Excision products of immunoglobulin gene rearrangements.
We have isolated circular DNAs from splenocytes of euthymic and athymic mice, and prepared the DNA libraries of 1.5 X 10(6) clones. Hundreds of clones homologous to immunoglobulin (Ig) heavy chain segments (DSP2 and DQ52-JH) or light chain segments (J kappa and J lambda) have been identified. Southern hybridization predicted that three of 12 euthymic mouse clones homologous to DQ52-JH and four of 10 athymic mouse clones homologous to DSP2 contained reciprocal recombination products of D-J joining. Some of these clones were characterized by sequencing: two clones contained the precise excision product of the recombination of a DSP2 segment with either JH2 or JH3 segment; two clones showed imprecise ligation of the DSP2-JH2 coding joint and precise ligation of the DFL16.1-JH3 reciprocal joint in the same molecule. They seem to represent a replacement of the pre-existing DSP2-JH2 rearrangement by joining an upstream DFL16 segment to a downstream JH3 segment. The presence in extrachromosomal DNA of a reciprocal recombination product of DH-JH joining is consistent with the view that immunoglobulin genes, like T cell receptor (TCR) genes, can be rearranged in B cell lineage by the looping-out and excision of chromosomal DNA.
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
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Toda
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Hirama
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Takeshita
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Yamagishi
D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D015342:DNA Probes; D004270:DNA, Circular / Q000032:analysis; D015321:Gene Rearrangement; D005803:Genes, Immunoglobulin; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D013154:Spleen / Q000166:cytology
D015342:DNA Probes; D004270:DNA, Circular; D007135:Immunoglobulin Variable Region