Evidence for an early appearance of modern post-switch isotypes in mammalian evolution; cloning of IgE, IgG and IgA from the marsupialMonodelphis domestica

Abstract

In birds, reptiles and amphibians the IgY isotype exhibits the functional characteristics of both of IgG and IgE. Hence, the gene for IgY most likely duplicated some time during early mammalian evolution and formed the ancestor of present day IgG and IgE. To address the question of when IgY duplicated and formed two functionally distinct isotypes, and to study when IgG and IgA lost their second constant domains, we have examined the Ig expression in a non-placental mammal, the marsupial Monodelphis domestica (grey short-tailed opossum). Screening of an opossum spleen cDNA library revealed the presence of all three isotypes in marsupials. cDNA clones encoding the entire constant regions of opossum IgE (epsilon chain), IgG (gamma chain) and IgA (alpha chain) were isolated, and their nucleotide sequences were determined. A comparative analysis of the amino acid sequences for IgY, IgA, IgE and IgG from various animal species showed that opossum IgE, IgG and IgA on the phylogenetic tree form branches clearly separated from their eutherian counterparts. However, they still conform to the general structure found in eutherian IgE, IgG and IgA. Our findings indicate that all the major evolutionary changes in the Ig isotype repertoire, and in basic Ig structure that have occurred since the evolutionary separation of mammals from the early reptile lineages, occurred prior to the evolutionary separation of marsupials and placental mammals.

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

“…A similar situation has also been observed for the heavy chain locus in many placental mammals. Duplications have been only rarely observed for the e chain, while multiple and relatively recent independent duplications seem to have resulted in multiple c chain genes [34]. Is there an advantage of having several C regions in the k chain locus, or is it only a way to create several J segments and thereby higher variability?…”

Mucosal Immunoglobulins

“…The genes for the heavy chain of IgA have been cloned from several species, including humans (Flanagan et al, 1984), nonhuman primates (Kawamura et al, 1989(Kawamura et al, , 1990Ueda et al, 1988;Scinicariello et al, 2006;Rogers et al, 2008), rodents (Tucker et al, 1981;Bruggemann et al, 1986), bats (Butler et al, 2011), pets and domesticated animals (Knight et al, 1988;Burnett et al, 1989;White et al, 1998;Brown and Butler, 1994;Wagner et al, 1997;Patel et al, 1995;Zhou et al, 2006), dolphins (Mancia et al, 2007), marsupials (Aveskogh and Hellman, 1998), monotremes (Belov et al, 2002;Vernersson et al, 2010), and birds (Mansikka, 1992;Magor et al, 1998;Choi et al, 2010;Huang et al, 2012;Guo et al, 2014), in some cases as part of species genome projects. Thus, DNA sequence information for IgA is available for a wide range of mammalian and an increasing number of bird species.…”

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

“…Partial cDNA clones of the ⑀-and ␥-chains were isolated by PCR using degenerated primers. The design and sequence of the primers have been described previously (21). Purified ⑀-and ␥-chain fragments were labeled with 32 P by random priming (Megaprime; Amersham) and used as probes in the platypus library.…”