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Editing anti-DNA B cells by Vlambdax.

Li Y, Louzoun Y, Weigert M - J. Exp. Med. (2004)

Bottom Line: However, the lambda locus, either of man or mouse, does not allow V gene replacement.We have found that in anti-DNA heavy chain transgenic mice (tgs) VH3H9/56R, B cells that express anti-DNA receptors comprised of lambda1 in association with an anti-DNA heavy chain often coexpress a kappa chain that prevents DNA binding.Here we describe a mechanism of preventing DNA binding by expression of a rarely used member of the Vlambda family, Vlambdax.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Princeton University, NJ 08544, USA. yijinli@uchicago.edu

ABSTRACT
Receptor editing is performed by replacement of Vkappa genes that contribute to autoreactivity. In addition, the Ckappa locus can be deleted by Vkappa rearrangement to intronic or 3' of Ckappa RS sequences (also referred to as kappa deletion elements). B cells that delete the Ckappa can then express lambda light chains. However, the lambda locus, either of man or mouse, does not allow V gene replacement. Nor does it appear to be deleted. Therefore, editing of autoreactive lambda B cells may require alternative pathways. We have found that in anti-DNA heavy chain transgenic mice (tgs) VH3H9/56R, B cells that express anti-DNA receptors comprised of lambda1 in association with an anti-DNA heavy chain often coexpress a kappa chain that prevents DNA binding. We speculate that such isotypically included cells may have low anti-DNA receptor densities, a feature that may lead to self-tolerance. Here we describe a mechanism of preventing DNA binding by expression of a rarely used member of the Vlambda family, Vlambdax. The lambdax B cells of the tgs also express CD25 and may represent B cells that have exhausted light chain editing possibilities.

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Sequences of the Vλx-Jλ2 and Vλx-Jλ1 junctions. (A) Mouse λ locus and the primers used in the experiments. (B) Eight Vλx-Jλ2 and seven Vλx-Jλ1 rearrangements were sequenced from randomly chosen PCR products cloned into pGEM®-T easy vector. IF, in frame rearrangement; OF, out-of-frame rearrangement. In the last two sequences of Vλx-Jλ1 rearrangement (bottom), the four nucleotides CTGG following Vλx have the same sequence as the beginning of germ line Jλ1 gene. After this sequence several nucleotides of Jλ1 are missing. Either a deletion occurred within the rearranged Jλ1 or these four nucleotides are N additions and not the beginning of Jλ1. The latter case would mean that there is a 10 nucleotide deletion at the beginning of the Jλ1.
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fig7: Sequences of the Vλx-Jλ2 and Vλx-Jλ1 junctions. (A) Mouse λ locus and the primers used in the experiments. (B) Eight Vλx-Jλ2 and seven Vλx-Jλ1 rearrangements were sequenced from randomly chosen PCR products cloned into pGEM®-T easy vector. IF, in frame rearrangement; OF, out-of-frame rearrangement. In the last two sequences of Vλx-Jλ1 rearrangement (bottom), the four nucleotides CTGG following Vλx have the same sequence as the beginning of germ line Jλ1 gene. After this sequence several nucleotides of Jλ1 are missing. Either a deletion occurred within the rearranged Jλ1 or these four nucleotides are N additions and not the beginning of Jλ1. The latter case would mean that there is a 10 nucleotide deletion at the beginning of the Jλ1.

Mentions: Vλ1 and Vλ2 can and do rearrange to different Jλs (Fig. 7 A, Jλ1, Jλ2, or Jλ3; reference 26). Alternate Jλ usage of Vλx has not been described. Whether rearrangement to other Jλs occur in the tgs was tested by sequence analysis. RT-PCR was performed using cDNA from sorted CD25+ cells together with the upstream Vλx primer and the downstream Jλ1 or Jλ2,3 primers. PCR products of both Vλx-Jλ1 and Vλx-Jλ2,3 were cloned and sequenced at random. Eight sequences of Vλx-Jλ2 rearrangements were in frame and have the same junction but only two of the seven Vλx-Jλ1 rearrangement were in frame (no Vλx-Jλ3 rearrangements were found). These Vλx-Jλ1 junctions have interesting features including possible N addition and large deletions (Fig. 7 B). Vλ-Jλ sequences usually do not exhibit this sort of diversity but SCID mice do have deletions at λ junctions (34). Thus, these B cells may have atypical TdT and DNA-PK expression.


Editing anti-DNA B cells by Vlambdax.

Li Y, Louzoun Y, Weigert M - J. Exp. Med. (2004)

Sequences of the Vλx-Jλ2 and Vλx-Jλ1 junctions. (A) Mouse λ locus and the primers used in the experiments. (B) Eight Vλx-Jλ2 and seven Vλx-Jλ1 rearrangements were sequenced from randomly chosen PCR products cloned into pGEM®-T easy vector. IF, in frame rearrangement; OF, out-of-frame rearrangement. In the last two sequences of Vλx-Jλ1 rearrangement (bottom), the four nucleotides CTGG following Vλx have the same sequence as the beginning of germ line Jλ1 gene. After this sequence several nucleotides of Jλ1 are missing. Either a deletion occurred within the rearranged Jλ1 or these four nucleotides are N additions and not the beginning of Jλ1. The latter case would mean that there is a 10 nucleotide deletion at the beginning of the Jλ1.
© Copyright Policy
Related In: Results  -  Collection

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fig7: Sequences of the Vλx-Jλ2 and Vλx-Jλ1 junctions. (A) Mouse λ locus and the primers used in the experiments. (B) Eight Vλx-Jλ2 and seven Vλx-Jλ1 rearrangements were sequenced from randomly chosen PCR products cloned into pGEM®-T easy vector. IF, in frame rearrangement; OF, out-of-frame rearrangement. In the last two sequences of Vλx-Jλ1 rearrangement (bottom), the four nucleotides CTGG following Vλx have the same sequence as the beginning of germ line Jλ1 gene. After this sequence several nucleotides of Jλ1 are missing. Either a deletion occurred within the rearranged Jλ1 or these four nucleotides are N additions and not the beginning of Jλ1. The latter case would mean that there is a 10 nucleotide deletion at the beginning of the Jλ1.
Mentions: Vλ1 and Vλ2 can and do rearrange to different Jλs (Fig. 7 A, Jλ1, Jλ2, or Jλ3; reference 26). Alternate Jλ usage of Vλx has not been described. Whether rearrangement to other Jλs occur in the tgs was tested by sequence analysis. RT-PCR was performed using cDNA from sorted CD25+ cells together with the upstream Vλx primer and the downstream Jλ1 or Jλ2,3 primers. PCR products of both Vλx-Jλ1 and Vλx-Jλ2,3 were cloned and sequenced at random. Eight sequences of Vλx-Jλ2 rearrangements were in frame and have the same junction but only two of the seven Vλx-Jλ1 rearrangement were in frame (no Vλx-Jλ3 rearrangements were found). These Vλx-Jλ1 junctions have interesting features including possible N addition and large deletions (Fig. 7 B). Vλ-Jλ sequences usually do not exhibit this sort of diversity but SCID mice do have deletions at λ junctions (34). Thus, these B cells may have atypical TdT and DNA-PK expression.

Bottom Line: However, the lambda locus, either of man or mouse, does not allow V gene replacement.We have found that in anti-DNA heavy chain transgenic mice (tgs) VH3H9/56R, B cells that express anti-DNA receptors comprised of lambda1 in association with an anti-DNA heavy chain often coexpress a kappa chain that prevents DNA binding.Here we describe a mechanism of preventing DNA binding by expression of a rarely used member of the Vlambda family, Vlambdax.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Princeton University, NJ 08544, USA. yijinli@uchicago.edu

ABSTRACT
Receptor editing is performed by replacement of Vkappa genes that contribute to autoreactivity. In addition, the Ckappa locus can be deleted by Vkappa rearrangement to intronic or 3' of Ckappa RS sequences (also referred to as kappa deletion elements). B cells that delete the Ckappa can then express lambda light chains. However, the lambda locus, either of man or mouse, does not allow V gene replacement. Nor does it appear to be deleted. Therefore, editing of autoreactive lambda B cells may require alternative pathways. We have found that in anti-DNA heavy chain transgenic mice (tgs) VH3H9/56R, B cells that express anti-DNA receptors comprised of lambda1 in association with an anti-DNA heavy chain often coexpress a kappa chain that prevents DNA binding. We speculate that such isotypically included cells may have low anti-DNA receptor densities, a feature that may lead to self-tolerance. Here we describe a mechanism of preventing DNA binding by expression of a rarely used member of the Vlambda family, Vlambdax. The lambdax B cells of the tgs also express CD25 and may represent B cells that have exhausted light chain editing possibilities.

Show MeSH
Related in: MedlinePlus