RT Journal Article
SR Electronic
T1 The generation of antibody diversity in the turtle.
JF The Journal of Immunology
JO J. Immunol.
FD American Association of Immunologists
SP 3797
OP 3805
VO 156
IS 10
A1 Turchin, A
A1 Hsu, E
YR 1996
UL http://www.jimmunol.org/content/156/10/3797.abstract
AB The Ab response in reptiles has been studied at the protein level, and in turtles some aspects resemble those of cold-blooded vertebrates from other classes. The genetic bases for these features are not clear. The present study is the first on the IgH organization and complexity of a reptilian Ig gene system. The approach to cloning turtle (Pseudemys scripta) sequences is entirely PCR based, and its efficacy is demonstrated by obtaining extensive information on a heretofore unexplored Ig gene system. A number of genomic VH sequences, representing possibly four families, were isolated, as was a genomic C mu 4 clone. These sequences, used as probes, provided proof that in the turtle there is a single IgH locus with multiple VH genes and one C mu gene. In Northern hybridizations, the C mu 4 probe detected two transcripts; of the four VH groups, only one was expressed, and multiple bands indicated the presence of at least two non-mu transcripts. Using reverse transcription-PCR on spleen or liver RNA, an IgM heavy chain sequence was obtained, as were a number of VDJ rearrangements. Among 32 unique VDJ rearrangements from one animal, there were 22 sequence variants at framework 4, suggesting either a very large number of J segments or somatic modification in the variable region. The latter interpretation is supported by point mutations found in framework 3 and CDR3. The number of changes is considerably greater than the deduced Taq misincorporation rate (0.05%).