Jacobs, F. | Search bioRxiv

bioRxiv2024

Transcriptomic profiling of unmethylated full mutation carriers implicates TET3 in FMR1 CGG repeat expansion methylation dynamics in Fragile X syndrome

BackgroundFragile X syndrome (FXS) is a neurodevelopmental disorder caused by the expansion of a CGG repeat in the 5UTR of the FMR1 (fragile X messenger ribonucleoprotein 1) gene. Healthy individuals possess a repeat 30-55 CGG units in length. Once the CGG repeat exceeds 200 copies it triggers methylation at the locus. This methylation covers the FMR1 promoter region and silences expression of the gene and the production of FMRP (fragile X messenger ribonucleoprotein). The loss of FMRP is responsible for a number of pathologies including neurodevelopmental delay and autism spectrum disorder. Methylation of the expanded repeat in the FMR1 locus is the causal factor for FXS, however it is not known why the expanded repeat triggers this epigenetic change or how exactly DNA methylation is established. Intriguingly, genetic engineering of expanded CGG repeats of over 300x in the FMR1 locus in mice remains unmethylated. Also in humans, in very rare cases, individuals can have an FMR1 CGG expansion >200x but the locus remains unmethylated. These unmethylated full mutation individuals give us a rare opportunity to investigate the mechanism of FMR1 promoter methylation. MethodsFibroblasts were obtained from a healthy control, an FXS patient and two unmethylated full expansion carriers. RNA was extracted and comparative transcriptomic analysis was performed on all samples. Whole genome sequencing was carried out on DNA from the two UFM carriers and the results analysed to investigate DNA variants that could explain the observed differences in gene expression. ResultsOur analyses focused on genes involved in epigenetic modification. We show that Tet methylcytosine dioxygenase 3 (TET3), a gene involved in DNA methylation, is significantly downregulated in UFM carriers compared to healthy controls or FXS patient derived cells. Genomic analyses reveal a number of rare variants present in the TET3 locus in UFM carriers when compared to the reference genome. No single variant has a significant predicted effect, raising the possibility that a trans acting variant could be driving the differential gene expression. ConclusionOur results suggest that TET3 is a candidate factor responsible for the lack of methylation of the expanded FMR1 locus. Further analyses are needed to further elucidate this relationship, however given its potential to directly interact with CGG repeats and its ambiguous role in 5-hydroxy-methylation of CG containing sequences, TET3 is a strong candidate for further exploration.

neuroscience↗

bioRxiv2022

Cytokine profiles in adults with imported malaria: insights from the PALUREA cohort study

The increase in worldwide travel is making imported malaria a growing health concern in nonendemic countries. Most data on the pathophysiology of malaria come from endemic areas. Little is known about cytokine profiles during imported malaria. We report cytokine profiles in adults with Plasmodium falciparum malaria included in PALUREA, a prospective cohort study conducted in France between 2006 and 2010. The patients were classified as having uncomplicated malaria (UM) or severe malaria (SM), with this last further categorized as very severe malaria (VSM) or less severe malaria (LSM). At hospital admission, eight blood cytokines were assayed in duplicate using Luminex technology: interleukin (IL)-1, IL-1{beta}, IL-2, IL-4, IL-10, tumor necrosis factor (TNF), interferon (IFN){gamma}, and macrophage migration inhibitory factor (MIF). These assays were repeated on days 1 and 2 in the SM group. Of the 278 patients, 134 had UM and 144 SM. At hospital admission, over half the patients had undetectable levels of IL-1, IL-1 {beta}, IL-2, IL-4, IFN {gamma}, and TNF, while IL-10 and MIF were significantly higher in the SM vs. the UM group. Higher IL-10 was significantly associated with higher parasitemia (R=0.32 [0.16-0.46]; P=0.0001). In the SM group, IL-10 elevation persisting from admission to day 2 was significantly associated with subsequent nosocomial infection. Of eight tested cytokines, only MIF and IL-10 were associated with disease severity in adults with imported P. falciparum malaria. At admission, many patients had undetectable cytokine levels, suggesting that circulating cytokine assays may not be helpful as part of the routine evaluation of adults with imported malaria. Author SummaryPlasmodium falciparum malaria is increasingly common in nonendemic areas. Improved understanding of its pathophysiology might help to decrease mortality. We therefore routinely assayed eight cytokines in 278 adults with imported P. falciparum malaria at hospital admission; in the group with severe malaria (n=144), we repeated the assays on the next two days. The cytokine levels were often undetectable, suggesting that cytokine storm might not be a driving mechanism at the time of clinical presentation. IL-10 and macrophage migration inhibitory factor (MIF) were significantly higher in the group with severe vs. uncomplicated disease. Thus, the roles for these two cytokines in severe malaria, may deserve further investigation. A complicating factor is that greater IL-10 elevation may be a response to a heavy parasite burden and/or may promote parasite replication. IL-10 elevation that persisted over the first 2 days after admission was significantly associated with subsequent nosocomial infections in the group with severe malaria suggesting its possible role in acquired immune suppression syndrome.

immunology↗