Characterization of the bovine immunoglobulin lambda light chain constant IGLC genes

To characterize the bovine immunoglobulin lambda light chain constant region (IGLC) genes, we have isolated a bacterial artificial chromosome (BAC) clone by a PCR based approach from a bovine genomic DNA library, constructed using a genital ridge cell line derived from a male Holstein fetus. The positive BAC clone, containing the bovine IGLC genes, was fully sequenced and had a 138 kb insert. Sequence analysis revealed that the bovine immunoglobulin lambda light chain locus consisted of four joining-constant gene recombination units spanning approximately 20 kb DNA in length. A detailed examination of the recombination signal sequences, RNA splicing sites and coding sequences of the four joining-constant gene recombination units suggested that only two IGLC genes (IGLC2 and IGLC3) were functional while the IGLC1 and IGLC4 appeared to be pseudogenes. This conclusion was further confirmed by a series of RT-PCR amplifications, which also showed that among these four genes the IGLC3 was preferentially expressed in cattle. Phylogenetic analysis indicated that the bovine IGLC genes were more closely related to their equivalents in sheep and goats than that to other mammals.