Evolution of pseudogenes in the immunoglobulin VH-gene family of the mouse.

A quantitative analysis of the complexity of the J558 VH-gene family in the mouse immunoglobulin heavy chain (Igh) gene locus has been performed. Considerable variations in the degree of complexity are observed in various Igh haplotypes derived from laboratory mice and wild mice. The BALB/c strain shows the highest degree of complexity of the J558 VH-gene family when all mice are compared. Multiple gene duplications seem to have occurred in the BALB/c-derived J558 VH-gene family less than 1-2 million years ago. This dating is supported by the divergence in coding and flanking regions of three strongly homologous VH-region genes. Two of these genes were generated by the duplication of a pseudogene about 1.5 X 10(5) years ago. A recent expansion of the J558 VH-gene family and therefore little time for evolutionary drift may explain why most of the pseudogenes in this family exhibit a largely intact structure. We also describe two VH-region genes which represent older pseudogenes in states of progressive disintegration.