The Atlas of Genetics and Cytogenetics in Oncology and Haematology (http://AtlasGeneticsOncology.org) is a peer-reviewed internet journal/encyclopaedia/database focused on genes implicated in cancer, cytogenetics and clinical entities in cancer and cancer-prone hereditary diseases. The main goal of the Atlas is to provide review articles that describe complementary topics, namely, genes, genetic abnormalities, histopathology, clinical diagnoses and a large iconography. This description, which was historically based on karyotypic abnormalities and in situ hybridization (fluorescence in situ hybridization) techniques, now benefits from comparative genomic hybridization and massive sequencing, uncovering a tremendous amount of genetic rearrangements. As the Atlas combines different types of information (genes, genetic abnormalities, histopathology, clinical diagnoses and external links), its content is currently unique. The Atlas is a cognitive tool for fundamental and clinical research and has developed into an encyclopaedic work. In clinical practice, it contributes to the cytogenetic diagnosis and may guide treatment decision making, particularly regarding rare diseases (because they are numerous and are frequently encountered). Readers as well as the authors of the Atlas are researchers and/or clinicians.
Neither the molecular mechanisms whereby cancer cells intrinsically are or become resistant to the DNA-damaging agent cisplatin nor the signaling pathways that account for cisplatin cytotoxicity have thus far been characterized in detail. In an attempt to gain further insights into the molecular cascades elicited by cisplatin (leading to resistance or underpinning its antineoplastic properties), we comparatively investigated the ability of cisplatin, C2-ceramide and cadmium dichloride, alone or in the presence of an array of mitochondrion-protective agents, to trigger the permeabilization of purified mitochondria. In addition, we compared the transcriptional response triggered by cisplatin, C2-ceramide and cadmium dichloride in non-small cell lung carcinoma A549 cells. Finally, we assessed the capacity of cisplatin, C2-ceramide and cadmium dichloride to reduce the clonogenic potential of a battery of yeast strains lacking proteins involved in the regulation of cell death, DNA damage signaling and stress management. This multipronged experimental approach revealed that cisplatin elicits signaling pathways that are for the most part “private,” i.e., that manifest limited overlap with the molecular cascades ignited by other inducers of mitochondrial apoptosis, and triggers apoptosis mainly in a transcription-independent fashion. Indeed, bona fide cisplatin-response modifiers that we have recently identified by a functional genome-wide siRNA screen are either not transcriptionally regulated during cisplatin-induced cell death or their transcriptional modulation reflects the activation of an adaptive response promoting cisplatin resistance
N-acetyl-cysteine; autophagy; bongkrekic acid; cyclosporine A; glutathione; large-amplitude swelling
Gene-set enrichment analyses (GEA or GSEA) are commonly used for biological characterization of an experimental gene-set. This is done by finding known functional categories, such as pathways or Gene Ontology terms, that are over-represented in the experimental set; the assessment is based on an overlap statistic. Rich biological information in terms of gene interaction network is now widely available, but this topological information is not used by GEA, so there is a need for methods that exploit this type of information in high-throughput data analysis.
We developed a method of network enrichment analysis (NEA) that extends the overlap statistic in GEA to network links between genes in the experimental set and those in the functional categories. For the crucial step in statistical inference, we developed a fast network randomization algorithm in order to obtain the distribution of any network statistic under the null hypothesis of no association between an experimental gene-set and a functional category. We illustrate the NEA method using gene and protein expression data from a lung cancer study.
The results indicate that the NEA method is more powerful than the traditional GEA, primarily because the relationships between gene sets were more strongly captured by network connectivity rather than by simple overlaps.
Diffuse intrinsic pontine glioma (DIPG) is one of the most frequent malignant pediatric brain tumor and its prognosis is universaly fatal. No significant improvement has been made in last thirty years over the standard treatment with radiotherapy. To address the paucity of understanding of DIPGs, we have carried out integrated molecular profiling of a large series of samples obtained with stereotactic biopsy at diagnosis. While chromosomal imbalances did not distinguish DIPG and supratentorial tumors on CGHarrays, gene expression profiling revealed clear differences between them, with brainstem gliomas resembling midline/thalamic tumours, indicating a closely-related origin. Two distinct subgroups of DIPG were identified. The first subgroup displayed mesenchymal and pro-angiogenic characteristics, with stem cell markers enrichment consistent with the possibility to grow tumor stem cells from these biopsies. The other subgroup displayed oligodendroglial features, and appeared largely driven by PDGFRA, in particular through amplification and/or novel missense mutations in the extracellular domain. Patients in this later group had a significantly worse outcome with an hazard ratio for early deaths, ie before 10 months, 8 fold greater that the ones in the other subgroup (p = 0.041, Cox regression model). The worse outcome of patients with the oligodendroglial type of tumors was confirmed on a series of 55 paraffin-embedded biopsy samples at diagnosis (median OS of 7.73 versus 12.37 months, p = 0.045, log-rank test). Two distinct transcriptional subclasses of DIPG with specific genomic alterations can be defined at diagnosis by oligodendroglial differentiation or mesenchymal transition, respectively. Classifying these tumors by signal transduction pathway activation and by mutation in pathway member genes may be particularily valuable for the development of targeted therapies.
Eleven samples of DNA from choriocarcinomas were studied by high resolution CGH-array 244 K. They were studied after histopathological confirmation of the diagnosis, of the androgenic etiology and after a microsatellite marker analysis confirming the absence of contamination of tumor DNA from maternal DNA. Three cell lines, BeWo, JAR, JEG were also studied by this high resolution pangenomic technique. According to aCGH analysis, the de novo choriocarcinomas exhibited simple chromosomal rearrangements or normal profiles. The cell lines showed various and complex chromosomal aberrations. 23 Minimal Critical Regions were defined that allowed us to list the genes that were potentially implicated. Among them, unusually high numbers of microRNA clusters and imprinted genes were observed.
Gliomas, the most frequent primitive CNS tumors, have been suggested to originate from astrocytes or from neural progenitors/stem cells. However, the precise identity of the cells at the origin of gliomas remains a matter of debate because no pre-neoplastic state has been yet identified. TGFα, an EGF family member, is frequently over-expressed in the early stages of glioma progression. We previously demonstrated that prolonged exposure of astrocytes to TGFα is sufficient to trigger their reversion to a neural progenitor-like state. To determine whether TGFα de-differentiating effects are associated with cancerous transforming effects, we grafted intra-cerebrally de-differentiated astrocytes. We show that these cells had the same cytogenomic profile as astrocytes, survived in vivo and did not give birth to tumors. When astrocytes de-differentiated with TGFα were submitted to oncogenic stress using gamma irradiation, they acquired cancerous properties: they were immortalized, showed cytogenomic abnormalities, and formed high-grade glioma-like tumors after brain grafting. In contrast, irradiation did not modify the lifespan of astrocytes cultivated in serum-free medium. Addition of TGFα after irradiation did not promote their transformation but decreased their lifespan. These results demonstrate that reversion of mature astrocytes to an embryonic state without genomic manipulation is sufficient to sensitize them to oncogenic stress.
Animals; Astrocytes; drug effects; metabolism; radiation effects; Brain Neoplasms; chemically induced; physiopathology; Cell Dedifferentiation; drug effects; physiology; radiation effects; Cell Transformation, Neoplastic; chemically induced; metabolism; radiation effects; Cells, Cultured; Culture Media, Serum-Free; pharmacology; Gamma Rays; adverse effects; Glioma; chemically induced; physiopathology; Mice; Mice, Inbred C57BL; Mice, Nude; Stem Cell Transplantation; Stem Cells; drug effects; metabolism; radiation effects; Stress, Physiological; physiology; radiation effects; Transforming Growth Factor alpha; metabolism; pharmacology; EGF; transdifferentiation; metaplasia; radial glia; erbB
Therapy-related acute leukemia (t-AML), is a severe complication of cytotoxic therapy used for primary cancer treatment. The outcome of these patients is poor, compared to people who develop de novo acute leukemia (p-AML). Cytogenetic abnormalities in t-AML are similar to those found in p-AML but present more frequent unfavorable karyotypes depending on the inducting agent. Losses of chromosome 5 or 7 are observed after alkylating agents while balanced translocations are found after topoisomerase II inhibitors. This study compared t-AML to p-AML using high resolution array CGH in order to find copy number abnormalities (CNA) at a higher resolution than conventional cytogenetics. More CNAs were observed in 30 t-AML than in 36 p-AML: 104 CNAs were observed with 63 losses and 41 gains (mean number 3.46 per case) in t-AML, while in p-AML, 69 CNAs were observed with 32 losses and 37 gains (mean number of 1.9 per case). In primary leukemia with a previously “normal” karyotype, 18% exhibited a previously undetected CNA, whereas in the (few) t-AML with a normal karyotype, the rate was 50%. Several minimal critical regions (MCRs) were found in t-AML and p-AML. No common MCRs were found in the two groups. In t-AML a 40kb deleted MCR pointed to RUNX1 on 21q22, a gene coding for a transcription factor implicated in frequent rearrangements in leukemia and in familial thrombocytopenia. In de novo AML, a 1Mb MCR harboring ERG and ETS2 was observed from patients with complex aCGH profiles. High resolution cytogenomics obtained by aCGH and similar techniques already published allowed us to characterize numerous non random chromosome abnormalities. This work supports the hypothesis that they can be classified into several categories: abnormalities common to all AML; those more frequently found in t-AML and those specifically found in p-AML.
Lung cancer in never smokers would rank as the seventh most common cause of cancer death worldwide.
Methods and Findings
We performed high-resolution array comparative genomic hybridization analysis of lung adenocarcinoma in sixty never smokers and identified fourteen new minimal common regions (MCR) of gain or loss, of which five contained a single gene (MOCS2, NSUN3, KHDRBS2, SNTG1 and ST18). One larger MCR of gain contained NSD1. One focal amplification and nine gains contained FUS. NSD1 and FUS are oncogenes hitherto not known to be associated with lung cancer. FISH showed that the amplicon containing FUS was joined to the next telomeric amplicon at 16p11.2. FUS was over-expressed in 10 tumors with gain of 16p11.2 compared to 30 tumors without that gain. Other cancer genes present in aberrations included ARNT, BCL9, CDK4, CDKN2B, EGFR, ERBB2, MDM2, MDM4, MET, MYC and KRAS. Unsupervised hierarchical clustering with adjustment for false-discovery rate revealed clusters differing by the level and pattern of aberrations and displaying particular tumor characteristics. One cluster was strongly associated with gain of MYC. Another cluster was characterized by extensive losses containing tumor suppressor genes of which RB1 and WRN. Tumors in that cluster frequently harbored a central scar-like fibrosis. A third cluster was associated with gains on 7p and 7q, containing ETV1 and BRAF, and displayed the highest rate of EGFR mutations. SNP array analysis validated copy-number aberrations and revealed that RB1 and WRN were altered by recurrent copy-neutral loss of heterozygosity.
The present study has uncovered new aberrations containing cancer genes. The oncogene FUS is a candidate gene in the 16p region that is frequently gained in never smokers. Multiple genetic pathways defined by gains of MYC, deletions of RB1 and WRN or gains on 7p and 7q are involved in lung adenocarcinoma in never smokers.
Benign infantile convulsions and paroxysmal dyskinesia are episodic cerebral disorders that can share common genetic bases. They can be co-inherited as one single autosomal dominant trait (ICCA syndrome); the disease ICCA gene maps at chromosome 16p12-q12. Despite intensive and conventional mutation screening, the ICCA gene remains unknown to date. The critical area displays highly complicated genomic architecture and is the site of deletions and duplications associated with various diseases. The possibility that the ICCA syndrome is related to the existence of large-scale genomic alterations was addressed in the present study.
A combination of whole genome and dedicated oligonucleotide array comparative genomic hybridization coupled with quantitative polymerase chain reaction was used. Low copy number of a region corresponding to a genomic variant (Variation_7105) located at 16p11 nearby the centromere was detected with statistical significance at much higher frequency in patients from ICCA families than in ethnically matched controls. The genomic variant showed no apparent difference in size and copy number between patients and controls, making it very unlikely that the genomic alteration detected here is ICCA-specific. Furthermore, no other genomic alteration that would directly cause the ICCA syndrome in those nine families was detected in the ICCA critical area.
Our data excluded that inherited genomic deletion or duplication events directly cause the ICCA syndrome; rather, they help narrowing down the critical ICCA region dramatically and indicate that the disease ICCA genetic defect lies very close to or within Variation_7105 and hence should now be searched in the corresponding genomic area and its surrounding regions.
Differentiating agents have been proposed to overcome the impaired cellular differentiation in acute myeloid leukemia (AML). However, only the combinations of all-trans retinoic acid or arsenic trioxide with chemotherapy have been successful, and only in treating acute promyelocytic leukemia (also called AML3). We show that iron homeostasis is an effective target in the treatment of AML. Iron chelating therapy induces the differentiation of leukemia blasts and normal bone marrow precursors into monocytes/macrophages in a manner involving modulation of reactive oxygen species expression and the activation of mitogen-activated protein kinases (MAPKs). 30% of the genes most strongly induced by iron deprivation are also targeted by vitamin D3 (VD), a well known differentiating agent. Iron chelating agents induce expression and phosphorylation of the VD receptor (VDR), and iron deprivation and VD act synergistically. VD magnifies activation of MAPK JNK and the induction of VDR target genes. When used to treat one AML patient refractory to chemotherapy, the combination of iron-chelating agents and VD resulted in reversal of pancytopenia and in blast differentiation. We propose that iron availability modulates myeloid cell commitment and that targeting this cellular differentiation pathway together with conventional differentiating agents provides new therapeutic modalities for AML.
Children with ependymoma may experience a relapse in up to 50% of cases depending on the extent of resection. Key biological events associated with recurrence are unknown.
To discover the biology behind the recurrence of ependymomas, we performed CGHarray and a dual-color gene expression microarray analysis of 17 tumors at diagnosis co-hybridized with the corresponding 27 first or subsequent relapses from the same patient. As treatment and location had only limited influence on specific gene expression changes at relapse, we established a common signature for relapse. Eighty-seven genes showed an absolute fold change ≥2 in at least 50% of relapses and were defined as the gene expression signature of ependymoma recurrence. The most frequently upregulated genes are involved in the kinetochore (ASPM, KIF11) or in neural development (CD133, Wnt and Notch pathways). Metallothionein (MT) genes were downregulated in up to 80% of the recurrences. Quantitative PCR for ASPM, KIF11 and MT3 plus immunohistochemistry for ASPM and MT3 confirmed the microarray results. Immunohistochemistry on an independent series of 24 tumor pairs at diagnosis and at relapse confirmed the decrease of MT3 expression at recurrence in 17/24 tumor pairs (p = 0.002). Conversely, ASPM expression was more frequently positive at relapse (87.5% vs 37.5%, p = 0.03). Loss or deletion of the MT genes cluster was never observed at relapse. Promoter sequencing after bisulfite treatment of DNA from primary tumors and recurrences as well as treatment of short-term ependymoma cells cultures with a demethylating agent showed that methylation was not involved in MT3 downregulation. However, in vitro treatment with a histone deacetylase inhibitor or zinc restored MT3 expression.
The most frequent molecular events associated with ependymoma recurrence were over-expression of kinetochore proteins and down-regulation of metallothioneins. Metallothionein-3 expression is epigenetically controlled and can be restored in vitro by histone deacetylase inhibitors.
Additional chromosomal abnormalities are currently detected in Burkitt's lymphoma. They play major roles in the progression of BL and in prognosis. The genes involved remain elusive. A whole-genome oligonucleotide array CGH analysis correlated with karyotype and FISH was performed in a set of 27 Burkitt's lymphoma-derived cell lines and primary tumors. More than half of the 145 CNAs<2 Mb were mapped to Mendelian CNVs, including GSTT1, glutathione s-transferase and BIRC6, an anti-apoptotic protein, possibly predisposing to some cancers. Somatic cell line-specific CNVs localized to the IG locus were consistently observed with the 244 K aCGH platform. Among 136 CNAs >2 Mb, gains were found in 1q (12/27), 13q (7/27), 7q (6/27), 8q(4/27), 2p (3/27), 11q (2/27) and 15q (2/27). Losses were found in 3p (5/27), 4p (4/27), 4q (4/27), 9p (4/27), 13q (4/27), 6p (3/27), 17p (3/27), 6q (2/27),11pterp13 (2/27) and 14q12q21.3 (2/27). Twenty one minimal critical regions (MCR), (range 0.04–71.36 Mb), were delineated in tumors and cell lines. Three MCRs were localized to 1q. The proximal one was mapped to 1q21.1q25.2 with a 6.3 Mb amplicon (1q21.1q21.3) harboring BCA2 and PIAS3. In the other 2 MCRs, 1q32.1 and 1q44, MDM4 and AKT3 appeared as possible drivers of these gains respectively. The 13q31.3q32.1 <89.58–96.81> MCR contained an amplicon and ABCC4 might be the driver of this amplicon. The 40 Kb 2p16.1 <60.96–61> MCR was the smallest gained MCR and specifically encompassed the REL oncogene which is already implicated in B cell lymphomas. The most frequently deleted MCR was 3p14.1 <60.43–60.53> that removed the fifth exon of FHIT. Further investigations which combined gene expression and functional studies are essential to understand the lymphomagenesis mechanism and for the development of more effective, targeted therapeutic strategies.
Lung cancer with EGFR mutation was shown to be a specific clinical entity. In order to better understand the biology behind this disease we used a genome wide characterization of loss of heterozygosity and amplification by Single Nucleotide Polymorphism (SNP) Array analysis to point out chromosome segments linked to EGFR mutations. To do so, we compared genetic profiles between EGFR mutated adenocarcinomas (ADC) and KRAS mutated ADC from 24 women with localized lung cancer.
Patterns of alterations were different between EGFR and KRAS mutated tumors and specific chromosomes alterations were linked to the EGFR mutated group. Indeed chromosome regions 14q21.3 (p = 0.027), 7p21.3-p21.2 (p = 0.032), 7p21.3 (p = 0.042) and 7p21.2-7p15.3 (p = 0.043) were found significantly amplified in EGFR mutated tumors. Within those regions 3 genes are of special interest ITGB8, HDAC9 and TWIST1. Moreover, homozygous deletions at CDKN2A and LOH at RB1 were identified in EGFR mutated tumors. We therefore tested the existence of a link between EGFR mutation, CDKN2A homozygous deletion and cyclin amplification in a larger series of tumors. Indeed, in a series of non-small-cell lung carcinoma (n = 98) we showed that homozygous deletions at CDKN2A were linked to EGFR mutations and absence of smoking whereas cyclin amplifications (CCNE1 and CCND1) were associated to TP53 mutations and smoking habit.
All together, our results show that genome wide patterns of alteration differ between EGFR and KRAS mutated lung ADC, describe two models of oncogenic cooperation involving either EGFR mutation and CDKN2A deletion or cyclin amplification and TP53 inactivating mutations and identified new chromosome regions at 7p and 14q associated to EGFR mutations in lung cancer.
Tetraploidy constitutes an adaptation to stress and an intermediate step between euploidy and aneuploidy in oncogenesis. Tetraploid cells are particularly resistant against genotoxic stress including radiotherapy and chemotherapy. Here, we designed a strategy to preferentially kill tetraploid tumor cells. Depletion of checkpoint kinase-1 (Chk1) by siRNAs, transfection with dominant-negative Chk1 mutants or pharmacological Chk1 inhibition killed tetraploid colon cancer cells yet had minor effects on their diploid counterparts. Chk1 inhibition abolished the spindle assembly checkpoint and caused premature and abnormal mitoses that led to p53 activation and cell death at a higher frequency in tetraploid than in diploid cells. Similarly, abolition of the spindle checkpoint by knockdown of Bub1, BubR1 or Mad2 induced p53-dependent apoptosis of tetraploid cells. Chk1 inhibition reversed the cisplatin resistance of tetraploid cells in vitro and in vivo, in xenografted human cancers. Chk1 inhibition activated p53-regulated transcripts including Puma/BBC3 in tetraploid but not in diploid tumor cells. Altogether, our results demonstrate that, in tetraploid tumor cells, the inhibition of Chk1 sequentially triggers aberrant mitosis, p53 activation and Puma/BBC3-dependent mitochondrial apoptosis.
Two collections of oligonucleotides have been designed for preparing pangenomic human and mouse microarrays. A total of 148 993 and 121 703 oligonucleotides were designed against human and mouse transcripts. Quality scores were created in order to select 25 342 human and 24 109 mouse oligonucleotides. They correspond to: (i) a BLAST-specificity score; (ii) the number of expressed sequence tags matching each probe; (iii) the distance to the 3′ end of the target mRNA. Scores were also used to compare in silico the two microarrays with commercial microarrays. The sets described here, called RNG/MRC collections, appear at least as specific and sensitive as those from the commercial platforms. The RNG/MRC collections have now been used by an Anglo-French consortium to distribute more than 3500 microarrays to the academic community. Ad hoc identification of tissue-specific transcripts and a ∼80% correlation with hybridizations performed on Affymetrix GeneChip™ suggest that the RNG/MRC microarrays perform well. This work provides a comprehensive open resource for investigators working on human and mouse transcriptomes, as well as a generic method to generate new microarray collections in other organisms. All information related to these probes, as well as additional information about commercial microarrays have been stored in a freely-accessible database called MEDIANTE.
We compared the relative precision and accuracy of expression measurements obtained from three different state-of-the-art commercial short and long-oligonucleotide microarray platforms (Affymetrix GeneChip™, GE Healthcare CodeLink™ and Agilent Technologies). The design of the comparison was chosen to judge each platform in the context of a multi-project program.
All wet-lab experiments and raw data acquisitions were performed independently by each commercial platform. Intra-platform reproducibility was assessed using measurements from all available targets. Inter-platform comparisons of relative signal intensities were based on a common and non-redundant set of roughly 3,400 targets chosen for their unique correspondence toward a single transcript. Despite many examples of strong similarities we found several areas of discrepancy between the different platforms.
We found a higher level of reproducibility from one-color based microarrays (Affymetrix and CodeLink) compared to the two-color arrays from Agilent. Overall, Affymetrix data had a slightly higher level of concordance with sample-matched real-time quantitative reverse-transcriptase polymerase chain reaction (QRT-PCR) data particularly for detecting small changes in gene expression levels.
Mammalian cells were observed to die under conditions in which nutrients were depleted and, simultaneously, macroautophagy was inhibited either genetically (by a small interfering RNA targeting Atg5, Atg6/Beclin 1-1, Atg10, or Atg12) or pharmacologically (by 3-methyladenine, hydroxychloroquine, bafilomycin A1, or monensin). Cell death occurred through apoptosis (type 1 cell death), since it was reduced by stabilization of mitochondrial membranes (with Bcl-2 or vMIA, a cytomegalovirus-derived gene) or by caspase inhibition. Under conditions in which the fusion between lysosomes and autophagosomes was inhibited, the formation of autophagic vacuoles was enhanced at a preapoptotic stage, as indicated by accumulation of LC3-II protein, ultrastructural studies, and an increase in the acidic vacuolar compartment. Cells exhibiting a morphology reminiscent of (autophagic) type 2 cell death, however, recovered, and only cells with a disrupted mitochondrial transmembrane potential were beyond the point of no return and inexorably died even under optimal culture conditions. All together, these data indicate that autophagy may be cytoprotective, at least under conditions of nutrient depletion, and point to an important cross talk between type 1 and type 2 cell death pathways.
The ‘Atlas of Genetics and Cytogenetics in Oncology and Haematology’ (http://www.infobiogen.fr/services/chromcancer) contains concise and updated cards on genes involved in cancer, cytogenetics and clinical entities in oncology, and cancer-prone diseases, a portal towards genetics/cancer, and teaching materials in genetics. This database is made for and by researchers and clinicians, who are encouraged to contribute. The Atlas is part of the genome project and it participates in research on cancer epidemiology.
Neisseria meningitidis colonizes the nasopharynx and, unlike commensal Neisseria species, is capable of entering the bloodstream, crossing the blood-brain barrier, and invading the meninges. The other pathogenic Neisseria species, Neisseria gonorrhoeae, generally causes an infection which is localized to the genitourinary tract. In order to investigate the genetic basis of this difference in disease profiles, we used a strategy of genomic comparison. We used DNA arrays to compare the genome of N. meningitidis with those of N. gonorrhoeae and Neisseria lactamica, a commensal of the nasopharynx. We thus identified sequences conserved among a representative set of virulent strains which are either specific to N. meningitidis or shared with N. gonorrhoeae but absent from N. lactamica. Though these bacteria express dramatically different pathogenicities, these meningococcal sequences were limited and, in contrast to what has been found in other pathogenic bacterial species, they are not organized in large chromosomal islands.
We report a random survey of 1 to 2% of the somatic genome of the free-living ciliate Paramecium tetraurelia by single-run sequencing of the ends of plasmid inserts. As in all ciliates, the germ line genome of Paramecium (100 to 200 Mb) is reproducibly rearranged at each sexual cycle to produce a somatic genome of expressed or potentially expressed genes, stripped of repeated sequences, transposons, and AT-rich unique sequence elements limited to the germ line. We found the somatic genome to be compact (>68% coding, estimated from the sequence of several complete library inserts) and to feature uniformly small introns (18 to 35 nucleotides). This facilitated gene discovery: 722 open reading frames (ORFs) were identified by similarity with known proteins, and 119 novel ORFs were tentatively identified by internal comparison of the data set. We determined the phylogenetic position of Paramecium with respect to eukaryotes whose genomes have been sequenced by the distance matrix neighbor-joining method by using random combined protein data from the project. The unrooted tree obtained is very robust and in excellent agreement with accepted topology, providing strong support for the quality and consistency of the data set. Our study demonstrates that a random survey of the somatic genome of Paramecium is a good strategy for gene discovery in this organism.
Phylogenetic analyses of retroviral elements, including endogenous retroviruses, have relied essentially on the retroviral pol gene expressing the highly conserved reverse transcriptase. This enzyme is essential for the life cycle of all retroid elements, but other genes are also endowed with conserved essential functions. Among them, the transmembrane (TM) subunit of the envelope gene is involved in virus entry through membrane fusion. It has also been reported to contain a domain, named the immunosuppressive domain, that has immunosuppressive properties most probably essential for virus spread within the host. This domain is conserved among a large series of retroviral elements, and we have therefore attempted to generate phylogenetic links between retroviral elements identified from databases following tentative alignments of the immunosuppressive domain and adjacent sequences. This allowed us to unravel a conserved organization among TM domains, also found in the Ebola and Marburg filoviruses, and to identify a large number of human endogenous retroviruses (HERVs) from sequence databases. The latter elements are part of previously identified families of HERVs, and some of them define new families. A general phylogenetic analysis based on the TM proteins of retroelements, and including those with no clearly identified immunosuppressive domain, could then be derived and compared with pol-based phylogenetic trees, providing a comprehensive survey of retroelements and definitive evidence for recombination events in the generation of both the endogenous and the present-day infectious retroviruses.
The ‘Atlas of Genetics and Cytogenetics in Oncology and
Haematology’ (http://www.infobiogen.fr/services/chromcancer) is
an Internet database aimed at genes involved in cancer, cytogenetics
and clinical entities in cancer, and cancer-prone diseases. It presents information
in concise and updated reviews (cards) or longer texts (deep insights),
a (new) case report section, a huge portal towards genetics and/or cancer
databases, and teaching items in genetics for students in medicine
and the sciences. This database is made for and by clinicians and
researchers in the above-mentioned fields, who are encouraged to contribute.
It deals with cancer research, genomics and cytogenomics. It is
at the crossroads of research, post-university teaching and telemedicine. The
Atlas is available at no cost.
The ‘Atlas of Genetics and Cytogenetics in Oncology and Haematology’ (http://www.infobiogen.fr/services/ chromcancer ) is a database devoted to chromosome abnormalities in cancer, cancer-prone diseases and genes involved in cancer. Information presented in each page is concise and updated. This database is made for and by: cytogeneticists, molecular biologists, clinicians in oncology and in haematology, and pathologists, who are encouraged to contribute.