High variability in complementarity-determining regions compensates for a low number of V gene families in the lambda light chain locus of the platypus.

Based on the analysis of a panel of variable (V) region sequences from the Australian duck-billed platypus and the Australian short beaked echidna, the monotremes were found to express a highly diversified Vlambda repertoire. High variability was observed both in sequence and in length of all three CDR regions. However, all monotreme sequences were found to form a separate branch on a distance tree, and the monotremes appear to express only two Vlambda gene families.

Cloning of IgE from the echidna (Tachyglossus aculeatus) and a comparative analysis of epsilon chains from all three extant mammalian lineages.

In continuation of our evolutionary studies of immunoglobulin (Ig) expression, we present here the cloning of IgE from a monotreme, the short-beaked echidna (Tachyglossus aculeatus). Including echidna IgE, 15 epsilon chain sequences have been isolated and each of the three mammalian lineages (placentals, marsupials and monotremes) is now represented by at least two sequences. Phylogenetic analyses based on all available epsilon chains and a selection of other mammalian Ig isotypes (IgM, IgA and IgG) were generated using three different algorithms.

Heavy chain V region diversity in the duck-billed platypus (Ornithorhynchus anatinus): long and highly variable complementarity-determining region 3 compensates for limited germline diversity.

In this work, to study the emergence of the H chain V region repertoire during mammalian evolution, we present an analysis of 25 independent H chain V regions from a monotreme, the Australian duck-billed platypus, Ornithorhynchus anatinus. All the sequences analyzed were found to form a single branch within the clan III of mammalian V region sequences in a distance tree. However, compared with a classical V gene family this branch was more diversified in sequence.