Identification et impacts des anomalies génétiques dans la genèse, l'évolution clinique et le traitement des gliomes

Human gliomas represent the most common primary brain tumours in adults. According to World Health Organization classification, gliomas are divided into astrocytomas with four grades (I, II, III, and IV), oligodendrogliomas with two grades (II and III), and oligoastrocytomas with two grades (II and III) based on the tumor cell phenotype. Pathological classification remains controversial due to the lack of specific immunohistochemical biomarker to recognize gliomas. Also, due to their natural propriety to infiltrate the normal parenchyma and to migrate far from the first location, total surgical resection remains often impossible then adjuvant treatment is needed. The established therapies for gliomas include surgery, radiotherapy and chemotherapy. Despite this arsenal of therapies, median survival of the most malignant grade glioblastoma is approximately 15 months. This is why the attempts to better understand the molecular biology of gliomas in the aim to define new molecular targets is a holy grail. Using conventional and molecular cytogenetic approaches and molecular genetic methods, we have investigated patients bearing gliomas and followed at CHUS. Our results display that the codeletion 1p/19q (1p-/19-) is not only a prognostic and predictive biomarker of oligodendrogliomas but also a diagnostic tool of this tumor. Our study has allowed us to build a glioma-bank containing around 150 samples of patients, which we continued to populate. We have also defined the cut-off positivity of FISH on touch preparation slides, which is 20%. In addition, we have developed a new, fast and reliable method to retrieve the 1p-/19q- in all samples 24 hours after sampling. This method was transferred to the clinical lab. Furthermore, we have successfully cultured the brain tumor samples and analyzed their caryotypes. This has permitted us to discover a new alternative translocation, which is responsable of 1p deletion in one oligoastrocytoma case. Since glioblastoma is characterized by genomic instability, and telomere disruption is a main cause of genomic instability, we investigated the nuclear telomere architecture in this type of tumour. We found that nuclear telomeric architecture could be a biomarker of glioblastoma since it can subdivide glioblastoma patients in three categories with significantly different outcomes and time to progression. We used high-throughput methods (one manual and one semi-automatic) to characterize the nuclear telomeric architecture in glioblastoma. The semi-automatic method can be transfer to the clinical lab since it can deliver the results nine hours after sampling. Then, this approach is usable to monitor this tumor and to evaluate the impact of different treatment options. We need to search the putative tumor suppressor genes on chromosomes 1 and 19. Furthermore, trying to understand the molecular basis of nuclear telomeric architecture will bring up new molecular target therapies

Caractérisation de deux anneaux dérivés du chromosome 22 découverts en période prénatale à l'aide de techniques de cytogénétique et de génétique moléculaire

Les anomalies chromosomiques peuvent être classées en anomalies de nombre et en anomalies de structure. L’identification des remaniements chromosomiques de structure est facilitée par les techniques de caryotypage à haute résolution et de cytogénétique moléculaire. L’utilisation de ces techniques a été essentielle pour la détection et la caractérisation de deux anneaux issus du même chromosome 22 diagnostiqués en période prénatale. Une amniocentèse a été effectuée à 163/7 semaines chez une femme de 39 ans pour âge maternel avancé. Après investigation, la formule chromosomique du fœtus a été déterminée: 47, XY, r(22)(p11.1p11.2), +r(22)(q11.1q13.31). L’anomalie chromosomique d’origine maternelle est survenue de novo. Le nombre de cellules foetales circulant dans le sang maternel est de 10 cellules par ml. Ce premier cas de deux anneaux constitutionnels du chromosome 22 est un exemple exceptionnel de monosomie partielle avec très peu de manifestations cliniques, malgré la richesse en gènes du segment délété.Objective: Cytogenetic and molecular genetic characterization of two constitutional ring chromosomes 22 identified during prenatal diagnosis. Materials and Methods: A 39 year-old woman, G4P2A1, had amniocentesis at 163/7 weeks of gestation. Conventional and molecular cytogenetic studies with microsatellite analysis of the fetal and parental cells were performed. Results: The fetus had two ring chromosomes derived from chromosome 22 with three breakpoints: one located at the centromere, another, at the p11.2 subband and the third, at the q13.31 subband. The distal part of the two derivative chromosomes was lost. Then, two rings resulted: a small and a large one. The small ring was formed by joining the end of p11.2 subband to a portion of the centromere; the other by joining the second part of the centromere to the end of q13.31 subband. The male fetus presents the following karyotype: 47, XY, r(22)(p11.1p11.2), +r(22)(q11.1q13.31). The proband’s chromosome aberration occurred de novo from the maternal chromosome. At the autopsy, the fetus showed minor clinical features. The number of fetal nucleated blood cells detected in peripheral maternal circulation, showing positive signals for Y chromosome and DiGeorge/VCF.TUPLE1 probes and absence of ARSA control signal, was 10 cells per mL. Conclusion: Despite the haploinsufficiency of many active genes, the fetus showed minor congenital malformations

Activité dominante négative des protéines p53 mutées

La protéine p53 dispose d’une fonction activatrice de l’expression de nombreux gènes cibles. Le rôle de facteur de transcription joué par la protéine p53 nécessite la formation d’une structure homotétramérique. Les résultats de certaines expérimentations montrent que les monomères p53 mutés ont la capacité de se lier à des monomères p53 sauvages pour constituer des complexes hétérotétramériques. La présence de monomères p53 mutés au sein de ces complexes hétérotétramériques peut avoir pour conséquence immédiate une inactivation des monomères sauvages. Cette capacité de liaison et d’inactivation des p53 mutées à l’égard des p53 sauvages est qualifiée d’« effet dominant négatif ». Plusieurs facteurs enrôlés dans cette activité dominante négative ont été identifiés. La compréhension des fonctions moléculaires complexes qui régissent cette activité constitue un des aspects importants qui permettrait de mieux discerner les mécanismes biologiques en jeu dans la cancérogenèse. Le but de cet article est de mettre en lumière des aspects jusqu’à présent occultés de l’activité dominante négative des protéines p53 mutées. De plus, nous allons souligner comment cette activité contribue à la cancérogenèse induite par les rayons ultraviolets.Tumor suppressor gene inactivation as proposed by the Knudson model implies a sequential inactivation of two alleles of a gene. For example, the first allele is inactivated by a missense mutation, and the second one is inactivated by a deletion or insertion. The alteration of the p53 tumor suppressor gene is far to correspond only to this model. In the great majority of cancers, the mutated allele of p53 coexists with the normal allele. It is well known that the transcriptional activity is one of the most important functions of p53. The p53 protein is active as a tetramer (this complex activates the expression of targeted genes by binding to its consensus DNA sequence called the p53 response element). Experimental evidence shows that wild-type p53 interacts with mutant proteins to form heterotetramers. In association with wild-type proteins, mutant proteins drive the wild-type subunits into a mutant conformation. This association leads to a loss of trans-activating function. The capacity of mutant subunits to form heterotetramers with wild-type subunits and to commit them into a mutant conformation is called « dominant negative effect ». Many p53 mutant proteins possess this dominant negative activity. Recently, several factors, which are implicated in the control of the dominant negative activity of p53 mutants, have been identified. The elucidation of these complex molecular functions, which are implicated in the dominant negative activity of the p53 mutated protein represents an important aspect in the comprehension of the biological mechanisms involved in carcinogenesis

Seroprevalence of transfusion-transmissible infections among family replacement donors and voluntary non-remunerated blood donors during the COVID-19 pandemic in sub Saharan Africa

Introduction : According to WHO,  regular, voluntary, unpaid blood donors are the safest group of donors, as they have the lowest prevalence of blood transmitted infections. However, family/replacement blood donors is widely used in sub Saharan Africa and this practice was exacerbated during the COVID 19 pandemic. This study aimed to compare the seroprevalence of infectious markers in family replacement blood donors and voluntary non-remunerated  blood donors during the COVID 19 pandemic in a country of sub Saharan Africa.   Materials and Methods Blood donors received at the National Centre of Blood Transfusion (NBTC) of Dakar from August 1st to October 31th 2021, were included in this study. All donors completed a pre-donation questionnaire. Donors identity, epidemiological parameters, reasons for donation and laboratory results were collected in the Inlog® software of the NBTC. The serological tests for HBV, HIV and HCV were performed with chemiluminescence technology. The Rapid Plasma Reagent test was used to find out treponemal antibodies. The determination of ABO and Rh blood groups was performed using monoclonal antisera following classical hemagglutination test on a plate. Results A total of 5002 donors were collected during this COVID-19 pandemic period. Blood family/replacement donors represented 54.0% and new voluntary donors represented 52.6%. Comparison of HIV, HCV and syphilis markers seroprevalence showed no statistically significant difference between new voluntary donors and new family replacement donors (p>0.05). However, for HBV the seroprevalence was significantly higher in new family replacement donors (p=0,002). Conclusion The proper supply of blood was impacted by the COVID-19 pandemic meanwhile replacement donations had contributed to limiting the damage observed with blood shortages. However, the significant differences noted on the seroprevalences of transfusion-transmissible infections between voluntary non-paid donors and family/replacement donors strengthens WHO recommendations for the selection of volunteer non-paid donors to lower transfusion-transmissible HBV in sub Saharan Africa.                

Efficiency of Manual Scanning in Recovering Rare Cellular Events Identified by Fluorescence In Situ Hybridization: Simulation of the Detection of Fetal Cells in Maternal Blood

Fluorescence in situ hybridization (FISH) and manual scanning is a widely used strategy for retrieving rare cellular events such as fetal cells in maternal blood. In order to determine the efficiency of these techniques in detection of rare cells, slides of XX cells with predefined numbers (1–10) of XY cells were prepared. Following FISH hybridization, the slides were scanned blindly for the presence of XY cells by different observers. The average detection efficiency was 84% (125/148). Evaluation of probe hybridization in the missed events showed that 9% (2/23) were not hybridized, 17% (4/23) were poorly hybridized, while the hybridization was adequate for the remaining 74% (17/23). In conclusion, manual scanning is a relatively efficient method to recover rare cellular events, but about 16% of the events are missed; therefore, the number of fetal cells per unit volume of maternal blood has probably been underestimated when using manual scanning

Traitement de substitution des usagers dépendants des opiacés: L’expérience du Centre de prise en charge intégré des addictions de Dakar

International audienceMethadone and buprenorphine are the two maintenance treatments in opiate addicts authorised in France since the end of the 1990’s. More recently, some African countries such as Senegal have implemented a new health policy focused on reducing the risks by encouraging the use of methadone as maintenance treatment. The objectives of maintenance therapy are to reduce morbidity and mortality related to the consumption of heroin and other street opioids, to promote the integration of drug users into the healthcare system, and more generally, to improve their social integration. However, this strategy might have limitations in practice. Here, we report the experience of the Integrated Addiction Treatment Center in Dakar, Senegal, and discuss ethical considerations at both the individual and collective levels, which may improve care of opiate-dependent users in practice, especially in Africa.La méthadone et la buprénorphine sont les deux traitements de substitution des opiacés autorisés en France depuis la fin des années 1990. Plus récemment, certains pays africains, comme le Sénégal, ont mis en place une nouvelle politique de santé axée sur la réduction des risques, en encourageant le recours aux traitements de substitution des opiacés. Les objectifs de la substitution sont de réduire la morbi-mortalité liée à la consommation d’héroïne ou d’autres opioïdes de rue, de favoriser l’insertion des usagers de drogue dans le système de soins, et, plus généralement, de faciliter leur insertion sociale. Cette nouvelle stratégie trouve néanmoins des limites dans la pratique. Nous rapportons dans cette revue l’expérience du Centre de prise en charge intégré des addictions de Dakar, au Sénégal, et proposons une réflexion éthique, tant individuelle que collective, afin d’améliorer le traitement de substitution des opiacés, notamment en Afrique

Antiphospholipid Antibodies and Systemic Scleroderma

Objective: Antiphospholipid antibodies (APLs) could be associated with an increased risk of vascular pathologies in systemic scleroderma. The aim of our study was to search for APLs in patients affected by systemic scleroderma and to evaluate their involvement in the clinical manifestations of this disease. Materials and Methods: We conducted a cross-sectional descriptive study, from January 2009 until August 2010, with patients received at the Department of Dermatology (Dakar, Senegal). Blood samples were taken at the hematology laboratory and were analyzed for the presence of APLs. Results: Forty patients were recruited. Various types of either isolated or associated APLs were found in 23 patients, i.e. 57.5% of the study population. The most frequently encountered antibody was IgG anti-β2 GPI (37.5% of the patients), followed by anticardiolipins (17.5%) and lupus anticoagulants (5%). No statistically significant association of positive antiphospholipid-related tests to any of the scleroderma complications could be demonstrated. Conclusion: A high proportion of patients showing association of systemic scleroderma and APLs suggests the presence of a morbid correlation between these 2 pathologies. It would be useful to follow a cohort of patients affected by systemic scleroderma in order to monitor vascular complications following confirmation of the presence of antiphospholipid syndrome

Three-Dimensional Nuclear Telomere Profiling as a Biomarker for Recurrence in Oligodendrogliomas: A Pilot Study

Mechanisms of recurrence in oligodendrogliomas are poorly understood. Recurrence might be driven by telomere dysfunction-mediated genomic instability. In a pilot study, we investigated ten patients with oligodendrogliomas at the time of diagnosis (first surgery) and after recurrence (second surgery) using three-dimensional nuclear telomere analysis performed with quantitative software TeloView® (Telo Genomics Corp, Toronto, Ontario, Canada). 1p/19q deletion status of each patient was determined by fluorescent in situ hybridization on touch preparation slides. We found that a very specific 3D telomeric profile was associated with two pathways of recurrence in oligodendrogliomas independent of their 1p/19q status: a first group of 8 patients displayed significantly different 3D telomere profiles between both surgeries (p < 0.0001). Their recurrence happened at a mean of 231.375 ± 117.42 days and a median time to progression (TTP) of 239 days, a period defined as short-term recurrence; and a second group of three patients displayed identical 3D telomere profiles between both surgery samples (p > 0.05). Their recurrence happened at a mean of 960.666 ± 86.19 days and a median TTP of 930 days, a period defined as long-term recurrence. Our results suggest a potential link between nuclear telomere architecture and telomere dysfunction with time to recurrence in oligodendrogliomas, independently of the 1p/19q status

Three-dimensional Nuclear Telomere Architecture Is Associated with Differential Time to Progression and Overall Survival in Glioblastoma Patients

The absence of biological markers allowing for the assessment of the evolution and prognosis of glioblastoma (GBM) is a major impediment to the clinical management of GBM patients. The observed variability in patients' treatment responses and in outcomes implies biological heterogeneity and the existence of unidentified patient categories. Here, we define for the first time three GBM patient categories with distinct and clinically predictive three-dimensional nuclear-telomeric architecture defined by telomere number, size, and frequency of telomeric aggregates. GBM patient samples were examined by three-dimensional fluorescent in situ hybridization of telomeres using two independent three-dimensional telomere-measurement tools (TeloView program [P1] and SpotScan system [P2]). These measurements identified three patients categories (categories 1–3), displaying significant differences in telomere numbers/nucleus (P1 = .0275; P2 ≤ .0001), telomere length (P1 and P2 = .0275), and number of telomeric aggregates (P1 = .0464; P2 ≤ .0001). These categories corresponded to patients with long-term, intermediate, and short-term survival, respectively (P = .0393). The time to progression analyses showed significant differences between the three categories (P = .0167). There was a correlation between time to progression, median survival, and nuclear telomere architecture. Our study suggests a link between patient outcome and three-dimensional nuclear-telomere organization and highlights the potential clinical power of telomere signatures as a new prognostic, predictive, and potentially pharmacodynamic biomarker in GBM. Furthermore, novel automated three-dimensional high-throughput scanning as developed here permits to obtain data from 300 nuclei in 20 minutes. This method is applicable to any cell type and scanning application

Homozygous sickle cell disease related mortality in Senegal (2011–2020)

Abstract Homozygous sickle cell disease (HSCD) is characterized by multiorgan morbidity and an increased risk of early death. We aim to describe the mortality rate, causes, and risk factors of death in HSCD between 2011 and 2020. We conducted a retrospective study with a duration of 10 years in the cohort of 2348 HSCD patients. The mortality rate was determined by reporting the number of deaths to the total number of patients followed in the year. Sociodemographic, clinical, biological data and causes of death were studied. Death risk factors were determined by a bivariate analysis comparing deceased and living HSCD patients. The mean age of death was 26 years (3–52). The sex ratio was 1.2. The mortality rate was 2.76%. The death rate was high in 2011 (3.2%) and low in 2020 (0.17%). We observed a significant reduction of mortality of 94.6%. Most of the common causes of death were acute anemia (40%), acute chest syndrome (24.6%), and infections (20%). Risk factors of death were age, vaso‐occlusive crises ≥3, acute chest syndrome, blood transfusion, and chronic complications. Mortality among HSCD has significantly decreased over the past 10 years in Senegal, and the main causes of death were acute anemia, acute chest syndrome, and infections