Starting life in space

As far as we know, animal development is a process that is unique to our planet. That does not mean, however, that development beyond our realm is impossible. As it starts to become feasible for us to look to the sky for another place to call home, we may start to appreciate the gravity of this question. In this issue, Lei et al. investigate for the first time the repercussions of space travel on the first decisions made by mouse embryos. Developing a novel micro-incubator, capable of automatic micrography and fixation, harboring some 3400 two-cell embryos, they investigate the consequences of development after being projected into the stratosphere in the SJ-10 satellite [1]

Starting life in space

As far as we know, animal development is a process that is unique to our planet. That does not mean, however, that development beyond our realm is impossible. As it starts to become feasible for us to look to the sky for another place to call home, we may start to appreciate the gravity of this question. In this issue, Lei et al. investigate for the first time the repercussions of space travel on the first decisions made by mouse embryos. Developing a novel micro-incubator, capable of automatic micrography and fixation, harboring some 3400 two-cell embryos, they investigate the consequences of development after being projected into the stratosphere in the SJ-10 satellite [1]

A dot-stripe Turing model of joint patterning in the tetrapod limb

Author contributions: Conceptualization: J.C.S., T.W.H.; Methodology: J.C.S., T.W.H.; Formal analysis: J.C.S., T.W.H.; Writing - original draft: J.C.S., T.W.H.; Writing - review & editing: J.C.S., T.W.H.; Supervision: T.W.H. Funding: T.W.H. is supported by a Wellcome Strategic Award to study cell fate decisions (105031/D/14/Z), an EMBO long-term fellowship (ALTF 606-2018) and a Cancer Research UK, Cambridge Institute core grant (C9545/A29580). Open access funding provided by the University of Cambridge. Deposited in PMC for immediate release.Peer reviewedPublisher PD

The dynamics of morphogenesis in stem cell-based embryology: Novel insights for symmetry breaking

Breaking embryonic symmetry is an essential prerequisite to shape the initially symmetric embryo into a highly organized body plan that serves as the blueprint of the adult organism. This critical process is driven by morphogen signaling gradients that instruct anteroposterior axis specification. Despite its fundamental importance, what triggers symmetry breaking and how the signaling gradients are established in time and space in the mammalian embryo remain largely unknown. Stem cell-based in vitro models of embryogenesis offer an unprecedented opportunity to quantitatively dissect the multiple physical and molecular processes that shape the mammalian embryo. Here we review biochemical mechanisms governing early mammalian patterning in vivo and highlight recent advances to recreate this in vitro using stem cells. We discuss how the novel insights from these model systems extend previously proposed concepts to illuminate the extent to which embryonic cells have the intrinsic capability to generate specific, reproducible patterns during embryogenesis

Size-regulated symmetry breaking in reaction-diffusion models of developmental transitions

The development of multicellular organisms proceeds through a series of morphogenetic and cell-state transitions, transforming homogeneous zygotes into complex adults by a process of self-organization. Many of these transitions are achieved by spontaneous symmetry breaking mechanisms, allowing cells and tissues to acquire pattern and polarity by virtue of local interactions without an upstream supply of information. The combined work of theory and experiment has elucidated how these systems break symmetry during developmental transitions. Given such transitions are multiple and their temporal ordering is crucial, an equally important question is how these developmental transitions are coordinated in time. Using a minimal mass-conserved substrate-depletion model for symmetry breaking as our case study, we elucidate mechanisms by which cells and tissues can couple reaction-diffusion driven symmetry breaking to the timing of developmental transitions, arguing that the dependence of patterning mode on system size may be a generic principle by which developing organisms measure time. By analyzing different regimes of our model, simulated on growing domains, we elaborate three distinct behaviours, allowing for clock-, timer-, or switch-like dynamics. By relating these behaviours to experimentally documented case studies of developmental timing, we provide a minimal conceptual framework to interrogate how developing organisms coordinate developmental transitions.Comment: 11 pages, 5 figures, Perspective Articl

Developmental clock and mechanism of de novo polarization of the mouse embryo.

Embryo polarization is critical for mouse development; however, neither the regulatory clock nor the molecular trigger that it activates is known. Here, we show that the embryo polarization clock reflects the onset of zygotic genome activation, and we identify three factors required to trigger polarization. Advancing the timing of transcription factor AP-2 gamma (Tfap2c) and TEA domain transcription factor 4 (Tead4) expression in the presence of activated Ras homolog family member A (RhoA) induces precocious polarization as well as subsequent cell fate specification and morphogenesis. Tfap2c and Tead4 induce expression of actin regulators that control the recruitment of apical proteins on the membrane, whereas RhoA regulates their lateral mobility, allowing the emergence of the apical domain. Thus, Tfap2c, Tead4, and RhoA are regulators for the onset of polarization and cell fate segregation in the mouse

Engaging Research with Policy and Action: What are the Challenges of Responding to Zoonotic Disease in Africa?

Zoonotic diseases will maintain a high level of public policy attention in the coming decades. From the spectre of a global pandemic to anxieties over agricultural change, urbanization, social inequality and threats to natural ecosystems, effectively preparing and responding to endemic and emerging diseases will require technological, institutional and social innovation. Much current discussion emphasizes the need for a ‘One Health’ approach: bridging disciplines and sectors to tackle these complex dynamics. However, as attention has increased, so too has an appreciation of the practical challenges in linking multi-disciplinary, multi-sectoral research with policy, action and impact. In this commentary paper, we reflect on these issues with particular reference to the African sub-continent. We structure the themes of our analysis on the existing literature, expert opinion and 11 interviews with leading One Health scholars and practitioners, conducted at an international symposium in 2016. We highlight a variety of challenges in research and knowledge production, in the difficult terrain of implementation and outreach, and in the politicized nature of decision-making and priority setting. We then turn our attention to a number of strategies that might help reconfigure current pathways and accepted norms of practice. These include: (i) challenging scientific expertise; (ii) strengthening national multi-sectoral coordination; (iii) building on what works; and (iv) re-framing policy narratives. We argue that bridging the research-policy-action interface in Africa, and better connecting zoonoses, ecosystems and well-being in the twenty-first century, will ultimately require greater attention to the democratization of science and public policy. This article is part of the themed issue ‘One Health for a changing world: zoonoses, ecosystems and human well-being’

Elizabeth Mumford

Elizabeth Mumford on One Health in the real worl

David Waltner Toews

David Waltner Toews on One Health in the real worl