Catherine Chevalier

Complete amino acid sequence of puroindoline, a new basic and cystine‐rich protein with a unique tryptophan‐rich domain, isolated from wheat endosperm by Triton X‐114 phase partitioning

A new basic protein has been isolated from wheat endosperm by Triton X‐114 phase partitioning. It contains five disulfide bridges and is composed of equal amounts of a polypeptide chain of 115 amino acid residues and of the same chain with a C‐terminus dipeptide extension. The most striking sequence feature is the presence of a unique tryptophan‐rich domain so that this protein isolated from wheat seeds has been named puroindoline. The similar phase partitioning behavior in Triton X‐114 of this basic eystine‐rich protein and of purothionins suggests that puroindoline may also be a membranotoxin that might play a role in the defense mechanism of plants against microbial pathogens.

The Germinal Center/Activated B-Cell Subclassification Has a Prognostic Impact for Response to Salvage Therapy in Relapsed/Refractory Diffuse Large B-Cell Lymphoma: A Bio-CORAL Study

PURPOSE To evaluate the prognostic value of the cell of origin (COO) in patients with relapsed/refractory diffuse large B-cell lymphoma (DLBLC), prospectively treated by rituximab, dexamethasone, high-dose cytarabine, and cisplatin (R-DHAP) versus rituximab, ifosfamide, carboplatin, and etoposide and followed by intensive therapy plus autologous stem-cell transplantation on the Collaborative Trial in Relapsed Aggressive Lymphoma (CORAL) trial. PATIENTS AND METHODS Among the 396 patients included on the trial, histologic material was available for a total of 249 patients at diagnosis (n = 189 patients) and/or at relapse (n = 147 patients), which included 87 matched pairs. The patient data were analyzed by immunochemistry for CD10, BCL6, MUM1, FOXP1, and BCL2 expression and by fluorescent in situ hybridization for BCL2, BCL6 and c-MYC breakpoints. The correlation with survival data was performed by using the log-rank test and the Cox model. RESULTS Characteristics of immunophenotype and chromosomal abnormalities were statistically highly concordant in the matched biopsies. In univariate analysis, the presence of c-MYC gene rearrangement was the only parameter to be significantly correlated with a worse progression-free survival (PFS; P = .02) and a worse overall survival (P = .04). When treatment interaction was tested, the germinal center B (GCB) -like DLBCL that was based on the algorithm by Hans was significantly associated with a better PFS in the R-DHAP arm. In multivariate analysis, independent prognostic relevance was found for the GCB/non-GCB the Hans phenotype interaction treatment (P = .04), prior rituximab exposure (P = .0052), secondary age-adjusted International Prognostic Index (P = .039), and FoxP1 expression (P = .047). Confirmation was obtained by gene expression profiling in a subset of 39 patients. CONCLUSION COO remains a major and independent factor in relapsed/refractory DLBCL, with a better response to R-DHAP in GCB-like DLBCL. This needs confirmation by a prospective study.

Essential role of Helicobacter pylori gamma-glutamyltranspeptidase for the colonization of the gastric mucosa of mice.

Constitutive expression of γ‐glutamyltranspeptidase (GGT) activity is common to all Helicobacter pylori strains, and is used as a marker for identifying H. pylori isolates. Helicobacter pylori GGT was purified from sonicated extracts of H. pylori strain 85P by anion exchange chromatography. The N‐terminal amino acid sequences of two of the generated endoproteolysed peptides were determined, allowing the cloning and sequencing of the corresponding gene from a genomic H. pylori library. The H. pylori ggt gene consists of a 1681 basepair (bp) open reading frame encoding a protein with a signal sequence and a calculated molecular mass of 61 kDa. Escherichia coli clones harbouring the H. pylori ggt gene exhibited GGT activity at 37°C, in contrast to E. coli host cells (MC1061, HB101), which were GGT negative at 37°C. GGT activity was found to be constitutively expressed by similar genes in Helicobacter felis, Helicobacter canis, Helicobacter bilis, Helicobacter hepaticus and Helicobacter mustelae. Western immunoblots using rabbit antibodies raised against a His‐tagged‐GGT recombinant protein demonstrated that H. pylori GGT is synthesized in both H. pylori and E. coli as a pro‐GGT that is processed into a large and a small subunit. Deletion of a 700 bp fragment within the GGT‐encoding gene of a mouse‐adapted H. pylori strain (SS1) resulted in mutants that were GGT negative yet grew normally in vitro. These mutants, however, were unable to colonize the gastric mucosa of mice when orally administered alone or together (co‐infection) with the parental strain. These results demonstrate that H. pylori GGT activity has an essential role for the establishment of the infection in the mouse model, demonstrating for the first time a physiological role for a bacterial GGT enzyme.

Genetically determined differences in sodium current characteristics modulate conduction disease severity in mice with cardiac sodium channelopathy.

Conduction slowing of the electric impulse that drives the heartbeat may evoke lethal cardiac arrhythmias. Mutations in SCN5A, which encodes the pore-forming cardiac sodium channel &agr; subunit, are associated with familial arrhythmia syndromes based on conduction slowing. However, disease severity among mutation carriers is highly variable. We hypothesized that genetic modifiers underlie the variability in conduction slowing and disease severity. With the aim of identifying such modifiers, we studied the Scn5a1798insD/+ mutation in 2 distinct mouse strains, FVB/N and 129P2. In 129P2 mice, the mutation resulted in more severe conduction slowing particularly in the right ventricle (RV) compared to FVB/N. Pan-genomic mRNA expression profiling in the 2 mouse strains uncovered a drastic reduction in mRNA encoding the sodium channel auxiliary subunit &bgr;4 (Scn4b) in 129P2 mice compared to FVB/N. This corresponded to low to undetectable &bgr;4 protein levels in 129P2 ventricular tissue, whereas abundant &bgr;4 protein was detected in FVB/N. Sodium current measurements in isolated myocytes from the 2 mouse strains indicated that sodium channel activation in myocytes from 129P2 mice occurred at more positive potentials compared to FVB/N. Using computer simulations, this difference in activation kinetics was predicted to explain the observed differences in conduction disease severity between the 2 strains. In conclusion, genetically determined differences in sodium current characteristics on the myocyte level modulate disease severity in cardiac sodium channelopathies. In particular, the sodium channel subunit &bgr;4 (SCN4B) may constitute a potential genetic modifier of conduction and cardiac sodium channel disease.

Immunosuppressive drug-free operational immune tolerance in human kidney transplant recipients: Part I. Blood gene expression statistical analysis

Survival of solid organ grafts depends on life‐long immunosuppression, which results in increased rates of infection and malignancy. Induction of tolerance to allografts would represent the optimal solution for controlling both chronic rejection (CR) and side effects of immunosuppression. Although spontaneous “operational tolerance” can occur in human kidney transplantation, the lack of noninvasive peripheral blood biological markers of this rare phenomenon precludes the identification of potentially tolerant patients in whom immunosuppression could be tapered as well as the development of new tolerance inducing strategies. Here, the potential of high throughput microarray technology to decipher complex pathologies allowed us to study the peripheral blood specific gene expression profile and corresponding EASE molecular pathways associated to operational tolerance in a cohort of human kidney graft recipients. In comparison with patients with CR, tolerant patients displayed a set of 343 differentially expressed genes, mainly immune and defense genes, in their peripheral blood mononuclear cells (PBMC), of which 223 were also different from healthy volunteers. Using the expression pattern of these 343 genes, we were able to classify correctly >80% of the patients in a cross‐validation experiment and classified correctly all of the samples over time. Collectively, this study identifies a unique PBMC gene signature associated with human operational tolerance in kidney transplantation by a classical statistical microarray analysis and, in the second part, by a nonstatistical analysis. J. Cell. Biochem. 103: 1681–1692, 2008.

Immune response and mitochondrial metabolism are commonly deregulated in DMD and aging skeletal muscle.

Duchenne Muscular Dystrophy (DMD) is a complex process involving multiple pathways downstream of the primary genetic insult leading to fatal muscle degeneration. Aging muscle is a multifactorial neuromuscular process characterized by impaired muscle regeneration leading to progressive atrophy. We hypothesized that these chronic atrophying situations may share specific myogenic adaptative responses at transcriptional level according to tissue remodeling. Muscle biopsies from four young DMD and four AGED subjects were referred to a group of seven muscle biopsies from young subjects without any neuromuscular disorder and explored through a dedicated expression microarray. We identified 528 differentially expressed genes (out of 2,745 analyzed), of which 328 could be validated by an exhaustive meta-analysis of public microarray datasets referring to DMD and Aging in skeletal muscle. Among the 328 validated co-expressed genes, 50% had the same expression profile in both groups and corresponded to immune/fibrosis responses and mitochondrial metabolism. Generalizing these observed meta-signatures with large compendia of public datasets reinforced our results as they could be also identified in other pathological processes and in diverse physiological conditions. Focusing on the common gene signatures in these two atrophying conditions, we observed enrichment in motifs for candidate transcription factors that may coordinate either the immune/fibrosis responses (ETS1, IRF1, NF1) or the mitochondrial metabolism (ESRRA). Deregulation in their expression could be responsible, at least in part, for the same transcriptome changes initiating the chronic muscle atrophy. This study suggests that distinct pathophysiological processes may share common gene responses and pathways related to specific transcription factors.

Identification of master genes involved in liver key functions through transcriptomics and epigenomics of methyl donor deficiency in rat: relevance to nonalcoholic liver disease.

SCOPE Our study aims to investigate molecular events associated to methyl donor deficiency (MDD) by analyzing the transcriptome and the methylome of MDD rats in liver. METHODS AND RESULTS Twenty-one-day-old rats born to mothers fed either with a standard diet or a MDD diet during gestation and lactation were compared. From a total of 44 000 probes for 26 456 genes, we found two gene clusters in MDD rats whose expression levels had significant differences compared with controls: 3269 overexpressed (p < 0.0009) and 2841 underexpressed (p < 0.0004) genes. Modifications of DNA methylation were found in the promoter regions of 1032 genes out of 14 981 genes. Ontological analyses revealed that these genes are mainly involved in glucose and lipid metabolism, nervous system, coagulation, ER stress, and mitochondrial function. CONCLUSION Putative master genes exhibiting changes in both gene expression and DNA methylation are limited to 266 genes and are mainly involved in the renin-angiotensin system (n = 3), mitochondrion metabolism (n = 18), and phospholipid homeostasis (n = 3). Most of these master genes participate in nonalcoholic fatty liver disease. The adverse effects of MDD on the metabolic process indicate the beneficial impact of folate and vitamin B12, especially during the perinatal period.

Non-coding RNAs revealed during identification of genes involved in chicken immune responses

Recent large-scale cDNA cloning studies have shown that a significant proportion of the transcripts expressed from vertebrate genomes do not appear to encode protein. Moreover, it was reported in mammals (human and mice) that these non-coding transcripts are expressed and regulated by mechanisms similar to those involved in the control of protein-coding genes. We have produced a collection of cDNA sequences from immunologically active tissues with the aim of discovering chicken genes involved in immune mechanisms, and we decided to explore the non-coding component of these immune-related libraries. After finding known non-coding RNAs (miRNA, snRNA, snoRNA), we identified new putative mRNA-like non-coding RNAs. We characterised their expression profiles in immune-related samples. Some of them showed changes in expression following viral infections. As they exhibit patterns of expression that parallel the behaviour of protein-coding RNAs in immune tissues, our study suggests that they could play an active role in the immune response.

Molecular risk stratification in advanced heart failure patients

Risk stratification in advanced heart failure (HF) is crucial for the individualization of therapeutic strategy, in particular for heart transplantation and ventricular assist device implantation. We tested the hypothesis that cardiac gene expression profiling can distinguish between HF patients with different disease severity. We obtained tissue samples from both left (LV) and right (RV) ventricle of explanted hearts of 44 patients undergoing cardiac transplantation or ventricular assist device placement. Gene expression profiles were obtained using an in‐house microarray containing 4217 muscular organ‐relevant genes. Based on their clinical status, patients were classified into three HF‐severity groups: deteriorating (n= 12), intermediate (n= 19) and stable (n= 13). Two‐class statistical analysis of gene expression profiles of deteriorating and stable patients identified a 170‐gene and a 129‐gene predictor for LV and RV samples, respectively. The LV molecular predictor identified patients with stable and deteriorating status with a sensitivity of 88% and 92%, and a specificity of 100% and 96%, respectively. The RV molecular predictor identified patients with stable and deteriorating status with a sensitivity of 100% and 96%, and a specificity of 100% and 100%, respectively. The molecular prediction was reproducible across biological replicates in LV and RV samples. Gene expression profiling has the potential to reproducibly detect HF patients with highest HF severity with high sensitivity and specificity. In addition, not only LV but also RV samples could be used for molecular risk stratification with similar predictive power.

Transcriptional orchestration of mitochondrial homeostasis in a cellular model of PGC-1-related coactivator-dependent thyroid tumor

The PGC-1 (Peroxisome proliferator-activated receptor Gamma Coactivator-1) family of coactivators (PGC-1α, PGC-1β, and PRC) plays a central role in the transcriptional control of mitochondrial biogenesis and oxidative phosphorylation (OXPHOS) processes. These coactivators integrate mitochondrial energy production into cell metabolism using complementary pathways. The XTC.UC1 cell line is a mitochondria-rich model of thyroid tumors whose biogenesis is almost exclusively dependent on PRC. Here we aim to propose an integrative view of the cellular pathways regulated by PRC through integration of cDNA and miRNA microarray data and chromatin immunoprecipitation results obtained from XTC.UC1 cells invalidated for PRC. This study showes that PRC induces a complex network of cellular functions interacting with at least one to five of the studied transcription factors (Estrogen Related Receptor alpha, ERR1; Nuclear-Respiratory Factors, NRF1 and NRF2; cAMP Response Element Binding, CREB; and Ying Yang, YY1). Our data confirm that ERR1 is a key partner of PRC in the regulation of mitochondrial functions and suggest a potential role of this complex in RNA processing. PRC is also involved in transcriptional regulatory complexes targeting 12 miRNAs, five of which are involved in the control of the OXPHOS process. Our findings demonstrate that the PRC coactivator can act in complex with several transcription factors and regulate miRNA expression to control the fine regulation of main metabolic functions in the cell. Therefore, in PGC-1α/β-associated pathologies, PRC, as a metabolic sensor, may ensure mitochondrial homeostasis.