forms of the Igh-J locus were found among these strains. The A/J mouse has an allele (e) which differs from the BALB/c allele (a) by 15 nucleotides. C57BL and SJL have the allele (b) with eight differences from BALB/c. The CBA allele (j) has two differences, and the CE allele (f) has a single nucleotide difference compared with the BALB/c sequence. Based on the JH, variable (V) and constant (C) region sequences we conclude that independent reshuffling of VH, JH, and CH gene clusters occurred during the evolution of Mus musculus.