EVALUATION OF GPX1 PRO198LEU POLYMORPHISM, GSTP1 EXPRESSION AND GENE PROMOTER METHYLATION IN MOROCCAN PATIENTS WITH BLADDER CANCER

Bladder cancer (BC) is the third most common male malignancy in Morocco. The risk factors for developing BC are multiples including dietary conditions, environmental exposure and oxidative stress. Glutathione Peroxidase-1 (GPX1) and Glutathione S-Transferase Pi (GSTP1) are two key enzymes in cell detoxification process. GPX1 Pro198Leu polymorphism is associated with a decrease of enzyme activity and may contribute to BC susceptibility. Deregulated expression of GSTP1 enzyme was reported in various human tumors, also, epigenetic silencing of GSTP1 gene by aberrant promoter methylation has been shown to be involved in the molecular pathway for cancer development. In this study, we aimed to assess the presence of GPX1 Pro198Leu polymorphism and determine the expression status of GSTP1-in relation to its promoter methylation- in Moroccan population to evaluate their association with the risk of developing BC in Moroccan patients. Genotyping of GPX1 Pro198Leu polymorphism was carried out by Sanger sequencing. GSTP1 expression was assessed by immunohistochemistry, GSTP1 promoter methylation status was studied by Methylation Specifiq PCR method. No significant association between GPX1 Pro198Leu polymorphism and BC occurrence was found (Pro/Leu vs. Pro/Pro: p=0.425). For the analysis of Pro198Leu polymorphism and progression of BC, no association was observed neither for stages (Pro/Leu vs. Pro/Pro: p=0.500) nor grades (Pro/Leu vs. Pro/Pro: p=0.415). GSTP1 expression was strong in 23.33%, moderate in 60% and weak in 13.33% of BC cases. Variability of the expression does not correlate with high-grade cancer or invasive-stage (p˃0.05). No GSTP1 promoter methylation was detected in all cases. Our results showed that GPX1 Pro198Leu polymorphism and GSTP1 expression are not closely associated with the risk of BC in our population, suggesting that the effect of these biomarkers on BC development might be a result of a combination with other genetic and epigenetic alterations and/or non-genetic variables such as diet and lifestyle factors

ASSESSMENT OF MOLECULAR BIOMARKERS FOR BLADDER CANCER DIAGNOSIS, GRADING AND PROGNOSIS

Worldwide, bladder cancer is a very significant public health problem, in terms of prevalence, mortality and management for individuals and their families. Bladder cancer is the fourth most commonly diagnosed cancer in men and one of the heaviest cancers in terms of cost. Although transurethral resection of the bladder followed by intravesical instillation of live attenuated Bacillus Calmette–Guérin (BCG) is considered as the gold standard for patients with intermediate and high risk, only a small portion of patient responds to the BCG-therapy. Bladder cancer management is faced by the therapy failure, great side effects and some difficulties in histological classification. Accordingly, growing interest is given to the use of genetic, epigenetic and immunologic biomarkers for molecular signature characterization and tumor stratification. In Morocco, great efforts have been made to contribute to the improvement of management of bladder cancer and many studies were made to evaluate some genetic and epigenetic biomarkers. Generated data is of a great interest for characterization of bladder cancer tumors in Morocco and could be used for better management of this disease

FRAXE-associated mental retardation protein (FMR2) is an RNA-binding protein with high affinity for G-quartet RNA forming structure

FRAXE is a form of mild to moderate mental retardation due to the silencing of the FMR2 gene. The cellular function of FMR2 protein is presently unknown. By analogy with its homologue AF4, FMR2 was supposed to have a role in transcriptional regulation, but robust evidences supporting this hypothesis are lacking. We observed that FMR2 co-localizes with the splicing factor SC35 in nuclear speckles, the nuclear regions where splicing factors are concentrated, assembled and modified. Similarly to what was reported for splicing factors, blocking splicing or transcription leads to the accumulation of FMR2 in enlarged, rounded speckles. FMR2 is also localized in the nucleolus when splicing is blocked. We show here that FMR2 is able to specifically bind the G-quartet-forming RNA structure with high affinity. Remarkably, in vivo, in the presence of FMR2, the ESE action of the G-quartet situated in mRNA of an alternatively spliced exon of a minigene or of the putative target FMR1 appears reduced. Interestingly, FMR1 is silenced in the fragile X syndrome, another form of mental retardation. All together, our findings strongly suggest that FMR2 is an RNA-binding protein, which might be involved in alternative splicing regulation through an interaction with G-quartet RNA structure

A Novel Function for Fragile X Mental Retardation Protein in Translational Activation

Fragile X syndrome, the most frequent form of inherited mental retardation, is due to the absence of Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein involved in several steps of RNA metabolism. To date, two RNA motifs have been found to mediate FMRP/RNA interaction, the G-quartet and the “kissing complex,” which both induce translational repression in the presence of FMRP. We show here a new role for FMRP as a positive modulator of translation. FMRP specifically binds Superoxide Dismutase 1 (Sod1) mRNA with high affinity through a novel RNA motif, SoSLIP (Sod1 mRNA Stem Loops Interacting with FMRP), which is folded as three independent stem-loop structures. FMRP induces a structural modification of the SoSLIP motif upon its interaction with it. SoSLIP also behaves as a translational activator whose action is potentiated by the interaction with FMRP. The absence of FMRP results in decreased expression of Sod1. Because it has been observed that brain metabolism of FMR1 null mice is more sensitive to oxidative stress, we propose that the deregulation of Sod1 expression may be at the basis of several traits of the physiopathology of the Fragile X syndrome, such as anxiety, sleep troubles, and autism

Localisation des gènes modulant la surcharge en fer dans un modèle murin d'hémochromatose

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Functional characterization of the AFF (AF4/FMR2) family of RNA-binding proteins: insights into the molecular pathology of FRAXE intellectual disability.

International audienceThe AFF (AF4/FMR2) family of genes includes four members: AFF1/AF4, AFF2/FMR2, AFF3/LAF4 and AFF4/AF5q31. AFF2/FMR2 is silenced in FRAXE intellectual disability, while the other three members have been reported to form fusion genes as a consequence of chromosome translocations with the myeloid/lymphoid or mixed lineage leukemia (MLL) gene in acute lymphoblastic leukemias (ALLs). All AFF proteins are localized in the nucleus and their role as transcriptional activators with a positive action on RNA elongation was primarily studied. We have recently shown that AFF2/FMR2 localizes to nuclear speckles, subnuclear structures considered as storage/modification sites of pre-mRNA splicing factors, and modulates alternative splicing via the interaction with the G-quadruplex RNA-forming structure. We show here that similarly to AFF2/FMR2, AFF3/LAF4 and AFF4/AF5q31 localize to nuclear speckles and are able to bind RNA, having a high apparent affinity for the G-quadruplex structure. Interestingly, AFF3/LAF4 and AFF4/AF5q31, like AFF2/FMR2, modulate, in vivo, the splicing efficiency of a mini-gene containing a G-quadruplex structure in one alternatively spliced exon. Furthermore, we observed that the overexpression of AFF2/3/4 interferes with the organization and/or biogenesis of nuclear speckles. These findings fit well with our observation that enlarged nuclear speckles are present in FRAXE fibroblasts. Furthermore, our findings suggest functional redundancy among the AFF family members in the regulation of splicing and transcription. It is possible that other members of the AFF family compensate for the loss of AFF2/FMR2 activity and as such explain the relatively mild to borderline phenotype observed in FRAXE patients