Marianne Bronner is a developmental biologist at the California Institute of Technology. At the International Society of Developmental Biology (ISDB) meeting in 2013 she was awarded the prestigious Conklin medal for her work on the cells of the neural crest. The Node interviewed Marianne at the ISDB meeting and asked her about her fascination for the neural crest and her passion for mentoring.

You initially trained as a biophysicist. How did you first become interested in developmental biology?

I really liked physics, chemistry and maths and only took one undergraduate course in biology. I majored in biophysics because that was the only option that incorporated all the things I wanted to do. After my undergraduate I wanted to a PhD, but didn’t know on what. I applied for programmes in biophysics, thinking I wanted to be a structural biologist. Because I had done so little biology, I had to take many biology courses when I got to graduate school. One of the courses I took was developmental biology and I learned about the work of Nicole LeDouarin and her beautiful quail-chick chimera experiments. I found it all fascinating, but I particularly gravitated towards the neural crest. There are times in your life when you go from being incredibly naïve to suddenly saying: ‘that’s it’. That was my moment, and I have worked on it ever since.
 

Your lab has worked over the years on different aspects of the neural crest. What do you find fascinating about it?

Everything! Initially I was mostly fascinated about how these cells could give rise to so many different derivatives, their multipotency. It relates back to the central question in developmental biology – how do you generate a complex organism from just a single cell – but I viewed it as a simpler system than the embryo as a whole. My initial experiments aimed to find out if single neural crest cells were multipotent or whether there was a mix of determined and undetermined cells in the neural crest.

However, there are certain questions that you really want to address, but the technologies to address them are not available. I worked on the lineage questions as far as I could but then realized I was stuck and couldn’t go much further. I got interested in migration, which is also fascinating- how the cells move to particular locations, and how their fate is linked to where they go. I started working on the interactions between neural crest cells and the extracellular matrix, analyzing pathways of migration. Later on, when more tools were available, I went back to the lineage question.

You have used a variety of model organisms to study the neural crest: from more standard models like Xenopus and zebrafish to lampreys and amphioxus. Why do you use such a range of models?

I started most of my work in chick, and my initial work on the neural crest was very vertebrate specific. I used Xenopus and chick because they were easy to manipulate. Around 1990 I started teaching at the embryology course at Woods Hole, and as I sat through the lectures of other people I realized that my focus had been quite narrow. This course looks at organisms ranging from simple marine species to mice and it got me thinking about evolutionary questions. The fascinating thing about the neural crest is that it is a vertebrate specific cell type. Why did these cells suddenly arise in the vertebrate lineage? To address this question I had to look across chordates, so I decided to work on a basal chordate and a closely related, non-vertebrate chordate.

At Woods Hole I met David McCauley, who was very interested in evo-devo and came to work for me. We decided to start working with lamprey, but this was not easy: lampreys are not genetically-tractable organisms, live in large deep lakes, and like salmon they swim into the streams where they were born, lay their eggs and die. You can’t exactly grow them in labs! David went up to the Great Lakes every year to collect embryos and did some basic embryology. Then we discovered FedEx, and we started setting up the lamprey system in our own lab. Another postdoc came to work on this project, Tatjana Sauka-Spengler, and she really took the lamprey into the genomic age: making cDNA libraries, BAC libraries and so on.

By this point were looking at the gene regulatory networks that define neural crest and we wanted to know how the gene regulatory networks in lampreys compared with those in other vertebrates. We found that most of these networks were already conserved all the way down to lamprey. But when we looked at the non-vertebrate chordate, the amphioxus (which does not have neural crest), the group of genes that were important for neural crest specification were present in the genome, but were not expressed in the presumptive neural crest region. We concluded that this is where the transition occurred.

What are the scientific questions that you are excited about? What directions do you want to go in with the neural crest?

I feel like I am asking the same questions I always have, but the way we can approach them now is much more sophisticated. For the last decade I have been trying to understand, from a gene regulatory perspective, how you make a neural crest cell: how a cell is first formed at the neural plate border, why it comes to reside within the dorsal neural tube and why it then migrates out of the neural tube. Now I want to try to understand how the cells decide whether they should become cranial facial cartilage, or neurons, or something else. I would like to do that by analysing the gene regulatory circuits that act during late cell migration and as cells terminally differentiate. People have looked at the very end point in the differentiation networks, and I have looked a lot at the beginning points, but that middle territory is still unexplored. We are already doing a lot of transcriptome analysis to identify all the players that come on during those times, and we now need to figure out what their function is and how that they fit into a circuit.

You have said before that your achievements in mentoring are those of which you are most proud. Why is that?

My concept of how to run a lab has been based on how to raise my children. I think you get a lot more out of people by loving them. I also feel like I owe the people who work for me a debt of gratitude, for all their hard work, and I try to help them becoming the best kind of scientist they can be. Everybody has different abilities: some people are very independent right from the start and can go off and build their careers, and others need a lot of guidance and help. I feel like I am a good mentor and I’m able to take people at many different levels and help them along the right pathway. In some cases that is just giving someone a nice environment where they can work in and do whatever they want. In other cases I really try to guide people and say: ‘at this point in your career you should do this’. When I look back at the people that I’ve trained, I see that some are doing similar things to what I do, while others have gone in different directions. I feel that I helped them getting where they are and that is extremely gratifying.

You seem to enjoy the mentoring process. Did you have a particularly inspiring mentor?

Surprisingly no- I was anti mentored! I think there are two different ways to learn how to be a good mentor: one is to have had good mentoring, and the other is to not. It is not that I didn’t have good mentoring- I just came out of nowhere. I would not recommend any career decisions that I have made.

I applied to grad schools together with this boy I was dating at the time, and I decided where to go based on where he wanted to go. We broke up within a year, and the school I went to was terrible for me: it was extremely sexist at that time, and I was one of the very few women in the biophysics programme. I then went on to work in a lab where the PI was horrible and very sexist too. I almost dropped out of research: I applied for a teaching job but did not get it. I was so disappointed that I decided instead to change labs.

I discovered I wanted to work on the neural crest and I moved to the lab of Alan Cohen. He was a very nice guy, but he had already decided he didn’t want to do science anymore and was going to med school. He was not around, but it was a permissive environment- I got on with my work and learnt most of what I needed from other people in the lab. I got my PhD fairly quickly, but since I didn’t have any mentors, I didn’t have people to write job recommendation letters for me. Malcolm Steinberg, who was at Princeton, was probably the closest thing I had to a mentor. He was a really good scientist and took a liking to me, so he wrote my job letters.

I got my job at UC Irvine not because of anything I had done but because they wanted to hire my husband. I took a non-tenured track job there, which really wasn’t a smart move, because it was very hard to convert it to a tenure track position (although luckily some great colleagues at Irvine helped me to do that later). I was right out of grad school and I had no postdoctoral experience. I didn’t really have anyone to rely on, which is maybe why it is so important to me to be a good mentor to others. I have learnt so much by trying different things and making mistakes that now I have a rather large body of knowledge about what not to do.

You say that you would not advise anyone to make the same decisions that you have, but do you have any advice for young scientists? 

You have to be happy. So when picking a lab, either for graduate school or for a postdoc, make sure that you can get along with the lab head. Make sure they are a strong mentor who supports people, not only when they are in their lab but also after they have left. Secondly, look at the environment in general, and make sure that you like the other people in the lab, not only the PI. You are going to be spending 4 years or more at this place, and you want be happy there. Choosing the right place is really important.

Choosing the right question is equally important. You want to find something that grabs you and that you will be happy working on for quite a long time, but it should also be something tractable. There are some questions out there that are extremely interesting but so difficult that they can discourage you.

Finally, make a network. Find people that can help you in addition to your mentor: it could be your peers or other faculty members. Getting lots of feedback on your work, especially from people that can give you a big picture view when you are in the middle of your experiments and really detailed oriented, is very helpful and it can help you correct your course and save time.

In the last year you had your work in cell biology recognised by the ASCB, and now, here at the ISDB, you won the Conklin medal. What do these prizes mean to you?

I am so thrilled- I have never won anything before! I’m particularly grateful because I know that one of the reasons I am getting recognition is thanks to the people I have trained. They are starting to move up in the faculty ranks and as they appreciate what I did for them, they are helping me get these awards. I am really happy, very grateful, and very touched. It is a lot of work to put together these nomination packages and it means a lot to me, especially because it has come from them.

What would people be surprised to find out about you?

I was born in Europe and I escaped from Hungary when I was 4 years old. My parents are holocaust survivors, and probably a big reason why I like mentoring is because I feel like I have to give back.

(8 votes)

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Can you imagine a supermarket where doctors could just go and pick the cells they need to cure their patients? Just like a pharmacy…or a blood bank?

Well, this is the dream most stem cell biologists are working towards. In order to make this dream a reality, scientists are trying (with more or less success!) to develop protocols with which they could use a stock of stem cells and differentiate them towards a cell fate of interest in order to obtain functional specialized cells…which ideally could then be used for cell replacement therapies and drug screenings.

In a recent study published in Development by S. Ogawa and colleagues, human pluripotent stem cells (hPSCs; ie: stem cells that can become any tissue of the body) were successfully differentiated into mature liver cells. To this end, the authors developed an elaborate in vitro liver differentiation protocol that consists of successive steps that recapitulate liver development. First, hPSC are differentiated into definitive endoderm and then to hepatoblasts (immature liver cells), a process dependent on activin/nodal signalling.  Subsequently, 3D cell aggregation and cAMP signalling are required to obtain hepatocyte-like cells, hepatocytes being mature liver cells.

In this picture, one can observe 3D cell aggregates the scientists produced from hPSCs. Cells express the proteins ASGR1 (in green in the picture) and ALBUMIN (ALB, in red in the picture), a combination that is specific to hepatocytes.

So in the future, if these cells are proven to function properly, they could potentially be used in therapies against all sorts of liver diseases, in drug screening studies or to produce bio-artificial liver devices!

S. Ogawa et al., Three-dimensional culture and cAMP signaling promote the maturation of human pluripotent stem cell-derived hepatocytes. Development 140, 3285 (August 2013). doi: 10.1242/dev.090266

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I have recently returned from a spate of international conferences that afforded me the opportunity to experience meetings for the first time as an editor, instead of as an active researcher. It was also the first time I had seen my former lab mates since leaving the bench, and the reunion was a very happy one indeed. I was surprised, however, by the avid interest in my new career, and even moreso by the hushed tones in which these conversations took place. It seemed that numerous people I spoke with harboured some interest in leaving the bench, although this had never been spoken of when we worked side-by-side. Even people I had never met before confided in me that they, too, were considering a career beyond the lab, although they could scarcely admit this to their colleagues. So why the secrecy?

Upon reflection, I can sympathise. The response to my own decision to leave the bench was mixed. My closest colleagues were happy for me, including my principle investigator (PI) at the time, but there were some who expressed great surprise and even disappointment. Notably, this seemed to come from higher up: senior postdocs and other PIs who had always imagined that I would stay on. “It’s a shame, you could have made it” was one such response. Though undoubtedly intended as a compliment, I was nonetheless bothered by this. Surely what constitutes “making it” is a personal decision.

It is often said that parents only want what is best for their children, and yet often parents will push their children in a particular direction. The same may also be true for PIs and their students. It is certainly important to encourage students to fulfill their potential, but care must be taken when deciding where that potential lies. The PI should not assume that the student has a burning desire to run their own lab. For many, this is undesirable, and when we consider the number of PhD being produced, it is certainly unrealistic (see Nature article “Education: the PhD factory”). Instead, careful consideration must be given to understanding the various strengths and weaknesses of each person, as well as their interests, motivations and goals: not just for their career but also for their life. These are big questions, and neglecting to address them may often lead to frustration and disappointment for both PI and student.

Most students these days are reasonably well aware of “alternative careers in science” (see careers post on the Node). Almost every major conference has the obligatory session, and some institutes and universities have taken an active approach to promoting this. This is an excellent first step, however I fear that it will not be enough. Instead, we need to change the attitude from within and remove the stigma associated with leaving the bench. A PhD provides training in much more than the specific subject at hand: there is an entire smorgasbord of critical skills that are learnt during the process: project management, conflict resolution, lateral thinking, public speaking, writing, teaching, and team-building are just some of these assets. And assets they are: there is a reason why the big banks and consulting companies will in theory accept candidates with a PhD in any discipline. The mere process of completing a PhD bestows these valuable skills upon the graduate.

There are a number of different approaches that can be taken to breakdown the barriers to career diversity in science. As a minimum, students should be educated about and gain exposure to a wider range of career paths as part of their studies. I’m not just talking about “tech transfer” but the whole gamut: teaching, journalism, publishing, politics, law, consulting, science outreach, and (shock horror) administration. The prevailing dogma that the very best PhD students should remain in academia must be challenged, and the challenge must come from within. Simply being good at something doesn’t mean one should be fated to it.

(9 votes)

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A major challenge when studying the cell biological bases underlying morphogenesis is represented by the gap between the sub-cellular and the tissue-organ scale (Figure 1). Ideally, one would like to follow tissue dynamics with sub-cellular resolution and obtain ultra-structural details about the organization of specific plasma membrane domains, cytoskeletal structures, intracellular compartments and vesicular carriers involved in signaling and adhesion. It is, indeed, the spatio-temporal modulation of membrane and cytoskeletal dynamics in individual cells or group of cells, which ultimately drive tissue remodeling during organismal development. Cell shape changes play, indeed, a fundamental role during embryonic development and are often initiated by expansion or contraction of specific plasma membrane domains. While the role of the cytoskeleton in driving plasma membrane remodeling is well established, the contribution of membrane trafficking remains an open question.

Figure 1. Scales in developmental biology: from organisms (left panel, cross section of a Drosophila m. embryo ~0.5 mm) to organelles (right panel, endosome ~0.5 microns). Tissue and organ morphogenesis depends on the modulation of intracellular machines operating in the nanometer scale.

In my laboratory, for example, we are interested in understanding how endocytosis contributes to shaping cells and tissues during morphogenesis.  Although, the role of endocytosis in signaling and cell polarity is well-established, to what extent endocytosis is directly involved in shaping cells is less understood. The cellularization of the early Drosophila embryo provides an ideal system for studying the mechanisms driving plasma membrane remodeling during morphogenesis. Over the course of one hour a syncitium of 6000 nuclei is divided into an equal number of polarized epithelial cells by invagination and growth of the apical plasma membrane (for video see, http://youtu.be/kwN1aNAvTwk). Scanning electron microscopy studies revealed that during this process the apical plasma membrane undergoes a dramatic morphological re-organization characterized by the retraction of villous protrusions and flattening of the apical surface. To date, however, the apical surface of the embryo has proven extremely difficult to visualize in real time using traditional live imaging techniques.

In our recently published paper (Fabrowski P. et al 2013) we adapted Total Internal Reflection Microscopy (TIFR-M) to visualize endocytic dynamics during surface flattening in live Drosophila embryos. This microscopy technique relies upon an evanescent wave that exclusively illuminates a region in close proximity (10-200 nm) to the coverslip. In cell culture, TIRF-M has been successfully employed to visualize vesicle fission and fusion events with the plasma membrane (Toomre D. et al 2000). Furthermore, because of its high sensitivity and low signal to noise ratio, TIRF-M can be applied also to image single molecules dynamics (Jain A. et al 2012).

Imaging living organisms is not as simple as imaging single molecules in solution or cells grown on glass coverslips. In living organisms, such as developing embryos, cells move, are not adhering to coverslips and autofluorescence sometime poses a serious limit to the imaging techniques that can be employed. In the Drosophila embryo, cells are enclosed by the vitelline membrane and are surrounded by peri-vitelline fluid. The vitelline membrane is a proteinaceous waxy layer that tends to be autofluorescent when illuminated with blue (488) light. It seemed therefore unlikely that TIRF-M could be employed to visualize plasma membrane dynamics in live embryos.  However, after several failed attempts, we realized that it was possible to direct the laser light with such an angle that an evanescent wave could be generated at the interface between the vitelline membrane and the peri-vitelline fluid. This approach allowed us to visualize, for the first time, the morphogenetic remodeling of the apical surface over the entire course of cellularization (see movie below and  also movie S1 in Fabrowski P et al. 2013)

Quantification of endosome dynamics, marked by the small GTPase Rab5 tagged with GFP at its endogenous locus, revealed a massive increase in apical endocytosis that correlates with changes in apical morphology (Figure 2, for video see, http://youtu.be/9X5uM85lBBM).

Figure 2. TIRF-M imaging of apical endocytic dynamics during plasma membrane remodeling in live Drosophila embryo. From left to right, thee snapshots of early, middle and late stages of cellularization showing the up-regulation of endocytic vesicles marked by Rab5 (green). The plasma membrane is labeled by Gap-43 and it is shown in white. Scale bar, 10 microns.

In a series of experiments, which I will not describe here in detail, we demonstrated that endocytosis is required for surface flattening. We, therefore, decided to investigate the endocytic mechanisms driving this morphogenetic process. The large quantities of plasma membrane contained in protrusions together with the relative fast kinetics of flattening (~10 minutes) raised the question of whether clatrhrin coated vesicles mediated endocytosis could, by itself, be sufficient to drive membrane remodeling. To address this question, we employed Correlative Light-Electron Microscopy (CLEM), a powerful, but time-consuming technique, that allows one to correlate fluorescently labeled particles onto a corresponding electron microscope image. By combining CLEM with electron tomography we reconstructed the 3D organization of GFP labeled endocytic membranes. In summary, the results of this analysis revealed that surface flattening is driven by the activation of a prominent tubular endocytic pathway characterized by the formation of tubular plasma membrane invaginations that serve as platforms for the de novo generation of vacuolar Rab5-positive endosomes. Thus, surface flattening is an endocytosis dependent morphogenetic process during which endosomes form directly at the plasma membrane rather than by fusion of incoming clathrin coated vesicles.

In conclusions, the application of these powerful microscopy techniques to multicellular systems will undoubtedly help bridging the gap between the sub-cellular and the tissue-organ scale. The possibility, for example, of visualizing endocytic events during tissue differentiation should help characterizing the molecular regulation and spatial organization of signaling systems in an in vivo context with an unprecedented level of resolution.

References

Jain A, Liu R, Xiang YK, Ha T. (2012) Single-molecule pull-down for studying protein interactions Nat Protoc. 7(3), 445-52. doi: 10.1038/nprot.2011.452.

Toomre D, Steyer JA, Keller P, Almers W, Simons K. (2000) Fusion of constitutive membrane traffic with the cell surface observed by evanescent wave microscopy. J Cell Biol. 149 (1), 33-40.

Fabrowski P, Necakov AS, Mumbauer S, Loeser E, Reversi A, Streichan S, Briggs JA, De Renzis S. (2013) Tubular endocytosis drives remodelling of the apical surface during epithelial morphogenesis in Drosophila. Nat Commun.4:2244. doi: 10.1038/ncomms3244.

(6 votes)

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Novartis Institutes for Biomedical Research (NIBR) is a world leader in pharmaceutical research with a widely recognized culture for nurturing innovation and scientific excellence to address unmet medical needs. China NIBR based in Shanghai is dedicated to the research and development of products addressing diseases prevalent to China, and providing innovation in the understanding and curing of Epigenetic causes of diseases.

Cell fate specification and differentiation of stem cells into distinct cellular lineages during mouse embryogenesis are tightly regulated genetically and epigenetically, particularly via the interplay between key development regulators and various epigenetic modulations.  Such interaction and similar mechanisms are also manifested during regeneration and aging processes.  Epigenetic dysregulation will cause abnormal embryonic development and various human diseases.  To aid target discovery and mechanistic understanding of regeneration, we are inviting applications for an Investigator position in the regenerative medicine research group. The successful candidate will be part of the developmental biology core, focusing on novel target discovery and disease modeling for regenerative medicine.  He/She will be responsible for elucidating the roles of key epigenetic regulators during development and regeneration by using combinatory mouse genetics and epigenomic profiling approaches.   The successful candidate will also participate in multi- disciplinary drug discovery and development team to support target discovery in disease areas of focus.

minimum requirements:

• Ph.D. in Developmental Biology, Cell Biology or related fields, minimal three years postdoc training
• Hands-on experience with mouse embryology, histology or pathology analysis; familiar with key developmental pathways such as Wnt, BMP, Notch etc.
• Deep understanding of epigenetics and proficient in research technologies such as ChIP-Seq, and DNA methylation analysis are required. .
• Highly self-motivated and highly collaborative team worker is essential. Previously industrial experience is preferable.

Please send your resume to sarah.qi@novartis.com, thanks!

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TED is a conference series of mostly amazing speakers across diverse fields in science, business, technology, culture, and global issues. They post tons of the talks on their website, www.ted.com, and not only do they have a full array of fascinating subject material, but they’re also a source of inspiration if you’re looking for ways to improve your presentation style or communicate with a broad audience.

Here is a round-up of 8 cool biology-themed talks to put on the next time you have a 5-20 minute incubation step.

1. Tyrone Hayes and Penelope Jagessar Chaffer: The toxic baby

A great collaboration between a filmmaker and frog biologist. They explore the chemicals in our environment and how these may be influencing human development and disease.

2. Munir Virani: Why I love vultures

A talk extolling the virtues of vultures, how they contribute to ecosystems and prevent the spread of disease, and the threats they face.

3. Cynthia Kenyon: Experiments that hint of longer lives

The story of a long-lived mutant in C. elegans, and the link between stress, metabolism, and lifespan.

4. Ellen Jorgensen: Biohacking — you can do it, too

Ellen Jorgensen is one of the founders of Genspace, a lab that teaches “regular people”  in the community to do molecular biology. She explains what they do (fun and interesting projects), and what they don’t do (create pathogens that will wipe out humanity).

5. Susan Lim: Transplant cells, not organs

Susan Lim highlights the problems with the current system of organ transplants, based on her moving personal experiences as a transplant surgeon in Singapore, and discusses her work on adipose stem cells.

6. Michael Dickinson: How a fly flies

A cool study of flight using model robot insects (!)

7. Emma Teeling: The secret of the bat genome

Emma Teeling is the Director of the Centre for Irish Bat Research, and discusses some of the unique biological features of bats, the rap bad they get in Western culture, and how they contribute to human agriculture, economics, and health.

8. Bonnie Bassler: How bacteria “talk”

Bacteria communicate for group behaviors like pathogenesis: Bonnie Bassler talks about the major advances made in her lab, with implications for all types of cell-cell communication.

(5 votes)

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As you may be aware, The Company of Biologists launched its own series of Workshops in 2010. Coming up this September is the workshop ‘Evolution of the human neocortex- how unique are we?’ Taking place at the beautiful Wiston House in Sussex, this workshop will bring together researchers from the fields of developmental and molecular biology, genetics and ethology to discuss our current view of human cortical evolution and what makes us unique.

The Company of Biologists’ Workshops are not just about facilitating the discussion of science between scientists, but also bringing that exciting science to the general public. This is why The Company of Biologists has organised an open lecture at the Royal Institution on Wednesday the 25th of September. This lecture is free and open to everyone, and will feature two of the researchers participating at the workshop. Svante Pääbo, from the Max Planck Institute for Evolutionary Anthropology will discuss his team’s work on the DNA of Neanderthals, while Arnold Kriegstein from the University of California San Francisco will discuss how the human brain compares with that of its close and distant relatives.

You can find more information on the workshop website and on the Royal Institution website.

The talk at the Royal Institution will take place on the 25^th of September. You can order your free ticket here.

Image from Wikimedia commons

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For decades, the development of the early embryo and patterning of tissues has been studied with the help of a workhorse of developmental biology, the frog embryo.  Xenopus embryos are large and undergo clear morphological changes throughout their development that make them very quick and easy to work with in answering questions surrounding the formation of early germ layers and processes such as gastrulation.

However, a major disadvantage to working with Xenopus embryos is the amount of yolk contained within them.  Unlike in organisms such as zebrafish embryos, which have a separate yolk cell from which to draw their nutrition, the fertilised Xenopus embryo contains large yolk platelets, predominantly in the lower (vegetal) half of the embryo.  This yolk is primarily made up of the protein vitellogenin and can account for half of the protein content of the cell – a problem that has contributed to the somewhat lagging development of Xenopus mass spectrometry proteomics.  But the yolk also results in an opaque embryo that limits the options for imaging live embryos with light microscopy.  Mouse embryos are also opaque and so a method of imaging these embryos would be of great interest to many fields of developmental biology.

One approach to overcome this problem – published recently in Nature – has been developed at the Karlsruhe Institute of Technology by Jubin Kashev and Ralf Hofmann, with contributions from Xenopus embryos from the lab of Carole LaBonne.  This technique is phase-contrast X-ray tomography, using synchrotron radiation.

That sounds more complex than it is!  Regular X-ray imaging is typically carried out by firing X-rays at a subject and building up an image of tissues depending on how much they absorb X-rays.  However this is not at a good enough resolution for small samples such as Xenopus embryos, and requires a high blast of radiation and additionally injection of some sort of reagent to add contrast to the image.  This is where the synchrotron comes in.  This provides a coherent wave of radiation that is slowed through different tissues in a distinctive pattern at high resolution.  A series of 2D images is produced whilst the embryo is rotated and these 2D images are used to build up a 3D picture – this is the tomography part.

The researchers were able to control timing and duration of X-ray blasts to minimize damage to the embryo whilst capturing as much of the process of gastrulation as possible between stages 11.5 and 12.5 (the authors comment that a 2 hour window of development is reasonable to capture before damage to the embryo becomes a significant problem).  They found further evidence for the idea that the archenteron expands by uptake of external water; and also suggest previously unseen adhesive interactions occur between mesoendodermal cells, forming a ridge of contracted ectoderm at the point where dorsal and ventral mesendoderm meet and ectodermal cells begin to spread over the surface of the gastrula.  They suggest this structure may be destroyed in the traditional process of taking explants for further study, hence why it has not been observed prior to these studies.

The obvious limitation in this approach is the current availability of synchrotrons (in the Research Highlight in Nature, it is suggested that there are only 8 facilities in the world!).  But it is exactly this sort of innovation, at the frontiers of developmental biology and biophysics, which can help us overcome the traditional limitations to studies in developmental biology.

Beware of the Frog

References:

Moosmann, J. et al. X-ray phase-contrast in vivo microtomography probes new aspects of Xenopus gastrulation. Nature 497, 374–377 (2013).

Nawy, T. Embryos under the X-ray. Nature Methods 10, 603 (2013)

(7 votes)

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Turtles are firmly protected from predators by the unique bony shell. These animals are even capable to retract their head and limbs within the shell, thus their defense system seems to function perfectly. The turtle shell, in particular its dorsal part (carapace), is a strange structure, since it is contiguous with the ribs and vertebrae, unlike other armoured animals. How could such an invulnerable body plan ever evolve? Until recently, the mystery on the origin of the turtle shell has been invulnerable, as the protective nature of the shell itself.

To uncover the above question, our laboratory has been systematically working on the embryonic development of the turtle shell. Fortunately in Japan, soft-shelled turtles are cultivated for diets by many farmers, and thus we picked up the Chinise soft-shelled turtle (Pelodiscus sinensis) as an item for the research.

In every summer, our laboratory purchases hundreds of turtle eggs from the farmer. The eggs are covered with hard, mineralized shells, just like chicken eggs. But, unlike the latter, the turtle egg requires sufficient moisture, otherwise they become dried out soon. We therefore put the eggs on a pile of fully moistened peat moss, and place them in an incubator adjusted at 30ºC, so that a high rate of survival can be expected. The eggshell of the turtle is semitransparent, and embryonic blood vessels and eyes are visible through the shell, enabling us to identify the developmental stage before sampling.

The turtle research team in our laboratory consists of only a few members (in 2013, three postdocs), but explores multilayerd subjects from genomes to fossils. We are currently investigating detailed histology, and gene expressions presumably responsible for the origin of the shell. Simultaneously we visit museum collections from time to time to examine fossil skeletons (unlike the other members of the lab, I majored in vertebrate paleontology). Through these investigations, we recently elucidated that the major part of the carapace is derived purely from endoskeletal ribs.

Discussion in the turtle team often provides us with new insights, or hunches, which would potentially help us drive our researches forward. This interaction is, I believe, a key to uncovering the evolutionary process of the turtle shell, in near future.

Hirasawa, T., H. Nagashima, and S. Kuratani. 2013. The endoskeletal origin of the turtle carapace. Nature Communications 4:2107 DOI: 10.1038/ncomms3107

Another recent paper from our laboratory:

Wang et al., 2013. The draft genomes of soft-shell turtle and green sea turtle yield insights into the development and evolution of the turtle-specific body plan. Nature Genetics 45:701-706 DOI: 10.1038/Ng.2615

Animations show origins of the turtle carapace (RIKEN CDB):

http://www.cdb.riken.jp/en/05_development/0506_turtle01.html

(8 votes)

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How can a single fertilized egg become a full little human? It is because I wanted to answer that question that I became a scientist.

When I started my PhD studying the formation of blood stem cells during development,, I learnt how complex development was and how hard it was to address these questions. Though fun and rewarding, big challenges are also part of a scientist’s life. During the difficult times, there were two activities in particular that kept me motivated, confident and enthusiastic about science: 1) doing science outreach and 2) reading scientific publications to keep up to date with the field.

1) As for science outreach, I found it extremely rewarding and humbling to communicate science to non-scientists. It always made me feel proud to realize that I, as a scientist, play a very important role in society, especially given that I work in the controversial field of stem cells. Indeed, when I talk to non-scientists about stem cells, I feel that I contribute to their understanding of the strengths and weaknesses of the field and that, in the long run, it will help end all the misconceptions out there that are detrimental for both science and society.

2) Reading publications. First because they made me feel like I was part of a big worldwide enterprise and also because some of them were… well, quite artistic and beautiful…and like a good piece of art, some of these figures, pictures and graphical displays, were fascinating.

So, this is why I am very excited about writing this monthly blog. Each month, I will share with you the beauty of stem cells by selecting and commenting on a cool stem cell image from a publication, following a similar format to Erin Campbell’s previous posts. This monthly blog is a collaborative project between the Node and EuroStemCell, and therefore my posts will also be available on the EuroStemCell website (http://www.eurostemcell.org/stem-cell-images).

I will be posting my first stem cell image soon…

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