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Author Notes:

Corresponding author: E-mail: sdas8@emory.edu.

Associate editor: Yoko Satta

Subjects:

Research Funding:

This work was supported by the National Institutes of Health (grant GM020293-35 to M.N.), by the CSUF (start-up money to N.N.), and by a CSUF Junior Faculty Research Grant (to N.N.).

Keywords:

  • immunoglobulin genes
  • cladistic molecular markers
  • antibody diversity
  • gene conversion
  • comparative genomics
  • repetitive elements

Analysis of the Immunoglobulin Light Chain Genes in Zebra Finch: Evolutionary Implications

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Journal Title:

Molecular Biology and Evolution

Volume:

Volume 27, Number 1

Publisher:

, Pages 113-120

Type of Work:

Article | Post-print: After Peer Review

Abstract:

All jawed vertebrates produce immunoglobulins (IGs) as a defense mechanism against pathogens. Typically, IGs are composed of two identical heavy chains (IGH) and two identical light chains (IGL). Most tetrapod species encode more than one isotype of light chains. Chicken is the only representative of birds for which genomic information is currently available and is an exception to the above rule because it encodes only a single IGL isotype (i.e., lambda). Here, we show that the genome of zebra finch, another bird species, encodes a single IGL isotype, that is, lambda, like the chicken. These results strongly suggest that the second isotype (i.e., kappa) present in both reptiles and mammals was lost in a very early stage of bird evolution. Furthermore, we show that both chicken and zebra finch contain a single set of functional variable, joining, and constant region genes and multiple variable region pseudogenes. The latter finding suggests that this type of genomic organization was already present in the common ancestor of these bird species and remained unchanged over a long evolutionary time. This conservation is in contrast with the high levels of variation observed in the mammalian IGL loci. The presence of a single functional variable region gene followed by multiple variable pseudogenes in zebra finch suggest that this species may be generating antibody diversity by a gene conversion-like mechanism like the chicken.

Copyright information:

© The Author 2009. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

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