Zika virus (ZIKV) infection results in embryonic microcephaly and has been declared a global health emergency by the World Health Organization. Disruption of the neural progenitor cells is considered to be the major cause of microcephaly; however, the fate of other cell types, including differentiated neurons and vascular cells, remains unknown. Since infected mouse embryos die perinatally, it also remains unknown whether ZIKV infection can cause postnatal microcephaly in animal models. Now, on p. 4127, Jian-Fu Chen and colleagues report a postnatal model for ZIKV infection using intracerebral inoculation of embryonic brains with the ZIKV. The infected pups survive after birth and show postnatal microcephaly, which bears relevance for a better understanding of the microcephaly observed in ZIKV-infected newborn humans. In addition to microcephaly, the postnatal mouse model recapitulates several aspects of fetal brain abnormalities associated with ZIKV in humans, including extensive neuronal apoptosis and loss, axonal rarefaction, corpus callosum diminishment, and reactive astrocyte and microglial cell accumulation. Furthermore, the authors show that ZIKV infection leads to increased vessel density and vessel diameter, and causes blood–brain barrier leakage in the developing brain. While further research is required to better characterise the approach, the development of a postnatal model for ZIKV infection is an important step forward in understanding this disease, and the findings reported by the authors offer novel insight into the pathology of ZIKV infection in the postnatal setting.
Initiation and subsequent growth of the mammalian tooth depends on distinct populations of epithelial and mesenchymal stem cells located in the labial cervical loop (LaCL) and the neurovascular bundle, respectively. In rodents, Sox2 marks the dental epithelial stem cells (DESCs) and has been shown to be an important regulator of tooth development, but the molecular mechanism by which this occurs has not been determined. In this issue (p. 4115), Brad Amendt and colleagues uncover a Pitx2/Sox2/Lef-1 network that controls the epithelial stem cell niche in the continuously erupting rodent incisor. The authors demonstrate that Sox2 is necessary for the maintenance of the stem cell niche, as inactivation of Sox2 leads to lower incisor arrest, as well as abnormalities in the upper incisor and molar teeth. Conditional overexpression of Lef-1 can partially rescue the Sox2-related defect in incisor growth, possibly owing to increased cell proliferation at embryonic stages and the formation of a new compartment of stem cells in the LaCL. The authors also provide evidence for physical interaction between Pitx2 and Sox2, and show how both factors are core components of the Pitx2/Sox2/Lef-1 network. Together, these findings represent a significant milestone in our understanding of the transcriptional control that defines dental stem cell development and differentiation.
Kathryn Anderson is Professor and Chair of the Developmental Biology Program at the Sloan Kettering Institute in New York. Her lab investigates the genetic networks underlying the patterning and morphogenesis of the early mouse embryo. We caught up with Kathryn at the 2016 Society for Developmental Biology – International Society of Differentiation joint meeting in Boston, where she was awarded the Edwin G. Conklin medal.
This Review discusses how and when transposable elements are expressed during development and how they modulate genome architecture, gene regulatory networks and protein function during embryogenesis.
Joachim Wittbrodt and colleagues present critical improvements to the DamID protocol improve specificity and sensitivity in determining genome-wide protein-DNA interactions in transient or stable transgenic animal lines.
Reinhard Köster and colleagues present Tamoxifen-induced Caspase activation in zebrafish. This enables fast, efficient and specific cell ablation via targeted apoptosis.
This meeting report from Steven Pollard highlights the major advances and emerging trends in quantitative stem cell biology as presented at the 5th annual Cambridge Stem Cell Symposium this year.
The first news came as a shock: so the British Railways are not always perfectly on time? For an Italian, that was a massive cultural shock. The second one was even more surprising: English weather is not that bad; actually, it is better than Parisian weather. But still, I was unable, on the train from Paris to Cambridge, to stop thinking about how exciting it will be to spend some time in a new lab and discover (brace yourself for the jargon) how to properly forward program induced pluripotent stem cells (iPSCs) into megakaryocytes (MKs).
I am Alessandro, a graduate student in Dr. Hana Raslova’s lab and I am currently trying to model and study the pathological mechanism of an inherited platelet disorder associated with a predisposition to develop leukemia. In our lab, we developed several iPSC models for haematological diseases and the transition from the undifferentiated, pluripotent state to the committed, haematopoietic state, in particular when it comes to the specification of MKs progenitors and mature cells, it is not an easy task. That is why I have found the approach developed by Dr. Ghevaert’s team extremely intriguing: instead of recapitulating in vitro the key developmental events of the primitive haematopoiesis, they took a more direct approach and imposed a combination of three transcription factors of great importance for MKs on the pluripotent stem cells. This transcriptional program, called forward programming, force the cells directly into the megakaryocytic fate, generating a highly proliferative cell that retains the main features of mature megakaryocytes, included the production of platelets. Indeed, such a tool would give a major boost to my project of disease modeling, mostly allowing me entire batteries of biochemical assays. After some e-mailing during last summer, Dr. Ghevaert kindly allowed me to visit the lab and try to forward program some of our cell lines.
Guided by the amazing Dr. Thomas Moreau, I was able to achieve this task and see myself the efficient conversion of my iPSCs into megakaryocytes, although some of them did not particularly appreciate the short stint in England and decided to proliferate less efficiently than the usual! Nonetheless, the time in Cambridge was incredibly fruitful: the folks there really helped me to blend in the lab and we had interesting conversations about our work and the different approaches; we also shared some enjoyable time off, listening to the Dr. Ghevaert’s skilled execution of some piano classics! And last but not least, Cambridge is such a lovely town, full of history and beauty, a pleasant alternative to the urban complexity of Paris.
The river Cam
I am really grateful to The Company of Biologists and the journal Disease Models and Mechanisms for their crucial support during this short stay. I hope that more young scientists will continue to benefit from your generous support. Many thanks to the entire Ghevaert’s team for hosting and a big merci to Thomas Moreau for his patience and all the scientific discussions we had.
Bellvitge Institute for Biomedical Research (IDIBELL) offers a postdoctoral contract to join the Transformation and Metastasis group led by Dr. Eva González-Suárez within the Cancer Epigenetics and Biology Program (PEBC) http://www.idibell.cat/modul/area-6-programa-depigenetica-i-biologia-del-cancer/ca & http://pebc.cat/
The laboratory of Dr Gonzalez Suarez is funded by the Susan G Komen Foundation and a European Research Council ERC-Consolidator grant. The candidate will join a project focused on understanding tumor-immune crosstalk in epithelial tumors.
The primary goal of Dr. Eva González-Suárez´s laboratory is to understand the signaling pathways implicated in epithelial stem cell fate, their alterations during cancer and metastasis, and the interactions between tumor cells and microenvironment. We have a multidisciplinary approach using mouse models, cell cultures, clinical samples and molecular and cell biology techniques to translate basic research into clinically relevant results.
REQUIREMENTS
We are looking for motivated postdoctoral scientists holding a PhD in a relevant discipline with interest in cancer biology. Candidates must have:
– An outstanding publication record in peer review journals
– Experience working with mouse models of cancer and patient derived xenografts.
– Strong technical skills in tumor immunology, molecular biology and lineage tracing.
WE OFFER
The opportunity to contribute to cutting-edge research projects and work closely with an international team of scientists and work in one of the leading labs in Europe.
A 3-year full time contract, immediate start. Renewal based on performance.
APPLICATION
Applications must include a CV with a cover letter and contacts for 2 references
Please apply by email to: egsuarez@idibell.cat. Please, clearly state in the subject of your email “Postdoc Position” and a link to your most outstanding publication
The Symposium aims to offer a broad view over the latest developments and updates in Bioimage analysis and can be attended independent of registration to training schools. It includes
A Showcase giving exposure to open source software packages and tools updates
Company’s products
Community round tables
Career path debates
Community progress report
Bioimage Analysis will be covered as a broad field of Research, Technology-development and Service-for-Data-Producers (i.e. researchers in Life Science) in the context of many types of BioImage data: Optical Microscopy, Electron Microscopy, Medical Imaging, among others.
More About NEUBIAS, Mobility Grants, Careers, Action
The Network
NEUBIAS is a network Action funded by COST (www.cost.eu), aiming to maximize the impact of advances in imaging technology on the Life Sciences, and to boost the productivity of bioimaging-based research projects in Europe. The Action intends to provide a stronger identity to Bioimage Analysts by organising a new type of meeting fostering interactions between all stakeholders (i.e. NEUBIAS 2020).
NEUBIAS also provides mobility funds for scientists willing to expand their knowledge in Bioimage Analysis and/or to develop Image Analysis capabilities for their research project. Check the next Call for Short Term Scientific Missions, closing on November 15th, 2016.
NEUBIAS also needs the input from the whole community to devise best-practice guidelines for the career path of BioImage Analysis, a new profession still not fully recognized in the field. If your work activity embraces Bioimage Analysis to support Life Science (as a service, collaboration etc…), please take 5 minutes to fill our new “Career Consultation”:
Gaby Martins (Event Host, co-organizer)
Sebastian Munck and Arne Seitz (Event Co-organizers)
Jean-Yves Tinevez (Training School co-Organizer)
Fabrice Cordelières and Paulo Aguiar (Training School Organizers)
Perrine Paul-Gilloteaux, Chong Zhang, Sébastien Tosi and Graeme Ball (Taggathon Organizers)
Julia Fernandez Rodriguez (STSMs coordinator)
Kota Miura (Vice Chair, Training School co organizer)
Julien Colombelli (Chair)
The original chimera was a beast made out of different beasts, with “the head of a lion and the tail of a serpent, while her body was that of a goat, and she breathed forth flames of fire”. Today’s biomedical definition is not too far from Homer’s, a chimera being an organism made up of cells from more than one zygote. As an experimental technique, chimeras have been used for decades to define the developmental potential of cells and the influence of the environment cells find themselves in (does a cell stick to its original fate if transplanted to a different location? Does the environment override an initial choice?). Even today, one stringent test for pluripotency is the ability of transplanted cells to give rise to all cell types in the chimeric organism.
The first mouse chimeras (1, 2) were made by aggregating two pre-implantation (cleavage stage) embryos together: the resultant embryos, twice the normal size, gave rise to normal sized chimeric pups. Subsequent techniques involved injecting exogenous cells into blastocysts. But what about the decisions that happen in later stages? Post-implantation mouse chimeras were pioneered by Rosa Beddington, and her two single author papers describing the work, published in 1981 and 1982 in the Journal of Embryology and Experimental Morphology (the forerunner of Development), are the subject of this Forgotten Classics highlight.
From Figure 3 in the 1981 paper. An 8th day mouse embryo.
The two papers should be read together, the second being a continuation and expansion of the first. The question that drove the project concerned the patterning of the epiblast (which was then referred to as the embryonic ectoderm), the tissue that gives rise to the embryo proper. The problem was articulated by Beddington as follows:
“During gastrulation the single epithelial sheet of embryonic ectoderm is converted into a highly complicated form, made up of a variety of tissue types and embodying the basic design of the foetus. This means that the key to foetal organization must lie in the orderly allocation of tissue primordia within the embryonic ectoderm”
The problem was the inaccessibility of the mouse embryo for experimental manipulation. In Beddington’s time, while rats could be cultured ex utero until the end of gastrulation, mouse culturing techniques did not achieve comparable successes. Her papers describe a technique by which embryos are dissected from the uterus at day 8, at the late-primitive-streak stage, and then cultured for 36 hours in rat serum. These 36 hours are “a time of intensive cell division and differentiation and also marked by substantial morphogenetic activity”. The culture produced early-somite-stage embryos that look normal when compared to in utero counterparts, with some minor differences (they were more translucent, and had expanded yolk sacs). The work was a technical feat: dissecting early mouse embryos is not easy, yet Beddington was blessed with legendary dissecting skills.
Figure 1 from the 1982 paper. Beddington’s drawing of a sagittal section through an 8th day embryo, showing cell types and transplantation sites
This technique allowed the assessment of epiblast cell lineage in the intact embryo. As encountered in the last Forgotten Classic, cell lineage analysis requires a marker, and Beddington chose 3H-thymidine (3H-T), a radiolabelled nucleoside you can visualise with autoradiography. In many ways 3H-T is not the ideal marker: unlike genetic markers it dilutes with cell divisions; subsequent work indicated it can inhibit DNA synthesis and be cytotoxic (although this does not seem to have been a problem with Beddington’s work); and, perhaps most annoyingly, once you have your stained and sectioned embryos, you have to cover them with autoradiographic stripping film for three weeks before processing and analysing the film. Three weeks! And even then, after this intricate and demanding procedure, defective processing meant Beddington had to discard whole batches of slides.
The method was to bathe day 8 embryos in 3H-T, remove cells from different regions of the epiblast, inject them into unstained, synchronous hosts, and see where the labelled cells ended up after 36 hours in culture. An elegant aspect of the work is the controls: controls that hadn’t been labelled; controls that had been bathed in 3H-T and cultured without dissection; controls that had been fixed before culturing. All of these experiments, diagrammed with characteristic artistry in the figure, were also carried out with reference to in utero development.
Figure 1 from the 1981 paper, showing the general strategy of the experiments.
With the method established – labelled controls looked pretty much the same as unlabelled controls, and the labelled cells could colonise host tissues and did not form structures you would not expect to see – the stage was set to address her main questions. Was cell fate spatially patterned in the epiblast? In other words, could you draw a fate map? And how plastic was this fate?
Beddington performed two types of injection. Orthotopic injections involved like-for-like injections, with labelled epiblast from a particular donor region injected into the same region in the host. These injections showed that different regions of the epiblast gave rise to different parts of the post-gastrulation embryo: for instance, distal epiblast could contribute to somites and notochord, but anterior epiblast could not. As Beddington acknowledged, this may not have been particularly surprising given results in the chick, but it was important to demonstrate that there was a consistent regionalised pattern of tissue allocation during gastrulation. You could begin to map the post-gastrulation embryo back to the epiblast.
Figure 2 from the 1981 paper, showing the transplantation technique. The embryo was held in place with a holding pipette, and donor cells inserted into the tissue with an injection pipette.
What orthotopic transplantation cannot reveal is whether this regionalisation reflects an inherent cell fate, or the consequence of epiblast cells perceiving extrinsic cues. Heterotopic transplantation, putting donor cells in a location in the host that is different from where they came from, allowed Beddington to get at this. She found no evidence for rigid cell fate in the epiblast: when transplanted to a different location, cells readily contributed structures other than those they form normally (although there were some ‘propensities’ of certain cells to contribute to one structure or another, suggesting some degree of cell fate restriction). Thus, cell fate at the epiblast stage is ‘plastic’, and could be readily influenced by the environment the cells find themselves in. So the story is a mix: you can draw a fate map on the epiblast, but the cells are happy, if we labour the metaphor a bit, to learn a new language when transplanted into another country.
These papers represent a landmark of mouse embryology. In the following decades, many of the molecular players in epiblast patterning have been identified, as well as the mechanisms that maintain epiblast cell potency, supporting and expanding Beddington’s work. The recent BSDB meeting celebrating the present and future of chimeric research shows that chimeras still have as much to tell us about development as they taught Rosa Beddington in the early 1980s.
“The findings of these works have revealed the regionalisation of cell fates in the germ layers of the gastrulating mouse embryo, pointing to the establishment of a basic body plan. These studies also outlined an experimental paradigm for the analysis of cell fate and potency in a mammalian embryo using innovative techniques of micromanipulation, lineage tracking and whole mouse embryo culture.
Recently, there is heightened interest in the application of these techniques to generate post-implantation chimeras for assessing the differentiation potential of stem cells, such as mouse epiblast stem cells and human pluripotent stem cells1 . It is therefore timely and newsworthy to highlight Rosa’s papers.”
1: Tam PPL (2016) Human stem cells can differentiate in post-implantation mouse embryos. Cell Stem Cell 18: 3-4. PMID 26748747 DOI:10.1016/j.stem.2015.12.010
“It is hard to remember a time before the fate map of the mammalian embryo had experimental backing, but in the late 70s, as mammalian embryo culture and manipulation techniques were just beginning to make great strides, it was the chick fate map that guided us and provided a template for investigation. These two papers by Rosa Beddington were remarkable in adapting newly devised rat embryo culture methods to allow investigation of mouse postimplantation embryos ex utero and, for the first time, developing methods for making experimental postimplantation mouse chimeras. Rosa used these techniques to approach two related aspects of embryonic cells: fate and potential, fate being the normal differentiation outcome of a cell in undisturbed development and potential being what that cell is capable of doing in altered circumstances, such as being placed heterotopically in a different position in the embryo.
These two papers comprise the bulk of Rosa’s thesis work for her D.Phil. from Oxford University in 1981. I was privileged to serve as her supervisor for this work and rereading the papers brought back the sheer gutsiness of this brilliant young student as she pioneered a new methodology for mouse embryology. It also sent me searching for my copy of her dissertation, typewritten, with original photos taped onto the pages, where I marvelled anew at the camera lucida drawings of serial sections with labelled cells marked in pen, and hand drawn embryos with color-coded fate maps in coloured pencil.
In the thesis, the work was divided into a chapter on cell fate (orthotopic tissue transplants in synchronous embryos) and a separate chapter on cell potency (heterotopic transplants in synchronous embryos). In the subsequent publications this fate vs. potential distinction is not highlighted and both papers refer to “potency” in the title. Although I don’t remember why this was done, I imagine it was because of Rosa’s exactitude in the definition of the terms, as even synchronous orthotopic tissue transplantation is a disruption and might be subtly altering ‘normal’ cell fate. As we understand more about altering cell states in the age of induced pluripotent stem cells, this assiduous attention to terminology and methodological detail is more relevant than ever. Rosa’s papers, nonetheless, ushered in an era of rapid advances in understanding cell fate and potential in the postimplantation mammalian embryo.”
Aidan Maartens
This post is part of a series on forgotten classics of developmental biology. You can read the introduction to the series here and read other posts in this series here. We also welcome suggestions for future Forgotten Classics.
A roundup of the Node’s highlights from October 2016.
October’s most discussed post came from Development’s Executive Editor Katherine Brown, who reported from a workshop on preprints in Cambridge and gave a journal’s perspective on the promises and challenges of preprinting. The comments section is worth reading, as is this recent post from the organiser of the workshop, Alfonso Martinez-Arias.
Here we highlight some developmental biology related content from other journals published by The Company of Biologists.
Helio Roque and colleagues describe that flies lacking MKS, a component of the transition zone in cilia, show abnormalities during development, but not in the adult.
Nicholas Pilon and colleagues describe how a mouse line found in a screen for genes involved in neural crest development provides a model for Waardenburg syndrome type 4.
Colin Bingle and colleagues develop an in vitro model of the murine middle ear epithelium, recapitulating cell populations and protein production.
In his Editorial, Senior Editor Ross Cagan gives some tips for those wanting to conduct drug screening in model systems
Johan de Rooij and colleagues disrupted αE-catenin function in developing zebrafish, and found that specifically disrupting αE-catenin mechnotransduction leads to defective convergence and extension.
Elly Ordan and Talila Volk describe how Amontillado, the Drosophila homologue of pheremone convertase 2, cleaves Slit to promote muscle patterning.
DMM is looking for an enthusiastic intern who wishes to gain experience in science publishing, including writing press releases, contributing to our social media activities, and supporting our Reviews Editor with commissioned articles. The internship is envisaged to last for 9 months at a salary of £20,000 per annum pro rata.
Our interns have a great track record of continuing on into important publishing roles.
Joining an experienced and successful team, the internship offers an ideal opportunity to gain in-depth experience on a growing Open Access journal in the exciting and fast-moving field of translational research. DMM publishes primary research articles and a well-regarded front section, including commissioned reviews and poster articles, thought-provoking editorials and interviews with leaders in the field. We also have an active social media presence and will be growing our press release programme. The intern will work alongside an established publishing team in our Cambridge offices.
Because the journal serves both basic biomedical researchers and clinicians, applicants will have a PhD or MD, ideally with some relevant research experience, and a broad knowledge of model organisms and disease issues.
Is the role for you? You would be expected to…
Support our Reviews Editor:
• Identify and commission topical front-section content from top-ranking scientists, see articles through peer review and work closely with authors to finalise articles for publication.
• Travel to international scientific conferences and research institutes, representing the journal, keeping abreast of the latest research and making contacts in the DMM community.
Develop your own areas of activity:
• Spot newsworthy articles, write informative press releases and handle any media enquiries.
• Interview high-profile scientists in the biomedical arena.
• Contribute to our social media output.
• Be creative – contribute other ideas for the journal’s development and promotion.
Essential requirements for the job are enthusiasm, commitment, judgement and integrity. Candidates should have excellent interpersonal skills and confidence, excellent oral and written communication skills, and a broad interest in research and the research community. They should also be willing to travel. Previous editorial experience is not required, but we would expect candidates to be able to demonstrate an interest in scientific communication.
Chapter 1: How Embryogenesis Began in Evolution
Chapter 2: Developmental Anatomy of the Axolotl
Chapter 3: Developmental Genetics: A Flying Tour
Chapter 4: Epigenetics: Higher Order Gene
Control
Chapter 5: The Cytoskeleton
Chapter 6: The Cell State Splitter and Differentiation Waves
Chapter 7: The Differentiation Tree and the Fate Map of the Axolotl
Chapter 8: Signal Transduction from the Cell State Splitter to the Nuclear State Splitter
Chapter 9: The Nuclear State Splitter
Chapter 10: Irritable Protoplasm: Forerunners to Differentiation Waves
Chapter 11: Why Evolution is Progressive
Chapter 12: Wholeness and the Implicate Embryo: Embryogenesis as Self-Construction of the Observer
Index
embryonic microcephaly and has been declared a global health emergency by the World Health Organization. Disruption of the neural progenitor cells is considered to be the major cause of microcephaly; however, the fate of other cell types, including differentiated neurons and vascular cells, remains unknown. Since infected mouse embryos die perinatally, it also remains unknown whether ZIKV infection can cause postnatal microcephaly in animal models. Now, on p. 4127, Jian-Fu Chen and colleagues report a postnatal model for ZIKV infection using intracerebral inoculation of embryonic brains with the ZIKV. The infected pups survive after birth and show postnatal microcephaly, which bears relevance for a better understanding of the microcephaly observed in ZIKV-infected newborn humans. In addition to microcephaly, the postnatal mouse model recapitulates several aspects of fetal brain abnormalities associated with ZIKV in humans, including extensive neuronal apoptosis and loss, axonal rarefaction, corpus callosum diminishment, and reactive astrocyte and microglial cell accumulation. Furthermore, the authors show that ZIKV infection leads to increased vessel density and vessel diameter, and causes blood–brain barrier leakage in the developing brain. While further research is required to better characterise the approach, the development of a postnatal model for ZIKV infection is an important step forward in understanding this disease, and the findings reported by the authors offer novel insight into the pathology of ZIKV infection in the postnatal setting.
Initiation and subsequent growth of the mammalian tooth depends on distinct populations of epithelial and mesenchymal stem cells located in the labial cervical loop (LaCL) and the neurovascular bundle, respectively. In rodents, Sox2 marks the dental epithelial stem cells (DESCs) and has been shown to be an important regulator of tooth development, but the molecular mechanism by which this occurs has not been determined. In this issue (p. 4115), Brad Amendt and colleagues uncover a Pitx2/Sox2/Lef-1 network that controls the epithelial stem cell niche in the continuously erupting rodent incisor. The authors demonstrate that Sox2 is necessary for the maintenance of the stem cell niche, as inactivation of Sox2 leads to lower incisor arrest, as well as abnormalities in the upper incisor and molar teeth. Conditional overexpression of Lef-1 can partially rescue the Sox2-related defect in incisor growth, possibly owing to increased cell proliferation at embryonic stages and the formation of a new compartment of stem cells in the LaCL. The authors also provide evidence for physical interaction between Pitx2 and Sox2, and show how both factors are core components of the Pitx2/Sox2/Lef-1 network. Together, these findings represent a significant milestone in our understanding of the transcriptional control that defines dental stem cell development and differentiation.
Kathryn Anderson is Professor and Chair of the Developmental Biology Program at the Sloan Kettering Institute in New York. Her lab investigates the genetic networks underlying the patterning and morphogenesis of the early mouse embryo. We caught up with Kathryn at the 2016 Society for Developmental Biology – International Society of Differentiation joint meeting in Boston, where she was awarded the Edwin G. Conklin medal.
This Review discusses how and when transposable elements are expressed during development and how they modulate genome architecture, gene regulatory networks and protein function during embryogenesis.
(No Ratings Yet)
Loading...
(3 votes)
(8 votes)
s.