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Hypermethylation of the promoters of tumour suppressor genes represses transcription of these genes, conferring growth advantages to cancer cells. How these changes arise is poorly understood. Here we show that the activity of oxygen-dependent ten-eleven translocation (TET) enzymes is reduced by tumour hypoxia in human and mouse cells. TET enzymes catalyse DNA demethylation through 5-methylcytosine oxidation. This reduction in activity occurs independently of hypoxia-associated alterations in TET expression, proliferation, metabolism, hypoxia-inducible factor activity or reactive oxygen species, and depends directly on oxygen shortage. Hypoxia-induced loss of TET activity increases hypermethylation at gene promoters in vitro . In patients, tumour suppressor gene promoters are markedly more methylated in hypoxic tumour tissue, independent of proliferation, stromal cell infiltration and tumour characteristics. Our data suggest that up to half of hypermethylation events are due to hypoxia, with these events conferring a selective advantage. Accordingly, increased hypoxia in mouse breast tumours increases hypermethylation, while restoration of tumour oxygenation abrogates this effect. Tumour hypoxia therefore acts as a novel regulator of DNA methylation. Genes silenced by hypoxia Tumours are epigenetically distinct from their tissue of origin, frequently showing increased DNA methylation of tumour suppressor gene promoters, but how these changes arise is poorly understood. Here, Diether Lambrechts and colleagues report that tumour hypoxia, pervasive in many solid tumours, reduces the activity of the oxygen-dependent ten-eleven translocation (TET) enzymes, which catalyse DNA demethylation through 5-methylcytosine oxidation. They show that oxygen is an important co-factor for TET activity, and hypoxia-induced loss of TET activity increases hypermethylation at gene promoters in vitro and at tumour suppressor genes in hypoxic tumours. The authors propose that tumour hypoxia directly reduces TET activity, leading to changes in DNA methylation and silencing gene expression. Countering hypermethylation by inhibiting DNA methylation or by normalizing tumour blood supply may therefore be of therapeutic benefit.

Previous studies have shown genome-wide associations between polymorphisms in the gene FTO (fat mass and obesity associated) and type 2 diabetes and obesity, and genetic manipulation of Fto in mice causes feeding dysregulation and body weight changes. Here Hess et al . show that FTO affects the activity and function of midbrain dopaminergic neurons and subsequent reward-related behaviors. The study also shows that FTO acts as a demethylating enzyme for specific mRNAs in vivo , including mRNAs in the dopaminergic signaling pathway. Dopaminergic (DA) signaling governs the control of complex behaviors, and its deregulation has been implicated in a wide range of diseases. Here we demonstrate that inactivation of the Fto gene, encoding a nucleic acid demethylase, impairs dopamine receptor type 2 (D2R) and type 3 (D3R) (collectively, 'D2-like receptor')-dependent control of neuronal activity and behavioral responses. Conventional and DA neuron–specific Fto knockout mice show attenuated activation of G protein–coupled inwardly-rectifying potassium (GIRK) channel conductance by cocaine and quinpirole. Impaired D2-like receptor–mediated autoinhibition results in attenuated quinpirole-mediated reduction of locomotion and an enhanced sensitivity to the locomotor- and reward-stimulatory actions of cocaine. Analysis of global N 6 -methyladenosine (m 6 A) modification of mRNAs using methylated RNA immunoprecipitation coupled with next-generation sequencing in the midbrain and striatum of Fto -deficient mice revealed increased adenosine methylation in a subset of mRNAs important for neuronal signaling, including many in the DA signaling pathway. Several proteins encoded by these mRNAs had altered expression levels. Collectively, FTO regulates the demethylation of specific mRNAs in vivo , and this activity relates to the control of DA transmission.

A well known, epidemiologically reproducible risk factor for human carcinomas is the long-term consumption of “red meat” of mammalian origin. Although multiple theories have attempted to explain this human-specific association, none have been conclusively proven. We used an improved method to survey common foods for free and glycosidically bound forms of the nonhuman sialic acidN-glycolylneuraminic acid (Neu5Gc), showing that it is highly and selectively enriched in red meat. The bound form of Neu5Gc is bioavailable, undergoing metabolic incorporation into human tissues, despite being a foreign antigen. Interactions of this antigen with circulating anti-Neu5Gc antibodies could potentially incite inflammation. Indeed, when human-like Neu5Gc-deficient mice were fed bioavailable Neu5Gc and challenged with anti-Neu5Gc antibodies, they developed evidence of systemic inflammation. Such mice are already prone to develop occasional tumors of the liver, an organ that can incorporate dietary Neu5Gc. Neu5Gc-deficient mice immunized against Neu5Gc and fed bioavailable Neu5Gc developed a much higher incidence of hepatocellular carcinomas, with evidence of Neu5Gc accumulation. Taken together, our data provide an unusual mechanistic explanation for the epidemiological association between red meat consumption and carcinoma risk. This mechanism might also contribute to other chronic inflammatory processes epidemiologically associated with red meat consumption.

Cardiovascular disease (CVD) events due to atherosclerosis cause one-third of worldwide deaths and risk factors include physical inactivity, age, dyslipidemia, hypertension, diabetes, obesity, smoking, and red meat consumption. However, ∼15% of first-time events occur without such factors. In contrast, coronary events are extremely rare even in closely related chimpanzees in captivity, despite human-like CVD–risk-prone blood lipid profiles, hypertension, and mild atherosclerosis. Similarly, red meat-associated enhancement of CVD event risk does not seem to occur in other carnivorous mammals. Thus, heightened CVD risk may be intrinsic to humans, and genetic changes during our evolution need consideration. Humans exhibit a species-specific deficiency of the sialic acid N-glycolylneuraminic acid (Neu5Gc), due to pseudogenization of cytidine monophosphate-N-acetylneuraminic acid (Neu5Ac) hydroxylase (CMAH), which occurred in hominin ancestors ∼2 to 3 Mya. Ldlr −/− mice with human-like Cmah deficiency fed a sialic acids (Sias)-free high-fat diet (HFD) showed ∼1.9-fold increased atherogenesis over Cmah wild-type Ldlr −/− mice, associated with elevated macrophage cytokine expression and enhanced hyperglycemia. Human consumption of Neu5Gc (from red meat) acts as a “xeno-autoantigen” via metabolic incorporation into endogenous glycoconjugates, as interactions with circulating anti-Neu5Gc “xeno-autoantibodies” potentiate chronic inflammation (“xenosialitis”). Cmah −/− Ldlr −/− mice immunized with Neu5Gc-bearing antigens to generate human-like anti-Neu5Gc antibodies suffered a ∼2.4-fold increased atherosclerosis on a Neu5Gc-rich HFD, compared with Neu5Ac-rich or Sias-free HFD. Lesions in Neu5Gc-immunized and Neu5Gc-rich HFD-fed Cmah −/− Ldlr −/− mice were more advanced but unexplained by lipoprotein or glucose changes. Human evolutionary loss of CMAH likely contributes to atherosclerosis predisposition via multiple intrinsic and extrinsic mechanisms, and future studies could consider this more human-like model.

Epigenetic reprogramming resets parental epigenetic memories and differentiates primordial germ cells (PGCs) into mitotic pro-spermatogonia or oogonia. This process ensures sexually dimorphic germ cell development for totipotency 1 . In vitro reconstitution of epigenetic reprogramming in humans remains a fundamental challenge. Here we establish a strategy for inducing epigenetic reprogramming and differentiation of pluripotent stem-cell-derived human PGC-like cells (hPGCLCs) into mitotic pro-spermatogonia or oogonia, coupled with their extensive amplification (about >10 10 -fold). Bone morphogenetic protein (BMP) signalling is a key driver of these processes. BMP-driven hPGCLC differentiation involves attenuation of the MAPK (ERK) pathway and both de novo and maintenance DNA methyltransferase activities, which probably promote replication-coupled, passive DNA demethylation. hPGCLCs deficient in TET1, an active DNA demethylase abundant in human germ cells 2 , 3 , differentiate into extraembryonic cells, including amnion, with de-repression of key genes that bear bivalent promoters. These cells fail to fully activate genes vital for spermatogenesis and oogenesis, and their promoters remain methylated. Our study provides a framework for epigenetic reprogramming in humans and an important advance in human biology. Through the generation of abundant mitotic pro-spermatogonia and oogonia-like cells, our results also represent a milestone for human in vitro gametogenesis research and its potential translation into reproductive medicine. A new strategy that involves signalling-molecule-driven differentiation can induce epigenetic reprogramming of human pluripotent stem cell-derived primordial germ cell-like cells to pro-spermatogonia and oogonia-like cells with massive propagation and high efficiency.

Mammals express the sialic acids N -acetylneuraminic acid (Neu5Ac) and N- glycolylneuraminic acid (Neu5Gc) on cell surfaces, where they act as receptors for pathogens, including influenza A virus (IAV). Neu5Gc is synthesized from Neu5Ac by the enzyme cytidine monophosphate- N -acetylneuraminic acid hydroxylase (CMAH). In humans, this enzyme is inactive and only Neu5Ac is produced. Ferrets are susceptible to human-adapted IAV strains and have been the dominant animal model for IAV studies. Here we show that ferrets, like humans, do not synthesize Neu5Gc. Genomic analysis reveals an ancient, nine-exon deletion in the ferret CMAH gene that is shared by the Pinnipedia and Musteloidia members of the Carnivora. Interactions between two human strains of IAV with the sialyllactose receptor (sialic acid—α2,6Gal) confirm that the type of terminal sialic acid contributes significantly to IAV receptor specificity. Our results indicate that exclusive expression of Neu5Ac contributes to the susceptibility of ferrets to human-adapted IAV strains. Ferrets constitute a useful model for influenza research because they are susceptible to human-adapted flu viruses. Here, the authors show that ferrets, like humans, lack a functional CMAH enzyme and synthesize a single type of sialic acid (Neu5Ac), resulting in naturally humanized influenza virus receptors.

Peptidylglycine-α-amidating monooxygenase (PAM) is a critical enzyme in the endocrine system responsible for activation, by amidation, of bioactive peptides. To define the clinical phenotype of carriers of genetic mutations associated with impaired PAM-amidating activity (PAM-AMA). We used genetic and phenotypic data from cohort studies: the Malmö Diet and Cancer (MDC; 1991-1996; reexamination in 2002-2012), the Malmö Preventive Project (MPP; 2002-2006), and the UK Biobank (UKB; 2012). Exome-wide association analysis was used to identify loss-of-function (LoF) variants associated with reduced PAM-AMA and subsequently used for association with the outcomes. This study included n∼4500 participants from a subcohort of the MDC (MDC-Cardiovascular cohort), n∼4500 from MPP, and n∼300,000 from UKB. Endocrine-metabolic traits suggested by prior literature, muscle mass, muscle function, and sarcopenia. Two LoF variants in the PAM gene, Ser539Trp (minor allele frequency: 0.7%) and Asp563Gly (5%), independently contributed to a decrease of 2.33 [95% confidence interval (CI): 2.52/2.15; P = 2.5E-140] and 0.98 (1.04/0.92; P = 1.12E-225) SD units of PAM-AMA, respectively. The cumulative effect of the LoF was associated with diabetes, reduced insulin secretion, and higher levels of GH and IGF-1. Moreover, carriers had reduced muscle mass and function, followed by a higher risk of sarcopenia. Indeed, the Ser539Trp mutation increased the risk of sarcopenia by 30% (odds ratio 1.31; 95% CI: 1.16/1.47; P = 9.8E-06), independently of age and diabetes. PAM-AMA genetic deficiency results in a prediabetic sarcopenic phenotype. Early identification of PAM LoF carriers would allow targeted exercise interventions and calls for novel therapies that restore enzymatic activity.

Carnitine is needed for transfer of long-chain fatty acids across the inner mitochondrial membrane for subsequent ß-oxidation. Carnitine can be synthesized by the body and is also obtained in the diet through consumption of meat and dairy products. Defects in carnitine transport such as those caused by defective activity of the OCTN2 transporter encoded by the SLC22A5 gene result in primary carnitine deficiency, and newborn screening programmes can identify patients at risk for this condition before irreversible damage. Initial biochemical diagnosis can be confirmed through molecular testing, although direct study of carnitine transport in fibroblasts is very useful to confirm or exclude primary carnitine deficiency in individuals with genetic variations of unknown clinical significance or who continue to have low levels of carnitine despite negative molecular analyses. Genetic defects in carnitine biosynthesis do not generally result in low plasma levels of carnitine. However, deletion of the trimethyllysine hydroxylase gene, a key gene in carnitine biosynthesis, has been associated with non-dysmorphic autism. Thus, new roles for carnitine are emerging that are unrelated to classic inborn errors of metabolism.

Carbonates exist in a few natural products, but their biosynthetic origins have been unclear. Genetic and biochemical characterization of a flavin-dependent monooxygenase from the cytochalasin cluster now demonstrates conversion of a ketone into a carbonate prior to other tailoring steps. Despite the remarkable versatility displayed by flavin-dependent monooxygenases (FMOs) in natural product biosynthesis, one notably missing activity is the oxidative generation of carbonate functional groups. We describe a multifunctional Baeyer-Villiger monooxygenase, CcsB, which catalyzes the formation of an in-line carbonate in the macrocyclic portion of cytochalasin E. This study expands the repertoire of activities of FMOs and provides a possible synthetic strategy for transformation of ketones into carbonates.

Our group previously investigated the levels of anti-Gal and anti-nonGal IgM and IgG in a cohort of 75 healthy humans of various backgrounds, and found some significant differences related to factors such as age, gender, ABO blood group, diet, vaccination history, and geographic location during childhood. We have now expanded our cohort (n = 84) to investigate the levels of anti-Neu5Gc and anti-nonGal/nonNeu5Gc antibodies in healthy humans. Anti-nonGal and anti-nonGal/nonNeu5Gc human IgM and IgG binding to pRBCs and pAECs from GTKO/CD46 and GTKO/CD46/Neu5GcKO pigs were measured by flow cytometry. Anti-Gal and anti-Neu5Gc IgM and IgG levels were measured by ELISA. In summary, (i) the great majority (almost 100%) of humans had anti-Neu5Gc IgM and IgG antibodies that bound to pAECs and approximately 50% had anti-Neu5Gc antibodies that bound to pRBCs, (ii) there was significantly less human antibody binding to pig cells that did not express either Gal or Neu5Gc compared with those that did not express Gal alone, (iii) the levels of both IgM and IgG binding to GTKO/CD46/Neu5GcKO pRBCs and pAECs were low, (iv) the level of anti-Neu5Gc IgG was higher in men than women, (v) the level did not change with age or diet, and there was some variability associated with (vi) previous vaccination history and (vii) the geographic region in which the individual spent his or her childhood. Our study confirms that human antibody binding to RBCs and AECs from GTKO/CD46/Neu5GcKO pigs is greatly reduced compared to binding to GTKO/CD46 cells. However, all humans appear to have a low level of antibody that binds to pAECs that is not directed to either Gal or Neu5Gc. Our findings require consideration in planning clinical trials of xenotransplantation.