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Rearrangement of immunoglobulin genes in shark germ cells
S S Lee1, D Fitch, M F Flajnik
1Department of Physiology, State University of New York Health Science Center at Brooklyn, Brooklyn, New York 11203, USA.
The Journal of Experimental Medicine
|May 17, 2000
Summary
Recombination activating genes (RAGs) in cartilaginous fishes may still be actively reshaping genomes. Recently rearranged fused VJ genes suggest RAG-like activity, potentially creating novel receptors expressed early in development.
Area of Science:
- Evolutionary immunology
- Genomics
- Molecular biology
Background:
- Adaptive immunity evolved in vertebrates, with recombination activating genes (RAGs) playing a key role.
- Immunoglobulin (Ig) light chain genes in cartilaginous fishes exhibit unique VJ-constant (C) cluster organizations, including fused VJ loci.
Purpose of the Study:
- To investigate the evolutionary role of RAG in cartilaginous fishes.
- To determine if fused VJ genes are archaic relics or recent rearrangements.
- To understand the functional significance of expressed germline-joined Ig sequences.
Main Methods:
- Analysis of immunoglobulin gene organization in cartilaginous fishes.
- Investigation of RAG-like activity and hairpin intermediate involvement.
- Gene expression studies during ontogeny.
Main Results:
- Some fused VJ genes in cartilaginous fishes are recently rearranged, indicating ongoing RAG-like activity.
- This activity appears to involve hairpin intermediates.
- Germline-joined Ig sequences are expressed at significant levels primarily early in development.
Conclusions:
- Fused VJ genes may represent a dynamic genomic process rather than solely archaic relics.
- Rejoined Ig genes could function as novel receptors independent of somatic RAG rearrangement.
- RAG remains an active force in altering vertebrate genomes.