Localization of the rat immunoglobulin lambda light chain locus to chromosome 11

Previous experiments using rat/mouse somatic cell hybrids have localized the rat c-myc gene to chromosome 7 (Sümegi et al. 1983), the rat immunoglobulin kappa locus to chromosome 4 (Perlmann et al. 1985), and the rat immunoglobulin heavy chain locus to chromosome 6 (Pear et al. 1986). Using a similar approach, we now report the localization of the rat immunoglobulin lambda light chain locus to chromosome 11.     

Analyses of chicken immunoglobulin light chain cDNA clones indicate a few germline V lambda genes and allotypes of the C lambda locus.

cDNA libraries of chicken spleen and Harder gland (a gland enriched with immunocytes) constructed in pBR322 were screened by differential hybridization and by mRNA hybrid-selected translation. Eleven L-chain cDNA clones were identified from which VL probes were prepared and each was annealed with kidney DNA restriction digests. All VL probes revealed the same set of bands, corresponding to about 15 germline VL genes of one subgroup. The nucleotide sequences of six VL clones showed greater than or equal to 85% homology, and the predicted amino acid sequences were identical or nearly identical to the major N-terminal sequence of L-chains in chicken serum. These findings, and the fact that the VL clones were randomly selected from normal lymphoid tissues, strongly indicate that the bulk of chicken L-chains is encoded by a few germline VL genes, probably much less than 15 since many of the VL genes are known to be pseudogenes. Therefore, it is likely that somatic mechanisms operating prior to specific triggering by antigen play a major role in the generation of antibody diversity in chicken. Analysis of the constant region locus (sequencing of CL gene and cDNAs) demonstrate a single CL isotype and suggest the presence of CL allotypes.     

The ATC (ataxia-telangiectasia complementation group C) locus localizes to 11q22-q23.

The multisystem autosomal recessive disease ataxia-telangiectasia (A-T) is determined by several genes, as evidenced by the existence of four complementation groups in this disorder. Using linkage analysis, the ATA (A-T complementation group A) gene was previously localized to chromosome 11, region q22-q23. Analysis of the segregation of RFLP markers from this region in a Jewish-Moroccan family assigned to group C indicates that the ATC (A-T complementation group C) gene localizes to chromosome 11q22-q23 as well.     

A linkage map of the mouse immunoglobulin lambda light chain locus

The mouse immunoglobulin lambda light chain locus has been linked using field inversion gel electrophoresis. The lambda light chain locus classically contains two V and four J-C gene segments in inbred mouse strains, and was physically mapped in the BALB/c cell line Wehi-3 which contains unrearranged lambda light chain gene segments. The locus is relatively small and spans 300 kb, as defined by a variety of single and double digests using methylation-sensitive restriction enzymes. The order of the lambda gene segments is V2-J2C2J4C4-V1-J3C3J1C1, as was originally proposed. No evidence for nonmethylated CpG rich areas (HTF islands) within the region was found. Fine mapping using the 1, 3 rearranged cell line J558 mapped the gap between the V and J-C gene segments in the lambda 1 gene cluster (VI-J3C3JIC1) to approximately 70 kb. The similar distance (60–100 kb) found in the lambda 2 gene cluster (V2-J2C2J4C4) is further evidence that duplication of an ancestral locus occurred.     

Allelic polymorphisms and RFLP in the human immunoglobulin lambda light chain locus

The organization of the human immunoglobulin lambda light chain locus (IGL) was recently described. This locus has been entirely sequenced. To evaluate the extent of the genomic variability existing inside that locus, we compiled all the available sequences of germline IGLV genes to find variants of Vλ sequences. We also looked for RFLP polymorphisms in a reputedly highly polymorphic human population from eastern Senegal, and compiled all RFLP data previously published. Analysis of these data indicates that IGLV alleles are frequent and increase the diversity of the lambda light chain repertoire in the human population. In contrast, RFLP and polymorphism by insertion and/or deletion are limited in that locus. This observation reinforces our hypothesis that the human IGL locus has undergone less evolutionary shuffling than the human kappa or heavy-chain loci. Received: 23 December 1998 / Accepted: 1 March 1999     

The neuroepithelioma breakpoint on chromosome 22 is proximal to the meningioma locus

The recurrent translocation breakpoint on chromosome 22 of neuroepithelioma has been localized between two probes, D22S1 and D22S15, by both in situ hybridization and somatic cell hybrids. These two probes have further been shown to be genetically linked at theta = 0.0 and a lod score of 5.3. The two probes were unaffected by a partial deletion of the chromosome 22 long arm of a meningioma, showing that the meningioma locus is distal to that of the neuroepithelioma.     

The immunoglobulin lambda locus in rat consists of two C lambda genes and a single V lambda gene

The immunoglobin lambda locus of the rat has been studied. Germ-line V lambda and C lambda genes were isolated from recombinant-phage libraries and characterized by nucleotide sequencing. The results showed that the lambda locus of the rat contains one single V lambda gene and two C lambda genes, thus representing one of the least complex lambda loci so far characterized. The two C lambda genes are separated by a spacer approx. 3 kb long. Two J segments are located at the 5' side of each C lambda gene. One of the C lambda genes (C lambda 1) probably represents a pseudogene, as the J lambda 1 segments have non-functional recombination and splice signals. The organization of the rat lambda locus resembles that of mouse, except that only one cluster is present in the rat. Thus since the evolutionary separation of the rat and mouse species ten MYR ( = 10(6) years) ago, either one cluster has been lost from the rat, or duplicated in the mouse.     

C lambda 2 and C lambda 4 immunoglobulin light chain genes in a wild-derived inbred mouse strain

A genomic clone containing the lambda constant (C) region genes (C lambda 2S and C lambda 4S) has been isolated from a genomic library from the mouse strain SPE. SPE is an inbred strain derived from progenitors trapped near Grenada in Spain and has been classified as mus 3 or mus spretus. The sequence of the C lambda 2S gene is virtually identical to that of BALB/c both in the coding region and in flanking sequences, suggesting that it is an expressed gene in the SPE strain. By contrast, the C lambda 4S gene on the same cluster has diverged in sequence from that of BALB/c and contains a large deletion that precludes its normal expression. Whereas BALB/c J lambda 4 region contains substitutions that probably preclude its usage, the SPE J lambda 4 gene includes all sequences required for a functional J gene. Comparison of the C lambda 2S and C lambda 4S gene sequences with those available for BALB/c C lambda 3 and C lambda 1 confirms the close relationship between the C lambda 1-C lambda 4 and C lambda 2-C lambda 3 gene pairs. The C lambda 3 gene of BALB/c is more closely related to C lambda 2S than is C lambda 1 of BALB/c to C lambda 4S. If it is assumed that C lambda 1 and C lambda 2 are respective duplicates of C lambda 4 and C lambda 3 and that these duplications occurred at the same time, then the C lambda 2 gene has been under stronger selective pressure than C lambda 4.     

Association of human lambda light chain V/J/C segments: serologic analysis and primary structure of the lambda VI Bence Jones protein THO

The complete amino acid sequence of the human monoclonal lambda VI light chain Bence Jones protein THO was determined. We have found it to have remarkable similarities to the previously sequenced lambda VI Bence Jones protein SUT. Immunochemical analyses demonstrated that both lambda VI chains belong to a V lambda VI sub-subgroup. The 98-residue V gene-encoded segments of proteins THO and SUT are closely homologous and are distinguished from other lambda VI chains by a one-residue deletion at the V-J recombination site. Proteins THO and SUT have identical 13-residue J segments and therefore are encoded by the same J lambda gene. Further, both proteins have identical 105-residue C regions that by sequence represent products of the C lambda 3 (Kern-, Oz+) gene. The primary structure and serologic properties of proteins THO and SUT imply at the protein level of association between certain types of V lambda, J lambda, and C lambda segments.     

Chromosomal mapping of the human catechol-O-methyltransferase gene to 22q11.1----q11.2.

Catechol-O-methyltransferase (COMT; EC 2.1.1.6) is a physiologically important enzyme in the metabolism of catecholamine neurotransmitters and catechol drugs. Using primers derived from the known rat cDNA sequence for COMT, we have used the polymerase chain reaction to produce an amplified DNA fragment corresponding to the complete coding region of the rat gene. With this fragment as a probe, we have hybridized DNAs from two panels consisting of human/rodent and human/hamster somatic cell hybrids carrying various translocations and deletions to refine the chromosomal location of human COMT. Southern blot analysis indicates that the human COMT gene is localized to 22q11.1----q11.2, a region to which several anonymous DNA sequences, but until now, no structural genes, have been assigned.     

Regional mapping of two human immunoglobulin V lambda genes and analysis of the V lambda locus in chronic myeloid leukaemia.

The human immunoglobulin V lambda locus has been studied in relation to chromosomal translocations involving chromosome 22. DNA probes for two V lambda genes which belong to different subgroups and do not cross hybridize, were used to show that both V lambda genes are located on the Philadelphia chromosome in chronic myeloid leukaemia (CML). Both genes map in band 22q11 to a region that is bounded on the distal side by the breakpoints for CML 9:22 translocations and on the proximal side by the breakpoint for an X:22 translocation. We have found no evidence for rearrangements or amplification of either V lambda gene in CML, in either the chronic or acute phases of the disease. In K562 cells which are derived from the pleural effusion of a patient with Ph1-positive CML, there appears to be no rearrangement of the V lambda genes, but they are both amplified about four times. We have estimated that the minimum size for the amplification unit in K562 cells is 186 kb.     

Novel susceptibility locus at 22q11 for diabetic nephropathy in type 1 diabetes

Background

Diabetic nephropathy (DN) affects about 30% of patients with type 1 diabetes (T1D) and contributes to serious morbidity and mortality. So far only the 3q21–q25 region has repeatedly been indicated as a susceptibility region for DN. The aim of this study was to search for new DN susceptibility loci in Finnish, Danish and French T1D families.

Methods and Results

We performed a genome-wide linkage study using 384 microsatellite markers. A total of 175 T1D families were studied, of which 94 originated from Finland, 46 from Denmark and 35 from France. The whole sample set consisted of 556 individuals including 42 sib-pairs concordant and 84 sib-pairs discordant for DN. Two-point and multi-point non-parametric linkage analyses were performed using the Analyze package and the MERLIN software. A novel DN locus on 22q11 was identified in the joint analysis of the Finnish, Danish and French families by genome-wide multipoint non-parametric linkage analysis using the Kong and Cox linear model (NPL_pairs LOD score 3.58). Nominal or suggestive evidence of linkage to this locus was also detected when the three populations were analyzed separately. Suggestive evidence of linkage was found to six additional loci in the Finnish and French sample sets.

Conclusions

This study identified a novel DN locus at chromosome 22q11 with significant evidence of linkage to DN. Our results suggest that this locus may be of importance in European populations. In addition, this study supports previously indicated DN loci on 3q21–q25 and 19q13.     

Chromatin opening is tightly linked to enhancer activation at the kappa light chain locus

Enhancers play an important role in chromatin opening but the temporal relationship between enhancer activation and the generation of an accessible chromatin structure is poorly defined. Recombination enhancers are essential for chromatin opening and subsequent V(D)J recombination at immunoglobulin loci. In mice, the kappa light chain locus displays an open chromatin structure before the lambda locus yet the same proteins, PU.1/PIP, trigger full enhancer activation of both loci. Using primary B cells isolated from distinct developmental stages and an improved method to quantitatively determine hypersensitive site formation, we find the kappa and lambda recombination enhancers become fully hypersensitive soon after transition to large and small pre-B-II cells, respectively. This correlates strictly with the stages at which these loci are activated. Since these cells are short-lived, these data imply that there is a close temporal relationship between full enhancer hypersensitive site formation and locus chromatin opening.