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The Department of Biology at Swarthmore College invites applications for a two-year visiting assistant professor position starting in August of 2019. Teaching responsibilities consist of one course with weekly laboratory sections each semester. The applicant’s course offerings are anticipated to include a team-taught introductory cell and molecular biology course, an intermediate-level genetics course, and another intermediate course aligned with the applicant’s interests. Additionally, there may be an opportunity to teach an advanced seminar-style course (with laboratory projects) in an area that is complementary to our existing curriculum. Funds are available for travel to professional meetings and to support undergraduate research students during the academic year and the summer.

Located in the immediate suburbs of Philadelphia and just 20 miles from Wilmington DE, Swarthmore College is a highly selective liberal arts college whose mission combines academic rigor with social responsibility. Swarthmore has a strong institutional commitment to diversity, and actively seeks and welcomes applications from candidates with exceptional qualifications, particularly those with demonstrable commitments to a more inclusive society and world. Swarthmore is an Equal Opportunity Employer. Applicants from traditionally underrepresented groups are strongly encouraged to apply. For more information on Faculty Diversity and Excellence at Swarthmore, see http://www.swarthmore.edu/faculty-diversity-excellence/information-candidates-new-faculty

Applicants should have a Ph.D., teaching experience, and a strong commitment to undergraduate education.  The strongest candidates will be expected to demonstrate a commitment to teaching that speaks to and motivates undergraduates from diverse backgrounds.

All application materials (cover letter, curriculum vitae, statements of teaching and research interests, and three letters of recommendation) should be submitted online at apply.interfolio.com/59011. Review of applications will begin on February 25th, 2019. For more information, please visit our website at www.swarthmore.edu/biology. Questions regarding this position should be addressed to the search chair, Brad Davidson, at genetics_search@swarthmore.edu

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Over on Twitter we’ve been having fun with our third instalment of the 12 GIFs of Christmas. For those not on Twitter, here are the GIFs – they represent some of the most cutting edge and inventive developmental biology of 2018, and also showcase the beauty of timelapse microscopy.

Transcription overlaid onto the rapid cell divisions of the early Drosophila embryo.

Temporal control of gene expression by the pioneer factor Zelda through transient interactions in hubs

Jeremy Dufourt, Antonio Trullo, Jennifer Hunter, Carola Fernandez, Jorge Lazaro, Matthieu Dejean, Lucas Morales, Saida Nait-Amer, Katharine N. Schulz, Melissa M. Harrison, Cyril Favard, Ovidiu Radulescu & Mounia Lagha

Nature Communications

Arabidopsis under lightsheet

Multiscale imaging of plant development by light-sheet fluorescence microscopy

Miroslav Ovečka, Daniel von Wangenheim, Pavel Tomančák, Olga Šamajová, George Komis & Jozef Šamaj

Nature Plants

Mouse development like you’ve never seen it before (including PGC migration)

In Toto Imaging and Reconstruction of Post-Implantation Mouse Development at the Single-Cell Level

Katie McDole, Léo Guignard, Fernando Amat, Andrew Berger, Grégoire Malandain, Loïc A. Royer, Srinivas C. Turaga, Kristin Branson, Philipp J. Keller

Cell

Amphipod embryogenesis

Multi-view light-sheet imaging and tracking with the MaMuT software reveals the cell lineage of a direct developing arthropod limb

Carsten Wolff,  Jean-Yves Tinevez, Tobias Pietzsch, Evangelia Stamataki, Benjamin Harich, Léo Guignard, Stephan Preibisch, Spencer Shorte, Philipp J Keller, Pavel Tomancak, Anastasios Pavlopoulos

eLife

The fly adult midgut over many hours

Long-term live imaging of the Drosophila adult midgut reveals real-time dynamics of division, differentiation and loss

Judy Lisette Martin, Erin Nicole Sanders, Paola Moreno-Roman, Leslie Ann Jaramillo Koyama, Shruthi Balachandra, XinXin Du, Lucy Erin O’Brien

eLife

Fate mapping the zebrafish embryo with the photoconvertible protein Kikume

Neuromesodermal progenitors are a conserved source of spinal cord with divergent growth dynamics

Andrea Attardi, Timothy Fulton, Maria Florescu, Gopi Shah, Leila Muresan, Martin O. Lenz, Courtney Lancaster, Jan Huisken, Alexander van Oudenaarden, Benjamin Steventon

Development

Colour-coded ascidian embryogenesis

Contact-dependent cell communications drive morphological invariance during ascidian embryogenesis

Leo Guignard, Ulla-Maj Fiuza, Bruno Leggio, Emmanuel Faure, Julien Laussu, Lars Hufnagel,Gregoire Malandain, Christophe Godin, Patrick Lemaire

bioRxiv

Convergence and extension in Xenopus

Spatial and temporal analysis of PCP protein dynamics during neural tube closure

Mitchell T Butler, John B Wallingford

eLife

Modelling development in silico

Theoretical tool bridging cell polarities with development of robust morphologies

Silas Boye Nissen, Steven Rønhild, Ala Trusina , Kim Sneppen

eLife

How Volvox turns itself inside out

The noisy basis of morphogenesis: Mechanisms and mechanics of cell sheet folding inferred from developmental variability

Pierre A. Haas, Stephanie S. M. H. Höhn , Aurelia R. Honerkamp-Smith, Julius B. Kirkegaard, Raymond E. Goldstein

PLOS Biology

From symmetrical to asymmetrical: the making of the heart tube

The heart tube forms and elongates through dynamic cell rearrangement coordinated with foregut extension

Hinako Kidokoro, Sayuri Yonei-Tamura, Koji Tamura, Gary C. Schoenwolf, Yukio Saijoh

Development

Isolated blastomeres in C. elegans

Cell-intrinsic and -extrinsic mechanisms promote cell-type-specific cytokinetic diversity

Tim Davies, Han X Kim, Natalia Romano Spica, Benjamin J Lesea-Pringle, Julien Dumont, Mimi Shirasu-Hiza, Julie C Canman

eLife

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2018 was a fun year on the Node, with a continued diversity of posts, more jobs than ever and our highest number of readers since our launch (regularly breaking the 30k page views per month barrier). Good vibes, and a good time to celebrate our most-read from the year, which includes three posts on statistics and data visualisation by Joachim Goedhart, a cover competition and a group ‘op-ed’ about the advantages of preprints.

1

Make a difference: the alternative for p-values

By Joachim Goedhart

2

Vote for a Development cover from the Quintay International Course on Developmental Biology

Soraya Villaseca’s Drosophila embryo won the vote

3

Visualizing data with R/ggplot2 – It’s about time

By Joachim Goedhart

4

Preprints promote transparency and communication

By Carmen Adriaens, Gautam Dey, Amanda Haage, Wouter Masselink, Sundar Ram Naganathan, Lauren Neves, Teresa Rayon, Samantha Seah, Srivats Venkataramanan.

This piece by a collection of early career researchers and members of the preLights team was written in response to an article in Nature. 

5

December in preprints

Our monthly collection of developmental biology (and related) preprints continued to be well read

6

Showing distributions

By Helena Jambor

7

Prevent p-value parroting

By Joachim Goedhart

8

The reported birth of CRISPR-edited humans: reactions from the field

We gathered reactions from developmental biologists, reproductive biologists and ethicists to one of the year’s biggest and most controversial science stories

9

The people behind the papers – Anjali Rao & Carole LaBonne

10

Sensing and making sense of clonal fragmentation in developing tissues

By Steffen Rulands and Benjamin Simons

Thanks for reading!

And if you haven’t, why not sign up to our email alerts – your weekly dose of developmental biology news, research highlights, interviews, meeting reports and jobs!

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Shoshkes Carmel lab has an opening for a passionate postdoctoral fellow in the field of Telocytes as niche cells. We are seeking for a candidate with a strong mouse genetics background. We apply “-omics”, genetics and live-imaging approaches to uncover key aspects in the cell biology of Telocytes, large stromal cells recently emerged to constitute the intestinal stem cell niche, and their role in intestinal homeostasis.

For more details please see: Shoshkes-Carmel M et al., Subepithelial telocytes are an important source of Wnts that support intestinal crypts. Nature 2018 May 2.

Please apply via email including a cover letter with a short statement of research interests and Curriculum Vitae to:

Dr. Michal Shoshkes-Carmel

Dept. of Developmental Biology and Cancer Research

Hebrew University, Hadassah-Medical School, Jerusalem, Israel.

Email: Michal.Shoshkes@mail.huji.ac.il

Lab website:  https://www.shoshkescarmelab.com/

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The Harvey Laboratory is looking to employ motivated and talented postdoctoral fellows to study the role of the Hippo pathway in organ size control and cancer. Our research is situated at both the Peter MacCallum Cancer Centre and Monash University in Melbourne, Australia.

We employ a range of techniques including Drosophila genetics, advanced microscopy, transcriptomics, bioinformatics, molecular biology and cancer cell biology. You will work in a supportive team, be a good communicator and also have the ability to work independently. You will possess expertise in a range of molecular and cell biology, biochemical and genetic techniques. Experience in Drosophila genetics is advantageous but not essential.

Peter MacCallum Cancer Centre is Australia’s largest specialist cancer centre with 600 research staff and students. We are located in Australia’s largest and most vibrant biomedical precinct with more than 10,000 researchers across multiple Universities, Research Institutes and Hospitals. Melbourne is a multi-cultural city with great food, weather, culture and sport and is often voted the world’s most liveable city.

For more information visit this link: https://www.petermac.org/research/labs/kieran-harvey

or email Prof Kieran Harvey (kieran.harvey@petermac.org):

Selected References:

1. Poon et al., (2018). A Hippo-like signaling pathway controls tracheal morphogenesis in Drosophila melanogaster.Developmental Cell.47: 564-575.

2. Manning et al., (2018). Dynamic fluctuations in subcellular localization of the Hippo pathway effector Yorkie in vivo.Current Biology.28: 1651-1660.

3. Degoutin et al., (2013).Riquiqui and Minibrain, regulators of the Hippo pathway downstream of Dachsous.Nature Cell Biology.15: 1176-1185.

4. Harvey et al., (2013). The Hippo pathway and human cancer. Nature Reviews Cancer.13: 246-257.

5. Poon, et al.,(2011). The sterile 20-like kinase Tao-1 controls tissue growth by regulating the Salvador-Warts-Hippo pathway. Developmental Cell.21: 896-906.

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Birds are a dominant group of land Vertebrates (probably the largest in numbers with +10000 species described), highly successful and diverse. Birds originated from members of the Theropoda: the meat-eating dinosaurs that included famous forms like T. rex or Velociraptor, well-known from the movies. The fact that birds are a kind of dinosaur has been a matter of debate not except from controversy, but largely accepted today. The two most important lines of evidence that allowed us to understand the true identity of birds have been the (incredibly detailed) fossil record of the non-avian to avian dinosaur transition, and birds’ embryological development. Embryology reveals the dinosaur within birds and in cases development can parallel in short time what we see to have happened in millions of years of fossil record. Alexander Vargas’s lab at the University of Chile focuses on this evolutionary transition, employing both fossils and embryos to understand the workings of evolution.

Researchers of comparative anatomy have documented how embryos show the dinosaur-bird link since the times of Darwin, mostly focusing on the postcranial skeleton. With this idea in mind, we set to study the development and evolution of the dinosaur skull. The head of birds is very unique, and two key differences when comparing birds to other reptiles are their skull and the huge brains and eyes birds possess. The bones composing the skull of birds are thin, light and mostly fused together in the adult. In addition, two bones (the postorbital and the prefrontal, located behind and in front of the eye respectively), were lost at different moments during the evolution of the dinosaurs leading to modern birds. Both in the fossil record and during embryonic time, how and when these bones disappeared, and if there were remnants of their presence as suggested by previous reports, were some of the questions we wanted to resolve in our recent paper in Nature Ecology and Evolution.

By looking at the fossil record of Theropods, we found two distinct “moments” when these bones were lost, at the origin of two recognizable clades: the postorbital was lost at the Euornithes node, close to modern birds; while the prefrontal was lost at the Pennaraptora node, right at the base of the clade containing dinosaurs like Oviraptor, Velociraptor, Archaeopteryx and modern birds. This bone has an interesting story, as in most early members of this clade, the prefrontal was not present, while the lacrimal bone acquired a T-shape (in contrast to the inverted L-shape of other dinosaurs that did possess a prefrontal). This T-shape, in which the T’s posterior tip occupies the position otherwise used by the prefrontal, suggested these bones were the result of fusion between the prefrontal and the lacrimal. The surprising part was that some dinosaurs seemed to be reverting into having a separate prefrontal bone. Some specimens of different species of these dinosaurs were showing a separate prefrontal bone, while at the same time losing that “tip” of the lacrimal that could have been the fused prefrontal. Even members of the same species would show variability in the presence or absence of the adult bone, as Deinonychus or Archaeopteryx specimens could have a prefrontal separated. To understand the basis of these changes in the cranium, we went to embryos.

Chicken embryos have been a preferred animal model for those willing to study embryonic development for more than 2000 years, and have provided the vast majority of the information we have today about skull development for birds. However, they are just one species among thousands, representing one of hundreds of distinct lineages. In an effort to include more of the disparity and diversity of birds, we collected embryonic series of six families of birds, including (of course) chicken, but also ducks, and species not normally used for developmental studies like lapwings, coots, budgerigar and tinamous (a member of the palaeognathae related to ostriches and emus), and also included embryonic stages of Alligator mississippiensis to broaden our sample to members of the two living archosaur groups, birds and crocodylians. By looking at the avian embryos and their developing ossifications alone, we confirmed the presence of more ossification centers than adult bones in the embryos of birds, but only by comparing them with alligator embryos and the fossil record were we able to interpret them in light of their evolutionary history.

In embryos of all the birds observed, two ossification centers develop and make up the adult lacrimal bone. These two ossifications were observed and identified as the lacrimal and prefrontal bones of chicken by Erdmann in 1940, but we also found two separate ossifications giving rise to the lacrimal of alligator embryos, which do form a separate prefrontal from another ossification center, meaning Erdmann’s identification of a prefrontal bone in the chick was mistaken. However, we did find an embryonic bone in one species, the Chilean tinamou, where in addition to the two ossification centers of the lacrimal, a third, well-developed ossification develops in a position similar to that of the embryonic Alligator and adult dinosaur prefrontal. This bone, however fused to the nasal bone, and becomes indistinguishable from its other pieces. In a way, the bone is doing what we think it did in dinosaurs like Velociraptor: developing as a separate center and later fusing to a neighboring bone. This separate embryonic origin can explain why it re-appeared in different specimens as a separate adult bone, as it likely failed to fuse. However, in the tinamou, it is doing something it did not do in Velociraptor as instead of the lacrimal, it is fusing to a different neighbor.

We also found an “extra” ossification not corresponding to any adult avian bone and just behind the eye that looks like the embryonic postorbital ossification of Alligator and the adult postorbital bone of dinosaurs, but instead of remaining separate as in these animals, fuses to the back of the frontal bone.

In a way, we were expecting to find this ossification, since the frontal of birds has been described as being formed from two separate portions, derived of two distinct embryonic germ layers; the mesoderm and the neural crest. Bones in the skull of vertebrates come in two flavors, as the most-rostral ones derive from neural crest cells and the ones in the back of the skull come from the mesoderm. We have known of this for years, thanks to careful chick-quail chimera experiments, and the double origin of the frontal has in fact created a lot of debate on the frontal identity itself. In other vertebrates, bones usually derive from one of these embryonic sources, and the frontal in particular is made up cells of neural crest origin. While other researchers also proposed the mesodermal portion could correspond to a separate bone that ended up fusing to the frontal, the identification of this portion as the parietal bone did not agree with many morphological criteria, anatomical correspondences nor with the evidence presented by the fossils. Our suggestion that the back portion of the avian frontal comes from the ossification that gives rise to the postorbital in other reptiles is consistent with the compared embryology of birds and crocodylians, as well as with the fossil record. This proposed homology implies the postorbital of Alligator should derive from mesoderm cells, something not yet corroborated as fate mapping of crocodilian embryos has not yet been done.

The history of transformations and fusions of the prefrontal and postorbital provides us with some interesting lessons on how evolution takes place, but also leaves us with a number of intriguing questions of how skull development is regulated. Upon fusing with a neighboring bone, both the prefrontal and postorbital apparently lost their own identities, becoming a non-independent part of the larger bone, not showing any morphological similarity to the separated bone of other species. Moreover, the cells that make up the independent ossification centers end up forming a structure in which there’s no trace or clue of their origin, even when coming from two very distinct embryonic sources as are the neural crest and mesoderm. Contrary to most of the bones in the body, which form a mold or cast of cartilage that is later replaced by bony tissue, many bones in the skull (particularly those of the face, skull roof, palate and jaws) develop directly into bone from mesenchymal condensations. We know a (staggering) lot more about how these cells invade the head and face or find their location than what we know about how the mesenchymal condensations are established and how they turn into individual bones. Between the migration of neural crest cells into the head, for example, and the onset of bone formation, there’s a gap in our understanding that has still to be bridged. Questions like what signals regulate the condensation mesenchyme, the beginning of bone formation or the spatial distribution of the ossification centers that form the bones are still poorly answered. Our knowledge on this kind of bone development derives from (and has been limited by) histological sections, which do not allow us to have a whole-picture of what’s going on in the whole head, and the study a few molecular markers that mostly label post-mesenchymatic condensation and pre-osteogenic stages of maturation. It is, in truth, by these limitations that our study relied only on bone staining to observe and compare the ossification patterns of different species. More understanding of the whole picture was not going to come from digging into deeper molecular mechanisms in the chicken, but from studying and comparing the development of more species, in a maybe simpler way, like Alizarin staining.

One interesting thing to consider is that one possible driver behind the huge modification of the skull in the evolution of birds might be the evolution of a big brain. Birds have enlarged brains compared to other reptiles and non-avian dinosaurs, and the enlargement of the brain would necessitate a re-structuring of the skull covering it. Other cases of evolution of big brains also result in evolution of the skull as a whole, and even loss of bones, maybe in a similar way than what we see in birds. In mammals, bones of mixed origin proved to be composites resulting from fusion of elements, including those supposedly lost long ago in the earliest mammalian lineage. Although these bones are located in the back of the skull, mammals also lost bones like the prefrontal or postorbital. The brain, being a huge structure lying directly underneath the developing skull-roof, can possibly influence mesenchymal condensations, bone deposition, ossification rate and overall timing and spatial development of the skull. How these structures interact and how they evolve in concert is yet to be studied and understood.

One last lesson we can derive from our results is the evolutionary meaning of the embryonic persistence of a structure. The ossification centers we found add to a longer list of stories in which the embryo retains at least a rudiment of a long-lost structure, which enables the evolution of new morphologies in later lineages. By retaining the prefrontal ossification, for example, some dinosaurs were (and still are) able to “experiment” a variety of morphological outcomes that include fusion with the lacrimal or nasal bones. It also worth noting that, at least in the case of the skull of birds, the adult bones end up fused together. So in a sense, the order or pattern in which ossification centers are beginning to fuse to each other could be less of adaptive significance than it is just a phenomenon of developmental drifting, in which a pattern is established and conserved. Itself, the high degree of bone fusion in the avian adult skull could be an extension of a trajectory started by those dinosaurs in which first two bones, then two others began fusing.

How does evolutionary change take place as shown by the fossil record and during embryonic time can be a question not just of “how dinosaurs looked like” but also an important source of understanding of developmental mechanisms at play every day.

1. Erdmann, K. (1940). Zur Entwicklungsgeschichte der Knochen im Schädel des Huhnes bis zum Zeitpunkt des Ausschlüpfens aus dem Ei. Zeitschrift für Morphologie und Ökologie der Tiere, 36(3), 315-400.
2. Le Lièvre, C. S. (1978). Participation of neural crest-derived cells in the genesis of the skull in birds. Development, 47(1), 17-37.
3. Noden, D. M. (1983). The role of the neural crest in patterning of avian cranial skeletal, connective, and muscle tissues. Developmental biology, 96(1), 144-165.
4. Evans, D. J., & Noden, D. M. (2006). Spatial relations between avian craniofacial neural crest and paraxial mesoderm cells. Developmental dynamics: an official publication of the American Association of Anatomists, 235(5), 1310-1325.
5. Piekarski, N., Gross, J. B., & Hanken, J. (2014). Evolutionary innovation and conservation in the embryonic derivation of the vertebrate skull. Nature communications, 5, 5661.
6. Maddin, H. C., Piekarski, N., Sefton, E. M., & Hanken, J. (2016). Homology of the cranial vault in birds: new insights based on embryonic fate-mapping and character analysis. Royal Society open science, 3(8), 160356.
7. Abzhanov, A., Rodda, S. J., McMahon, A. P., & Tabin, C. J. (2007). Regulation of skeletogenic differentiation in cranial dermal bone. Development, 134(17), 3133-3144.

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Stockholm University, Sweden, invites applications for one postdoctoral position in the laboratory of Professor Mattias Mannervik at the Department of Molecular Biosciences, The Wenner-Gren Institute (http://www.su.se/mbw). The position is scheduled to start as soon as possible.

Transcriptional coregulators are proteins that facilitate communication between transcription factors and the basal transcription apparatus, in part by affecting chromatin through post-translational modification of histones. As such, they contribute to generation of cell-type specific gene regulatory networks and epigenetic control of animal development (see Mannervik et al. Science, 284, 606-609, Boija et al. Mol Cell, 68, 491-503). This laboratory is using genomic, genetic, and transgenic approaches in Drosophila melanogaster to elucidate the molecular mechanisms of transcriptional and chromatin regulator function during development. In this project two approaches are used to investigate the in vivo role of histone modifications in gene expression. A histone replacement system is used to examine the effects of amino acid substitutions in the histones on organismal development, and a modified CRISPR/Cas9 system is employed to target chromatin modifying enzymes to endogenous loci.

The position is available immediately and requires a recent Ph.D. as well as extensive experience in molecular biology techniques. The successful applicant should have a high-quality publication record, and motivation to study underlying mechanisms of gene regulation in development. The position will be funded with a fellowship, and includes health insurance.

Stockholm University is one of the largest and most prominent universities in Sweden, located in the nation’s capital city, beautifully surrounded by the first national city park in the world. For further information, see http://www.su.se/english/ and http://www.academicstockholm.se/

Application: 
Applications marked with reference number SU 465-0156-18 should be submitted electronically as a single PDF file to mattias.mannervik@su.se and to birgitta.olsson@su.se
The application deadline is February 1, 2019.

Applications should comprise the following:
1) a personal statement describing your interest in this project (1-2 paragraphs), research experience (1–2 paragraphs) and career goals (1-2 paragraphs)
2) curriculum vitae
3) bibliography
4) names, e-mail adresses, and phone numbers of three references

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