Author Correction: Methylation of reverse osmosis membrane for superior anti-fouling performance via blocking carboxyl groups in polyamide
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Perfluoroalkyl substances concentration from groundwater via direct contact membrane distillation
A significant yet largely untapped reservoir of polluted water arises from groundwater, where the diffusion of PFAS has been shown to be alarmingly on the rise, driven by prolonged accumulation and restricted avenues for degradation. Direct contact membrane distillation (DCMD) was used to concentrate and remove perfluorooctanoic acid compounds from contaminated groundwater for the first time using commercially available poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) membranes. The temporal membrane fouling propensity over the DCMD test was assessed by analysing the morphological and chemical structural changes of the pristine and used membranes. Over 120 h of test using 10 mg/L PFOA-contaminated model groundwater as feed, the PVDF membrane exhibited a lower extent of flux decline of 15% compared to that 43% obtained by PTFE membrane using feed temperature of 60 oC. This study provides a practical route to pre-concentrate the amphiphilic PFAS contaminants from groundwater.
Rapid brain tumor classification from sparse epigenomic data
Although the intraoperative molecular diagnosis of the approximately 100 known brain tumor entities described to date has been a goal of neuropathology for the past decade, achieving this within a clinically relevant timeframe of under 1 h after biopsy collection remains elusive. Advances in third-generation sequencing have brought this goal closer, but established machine learning techniques rely on computationally intensive methods, making them impractical for live diagnostic workflows in clinical applications. Here we present MethyLYZR, a naive Bayesian framework enabling fully tractable, live classification of cancer epigenomes. For evaluation, we used nanopore sequencing to classify over 200 brain tumor samples, including 10 sequenced in a clinical setting next to the operating room, achieving highly accurate results within 15 min of sequencing. MethyLYZR can be run in parallel with an ongoing nanopore experiment with negligible computational overhead. Therefore, the only limiting factors for even faster time to results are DNA extraction time and the nanopore sequencer’s maximum parallel throughput. Although more evidence from prospective studies is needed, our study suggests the potential applicability of MethyLYZR for live molecular classification of nervous system malignancies using nanopore sequencing not only for the neurosurgical intraoperative use case but also for other oncologic indications and the classification of tumors from cell-free DNA in liquid biopsies.
Atlas of imprinted and allele-specific DNA methylation in the human body
Allele-specific DNA methylation reflects genetic variation and parentally-inherited changes, and is involved in gene regulation and pathologies. Yet, our knowledge of this phenomenon is largely limited to blood. Here we present a comprehensive atlas of allele-specific DNA methylation using deep whole-genome sequencing across 39 normal human cell types. We identified 325k regions, covering 6% of the genome and 11% of CpGs, that show a bimodal distribution of methylated and unmethylated molecules. In 34k of these regions, genetic variations at individual alleles segregate with methylation patterns, validating allele-specific methylation. We also identified 460 regions showing parental allele-specific methylation, the majority of which are novel, as well as 78 regions associated with known imprinted genes. Surprisingly, sequence-dependent and parental allele-dependent methylation is often restricted to specific cell types, revealing unappreciated variation of allele-specific methylation across the human body. Finally, we validate tissue-specific, maternal allele-specific methylation of CHD7, offering a potential mechanism for the paternal bias in the inheritance mode of CHARGE syndrome associated with this gene. The atlas provides a resource for studying allele-specific methylation and regulatory mechanisms underlying imprinted expression in specific human cell types.
Histone H3 lysine 4 methylation recruits DNA demethylases to enforce gene expression in Arabidopsis
Patterning of DNA methylation in eukaryotic genomes is controlled by de novo methylation, maintenance mechanisms and demethylation pathways. In Arabidopsis thaliana, DNA demethylation enzymes are clearly important for shaping methylation patterns, but how they are regulated is poorly understood. Here we show that the targeting of histone H3 lysine four trimethylation (H3K4me3) with the catalytic domain of the SDG2 histone methyltransferase potently erased DNA methylation and gene silencing at FWA and also erased CG DNA methylation in many other regions of the Arabidopsis genome. This methylation erasure was completely blocked in the ros1 dml2 dml3 triple mutant lacking DNA demethylation enzymes, showing that H3K4me3 promotes the active removal of DNA methylation. Conversely, we found that the targeted removal of H3K4me3 increased the efficiency of targeted DNA methylation. These results highlight H3K4me3 as a potent anti-DNA methylation mark and also pave the way for development of more powerful epigenome engineering tools.
Exploring changes in social spider DNA methylation profiles in all cytosine contexts following infection
Living at high density and with low genetic diversity are factors that should both increase the susceptibility of organisms to disease. Therefore, group living organisms, especially those that are inbred, should be especially vulnerable to infection and therefore have particular strategies to cope with infection. Phenotypic plasticity, underpinned by epigenetic changes, could allow group living organisms to rapidly respond to infection challenges. To explore the potential role of epigenetic modifications in the immune response to a group-living species with low genetic diversity, we compared the genome-wide DNA methylation profiles of five colonies of social spiders (Stegodyphus dumicola) in their natural habitat in Namibia at the point just before they succumbed to infection to a point at least six months previously where they were presumably healthier. We found increases in genome- and chromosome-wide methylation levels in the CpG, CHG, and CHH contexts, although the genome-wide changes were not clearly different from zero. These changes were most prominent in the CHG context, especially at a narrow region of chromosome 13, hinting at an as-of-yet unsuspected role of this DNA methylation context in phenotypic plasticity. However, there were few clear patterns of differential methylation at the base level, and genes with a known immune function in spiders had mean methylation changes close to zero. Our results suggest that DNA methylation may change with infection at large genomic scales, but that this type of epigenetic change is not necessarily integral to the immune response of social spiders.
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