Zebrafish Pou5f1-dependent transcriptional networks in temporal control of early development

Time-resolved transcriptome analysis of early pou5f1 mutant zebrafish embryos identified groups of developmental regulators, including SoxB1 genes, that depend on Pou5f1 activity, and a large cluster of differentiation genes which are prematurely expressed.Pou5f1 represses differentiation genes indirectly via activation of germlayer-specific transcriptional repressor genes, including her3, which may mediate in part Pou5f1-dependent repression of neural genes.A dynamic mathematical model is established for Pou5f1 and SoxB1 activity-dependent temporal behaviour of downstream transcriptional regulatory networks. The model predicts that Pou5f1-dependent increase in SoxB1 activity significantly contributes to developmental timing in the early gastrula.Comparison to mouse Pou5f1/Oct4 reveals evolutionary conserved targets. We show that Pou5f1 developmental function is also conserved by demonstrating rescue of Pou5f1 mutant zebrafish embryos by mouse POU5F1/OCT4

Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser.

G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent pathways. Here we report the crystal structure of a constitutively active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin, determined by serial femtosecond X-ray laser crystallography. Together with extensive biochemical and mutagenesis data, the structure reveals an overall architecture of the rhodopsin-arrestin assembly in which rhodopsin uses distinct structural elements, including transmembrane helix 7 and helix 8, to recruit arrestin. Correspondingly, arrestin adopts the pre-activated conformation, with a ∼20° rotation between the amino and carboxy domains, which opens up a cleft in arrestin to accommodate a short helix formed by the second intracellular loop of rhodopsin. This structure provides a basis for understanding GPCR-mediated arrestin-biased signalling and demonstrates the power of X-ray lasers for advancing the frontiers of structural biology

Single-shot diffraction data from the Mimivirus particle using an X-ray free-electron laser

Citation: Ekeberg, T., Svenda, M., Seibert, M. M., Abergel, C., Maia, F. R. N. C., Seltzer, V., . . . Hajdu, J. (2016). Single-shot diffraction data from the Mimivirus particle using an X-ray free-electron laser. Scientific Data, 3. doi:10.1038/sdata.2016.60Free-electron lasers (FEL) hold the potential to revolutionize structural biology by producing X-ray pules short enough to outrun radiation damage, thus allowing imaging of biological samples without the limitation from radiation damage. Thus, a major part of the scientific case for the first FELs was three-dimensional (3D) reconstruction of non-crystalline biological objects. In a recent publication we demonstrated the first 3D reconstruction of a biological object from an X-ray FEL using this technique. The sample was the giant Mimivirus, which is one of the largest known viruses with a diameter of 450 nm. Here we present the dataset used for this successful reconstruction. Data-analysis methods for single-particle imaging at FELs are undergoing heavy development but data collection relies on very limited time available through a highly competitive proposal process. This dataset provides experimental data to the entire community and could boost algorithm development and provide a benchmark dataset for new algorithms

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

A multi-country test of brief reappraisal interventions on emotions during the COVID-19 pandemic.

The COVID-19 pandemic has increased negative emotions and decreased positive emotions globally. Left unchecked, these emotional changes might have a wide array of adverse impacts. To reduce negative emotions and increase positive emotions, we tested the effectiveness of reappraisal, an emotion-regulation strategy that modifies how one thinks about a situation. Participants from 87 countries and regions (n = 21,644) were randomly assigned to one of two brief reappraisal interventions (reconstrual or repurposing) or one of two control conditions (active or passive). Results revealed that both reappraisal interventions (vesus both control conditions) consistently reduced negative emotions and increased positive emotions across different measures. Reconstrual and repurposing interventions had similar effects. Importantly, planned exploratory analyses indicated that reappraisal interventions did not reduce intentions to practice preventive health behaviours. The findings demonstrate the viability of creating scalable, low-cost interventions for use around the world

DNA methylation dynamics during epigenetic reprogramming in the germline and preimplantation embryos.

Methylation of DNA is an essential epigenetic control mechanism in mammals. During embryonic development, cells are directed toward their future lineages, and DNA methylation poses a fundamental epigenetic barrier that guides and restricts differentiation and prevents regression into an undifferentiated state. DNA methylation also plays an important role in sex chromosome dosage compensation, the repression of retrotransposons that threaten genome integrity, the maintenance of genome stability, and the coordinated expression of imprinted genes. However, DNA methylation marks must be globally removed to allow for sexual reproduction and the adoption of the specialized, hypomethylated epigenome of the primordial germ cell and the preimplantation embryo. Recent technological advances in genome-wide DNA methylation analysis and the functional description of novel enzymatic DNA demethylation pathways have provided significant insights into the molecular processes that prepare the mammalian embryo for normal development. Genes Dev 2014 Apr 15; 28(8):812-828

Infertility-Causing Haploinsufficiency Reveals TRIM28/KAP1 Requirement in Spermatogonia

Spermatogenesis relies on exquisite stem cell homeostasis, the carefully balanced self-renewal and differentiation of spermatogonial stem cells (SSCs). Disturbing this equilibrium will likely manifest through sub- or infertility, a global health issue with often idiopathic presentation. In this respect, disease phenotypes caused by haploinsufficiency of otherwise vital developmental genes are of particular interest. Here, we show that mice heterozygous for Trim28, an essential epigenetic regulator, suffer gradual testicular degeneration. Contrary to previous reports we detect Trim28 expression in spermatogonia, albeit at low levels. Further reduction through Trim28 heterozygosity increases the propensity of SSCs to differentiate at the cost of self-renewal

Trim28 is required for epigenetic stability during mouse oocyte to embryo transition.

Phenotypic variability in genetic disease is usually attributed to genetic background variation or environmental influence. Here, we show that deletion of a single gene, Trim28 (Kap1 or Tif1β), from the maternal germ line alone, on an otherwise identical genetic background, results in severe phenotypic and epigenetic variability that leads to embryonic lethality. We identify early and minute epigenetic variations in blastomeres of the preimplantation embryo of these animals, suggesting that the embryonic lethality may result from the misregulation of genomic imprinting in mice lacking maternal Trim28. Our results reveal the long-range effects of a maternal gene deletion on epigenetic memory and illustrate the delicate equilibrium of maternal and zygotic factors during nuclear reprogramming