Genetic polymorphism at the kappa chain locus in mice: comparisons of restriction enzyme hybridization fragments of variable and constant region genes

Characterization of a V kappa family in Mus musculus castaneus: expansion at the subset level

We have examined the same kappa chain variable (V kappa) region family in several mouse species in order to observe short-term, incremental change at immunoglobulin (Ig) multigene loci. In the present study, the Igk-V24 family has been characterized in a Mus m. castaneus colony derived from individuals originating in Thailand and compared to the same family in Mus m. domesticus (BALB/c) and Mus pahari, representing about 1-2 and about 5-9 million years of evolution, respectively. Southern hybridization of genomic DNA with a probe encoding the prototype Igk-V24 coding region reveals restriction fragment patterns indicative of two distinct M. m. castaneus haplotypes. These haplotypes appear to result from an unequal recombination between similar gene arrays, as their restriction patterns are unique but contain many common fragments. The complexity of these patterns indicates a marked expansion in the Igk-V24 family of M. m. castaneus relative to BALB/c and M. pahari. Additional analyses using probes specific for individual subsets demonstrate that the expansion is not general throughout the entire family, but is restricted to particular subsets and therefore to relatively short chromosomal segments. One subset alone accounts for most of the expansion and comprises over 40% of the entire M. m. castaneus family. The wide range of Igk-V24 family complexity seen among M. m. castaneus, M. m. domesticus, and M. pahari, as well as among the different M. m. castaneus family subsets, suggests a model of random evolution in V kappa family copy number rather than one which is selective.

Characterization of a V kappa family in Mus musculus castaneus: sequence analysis

To examine genetic variation at immunoglobulin (Ig) multigene loci over short spans of evolutionary time, we have compared members of an Ig kappa chain variable (V kappa) region family from several mouse species. In this study, seven unique Igk-V24 family members have been isolated from Mus m. castaneus and characterized by nucleotide sequence determination for comparison to their counterparts in Mus m. domesticus (BALB/c), and Mus pahari, representing 1-2 million years of evolution in the former case and 5-8 million years in the latter. Parsimony, together with evolutionary distances calculated for various pairs of Igk-V24 family coding regions, relate all family members to a common progenitor existing roughly 24 million years ago (Mya). A significant portion of the M. m. castaneus family consists of pseudogene segments in various degrees of progressive degeneration. The substitution patterns and divergence rates for all gene segments are characteristic of their respective subsets, especially in the areas flanking the coding regions. Complex and variable patterns of diversity are seen in potentially expressed coding regions, which appear to reflect quite different selective pressures on various subregions within the V kappa protein domain. These results indicate that evolutionary pressures are operating at the level of family subsets, their individual members, and subregions within similar molecules.

Selection of immunoglobulin variable regions in autoimmunity to DNA

Results from our analyses of variable region gene usage among spontaneous anti-DNA antibodies in autoimmune mice have indicated that both the early IgM and later-appearing IgG autoantibodies to DNA are generated by clonally selected B cells. The recurrent usage of particular variable region genes among all the anti-DNA hybridomas analyzed and reported to date supports this hypothesis. The preferential expression of particular light and heavy chain variable region genes among selected populations of both IgM and IgG anti-DNA hybridomas likewise supports the hypothesis. Both IgM and IgG antibody-producing B cells are derived from the same clonal precursor population and may be derived from the same B cell clonal precursor within an individual mouse. The selective and recurrent expression of germline and somatically-derived structures that would be expected to promote protein binding to DNA within anti-DNA antibody variable regions, particularly arginines in both light and heavy chain complementarity-determining regions, indicates that DNA or DNA-containing complexes may be the antigen that stimulates anti-DNA antibody in autoimmune mice. The progressive increase in the specificity of spontaneous anti-DNA antibodies for native DNA as the autoimmune response matures from IgM to IgG likewise suggests that DNA may be the antigenic stimulus for spontaneous anti-DNA in autoimmune mice. A hypothetical, computer-generated model of anti-DNA antibody binding to DNA provides an interesting paradigm for the molecular basis of antibody specificity for DNA.

The role of germline gene expression and somatic mutation in the generation of autoantibodies to DNA

Several distinctive features of anti-DNA autoantibodies have been identified by a detailed analysis of the available heavy and light chain sequences. They include unique VH gene segments that are not normally expressed in antibodies to external antigens, somatic mutations which may serve to change the antigenic specificity as well as to increase affinity, a less stringent choice of light chains, and a unique basic peptide in the heavy chain CDR3. It is proposed that in the majority of cases, the regulatory mechanism of self-tolerance in the healthy animal operates via VH gene expression to prevent the synthesis of potentially high affinity anti-DNA autoantibodies.

The molecular basis of a VH gene polymorphism that determines the expression of a major idiotype

The strain A immune response to a synthetic antigen (p-azophenylarsonate) is dominated by antibodies bearing an idiotype encoded by VH genes derived from a single germline VH gene segment called VHIdCR (a member of the J558 family). Balb/c mice fail to produce this idiotype. Southern blotting analyses with a probe derived from VHIdCR have shown that differences in patterns of hybridization and in intensity of bands are seen between the two strains. We demonstrate by DNA cloning and sequence analyses that Balb/c mice have no allelic version of VHIdCR. This result constrasts with that reported for interstrain comparisons of VH genes encoding antibodies to environmental pathogens where evolutionary conservation of VH sequence information is seen. We suggest, on the basis of these and earlier results, that domination of the anti-Ars immune response by antibodies encoded by VHIdCR is not the indirect consequence of evolutionary or somatic selection pressures acting on the VHIdCR gene segment.

Evolution of the immunoglobulin heavy chain variable region (Igh-V) locus in the genus Mus

The evolution of the mouse immunoglobulin heavy chain variable region (Igh-V) locus was investigated by the comprehensive analysis of variable region (Vh) gene family content and restriction fragment polymorphism in the genus Mus. The examination of natural Mus domesticus populations suggests an important role for recombination in the generation of the considerable restriction fragment polymorphism found at the Igh-V locus. Although the sizes of individual Vh gene families vary widely both within and between different Mus species, evolutionary trends of Vh gene family copy number are revealed by the analysis of homologues of mouse Vh gene families in Rattus and Peromyscus. Processes of duplication, deletion, and sequence divergence all contribute to the evolution of Vh gene copy number. Certain Vh gene families have expanded or contracted differently in the various muroid lineages examined. Collectively, these findings suggest that the evolution of individual Vh family size is not driven by strong selective pressure but is relatively neutral, and that gene flow, rather than selection, serves to maintain the high level of restriction fragment polymorphism seen in M. domesticus.

Molecular analysis of the murine C4b-binding protein gene. Chromosome assignment and partial gene organization

Murine C4b-binding protein (C4BP) is a regulatory molecule in the classical pathway of complement. C4BP is composed predominantly of short consensus repeats (SCRs) approximately 60 amino acids in length, which contain a framework of conserved residues. The SCRs are found in many complement molecules and a growing number of noncomplement molecules as well and are a major structural feature of some of these molecules. To characterize the structure of the murine C4BP gene, a cosmid library constructed from Balb/c liver DNA was screened. Several nearly identical, overlapping clones were identified; however, none of the clones, alone or in combination, covered the entire C4BP gene. One clone (D26) was chosen for detailed analysis and found to contain all but the leader region, the first SCR, and the first half of the second SCR. The SCRs three through six were each encoded by single exons. Only the latter half of the second SCR was present on the clone, and it was encoded by a single exon, demonstrating that murine C4BP has a split SCR at the genomic level. Structural mapping of this portion of the gene demonstrates that the region extending from the second half of the second SCR through the nonrepeat and untranslated region spans approximately 12 kb; however, genomic Southern blot analysis suggests that the gene is between 20 and 30 kb in length. Analysis of the 3' genomic sequence demonstrates that this region of the gene has homology with SV-40 late (class II) RNA sequences. These sequences may play a role in 3' cleavage of the precursor RNA prior to polyadenylation.(ABSTRACT TRUNCATED AT 250 WORDS)

Different large deletions of T cell receptor V beta genes in natural populations of mice

A panel of geographically separate Mus m. domesticus and Swiss mice from several sources was screened for deletions in the T cell receptor variable (V) beta locus. Four out of forty-three strains tested show a deletion identical to or larger than the deletion previously described in SJL mice. To our knowledge, this is the first time that such important V beta deletions are described in inbred or partially inbred wild-derived strains of mice. On the other hand there seems to be very little polymorphism between the remaining V beta genes. Expression of V beta genes in peripheral and intra-thymic T cells was tested using antibodies specific for different V beta polypeptide chains. Flow cytometry analysis revealed a high expression of V beta 6 and V beta 17 genes in the Copacabana Swiss-derived strain and an absence of V beta 17 expression in the WLA wild-derived strain. The three Mus m. domesticus strains (WLA, DDO and WBG) having deleted two to three additional V beta subfamilies compared to SJL present no apparent immune deficiencies or autoimmune disorders. We conclude that relatively few V beta genes may suffice for unimpaired survival of wild mice and that there is a selective pressure for the structural conservation of the remaining V beta genes.

Prp (proline-rich protein) genes linked to markers Es-12 (esterase-12), Ea-10 (erythrocyte alloantigen), and loci on distal mouse chromosome 6

The closely linked proline-rich protein (Prp) genes, coding for abundant salivary proteins, are located on distal mouse chromosome 6. They are part of a conserved linkage group that is represented on human chromosome 12p. Two other markers, Ea-10 and Es-12, that were previously unassigned to a chromosome are closely linked to Prp genes in the mouse.

Complexity, polymorphism, and recombination of mouse T-cell receptor alpha gene families

Genomic DNA from a large panel of inbred strains of mice were hybridized sequentially with 15 V alpha, 2 V delta, 1 C alpha, and 1 C delta probes. Most of the V alpha probes detected a high degree of polymorphism and have allowed the definition of five mouse T-cell receptor alpha (Tcr alpha) haplotypes. One of these haplotypes (Tcre alpha) appears to arise from a recombination between the Tcrb alpha and Tcra alpha haplotypes, the latter being the most frequently found in the conventional inbred strains. This recombination event clearly indicates that the members of at least 11 V alpha sub-families are not closely linked but highly interspersed with one another on chromosome 14.

Structural and evolutionary comparisons of four alleles of the mouse Igk-J locus which encodes immunoglobulin kappa light chain joining (J kappa) segments

The Igk-J locus of the mouse encodes the immunoglobulin kappa light chain joining (J) segments. Four Igk-J alleles have been described on the basis of restriction enzyme length polymorphisms. The nucleotide sequences of the Igk-Ja allele (type strain, C.C58), Igk-Jc allele (type strain, SJL/J), and Igk-Jd allele (type strain, SK/CamRk) have been determined and are compared with the previously reported Igk-Jb allele sequence (type strain, BALB/c). The mouse sequences are also compared with published sequences for rat and human J kappa sequences. Far more differences were found between the Igk-Ja allele and the other mouse alleles than between any two of the latter. These result in two amino acid substitutions which distinguish the J2 and J3' segments of the Igk-Ja allele from the other three alleles. Use of the Phylogenetic Analysis Using Parsimony program to generate a phylogenetic tree strongly indicates that after divergence from the rat ancestor, there appears to have been an early split between the Igk-Ja allele and the evolutionary precursor of the other mouse alleles. There also appears to have been far less divergence from the ancestral condition in the Igk-Ja allele than in the other alleles. Also, the presence of only one convergent mutation among the four mouse alleles provides strong evidence against any crossing over within the Igk-J locus during the history of these alleles. Finally, the differences in rates of evolution of the Igk-J alleles are in marked contrast to the relatively uniform rates of divergence of four alleles of a mouse V kappa gene, Igk-VSer.

Characterization of the heavy and light chain immunoglobulin variable region genes used in a set of anti-digoxin antibodies

Five murine A/J hybridomas (the 35-20 group) produce anti-digoxin antibodies that have homologous heavy and light chain immunoglobulin variable regions (VH and VL), yet differ from each other in fine specificity and affinity for digoxin and related cardiac glycosides [Mudgett-Hunter et al. Molec. Immun. 22, 477-488 (1985)]. To determine the origin of the VH and VL genes used in this set of hybridomas, the rearranged VH and VL genes from one of the 35-20 group hybridomas, 40-140, were cloned. The expressed V region, the leader exon and the 5' transcription control regions were sequenced. VH40-140 is a member of the VH36-60 gene family and has greater than 90% homology with several members of that family. A VH40-140 hybridization probe detected two members of the VH36-60 gene family not previously described. The VL40-140 region, a member of the Vk9 subgroup, is nearly identical to the Vk region used by the myeloma T1. Southern analysis with several restriction endonucleases and hybridization probes indicated that the 35-20 group hybridomas each use the same heavy and light chain variable region gene segments in the assembly of their expressed antibody genes. Functional rearranged antibody genes were detected with JH and VH heavy chain probes and with Jk and Vk light chain probes. The availability of the clones of the one heavy and the one light chain variable region gene segment used by the 35-20 hybridoma group will facilitate the use of in vitro mutagenesis in studies of the structural basis of fine specificity in the digoxin antigen-antibody system.

Complexity, polymorphism, and connectivity of mouse Vk gene families

To define the polymorphism and extent of the mouse immunoglobulin kappa (Igk) gene complex, we have analyzed restriction-enzyme digested genomic DNA from 33 inbred strains of mice with labeled DNA probes corresponding to 16 Vk protein groups (1 of them previously undescribed) and the Jk/Ck region (V, variable; J, joining; C, constant). These probes detected between 1 and 25 distinct restriction enzyme fragments (REF) that appeared in up to eight polymorphic patterns, thus defining eight mouse Igk haplotypes. The investigated portion of the Vk repertoire was estimated to encompass between 60 and 120 discernable Vk gene-containing REFs. In contrast to mouse VH gene families, several Vk gene families defined by these probes appeared to overlap. This observation has implications for Vk gene analyses by nucleic acid hybridization and raises the possibility that the Vk gene complex is a continuum of related sequences.

The mouse Igh-1a and Igh-1b H chain constant regions are derived from two distinct isotypic genes

Genetic and structural analyses of the mouse genes encoding constant region of immunoglobulin subclass (Igh-C) have shown that recombination is rare within this cluster which is inherited as a set designated the Igh haplotype. Recent molecular analyses have demonstrated that either DNA exchanges or gene duplications have probably occurred during the evolution of this set of genes. In order to assess the generality of the duplication processes, the presence and expression of two allelic forms of the Igh-1 (gamma 2a) gene (Igh-1a and Igh-1b) were examined in a large panel of wild mice belonging to Mus musculus domesticus and Mus musculus musculus species. Our data indicate that certain M. m. domesticus animals and most animals in the M. m. musculus group coexpress the two allelic forms of Igh-1. Moreover, genetic studies show that these two immunoglobulin types are encoded by tandemly arranged genes. We propose that wild mice, from which laboratory mice are derived, carry three isotypic gamma 2 genes (Igh-1a, Igh-1b, Igh-3), and these have given rise to the two isotypes seen in laboratory strains by a deletion/insertion mechanism.

Restriction fragment analysis of V preB and lambda 5 within the genus Mus

DNA from a panel of inbred strains of mice and colony bred mice, isolated from different geographical locations, was hybridized to mouse V preB and lambda 5 probes under stringent conditions, indicating sequence similarities greater than 80%. The probe for lambda 5 detects one gene and the probe for V preB detects two genes (V preB1 and V preB2) in the inbred strains of mice examined under the stringency used. No restriction endonuclease fragment length polymorphisms (RFLP) were detected with the V preB and lambda 5 DNA probes among the inbred strains of mice using Bam HI and Hind III. Very few RFLP were detected among Mus musculus subspecies, and the intensity of the hybridization did not differ significantly with either DNA probe. The number of RFLP increased slightly when different species and subgenera were examined, and the intensity of the hybridization signal began to decrease in samples from the different subgenera, suggesting a slight decrease in sequence similarity for both V preB genes with increased time of divergence. Fewer RFLP were detected with the lambda 5 DNA probe. DNA from 11 different Mus species representing 4 subgenera, genetically isolated from laboratory mice for approximately 1-12 million years, continued to hybridize under high stringency conditions using both DNA probes. A comigrating lambda 5 and V preB restriction endonuclease fragment was detected in most of the samples examined, suggesting the close physical linkage of V preB1 and lambda 5 is maintained within the genus Mus. These results suggest that V preB1, V preB2 and lambda 5 have been present for over 12 million years.

Genetic control of early antibody responses

By using a pair of strains that have similar VK haplotypes but different VH haplotypes (e.g. BALB/c and C57BL) it is possible to demonstrate VH-controlled genetic differences in antibodies. By using a pair that have similar VH haplotypes but different VK haplotypes (RF and BALB/c) it is possible to demonstrate VK-controlled genetic differences in antibodies. A plausible explanation for the high frequency of certain V-gene combinations in the primary response is a high affinity of the product without somatic mutations. The products of two such major primary response combinations (VHOx1/VKOX1(H3) and VH186.2/V lambda 1) have an affinity for the immunogen well above 10(6). One combination of V genes, VHOx1/VKOx1(H3) has a major role in the primary anti-phOx response of several mouse strains - the product is idiotype 260. C57BL/10 mice lack the VHOx1 and RF mice the VKOx1(H3) gene. They use the remaining partner of the pair for the response in combination with other genes, but the affinity of the product is lower than the affinity of id. 260. Concordantly, the frequency of these "half-idiotypes" is lower in the primary response than the frequency of the full combination (23% and 16% instead of 50%). When the product of a V-gene combination is very frequent in the primary response, the affinity for the immunogen must be high, but the reverse is not always true. The product of a combination can have an unusually high affinity but the frequency is low. The simplest explanation then is that the frequency of available virgin B cells is low. It can be low because of a low rearrangement frequency of one of the V genes, VH or VK. Another possibility is that only a small proportion of B cells that have the particular combination rearranged can be recruited to the response. We have discussed an example where strict heavy chain CDR3 requirements must strongly limit available B cells.

Genes that modify expression of major urinary proteins in mice

A survey of major urinary proteins (MUPs) from eight BALB/c mouse substrains by isoelectric focusing identified a common pattern with about 10 protein bands in males. One substrain, BALB/cJPt, differed in that it expressed two variant MUP patterns, designated 4.1lo and null. To find the chromosomal location of the gene which determines the 4.1lo phenotype, BALB/cJPt-MUP-4.1lo was crossed with a wild-derived Mus musculus domesticus inbred strain (CLA) that expresses the common BALB/c MUP pattern. The F1 phenotype revealed that the gene(s) controlling the MUP-4.1lo trait was recessive. A restriction fragment polymorphism between these strains found with a MUP cDNA probe allowed us to establish that a gene determining the MUP-4.1lo trait was not linked to the MUP structural genes on chromosome 4. Assays for other chromosomal marker loci revealed that a gene determining the MUP-4.1lo trait, designated Mupm-1, was closely linked to Myc-1 on chromosome 15. To determine the genetic basis of the null trait, BALB/cJPt-MUP-null mice were crossed with BALB/cJPt-MUP-4.1lo mice. A MUP restriction fragment polymorphism between these two lines was tightly linked to a gene or genes involved in determining the MUP-null phenotype. The two variant MUP phenotypes in BALB/cJ mice are determined by separate genes, one of which is located on chromosome 4 and the other on chromosome 15. The chromosomal location of Mupm-1 suggests that it produces a trans-acting factor which regulates MUP expression.

Genes that modify expression of major urinary proteins in mice

A survey of major urinary proteins (MUPs) from eight BALB/c mouse substrains by isoelectric focusing identified a common pattern with about 10 protein bands in males. One substrain, BALB/cJPt, differed in that it expressed two variant MUP patterns, designated 4.1lo and null. To find the chromosomal location of the gene which determines the 4.1lo phenotype, BALB/cJPt-MUP-4.1lo was crossed with a wild-derived Mus musculus domesticus inbred strain (CLA) that expresses the common BALB/c MUP pattern. The F1 phenotype revealed that the gene(s) controlling the MUP-4.1lo trait was recessive. A restriction fragment polymorphism between these strains found with a MUP cDNA probe allowed us to establish that a gene determining the MUP-4.1lo trait was not linked to the MUP structural genes on chromosome 4. Assays for other chromosomal marker loci revealed that a gene determining the MUP-4.1lo trait, designated Mupm-1, was closely linked to Myc-1 on chromosome 15. To determine the genetic basis of the null trait, BALB/cJPt-MUP-null mice were crossed with BALB/cJPt-MUP-4.1lo mice. A MUP restriction fragment polymorphism between these two lines was tightly linked to a gene or genes involved in determining the MUP-null phenotype. The two variant MUP phenotypes in BALB/cJ mice are determined by separate genes, one of which is located on chromosome 4 and the other on chromosome 15. The chromosomal location of Mupm-1 suggests that it produces a trans-acting factor which regulates MUP expression.

Biased usage of certain Vk gene families by autoantibodies and their polymorphism in autoimmune mice

Of 79 hybridomas derived from stimulated or unstimulated autoimmune disease prone mouse strains, secreting autoantibodies of various specificities more than 65% use V genes from five Vk families, namely, Vk1, Vk4, Vk8, Vk10 and Vk19. Restriction fragment length polymorphism (RFLP) analysis of genomic DNAs from autoimmune prone mouse strains, tight skin, NZB and SJL show marked differences in the polymorphism of the Vk1, Vk10 and Vk19 gene families.

Genetic relationships of Mlsa among polymorphic loci on distal mouse chromosome 1

The segregation of Mlsa with respect to genes localized distally on mouse chromosome 1 was examined in two sets of recombinant inbred (RI) strains. In order to localize Mlsa, a linkage map based on analysis of both interspecific backcross mice and multiple sets of RI strains was utilized: (centromere) - Ren-1,2 - 10 centimorgans (cM) - At-3 - 8cM-Apo-A2/Ly-17 - 2cM - Spna-1 - 4cM - Akp-1 - (telomere). The Mlsa allele was mapped to a region that extended just centromeric of Ly-17 (one crossover in 40 RI strains) to just telomeric of Spna-1 (no crossover in 40 RI strains). The identification of multiple polymorphic loci in the region of Mlsa should allow precise gene localization and assist in efforts to clone this gene.

Establishment of a molecular genetic map of distal mouse chromosome 1: further definition of a conserved linkage group syntenic with human chromosome 1q

A linkage map of distal mouse chromosome 1 was constructed by restriction fragment length polymorphism analysis of DNAs from seven sets of recombinant inbred (RI) strains. The data obtained with seven probes on Southern hybridization combined with data from previous studies suggest the gene order Cfh, Pep-3/Ren-1,2, Ly-5, Lamb-2, At-3, Apoa-2/Ly-17,Spna-1. These results confirm and extend analyses of a large linkage group which includes genes present on a 20-30 cM span of mouse chromosome 1 and those localized to human chromosome 1q21-32. Moreover, the data indicate similar relative positions of human and mouse complement receptor-related genes REN, CD45, LAMB2, AT3, APOA2, and SPTA. These results suggest that mouse gene analyses may help in detailed mapping of human genes within such a syntenic group.

T-cell receptor VT beta genes in natural populations of mice

The composition of 15 VT beta gene subfamilies has been examined by Southern hybridization among a broad spectrum of colony bred rat and mouse species extending phylogenetically from Rattus to Mus musculus domesticus. Most mouse species contain a similar content of VT beta genes as determined by the number of hybridizing restriction fragment (RF) bands. Furthermore, the extent of restriction fragment length polymorphism (RFLP) appears to be limited. Some VT beta gene families, however, are missing from Rattus (VT beta 7, VT beta 12) and M. shortridgei (VT beta 9, VT beta 16). Extension of the VT beta survey to a panel of 38 wild caught mice reveals that nearly a third lack specific hybridization to the VT beta 5 probe. Previous reports have established that the mouse inbred strains SJL, C57BR, C57L, and SWR lack 50% of their VT beta repertoire, including VT beta 5 (Behlke et al. 1985). This study demonstrates that natural populations of mice also carry a significantly reduced VT beta gene repertoire.

The genetic origin of murine lupus-associated autoantibodies

Systemic lupus erythematosus and rheumatoid arthritis in human and murine systems are characterized by circulating autoantibodies and immune complex deposition in various organs causing tissue damage and disease. To define the molecular and clonotypic origin of these anti-self responses, and to determine whether abnormalities in Ig genes or somatic mechanisms generating autoantibody diversity may contribute to lupus etiology, we performed molecular analyses of the Ig germline gene organization and the Ig gene segments expressed in monoclonal autoantibodies from autoimmune mice. Comparative restriction fragment length polymorphism analysis of a large number of Ig gene loci from autoimmune and normal mice indicated that (a) lupus can develop in different Ig heavy and kappa light chain variable region gene haplotypes, and (b) the Ig germline genes in lupus mice might be normal. To determine whether autoantibodies are encoded by unique Ig gene segments present in the normal germline repertoire, but not expressed in exogenous responses, we compared nucleic acid sequences encoding lupus autoantibodies and antibodies against foreign antigens. Similar, and in some instances even identical, gene segments were expressed in both types of antibodies, indicating that anti-self and anti-foreign responses use the same, or at least an overlapping, germline gene repertoire. A large variety of Ig variable, diversity, and joining gene segments encoded these autoantibodies with different specificities. Hence, the overall murine lupus-associated anti-self response may be essentially unrestricted. Furthermore, limited evidence has been obtained that both germline genes and somatically mutated genes encode autospecificity, making gross abnormalities in mechanisms for somatic mutation of Ig variable genes unlikely.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of V kappa gene polymorphism on the induction of silent idiotypes in the arsonate system

It has been previously shown that it is possible to modify the expressed repertoire of a given individual using idiotypic manipulation. For example, A/J mice respond to arsonate challenge by synthesizing a dominant idiotype, CRIA, whereas BALB/c mice do not. However, after treatment with rabbit polyclonal anti-CRIA antibodies (Ab2 or anti-idiotypic antibodies) and arsonate, BALB/c mice are able to synthesize a CRIA-like idiotype. To determine whether this modification of repertoire is dependent on the immunoglobulin loci (Ig-h, kappa), we have analyzed the anti-arsonate response after anti-idiotypic treatment of three strains of mice (C58, C.C58, AKR), chosen because they are among a small group of strains which express Kappa V regions not seen in other strains. There are also L chains lacking in these strains which are expressed in other mice. The C58 and C.C58 strains share the same Ig-h locus (Ig-ha) with BALB/c mice but C.C58 are congenic mice, that express the kappa loci on a BALB/c genetic background. AKR mice express the Ig-hd haplotype. AKR, C58 and C.C58 do not produce CRIA positive antibodies in response to arsonate; a defect which has been previously mapped to the kappa locus. These three strains of mice (C58, C.C58 and AKR) were treated with rabbit anti-CRIA and boosted with Ars-KLH. The results show that after such treatment, the C.C58 mice were able to express CRIA-like antibodies which are serologically identical to those of BALB/c.

Allelic variants of Ly-5 in inbred and natural populations of mice

Allelic variants of Ly-5 in inbred commensal and other natural populations of mice were analyzed by patterns of restriction fragment length polymorphisms (RFLP) and Southern hybridization using an Ly-5 cDNA probe and by cell-surface staining with a panel of antibodies directed against polymorphic and nonpolymorphic Ly-5 determinants. New Ly-5 alleles were defined by RFLPs generated by both Eco RI and Bam HI restriction enzyme digests. The Mus musculus subspecies and other species within the genus Mus showed a strong correlation between allelic variants defined by restriction enzymes and serologic specificities. The data also suggest the conservation of the Ly-5 gene throughout the genus Mus.

Structural differences in a single gene encoding the V kappa Ser group of light chains explain the existence of two mouse light-chain genetic markers

Two phenotypic markers of mouse immunoglobulin kappa light chains, the IB-peptide marker and the Ef1a isoelectric focusing marker, are expressed by the C58/J, AKR/J, RF/J, and PL/J strains (called expressor strains) but not by BALB/c and most inbred strains. Expression is linked to the kappa light-chain locus and the Lyt-2/Lyt-3 genes on chromosome 6. Light chains bearing these markers belong to a group of variable region kappa chain (V kappa) regions called V kappa Ser, which has a serine amino terminus and a framework 1 region not observed to date among BALB/c light chains. Southern hybridization of genomic DNA with a V kappa Ser-specific cDNA probe has demonstrated a single strongly hybridizing DNA fragment in all strains of mice tested. Characteristic restriction enzyme polymorphisms define the V kappa Ser alleles of expressor (Igk-VSera) and nonexpressor (Igk-VSerb) strains. In the present study, the unrearranged V kappa Ser gene and its flanking regions from an expressor (C.C58) and nonexpressor (BALB/c) strain have been cloned and their nucleotide sequences determined. The C.C58 V kappa Ser gene isolated (the Igk-VSera allele) was shown to code for the two phenotypic markers described. While the nucleotide sequence of the BALB/c coding region (the Igk-VSerb allele) shows 97% identity with the C.C58 gene, single nucleotide substitutions lead to structural changes in the encoded protein which render it IB-negative and Ef1a-negative. These differences alone can explain the failure of strains containing the BALB/c allele to express these kappa-chain phenotypic markers. Also, the BALB/c gene contains a single substitution in a conserved octamer sequence approximately equal to 100 nucleotides upstream of the coding region, which could affect its expression. Finally, the C.C58 allele contains a BAM5/R repetitive DNA element approximately equal to 1200 nucleotides upstream of the coding regions that is not present in BALB/c. This element gives rise to the EcoRI and BamHI restriction enzyme polymorphisms, which distinguish the Igk-VSera and Igk-VSerb alleles.

The context of T-cell receptor gamma chain genes among wild mouse species

We have examined the context of mouse T-cell receptor gamma (Tcr gamma) chain variable (V gamma) and constant (C gamma) genes among a panel of geographically isolated species of mice. Our Southern hybridization survey with C gamma reveals that essentially three C gamma genes are found among mouse species extending phylogenetically from inbred mice through the feral species Mus pahari. However, a V gamma DNA probe detects three to nine V gamma restriction fragment bands among the same group of mice. These results suggest that certain feral mice such as M. pahari, M. platythrix, and M. shortridgei have amplified numbers of V gamma genes. Studies of individual mice from these particular species indicate the highly amplified V gamma content is not the result of a catastrophic gene duplication or deletion event. We conclude that certain species of mice maintain increased content of V gamma presumably for increased diversity in a T-cell response.

The organization of immunoglobulin variable kappa chain genes on mouse chromosome 6

One mouse with a known recombination (NAK) at the Igk locus on chromosome 6 and two new recombinants [B6.PL (75NS) and B6.PL (85NS)] were examined using a series of probes, each of which is specific for a set of immunoglobulin (Ig) Vk genes. Under high stringency conditions, each probe detects from 1 to 19 Bam HI restriction endonuclease fragments (REFs) in genomic DNA by Southern transfer hybridization techniques. Analysis of the REF patterns indicate that the NAK recombination event occurred within the variable region of Igk. The REF patterns of the two B6.PL congenic mice provided two additional recombination events which could be examined. Although some of the REFs had shared mobility among the parental strains, at least 1 and up to 13 polymorphic REFs were present for a given probe among the NZB and AKR parental strains. The results from the NAK mouse indicate that at least some members of Vk4, Vk8, Vk10, and Vk21 were on one side of the recombination event linked to the Lyt-2 alpha and Igk-Ef1 alpha alleles of AKR, while the Vk9, Vk11, and Vk24 REF patterns came from the NZB parental strain linked to the Igk-Ef2 beta (Vk1) allele. The two B6.PL congenics produced a refined map on the Lyt-2, Lyt-3 side of the Vk region. The B6.PL (85NS) mice retained the Vk21 REF pattern of the Lyt-2 alpha, Lyt-3 alpha donor strain PL/J, while displaying the C57BL/6 REF pattern for the other Vk gene groups tested. The B6.PL (75NS) mice retained the REF patterns of PL/J for Vk21 and Ef-1, indicating a third recombination. This indicates the Vk gene order is (Lyt-2; Vk21); Ef-1; (Vk4; Vk8; Vk10); and (Vk9; Vk11; Vk24; Ef-2).

Structural polymorphism of V kappa 21 E and V kappa 21 D gene products in laboratory mice

The aim of the present work was to study structural polymorphism of V kappa genes products. To this end we isolated immunoglobulins expressing the V kappa 21 D and V kappa 21 E gene products from the normal sera of several inbred strains of mice using a monoclonal antibody that selectively recognizes V kappa 21 D and V kappa 21 E subgroups. Analysis of the isoelectric focusing pattern of the light chain of these immunoglobulins revealed the existence of 3 clearly different phenotypes. The first one is shared by most inbred strains of mice, the second one is expressed by C58/J, AKR and PL/J and the third one defines V kappa 21 D-E light chains of SJL and SJA mice. Genetic analysis revealed that the locus controlling V kappa 21 D-E chain structure is closely linked to the Ly2-3 and to the Ig Kappa-Ef1 loci. Finally, using recombinant mouse strains, we could also order V kappa 21 D-E genes with respect to the known loci affecting V kappa polymorphism. Taken together our data argue against the possibility that the polymorphism observed results from strain-specific expression of V kappa genes common to all mice, but rather suggest that different allelic form of the same V kappa gene subgroup exist in different strains.

Murine T-cell receptor mutants with deletions of beta-chain variable region genes

Genomic Southern blots of DNA from eight strains of mice were examined for restriction fragment length polymorphisms in their loci encoding the variable region of the T-cell receptor beta chain (V beta), using 16 different V beta-specific probes. Mouse strains BALB/c, C57BL/6, C3H, and PL were identical, while strains SJL, C57BR, C57L, and SWR shared several polymorphisms with respect to the other four strains. In addition, SJL, C57L, C57BR, and SWR DNAs were missing 50% of the hybridizing bands visualized in BALB/c DNA. A cDNA library from concanavalin A-stimulated SJL spleen blasts was constructed and examined for V beta gene usage. Ten genes were found to account for all V beta-containing clones isolated, including three newly identified V beta genes. All 10 of these genes were found to be present in BALB/c mice. We conclude that SJL, C57L, C57BR, and SWR mice represent V beta deletion mutants of the BALB/c genotype.

Localization of CT beta and C kappa on mouse chromosome 6

In the mouse three lymphocyte gene families have been positioned on the proximal region of chromosome 6. Originally the immunoglobulin kappa light chain (Igk) and the thymocyte surface antigens Lyt-2 and Lyt-3 were assigned to chromosome 6, and recently the beta chain of the T-cell receptor for antigen was positioned proximal to Igk. Molecular clones which recognize the constant (C) region of the beta chain of the T-cell receptor for antigen (CT beta) and the constant region of the immunoglobulin kappa (C kappa) chain were used to determine recombination frequencies with respect to the morphological marker hypodactyly (Hd). SJL/JL W pi mice were mated with C.B6.C3-Hd/+ mice, and the progeny expressing the Hd phenotype were mated with SJL/JL W pi mice. Backcross progeny which expressed the Hd phenotype were nephrectomized, and kidney DNA was examined by Southern hybridization for the polymorphic restriction endonuclease fragment (REF) patterns of the parental mice. Of the 88 progeny tested in this three-point cross, 3 CT beta and 4 C kappa homozygote REF patterns were detected. These homozygotes were mutually exclusive. This implies the following gene order: centromere-CT beta-Hd-Igk and CT beta 1 would be 7.95 +/- 2.88 centimorgans from C kappa.

Genetic polymorphism at the mouse immunoglobulin J kappa locus (Igk-J) as demonstrated by Southern hybridization and nucleotide sequence analysis

Comparison of the nucleotide sequences of the C.C58 M75 myeloma kappa chain gene and the BALB/c germ-line J kappa segments suggested that the J kappa regions of C.C58 and BALB/c might be distinguished by restriction enzyme polymorphisms. This was shown to be the case in Southern hybridizations of Hinf I and Acc I digests of liver DNA from these and other strains with a J kappa-specific probe. Tests of a wide variety of inbred, congenic, recombinant, and recombinant-inbred strains provided evidence for three alleles, Igk-Ja, Igk-Jb, and Igk-Jc, the type strains for which are C58/J, BALB/c, and SJL/J, respectively. Analysis of the B6.PL(85NS) congenic strain suggests that the Igk-J locus lies in the neighborhood of the Lyt-2/Lyt-3 loci, approximately 0.30 cM from the V gene segment determining the Igk-VSer and Igk-Efl polymorphisms. Finally, nucleotide substitutions lead to amino acid sequence differences between the C.C58 M 75 kappa gene and the BALB/c germ line in J kappa 2 and J kappa 4. Two of these substitutions reflect true germ-line differences, raising the possibility that idiotype differences observed among strains could reflect J kappa as well as V kappa differences.