Phylogeny, genomic organization and expression of λ and κ immunoglobulin light chain genes in a reptile, Anolis carolinensis

The reptiles are the last major taxon of jawed vertebrates in which immunoglobulin light chain isotypes have not been well characterized. Using the recently released genome sequencing data, we show in this study that the reptile Anolis carolinensis expresses both λ and κ light chain genes. The genomic organization of both gene loci is structurally similar to their respective counterparts in mammals. The identified λ locus contains three constant region genes each preceded by a joining gene segment, and a total of 37 variable gene segments. In contrast, the κ locus contains only a single constant region gene, and two joining gene segments with a single family of 14 variable gene segments located upstream. Analysis of junctions of the recombined VJ transcripts reveals a paucity of N and P nucleotides in both expressed λ and κ sequences. These results help us to understand the generation of the immunoglobulin repertoire in reptiles and immunoglobulin evolution in vertebrates.