A loss-of-function approach in mice is used to show that the methylcytosine dioxygenase Tet1 has a role in regulating meiosis and meiotic gene activation in female germ cells; Tet1 deficiency does not greatly affect genome-wide demethylation but has a more specific effect on the expression of a subset of meiotic genes. DNA methylation on cytosine is an important epigenetic modification, and the mechanisms controlling 5-methylcytosine (5mC) dynamics constitute an active area of research. The Tet family of dioxygenases can catalyse oxidation of 5mC to produce derivatives such as 5-hydroxymethylcytosine (5hmC), but little is known about the biological function of Tet proteins. Here, a loss-of-function approach in mice is used to show that Tet1 has a role in meiosis and meiotic gene activation in female germ cells. Tet1 deficiency does not greatly impact genome-wide demethylation, but has a more specific effect on the expression of a subset of meiotic genes. Meiosis is a germ-cell-specific cell division process through which haploid gametes are produced for sexual reproduction1. Before the initiation of meiosis, mouse primordial germ cells undergo a series of epigenetic reprogramming steps2,3, including the global erasure of DNA methylation at the 5-position of cytosine (5mC) in CpG-rich DNA4,5. Although several epigenetic regulators, such as Dnmt3l and the histone methyltransferases G9a and Prdm9, have been reported to be crucial for meiosis6, little is known about how the expression of meiotic genes is regulated and how their expression contributes to normal meiosis. Using a loss-of-function approach in mice, here we show that the 5mC-specific dioxygenase Tet1 has an important role in regulating meiosis in mouse oocytes. Tet1 deficiency significantly reduces female germ-cell numbers and fertility. Univalent chromosomes and unresolved DNA double-strand breaks are also observed in Tet1-deficient oocytes. Tet1 deficiency does not greatly affect the genome-wide demethylation that takes place in primordial germ cells, but leads to defective DNA demethylation and decreased expression of a subset of meiotic genes. Our study thus establishes a function for Tet1 in meiosis and meiotic gene activation in female germ cells.

After fertilization in mammals, the maternal and paternal genomes undergo epigenetic reprogramming to prepare for the transition from germ cell to somatic cell transcription programs. One of the events involved in this process is the rapid demethylation of the paternal genome. To identify factors involved in this process, a live-cell imaging system was developed to monitor paternal DNA methylation state in zygotes. Elp3, a component of the elongator complex, is found to be important for paternal DNA demethylation. After fertilization in mammals, the maternal and paternal genomes undergo epigenetic reprogramming to prepare for the transition from germ cell to somatic cell transcription programs. One of the events that takes place is the demethylation of the paternal genome. To identify the factors involved in this process, a live cell imaging system is now used to monitor the paternal DNA methylation state in zygotes; Elp3, a component of the elongator complex, is found to have an important role. The life cycle of mammals begins when a sperm enters an egg. Immediately after fertilization, both the maternal and paternal genomes undergo dramatic reprogramming to prepare for the transition from germ cell to somatic cell transcription programs1. One of the molecular events that takes place during this transition is the demethylation of the paternal genome2,3. Despite extensive efforts, the factors responsible for paternal DNA demethylation have not been identified4. To search for such factors, we developed a live cell imaging system that allows us to monitor the paternal DNA methylation state in zygotes. Through short-interfering-RNA-mediated knockdown in mouse zygotes, we identified Elp3 (also called KAT9), a component of the elongator complex5, to be important for paternal DNA demethylation. We demonstrate that knockdown of Elp3 impairs paternal DNA demethylation as indicated by reporter binding, immunostaining and bisulphite sequencing. Similar results were also obtained when other elongator components, Elp1 and Elp4, were knocked down. Importantly, injection of messenger RNA encoding the Elp3 radical SAM domain mutant, but not the HAT domain mutant, into MII oocytes before fertilization also impaired paternal DNA demethylation, indicating that the SAM radical domain is involved in the demethylation process. Our study not only establishes a critical role for the elongator complex in zygotic paternal genome demethylation, but also indicates that the demethylation process may be mediated through a reaction that requires an intact radical SAM domain.

Background— Pulmonary arterial hypertension (PAH) is a rare but fatal lung disease of diverse origins. PAH is now further subclassified as idiopathic PAH, familial PAH, and associated PAH varieties. Heterozygous mutations in BMPR2 can be detected in 50% to 70% of patients with familial PAH and 10% to 40% of patients with idiopathic PAH. Although endothelial cells have been suspected as the cellular origin of PAH pathogenesis, no direct in vivo evidence has been clearly presented. The present study was designed to investigate whether endothelial Bmpr2 deletion can predispose to PAH. Methods and Results— The Bmpr2 gene was deleted in pulmonary endothelial cells using Bmpr2 conditional knockout mice and a novel endothelial Cre transgenic mouse line. Wide ranges of right ventricular systolic pressure were observed in mice with heterozygous (21.7 to 44.1 mm Hg; median, 23.7 mm Hg) and homozygous (20.7 to 56.3 mm Hg; median, 27 mm Hg) conditional deletion of Bmpr2 in pulmonary endothelial cells compared with control mice (19.9 to 26.7 mm Hg; median, 23 mm Hg) at 2 to 7 months of age. A subset of mice with right ventricular systolic pressure >30 mm Hg exhibited right ventricular hypertrophy and an increase in the number and wall thickness of muscularized distal pulmonary arteries. In the lungs of these mice with high right ventricular systolic pressure, the expression of proteins involved in the pathogenesis of PAH such as serotonin transporter and tenascin-C was elevated in distal arteries and had a high incidence of perivascular leukocyte infiltration and in situ thrombosis. Conclusions— Conditional heterozygous or homozygous Bmpr2 deletion in pulmonary endothelial cells predisposes mice to develop PAH.

Infectious diseases account for more than 20% of global mortality and viruses are responsible for about one-third of these deaths. Highly infectious viral diseases such as severe acute respiratory (SARS), Middle East respiratory syndrome (MERS) and coronavirus disease (COVID-19) are emerging more frequently and their worldwide spread poses a serious threat to human health and the global economy. The current COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As of 27 July 2020, SARS-CoV-2 has infected over 16 million people and led to the death of more than 652,434 individuals as on 27 July 2020 while also causing significant economic losses. To date, there are no vaccines or specific antiviral drugs to prevent or treat COVID-19. Hence, it is necessary to accelerate the development of antiviral drugs and vaccines to help mitigate this pandemic. Non-Conventional antiviral agents must also be considered and exploited. In this regard, nanoparticles can be used as antiviral agents for the treatment of various viral infections. The use of nanoparticles provides an interesting opportunity for the development of novel antiviral therapies with a low probability of developing drug resistance compared to conventional chemical-based antiviral therapies. In this review, we first discuss viral mechanisms of entry into host cells and then we detail the major and important types of nanomaterials that could be used as antiviral agents. These nanomaterials include silver, gold, quantum dots, organic nanoparticles, liposomes, dendrimers and polymers. Further, we consider antiviral mechanisms, the effects of nanoparticles on coronaviruses and therapeutic approaches of nanoparticles. Finally, we provide our perspective on the future of nanoparticles in the fight against viral infections.

ALK1 belongs to the type I receptor family for transforming growth factor-β family ligands. Heterozygous ALK1 mutations cause hereditary hemorrhagic telangiectasia type 2 (HHT2), a multisystemic vascular disorder. Based largely on in vitro studies, TGF-β1 has been considered as the most likely ALK1 ligand related to HHT, yet the identity of the physiologic ALK1 ligand remains controversial. In cultured endothelial cells, ALK1 and another TGF-β type I receptor, ALK5, regulate angiogenesis by controlling TGF-β signal transduction, and ALK5 is required for ALK1 signaling. However, the extent to which such interactions between these 2 receptors play a role in pathogenesis of HHT is unknown. We directly addressed these issues in vivo by comparing the phenotypes of mice in which the Alk1, Alk5, or Tgfbr2 gene was conditionally deleted in restricted vascular endothelia using a novel endothelial Cre transgenic line. Alk1-conditional deletion resulted in severe vascular malformations mimicking all pathologic features of HHT. Yet Alk5- or Tgfbr2-conditional deletion in mice, or Alk5 inhibition in zebrafish, did not affect vessel morphogenesis. These data indicate that neither ALK5 nor TGFBR2 is required for ALK1 signaling pertinent to the pathogenesis of HHT and suggest that HHT might not be a TGF-β subfamily disease.