Biomedical subjects

Sophie Rousseaux

Publications and source records attributed to Sophie Rousseaux.

11 recordsLinked to original sources

PubMed2025

Immediate and durable effects of maternal tobacco consumption on placental DNA methylation: a replication and discovery study.

An increasing number of epigenome-wide association studies report tobacco smoking-associated DNA methylation levels. However, comprehensive replication studies remain scarce, particularly in placenta, despite their crucial interest in such a large-scale context. Using DNA methylation data from the EPIC array of 341 new placentas (85 smokers, 219 non-smokers, and 37 former smokers) from the EDEN cohort, we used a candidate approach to replicate maternal smoking-associated CpGs and regions previously identified using the 450K array, and an exploratory approach to discover new associations within EPIC-specific CpGs. Smoking-associated changes in DNA methylation in CpGs and regions were classified as either transient or persistent (indicating epigenetic memory), depending on the stability of their association with smoking status. Among candidate loci, 38% of probes and 9% of regions were replicated, providing robust evidence of effects of prenatal smoke exposure on methylation patterns of these loci. LEKR1 was the top hit in both the initial and replication studies. Most of the replicated loci were transient CpGs (i.e. current smokers), while persistent CpGs (i.e. former smokers) remained scarce and somewhat inconsistent with previous findings. The additional exploratory analysis identified 733 novel probes and 75 novel regions, including 18% and 30% of transient loci, respectively. Results suggested that most of the effects were related to in utero exposure only, supporting pregnant women's efforts to quit smoking. This replication study also evidences the importance of reproducible work in omic investigations to provide a more in-depth and robust understanding of the effects of environmental exposures on health biomarkers..

DNA methylation↗

PubMed2025

Mitochondrial dysfunction fuels drug resistance in adult T-cell acute lymphoblastic leukemia.

BACKGROUND: T-cell acute lymphoblastic leukemia (T-ALL) is a relatively rare hematological malignancy, characterized by the uncontrolled proliferation of immature T lymphoblasts and associated with a generally unfavorable prognosis. Our previous research has demonstrated that decreased mitochondrial activity is associated with the aggressiveness of T-ALL tumors. However, the mechanisms underlying this phenomenon and its contribution to treatment resistance remain largely elusive. METHODS: We have built up the largest known T-ALL tumor bank, with a median follow-up of 32 months, including our transcriptomic data from 79 newly sequenced tumors that adds to the 54 publicly accessible samples. Computational analyses and a series of functional assays were performed to investigate the molecular links between altered mitochondrial activity and drug resistance. RESULTS: The transcriptomic analysis revealed that down-regulation of mitochondrial activity is a potent driver of ABCB1 activation, a gene strongly associated with multidrug resistance. In tumors with low mitochondrial activity, the impaired fatty acids β-oxidation leads to intracellular lipid accumulation, which is directly involved in ABCB1 activation. Indeed, our data show that lipid neo-synthesis and accumulation promotes the activation of lipogenic transcription factors, liver X receptors (LXRs), which act as drivers of ABCB1 expression. Tumor data analyses confirmed that high ABCB1 expression in tumour samples is indeed associated with reduced mitochondrial gene expression, lipid droplet enrichment, increased tumour aggressiveness, and significantly shorter patient survival. CONCLUSIONS: Our study demonstrates that reduced mitochondrial activity drives multidrug resistance in adult T-ALL via lipid-mediated activation of ABCB1. These findings enhance our understanding of the biology of aggressive T-ALL and provide insight into mechanisms of resistance to conventional chemotherapy. Consequently, we propose that targeting de novo lipogenesis and restricting dietary fats, such as caprylic acid, may help overcome treatment resistance in patients with T-ALL exhibiting low mitochondrial activity. TRIAL REGISTRATION: The clinical trial was registered under the identifiers ChiCTR-ONRC-14004968 and ChiCTR2000031553 at ClinicalTrials.gov.

Adult↗

PubMed2006

Post-meiotic shifts in HSPA2/HSP70.2 chaperone activity during mouse spermatogenesis.

HSPA2 (formerly HSP70.2) is a testis-specific member of the HSP70 family known to play a critical role in the completion of meiosis during male germ cell differentiation. Although abundantly present in post-meiotic cells, its function during spermiogenesis remained obscure. Here, using a global proteomic approach to identify genome-organizing proteins in condensing spermatids, we discovered an unexpected role for HSPA2, which acquires new functions and becomes tightly associated with major spermatid DNA-packaging proteins, transition proteins 1 and 2. Hence, HSPA2 is identified here as the first transition protein chaperone, and these data shed a new light on the yet totally unknown process of genome-condensing structure assembly in spermatids.

Animals↗

PubMed2005

A solution to the 2-pyridyl organometallic cross-coupling problem: regioselective catalytic direct arylation of pyridine N-oxides.

Direct arylation reactions of pyridine N-oxides occur in excellent yield with complete selectivity for the 2-position with a wide range of aryl bromides. This reactivity permits the use of inexpensive, commercially available, and bench-stable pyridine N-oxides as replacements for problematic 2-metallapyridines in palladium-catalyzed cross-coupling reactions.

Journal Article↗

PubMed2005

Establishment of male-specific epigenetic information.

The setting of male-specific epigenetic information is a complex process, which involves a major global re-organisation, as well as localized changes of the nucleus structure during the pre-meiotic, meiotic and post-meiotic stages of the male germ cell differentiation. Although it has long been known that DNA methylation in targeted regions of the genome is associated with male-specific genomic imprinting, or that most core histones are hyperacetylated and then replaced by sperm-specific proteins during the post-meiotic condensation of the nucleus, many questions remain unanswered. How these changes interact, how they affect the epigenetic information and how the paternal epigenetic marks contribute to the future genome are indeed major issues remaining to be explored.

Animals↗

PubMed2005

How to pack the genome for a safe trip.

The transformation of the somatic chromatin into a unique and highly compact structure occurring during the post-meiotic phase of spermatogenesis is one of the most dramatic known processes of chromatin remodeling. Paradoxically, no information is available on the mechanisms controlling this specific reorganization of the haploid cell genome. The only existing hints suggest a role for histone variants, as well as for stage-specific post-translational histone modifications,before and during the incorporation of testis-specific basic nuclear proteins. Moreover, the exact functions of the latter remain obscure. This chapter summarizes the major chromatin-associated events taking place during the post-meiotic differentiation of male haploid cells in mammals and discusses some of the basic issues that remain to be solved to finally understand chromatin remodeling during spermatogenesis.

Animals↗

PubMed2005

Testis-specific histone H3 expression in somatic cells.

Histone variants functionally differentiate individual nucleosomes and, hence, act as key regulators of chromatin structure and function. Large-scale proteomic projects are now valuable sources of histone-variant discovery, showing, in particular, that somatic mammalian cells express a larger panel of histone H3 variants than previously thought, including testis-specific variants and as yet uncharacterized species. These data also suggest a tight relationship between the complexity of histone-variant expression and physiopathological states of the cells.

Amino Acid Sequence↗

PubMed2004

No long-term increase in sperm aneuploidy rates after anticancer therapy: sperm fluorescence in situ hybridization analysis in 26 patients treated for testicular cancer or lymphoma.

PURPOSE: Lymphomas and testicular cancers are the most frequent malignancies among young men. With recent improvement of survival rates, for many patients, the question is raised of the consequences of the anticancer treatments on their fertility and more specifically of a potential genetic risk for the offspring. This article presents the study of sperm aneuploidy rates in the largest population of cancer-treated patients studied thus far. EXPERIMENTAL DESIGN: In the present study, 38 patients were initially included 7 months to 5 years after a cancer treatment by chemotherapy and/or radiotherapy for testicular cancer (n = 19) or lymphoma (n = 19). Twelve of them were azoospermic. Sperm aneuploidy rates of chromosomes X, Y, 13, 18, and 21 were analyzed by multicolor fluorescent in situ hybridization in the 26 other patients. RESULTS: In most cases, the disomy/diploidy rates after cancer therapy did not significantly differ from those observed in the group of control healthy donors. Only five patients (one lymphoma and four testicular cancer) showed significant but still moderate increases in disomic and/or diploid sperm. For the lymphoma patient, the short posttherapeutic delay after the treatment could explain the elevated aneuploidy rates, whereas no risk factor in the clinical, biological, or therapeutic records could be identified in any of the four testicular cancer patients with elevated sperm aneuploidy rates. CONCLUSIONS: These data suggest an absence of long-term effect of anticancer therapy on sperm aneuploidy rates, and therefore, no long-term increased risk of aneuploidy for the offspring obtained either spontaneously or after assisted reproductive techniques.

Adolescent↗

PubMed2004

The role of histones in chromatin remodelling during mammalian spermiogenesis.

One of the most dramatic chromatin remodelling processes takes place during mammalian spermatogenesis. Indeed, during the postmeiotic maturation of male haploid germ cells, or spermiogenesis, histones are replaced by small basic proteins, which in mammals are transition proteins and protamines. However, nothing is known of the mechanisms controlling the process of histone replacement. Two hints from the literature could help to shed light on the underlying molecular events: one is the massive synthesis of histone variants, including testis-specific members, and the second is a stage specific post-translational modification of histones. A new testis-specific 'histone code' can therefore be generated combining both histone variants and histone post-translational modifications. This review will detail these two phenomena and discuss possible functional significance of the global chromatin alterations occurring prior to histone replacement during spermiogenesis.

Amino Acid Sequence↗

PubMed2003

Cdyl: a new transcriptional co-repressor.

Cdyl (chromodomain-Y-like) is a chromodomain-containing protein that is predominantly expressed during mouse spermiogenesis. In its carboxy-terminal portion, there is a domain with homology to the coenzyme A (CoA) pocket of the enoyl-CoA hydratase/isomerase, which is shown here to be able to bind CoA and histone deacetylases (HDACs). It also efficiently represses transcription. Moreover, the binding of Hdac1 represses the ability of Cdyl to bind CoA, and a Cdyl-CoA interaction only occurs in the absence of HDACs. These data suggest that Cdyl is primarily a transcriptional co-repressor. However, the degradation of cellular Hdac1 and Hdac2, as observed here in the elongating spermatids, may provide an HDAC-free environment in which Cdyl could bind CoA and participate in the global chromatin remodelling that occurs in these cells.

Amino Acid Sequence↗

PubMed2003

Acetylation-dependent chromatin reorganization by BRDT, a testis-specific bromodomain-containing protein.

The association between histone acetylation and replacement observed during spermatogenesis prompted us to consider the testis as a source for potential factors capable of remodelling acetylated chromatin. A systematic search of data banks for open reading frames encoding testis-specific bromodomain-containing proteins focused our attention on BRDT, a testis-specific protein of unknown function containing two bromodomains. BRDT specifically binds hyperacetylated histone H4 tail depending on the integrity of both bromodomains. Moreover, in somatic cells, the ectopic expression of BRDT triggered a dramatic reorganization of the chromatin only after induction of histone hyperacetylation by trichostatin A (TSA). We then defined critical domains of BRDT involved in its activity. Both bromodomains of BRDT, as well as flanking regions, were found indispensable for its histone acetylation-dependent remodelling activity. Interestingly, we also observed that recombinant BRDT was capable of inducing reorganization of the chromatin of isolated nuclei in vitro only when the nuclei were from TSA-treated cells. This assay also allowed us to show that the action of BRDT was ATP independent, suggesting a structural role for the protein in the remodelling of acetylated chromatin. This is the first demonstration of a large-scale reorganization of acetylated chromatin induced by a specific factor.

3T3 Cells↗