The IgH Eµ-MAR regions promote UNG-dependent error-prone repair to optimize somatic hypermutation

Intoduction

Two scaffold/matrix attachment regions (5'- and 3'-MARs_Eµ ) flank the intronic core enhancer (cEµ) within the immunoglobulin heavy chain locus (IgH). Besides their conservation in mice and humans, the physiological role of MARs_Eµ is still unclear and their involvement in somatic hypermutation (SHM) has never been deeply evaluated.

Methods

Our study analyzed SHM and its transcriptional control in a mouse model devoid of MARs_Eµ , further combined to relevant models deficient for base excision repair and mismatch repair.

Results

We observed an inverted substitution pattern in of MARs_Eµ -deficient animals: SHM being decreased upstream from cEµ and increased downstream of it. Strikingly, the SHM defect induced by MARs_Eµ -deletion was accompanied by an increase of sense transcription of the IgH V region, excluding a direct transcription-coupled effect. Interestingly, by breeding to DNA repair-deficient backgrounds, we showed that the SHM defect, observed upstream from cEµ in this model, was not due to a decrease in AID deamination but rather the consequence of a defect in base excision repair-associated unfaithful repair process.

Discussion

Our study pointed out an unexpected "fence" function of MARs_Eµ regions in limiting the error-prone repair machinery to the variable region of Ig gene loci.

Distinct B-Cell Specific Transcriptional Contexts of the BCL2 Oncogene Impact Pre-Malignant Development in Mouse Models

Simple Summary

Beyond the classical t(14;18) translocation associated with follicular lymphoma, BCL2 is deregulated in multiple B-cell malignancies, including some cases of myeloma, and through diverse genetic anomalies. It is currently unclear how the various deregulation patterns mechanistically impact the phenotype of theses malignancies. We designed two different BCL2 deregulation models in transgenic mice, whereby the oncogene was either associated with the IgH3′RR superenhancer, as in t(14;18), or inserted into the kappa light chain locus. We compared the impact of these models on B-cell fate and lymphoid tissues. Linkage to the IgH superenhancer showed a quite specific impact on germinal center B cell populations. The Ig kappa model was much less specific and strongly boosted the plasma cell in-flow and the accumulation of long-lived plasma cells.

Abstract

Upregulated expression of the anti-apoptotic BCL2 oncogene is a common feature of various types of B-cell malignancies, from lymphoma to leukemia or myeloma. It is currently unclear how the various patterns of deregulation observed in pathology eventually impact the phenotype of malignant B cells and their microenvironment. Follicular lymphoma (FL) is the most common non-Hodgkin lymphoma arising from malignant germinal center (GC) B-cells, and its major hallmark is the t(14:18) translocation occurring in B cell progenitors and placing the BCL2 gene under the control of the immunoglobulin heavy chain locus regulatory region (IgH 3′RR), thus exposing it to constitutive expression and hypermutation. Translocation of BCL2 onto Ig light chain genes, BCL2 gene amplification, and other mechanisms yielding BCL2 over-expression are, in contrast, rare in FL and rather promote other types of B-cell lymphoma, leukemia, or multiple myeloma. In order to assess the impact of distinct BCL2 deregulation patterns on B-cell fate, two mouse models were designed that associated BCL2 and its full P1-P2 promoter region to either the IgH 3′RR, within a “3′RR-BCL2” transgene mimicking the situation seen in FL, or an Ig light chain locus context, through knock-in insertion at the Igκ locus (“Igκ-BCL2” model). While linkage to the IgH 3′ RR mostly yielded expression in GC B-cells, the Igκ-driven up-regulation culminated in plasmablasts and plasma cells, boosting the plasma cell in-flow and the accumulation of long-lived plasma cells. These data demonstrate that the timing and level of BCL2 deregulation are crucial for the behavior of B cells inside GC, an observation that could strongly impact the lymphomagenesis process triggered by secondary genetic hits.

Functional anatomy of the immunoglobulin heavy chain 3΄ super-enhancer needs not only core enhancer elements but also their unique DNA context

Cis-regulatory elements feature clustered sites for transcription factors, defining core enhancers and have inter-species homology. The mouse IgH 3΄ regulatory region (3'RR), a major B-cell super-enhancer, consists of four of such core enhancers, scattered throughout more than 25 kb of packaging 'junk DNA', the sequence of which is not conserved but follows a unique palindromic architecture which is conserved in all mammalian species. The 3'RR promotes long-range interactions and potential IgH loops with upstream promoters, controlling class switch recombination (CSR) and somatic hypermutation (SHM). It was thus of interest to determine whether this functional architecture also involves the specific functional structure of the super-enhancer itself, potentially promoted by its symmetric DNA shell. Since many transgenic 3'RR models simply linked core enhancers without this shell, it was also important to compare such a 'core 3'RR' (c3'RR) with the intact full-length super-enhancer in an actual endogenous IgH context. Packaging DNA between 3'RR core enhancers proved in fact to be necessary for optimal SHM, CSR and IgH locus expression in plasma cells. This reveals that packaging DNA can matter in the functional anatomy of a super-enhancer, and that precise evaluation of such elements requires full consideration of their global architecture.

Identification of Glycolytic Enzyme Polypeptides on the Two-Dimensional Protein Map of Saccharomyces cerevisiae and Application to the Study of Some Wine Yeasts

Using a modification of the basic two-dimensional polyacrylamide gel electrophoresis technique, the polypeptides of the protein map of Saccharomyces cerevisiae involved in glycolysis were investigated. This study resulted in a reassignment of two of the seven glycolytic enzyme polypeptides previously identified (Ludwig et al., Mol. Cell. Biol. 2:117-126, 1982), those corresponding to phosphoglycerate kinase and to alcohol dehydrogenase. It also resulted in the identification of two additional glycolytic polypeptides, the enolase B monomer and the glyceraldehyde phosphate dehydrogenase B monomer. The glycolytic enzymes polypeptides so identified were investigated in 5 laboratory strains (all S. cerevisiae) and in 11 commerical strains used for wine making (S. cerevisiae and Saccharomyces bayanus). It appeared highly significant that a particular electrophoretic variant of the glyceraldehyde phosphate dehydrogenase B monomer was found only in the wine yeasts. Furthermore, it was strongly suggested that S. cerevisiae and S. bayanus strains are distinguishible on the basis of a different electrophoretic migration of the enolase B monomer.

Molecular tools for identification of Penicillium starter cultures used in the food industry

The main goal of this work was to develop rapid and accurate molecular tools to discriminate species of white industrial Penicillia. We applied three different polymerase chain reaction (PCR) based techniques. Sequences of the ITS region of the rRNA gene unit and of the 5' end of the beta tubulin gene yielded 1.2% and 5.8% nucleotide variability respectively, between Penicillium camembertii and Penicillium nalgiovense. Polymorphic restriction sites were found in both sequences. These may be used in diagnostic PCR-RFLP analysis to rapidly distinguish between the two Penicillium species. Random amplified polymorphic DNA (RAPD) markers were also useful to differentiate these two species, but no polymorphism was found at the subspecific level, which evidenced a high level of homogeneity of the isolates studied. By means of these three techniques, the real identity of industrial strains of Penicillium chrysogenum and P. nalgiovense could be demonstrated. The comparison of these isolates with type strains of the two species suggested that the former corresponds to P. nalgiovense. The genetic relatedness between P. naglovense and Penicillium dipodomyis was also confirmed.

[Spinal anesthesia with bupivacaine for surgery of the hip in the elderly]

In 60 elderly patients, spinal anaesthesia for orthopaedic hip surgery was induced randomly with 15 mg bupivacaine 0.375% without glucose (Group I), 2.5% glucose (Group II) or 7.5% glucose (Group III), in 4 ml. The injection was made in the lateral position, and the patients turned supine immediately after. The onset, extent and duration of sensory and motor blockade, the cardiovascular effects and the quality of anaesthesia were evaluated. The hyperbaric solutions produced a greater cephalad spread of analgesia (T8,9 and T9,8 respectively) than the glucose-free solution (T10,5). The mean duration of analgesia at the L2 level with the isobaric solution was significantly greater: 187 min versus 171 min and 150 min with the hyperbaric solutions. All the patients had complete motor blockade of the lower limb. The mean duration of the motor block was significantly shorter for the 2.5% and 7.5% glucose solutions (137 and 125 min respectively for Bromage's degree 3) versus 170 min for the glucose-free solution. Although the pre-anaesthetic arterial pressures in the three groups did not differ significantly, the systolic, mean and diastolic arterial pressures decreased only by about 20 to 25% in all groups. It was suggested to take into account the more rapid infusion of lactated Ringer's solution (20 ml X kg-1) in Group III. Anaesthesia was satisfactory in 95% of patients in Group I and Group II, and 90% in Group III. Glucose-free bupivacaine produced a long-lasting blockade suitable for hip surgery of long duration.