Marsupial light chains: complexity and conservation of lambda in the opossum Monodelphis domestica

Lucero, J. E., Rosenberg, G. H., and Miller, R. D.

Abstract:
The Ig lambda chains in the South American opossum, Monodelphis domestica, were analyzed at the expressed cDNA and genomic organization level, the first described for a non-placental mammal. The V segment repertoire in the opossum was found to be comprised of at least three, diverse V families. Each of these families appear to be related to distinct V families present in placental mammals, suggesting the divergence of these genes prior to the separation of metatherians and eutherians more than 100 million years ago. Based on framework and constant region sequences from full length cDNAs and intron sequences from genomic clones, it appears that there are multiple, functional J-C pairs in the opossum locus. The opossum J-C sequences are phylogenetically clustered, suggesting that these gene duplications are more recent and species specific. Sequence analysis of a large set of functional, expressed V-J recombinations is consistent with an unbiased, highly diverse lambda light chain repertoire in the adult opossum. Overall, the complexity of the Ig lambda locus appears to be greater than that found in the Ig heavy chain locus in the opossum, and light chains are therefore likely to contribute significantly to Ig diversity in this species.