Biomedical subjects

Samuel Granjeaud

Publications and source records attributed to Samuel Granjeaud.

15 recordsLinked to original sources

PubMed2006

MicroArray Facility: a laboratory information management system with extended support for Nylon based technologies.

BACKGROUND: High throughput gene expression profiling (GEP) is becoming a routine technique in life science laboratories. With experimental designs that repeatedly span thousands of genes and hundreds of samples, relying on a dedicated database infrastructure is no longer an option.GEP technology is a fast moving target, with new approaches constantly broadening the field diversity. This technology heterogeneity, compounded by the informatics complexity of GEP databases, means that software developments have so far focused on mainstream techniques, leaving less typical yet established techniques such as Nylon microarrays at best partially supported. RESULTS: MAF (MicroArray Facility) is the laboratory database system we have developed for managing the design, production and hybridization of spotted microarrays. Although it can support the widely used glass microarrays and oligo-chips, MAF was designed with the specific idiosyncrasies of Nylon based microarrays in mind. Notably single channel radioactive probes, microarray stripping and reuse, vector control hybridizations and spike-in controls are all natively supported by the software suite. MicroArray Facility is MIAME supportive and dynamically provides feedback on missing annotations to help users estimate effective MIAME compliance. Genomic data such as clone identifiers and gene symbols are also directly annotated by MAF software using standard public resources. The MAGE-ML data format is implemented for full data export. Journalized database operations (audit tracking), data anonymization, material traceability and user/project level confidentiality policies are also managed by MAF. CONCLUSION: MicroArray Facility is a complete data management system for microarray producers and end-users. Particular care has been devoted to adequately model Nylon based microarrays. The MAF system, developed and implemented in both private and academic environments, has proved a robust solution for shared facilities and industry service providers alike.

Cloning, Molecular↗

PubMed2006

The disparate nature of "intergenic" polyadenylation sites.

The termination of mature eukaryotic mRNAs occurs at specific polyadenylation sites located downstream from stop codons in the 3'-untranslated region (UTR). An accurate delineation of these sites is essential for the study of 3'-UTR-based gene regulation and for the design of pertinent probes for transcriptome analysis. Although typical poly(A) sites are located between 0 and 2 kb from the stop codon, EST sequence analyses have identified sites located at unexpectedly long ranges (5-10 kb) in a number of genes. Here we perform a complete mapping of EST and full-length cDNA sequences on the mouse and human genome to observe putative poly(A) sites extending beyond annotated 3'-ends and into the intergenic regions. We introduce several quality parameters for poly(A) site prediction and train a classification tree to associate P-values to predicted sites. We observe a higher than background level of high-scoring sites up to 12-15 kb past the stop codon, both in human and mouse. This leads to an estimate of about 5000 human genes having unreported 3'-end extensions and about 3500 novel polyadenylated transcripts lying in present "intergenic" regions. These high-scoring, long-range poly(A) sites corresponding to novel transcripts and gene extensions should be incorporated into current human and mouse gene repositories.

3' Untranslated Regions↗

PubMed2005

Gene profiling reveals specific oncogenic mechanisms and signaling pathways in oncocytic and papillary thyroid carcinoma.

The oncogenic pathways in mitochondrial-rich thyroid carcinomas are not clearly understood. To investigate the possible implication of mitochondrial abundance in the genesis of thyroid tumors, we have explored the gene expression profile of six oncocytic carcinomas and six mitochondrial-rich papillary carcinomas using cDNA-microarray technology. A supervised approach allowed us to identify 83 genes differentially expressed in the two types of carcinoma. These genes were classified according to their ontologic profiles. Three genes, NOS3, alpha-actinin-2 and alpha-catenin, suspected of playing a role in tumor genesis, were explored by quantitative RT-PCR analysis and immunohistochemistry. Of the 59 genes overexpressed in papillary carcinomas, 51% were involved in cell communication. Of the 24 genes overexpressed in oncocytic carcinomas, 84% were involved in mitochondrial and cellular metabolism. Our results suggest that mitochondrial respiratory chain complexes III and IV play a significant role in the regulation of reactive oxygen species production by oncocytic tumors.

Actinin↗

PubMed2004

Genomic organization and the tissue distribution of alternatively spliced isoforms of the mouse Spatial gene.

BACKGROUND: The stromal component of the thymic microenvironment is critical for T lymphocyte generation. Thymocyte differentiation involves a cascade of coordinated stromal genes controlling thymocyte survival, lineage commitment and selection. The "Stromal Protein Associated with Thymii And Lymph-node" (Spatial) gene encodes a putative transcription factor which may be involved in T-cell development. In the testis, the Spatial gene is also expressed by round spermatids during spermatogenesis. RESULTS: The Spatial gene maps to the B3-B4 region of murine chromosome 10 corresponding to the human syntenic region 10q22.1. The mouse Spatial genomic DNA is organised into 10 exons and is alternatively spliced to generate two short isoforms (Spatial-alpha and -gamma) and two other long isoforms (Spatial-delta and -epsilon) comprising 5 additional exons on the 3' site. Here, we report the cloning of a new short isoform, Spatial-beta, which differs from other isoforms by an additional alternative exon of 69 bases. This new exon encodes an interesting proline-rich signature that could confer to the 34 kDa Spatial-beta protein a particular function. By quantitative TaqMan RT-PCR, we have shown that the short isoforms are highly expressed in the thymus while the long isoforms are highly expressed in the testis. We further examined the inter-species conservation of Spatial between several mammals and identified that the protein which is rich in proline and positive amino acids, is highly conserved. CONCLUSIONS: The Spatial gene generates at least five alternative spliced variants: three short isoforms (Spatial-alpha, -beta and -gamma) highly expressed in the thymus and two long isoforms (Spatial-delta and -epsilon) highly expressed in the testis. These alternative spliced variants could have a tissue specific function.

Alternative Splicing↗

PubMed2004

Transcriptional profiling reveals coordinated up-regulation of oxidative metabolism genes in thyroid oncocytic tumors.

Oncocytomas are large cell tumors characterized by an abnormal proliferation of mitochondria. To investigate this phenomenon in thyroid oncocytomas, we determined gene expression profiles of 87 samples using microarrays of 6720 PCR products from cDNA clones. Samples included 29 thyroid oncocytomas and six papillary carcinomas, the remainder representing other thyroid pathologies or mitochondria-rich tumor samples, normal thyroid samples, and two thyroid cell lines. Hierarchical clustering and supervised analysis identified two specific oncocytic clusters and 163 distinctly regulated genes between oncocytoma and normal thyroid. Differential expression of five selected genes (APOD, BCL-2, COX, CTSB, and MAP2) was confirmed by immunohistochemistry. The two specific oncocytic clusters were rich in mitochondrial genes and revealed coordinated expression of nuclear and mitochondrial respiratory chain genes. We also observed the up-regulation of genes involved in mitochondrial biogenesis, such as nuclear respiratory factor 1 and the endothelial nitric oxide synthase. Several oxidative metabolism genes were overexpressed in oncocytomas, including those from the tricarboxylic acid cycle (MDH1) and cytosolic glycolysis (GAPD, ENO1, and GPI). On the contrary, the lactate dehydrogenase A gene, involved in anaerobic metabolism, was down-regulated. Our results suggest that, unlike a large number of solid tumors, thyroid oncocytomas produce energy through an aerobic pathway.

Adenoma, Oxyphilic↗

PubMed2003

Small lymphocytic lymphoma, marginal zone B-cell lymphoma, and mantle cell lymphoma exhibit distinct gene-expression profiles allowing molecular diagnosis.

Non-germinal center small B-cell lymphomas represent a heterogeneous group of non-Hodgkin lymphomas, the most frequent histologic subtypes being small lymphocytic lymphoma (SLL), splenic marginal zone B-cell lymphoma (MZL), and mantle cell lymphoma (MCL). In order to identify genomic signatures specific for each disease, we analyzed 128 primary tumors using high-density microarrays. Several clusters of genes significantly discriminated the 3 histologic subtypes. Genes associated with cell adhesion, angiogenesis, and inhibition of apoptosis were up-regulated in SLL. Genes associated with intracellular signaling via the AKT1 pathway were up-regulated in splenic MZL. Genes associated with cell cycle control and multidrug resistance were up-regulated in MCL. Using 44 genes selected within the gene clusters discriminant for the 3 lymphoma subtypes, we generated a class prediction score that allowed us to classify the 3 entities in 96% of the cases, including borderline cases. Whereas specific transcriptional profiles easily distinguished all MZL samples, SLL samples, and most of the MCL samples into separate groups, few MCL cases exhibited MZL-type transcriptional profiles. This study demonstrates that SLL, splenic MZL, and MCL possess specific transcriptional profiles that may be relevant to the pathogenesis and the diagnosis of these histologic subtypes.

Biopsy↗

PubMed2003

The strategy of T cell antigen-presenting cell encounter in antigen-draining lymph nodes revealed by imaging of initial T cell activation.

The development of an immune response critically relies on the encounter of rare antigen (Ag)-specific T cells with dendritic cells (DCs) presenting the relevant Ag. How two rare cells find each other in the midst of irrelevant other cells in lymph nodes (LNs) is unknown. Here we show that initial T cell activation clusters are generated near high endothelial venules (HEVs) in the outer paracortex of draining LNs by retention of Ag-specific T cells as they exit from HEVs. We further show that tissue-derived DCs preferentially home in the vicinity of HEVs, thus defining the site of cluster generation. At this location DCs efficiently scan all incoming T cells and selectively retain those specific for the major histocompatibility complex-peptide complexes the DCs present. Such strategic positioning of DCs on the entry route of T cells into the paracortex may foster T cell-DC encounter and thus optimize initial T cell activation in vivo.

Animals↗

PubMed2003

Gene expression profiling of multiple myeloma reveals molecular portraits in relation to the pathogenesis of the disease.

Although multiple myeloma (MM) is a unique entity, a marked heterogeneity is actually observed among the patients, which has been first related to immunoglobulin (Ig) types and light chain subtypes and more recently to chromosomal abnormalities. To further investigate this genetic heterogeneity, we analyzed gene expression profiles of 92 primary tumors according to their Ig types and light chain subtypes with DNA microarrays. Several clusters of genes involved in various biologic functions such as immune response, cell cycle control, signaling, apoptosis, cell adhesion, and structure significantly discriminated IgA- from IgG-MM. Genes associated with inhibition of differentiation and apoptosis induction were up-regulated while genes associated with immune response, cell cycle control, and apoptosis were down-regulated in IgA-MM. According to the expression of the 61 most discriminating genes, BJ-MM represented a separate subgroup that did not express either the genes characteristic of IgG-MM or those of IgA-MM at a high level. This suggests that transcriptional programs associated to the switch could be maintained up to plasma cell differentiation. Several genes whose products are known to stimulate bone remodeling discriminate between kappa- and lambda-MM. One of these genes, Mip-1alpha, was overexpressed in the kappa subgroup. In addition, we established a strong association (P =.0001) between kappa subgroup expressing high levels of Mip-1alpha and active myeloma bone disease. This study shows that DNA microarrays enable us to perform a molecular dissection of the bioclinical diversity of MM and provide new molecular tools to investigate the pathogenesis of malignant plasma cells.

Adult↗

PubMed2003

Overexpression of dominant-negative Ikaros 6 protein is restricted to a subset of B common adult acute lymphoblastic leukemias that express high levels of the CD34 antigen.

Ikaros is a critical regulator of hematopoiesis. Its effects result in part from the balance between the isoforms that are produced by differential splicing of the pre-mRNA. Short isoforms that lack the DNA-binding domain act as dominant negatives by binding long isoforms through the C-terminal zinc-finger domain, which allows for the homo- or heterodimerization of the proteins. There are a number of evidences that different subsets of murine hematopoietic progenitors - as defined by phenotype - have different patterns of Ikaros expression. Forced expression of short isoforms (Ik5, Ik6 or Ik7) in murine or human hematopoietic progenitors alters the differentiation capacities of these cells. Human leukemias provide additional information: because of the blockade in differentiation, leukemias represent an equivalent of a particular stage of human hematopoietic hierarchy. We and others have shown that human acute leukemias are heterogeneous for the pattern of Ikaros isoform expression. The present study focused on adult de novo B ALLs and the Ikaros 6 isoform. ProB (BI, n=3), common B (BII, n=15) and preB (BIII, n=3) ALL were identified by their phenotype. RT-PCR and Western blot analyses of blast cell protein lysates suggest that approximately 50% of BII leukemias overexpress Ikaros 6 RNA and protein. Comparison of BII cells with high or normal levels of Ik6 shows a higher level of expression for the membrane stem cell antigen CD34 in the former, as detected with flow cytometry and confirmed with DNA arrays.

Adolescent↗

PubMed2002

Expression profiling in mouse fetal thymus reveals clusters of coordinately expressed genes that mark individual stages of T-cell ontogeny.

To search for genes that participate in regulatory networks sustaining mouse embryonic T-cell development, we have performed expression profiling using nylon macroarrays. Labeled samples representative of individual developmental stages were utilized, taking advantage of cell homogeneity during early thymus ontogeny. cDNAs revealing differential expression were further selected using labeled samples derived from lymphoid versus non-lymphoid tissues, and from mutant thymi exhibiting T-cell developmental defects. We thus identified clusters of coexpressed genes during T-cell embryogenesis and characterized their sequences through bioinformatics. We compare our results with those from other profiling analyses in the immune system, and discuss their implications for the definition of genes whose products are involved in T-cell development.

Animals↗

PubMed2002

Inducible antibacterial defense system in C. elegans.

The term innate immunity refers to a number of evolutionary ancient mechanisms that serve to defend animals and plants against infection. Genetically tractable model organisms, especially Drosophila, have contributed greatly to advances in our understanding of mammalian innate immunity. Essentially, nothing is known about immune responses in the nematode Caenorhabditis elegans. Using high-density cDNA microarrays, we show here that infection of C. elegans by the Gram-negative bacterium Serratia marcescens provokes a marked upregulation of the expression of many genes. Among the most robustly induced are genes encoding lectins and lysozymes, known to be involved in immune responses in other organisms. Certain infection-inducible genes are under the control of the DBL-1/TGFbeta pathway. We found that dbl-1 mutants exhibit increased susceptibility to infection. Conversely, overexpression of the lysozyme gene lys-1 augments the resistance of C. elegans to S. marcescens. These results constitute the first demonstration of inducible antibacterial defenses in C. elegans and open new avenues for the investigation of evolutionary conserved mechanisms of innate immunity.

Animals↗

PubMed2002

Gene expression profiling defines molecular subtypes of classical Hodgkin's disease.

Although the prognosis of Hodgkin's disease is relatively good, around 20% of patients do not benefit from current therapies and succumb to their disease. A large-scale molecular characterization of disease might help improve HD management. Using cDNA arrays, we studied the mRNA expression levels of approximately 1000 selected genes in 34 benign and malignant lymphoid samples including 21 classical Hodgkin's disease (HD) tissue samples. Hierarchical clustering identified three main molecular groups of HD tumours relevant with respect to histology and clinical outcome (response to therapy and survival). Samples from all bad outcome HD (BOHD) patients clustered in one group whereas the two other groups contained most good outcome HD (GOHD) cases. The nodular sclerosis GOHD samples overexpressed genes involved in apoptotic induction and cell signalling, including cytokines, while the BOHD samples were characterized by the upregulation of genes involved in fibroblast activation, angiogenesis, extracellular matrix remodelling, cell proliferation, and the downregulation of tumour suppressor genes. Our results establish a molecular taxonomy of HD correlating with response to therapy and clinical outcome, thereby suggesting the possibility of improving the current prognostic classification.

Apoptosis↗

PubMed2002

Gene expression profiles of poor-prognosis primary breast cancer correlate with survival.

The extensive heterogeneity of breast cancer complicates the precise assessment of tumour aggressiveness, making therapeutic decisions difficult and treatments inappropriate in some cases. Consequently, the long-term metastasis-free survival rate of patients receiving adjuvant chemotherapy is only 60%. There is a genuine need to identify parameters that might accurately predict the effectiveness of this treatment for each patient. Using cDNA arrays, we profiled tumour samples from 55 women with poor-prognosis breast cancer treated with adjuvant anthracycline-based chemotherapy. Gene expression monitoring was applied to a set of about 1000 candidate cancer genes. Differences in expression profiles provided molecular evidence of the clinical heterogeneity of disease. First, we confirmed the capacity of a 23-gene predictor set, identified in a previous study, to distinguish between tumours associated with different survival. Second, using a refined gene set derived from the previous one, we distinguished, among the 55 clinically homogeneous tumours, three classes with significantly different clinical outcome: 5-year overall survival and metastasis-free survival rates were respectively 100% and 75% in the first class, 65% and 56% in the second and 40% and 20% in the third. This discrimination resulted from the differential expression of two clusters of genes encoding proteins with diverse functions, including the estrogen receptor (ER). Another finding was the identification of two ER-positive tumour subgroups with different survival. These results indicate that gene expression profiling can predict clinical outcome and lead to a more precise classification of breast tumours. Furthermore, the characterization of discriminator genes might accelerate the development of new specific and alternative therapies, allowing more rationally tailored treatments that are potentially more efficient and less toxic.

Breast Neoplasms↗

PubMed2002

Prognosis of breast cancer and gene expression profiling using DNA arrays.

Breast cancer is a complex genetic disease characterized by the accumulation of multiple molecular alterations. The resulting clinical heterogeneity makes current therapeutic strategies-based on clinicopathlogical factors-less than perfectly adapted to each patient. Today, DNA arrays, by allowing the simultaneous and quantitative analysis of the mRNA expression levels of thousands of genes in a single assay, provide novel tools to tackle this complexity. Potential applications are multiple in the cancer field and the first research results are promising. Using home-made DNA arrays in an approach easily compatible with academic research-nylon support and radioactive detection-we identified a predictor set of 23 genes whose expression patterns differentiated two groups of breast cancer patients with different survival after adjuvant chemotherapy. We then validated and further extended these results in a larger, independent and homogeneous series of poor prognosis primary breast cancers treated with adjuvant anthracyclin-based chemotherapy. We confirmed the prognostic classification provided by the 23-gene set predictor. We then improved the predictor set and refined the classification by sorting the tumors into three classes with significantly different long-term survival. These results show the potential of the technology with an accessible approach for academic research teams. We also showed that nylon DNA arrays with radioactive detection are associated with excellent sensitivity, an advantage in clinical situations where the amount of available material is limited.

Breast Neoplasms↗

PubMedDate not supplied

Gene expression profiling of breast carcinomas using nylon DNA arrays.

Clinically very heterogeneous, breast cancer prognosis and treatment response are difficult to predict with the current prognostic histoclinical parameters. Mammary oncogenesis remains poorly understood. DNA array technology allows the simultaneous analysis of the mRNA expression levels of thousands of genes in biological samples. Applied to breast tumours, expression profiles will boost our knowledge of oncogenesis, will offer new potential therapeutic targets and new prognostic and predictive markers. Today, the most accessible approach for academic research teams is that of Nylon DNA arrays with radioactive detection, which in addition allows profiling of small clinical samples.

Breast Neoplasms↗