Molecular basis of the TaqI p49a,f polymorphism in the DYS1 locus containing DAZ genes.

The previously described TaqI p49a,f polymorphism at the DYS1 locus in the non-recombinant part of the Y chromosome is widely exploited to investigate many facets of human population genetics. It has been shown that the DYS1 locus corresponds to the four DAZ genes in the AZF-c region of the Y chromosome. As the DNA sequence of the DAZ genes is known in its entirety, it is now possible to establish correspondences between the main Southern polymorphic TaqI bands (A, C, D, F and I) at the DYS1 locus and TaqI fragments deduced from the sequence, by way of comparing band sizes and sequence homologies between hybridized fragments. Transitions between polymorphic forms for each variable TaqI fragment can be explained regarding the restriction maps, by postulating a parsimonious number of TaqI site losses during human evolution. Most of the codon changes caused by TaqI site losses located in the exons of the four DAZ genes have potentially high selective values.

Genomic exploration of the hemiascomycetous yeasts: 2. Data generation and processing.

The generation of sequencing data for the hemiascomycetous yeast random sequence tag project was performed using the procedures established at GENOSCOPE. These procedures include a series of protocols for the sequencing reactions, using infra-red labelled primers, performed on both ends of the plasmid inserts in the same reaction tube, and their analysis on automated DNA sequencers. They also include a package of computer programs aimed at detecting potential assignation errors, selecting good quality sequences and estimating their useful length.

IgM anti-myeloperoxidase antibody-secreting lymphocytes are present in the peripheral repertoire of lupus mice but rarely differentiate into IgG-producing cells.

Two IgM, kappa anti-myeloperoxidase (MPO) monoclonal antibodies, 6D6 and 9B5, bound to MPO in a solid-phase enzyme-linked immunosorbent assay were derived from the splenocytes of (NZB x NZW) F1 and MRL/lpr-lpr mice, respectively. 6D6 gave a characteristic perinuclear immunofluorescence staining pattern on ethanol-fixed human neutrophils, bound to the native form of MPO by immunoblotting and had a high constant affinity for MPO as demonstrated by real-time specific interaction. 9B5 produced a cytoplasmic immunofluorescence staining pattern, reacted with the heavy chain of MPO and had a low constant affinity for MPO. The heavy-and light-chain variable region genes of monoclonal antibodies (mAb) 6D6 and 9B5 were sequenced and found to be highly homologous to germline genes and to contain negatively charged amino acids in the complementarity determining regions. IgM MPO-binding activity was observed in most BW and MRL/lpr-lpr mouse sera, which may correspond to polyclonal activation of B cells, whereas IgG anti-MPO antibodies could be rarely detected. Thus, this study indicates that (i) BW and MRL/lpr-lpr mice do not delete IgM anti-MPO secreting B cells, do not maintain these B cells in a state of anergy, but most individuals are not able to spontaneously induce the class-switching of this autoantibody population; (ii) IgM anti-MPO antibodies can recognize different epitopes on MPO and produce different immunofluorescence staining pattern on ethanol-fixed human neutrophils, as demonstrated by the immunochemical properties of the two lupus-mouse derived mAb.

Early anti-nucleosome autoantibodies from a single MRL+/+ mouse: fine specificity, V gene structure and pathogenicity.

In systemic lupus erythematosus, the nucleosome assumes a central role in the autoimmune response to self antigens. To gain insight into the etiology and pathogenesis of anti-nucleosome antibodies (Ab), we analyzed a panel of six IgG-secreting hybridomas derived from a single young MRL +/+ mouse at the onset of the autoimmune response. All monoclonal antibodies (mAb) bound exclusively the native nucleosome, and represented five different clonotypes that recognized diverse nucleosomal epitopes, typical of a polyclonal response. The VH-complementarity-determining region (CDR)3 regions exhibited unique stretches of charged amino acids with different polarity that may be important for the interaction with the nucleosome. These early anti-nucleosome mAb displayed striking structural differences with not only anti-DNA, but also with anti-nucleosome Ab, that appear later in disease. Two of the mAb deposited in kidney glomeruli after in vivo administration to RAG-1-deficient mice, suggesting that diverse B cell clones, possibly selected by the nucleosome itself, may play a role in the initiation of kidney damage.

Idiotypic analysis of anti-nucleosome monoclonal antibodies derived from lupus mice.

3F6 and 2E1 are anti-(H2A-H2B) monoclonal antibodies derived from a 12-month-old (NZBxNZW)F1 mouse that diverged from the same clonal precursor by somatic mutations. Rabbit anti-idiotypic antisera were prepared against these two monoclonal antibodies and used as probes to analyse the properties and expression of 3F6 and 2E1 idiotypes. Both idiotypes were conformational, distant from the antigen binding site and did not correlate with a VH- or VL-chain usage. 3F6 was preferentially bound by anti-3F6 idiotype but was weakly recognized by anti-2E1 idiotype suggesting, since 3F6 derives from 2E1, that 3F6 bore idiotypic determinants generated by somatic mutations. While none of the murine anti-DNA monoclonal antibodies tested expressed 2E1 or 3F6 idiotypes, 3F6 idiotype could be detected on approximately one-third of anti-(H2A-H2B) monoclonal antibodies derived from other lupus strains of mice, demonstrating the presence of cross-reactive idiotypes on autoantibodies directed against a nucleosome that could result from somatic mutations.

Structural properties and mutation patterns of anti-nucleosome monoclonal antibodies are similar to those of anti-DNA antibodies.

Four monoclonal antibodies (mAb) derived from an (NZB x NZW)F1 mouse bound to nucleosomes, total histones and to the H2A-H2B dimers but not to individual histones or DNA. Sequencing of their heavy (H)- and light (L)-chain variable region genes showed that they derived by somatic mutations from the same B cell precursor. The distribution of negatively and positively charged amino acids in the H-chain complementarity-determining regions was very similar to that observed not only in anti-H2A-H2B mAb derived from different lupus-prone mouse strains but also in anti-DNA mAb. Combined analysis of the mAb structures and their interactions with immobilized H2A-H2B dimer or total histones by plasmon resonance allowed us to assign the H-chain mutations a major role in the binding profiles of these anti-nucleosome mAb. Interestingly, four of the five H-chain mutations that distinguished mAb 3F6 from 2E1 generated negatively or positively charged amino acid residues, and two of them occurred at positions 56 and 76, which are frequently involved in the maturation process of anti-DNA antibodies. A modeling study of the 3F6 variable fragment (Fv) predicted that acidic residues occupy the cleft of the Ab combining site and have the potential to participate in electrostatic interactions. Thus, the demonstration that (NZB x NZW)F1-derived anti-H2A-H2B antibodies share certain structural features and mutation patterns with anti-DNA mAb suggest that common selection and maturation processes account for the production of these lupus-related autoantibodies.

Do naturally occurring autoantibodies participate in the constitution of the pathological B-cell repertoire in systemic lupus erythematosus?

Systemic lupus erythematosus (SLE) is the prototype of systemic autoimmune diseases. In both human and mouse SLE diseases, the autoimmune response targets a restricted set of autoantigens. Many of them are nucleic acids and proteins involved in the synthesis and processing of DNA or RNA, a characteristic which should be taken into consideration to elucidate the origins of non organ-specific autoantibodies. Several observations, in particular those obtained from experimental models of SLE induced in normal mice, suggest that the breakdown of B-cell tolerance occurs in the periphery. Herewith, we present data further supporting the proposition that SLE-associated autoantibodies originate from natural autoantibody-secreting B cells activated in the internal environment of lupus mice. Thus, one may hypothesize that certain clones of the expanded primary B-cell repertoire are selected to differentiate into harmful IgG autoantibody-secreting clones, thereby raising the question of the nature of immunogenic structures involved in SLE. Our analysis of the immunochemical and structural properties of anti-nucleosome and anti-myeoloperoxidase monoclonal antibodies derived from (NZB x NZW)F1 mice leads us to propose that complexes formed by the association of DNA and DNA-binding proteins and, more generally, by anionic molecules associated with proteins, possess a selective advantage over other autoantigens to induce the differentiation of certain B-cell clones and the very special profile of the SLE-autoimmune response. These DNA/DNA-protein complexes could also play a role in the activation of the T-cell compartment in SLE.