“I also here salute the echinoderms as a noble group especially designed to puzzle the zoologist.”

Libbie Hyman, 1955

Echinoderms are fascinating creatures. They have extensive regenerative capabilities, a mutable connective tissue that dynamically (and deliberately) changes its stiffness, and a complex system of hydraulic canals involved in the circulation of internal fluids and locomotion.

However, the most notable feature of echinoderms is the pentamerous symmetry of their bodies, derived from a bilateral ancestor. These exclusively marine deuterostomes are mostly bottom dwellers with a biphasic life cycle, where the adult tissues develop inside a bilateral planktonic larva (swimming in the water column) and metamorphose into a benthic juvenile.

A planktonic pluteus larva of a sea biscuit.

During my master’s project at University of São Paulo, Brazil, I studied the development of a different kind of sea urchin, a sea biscuit. Sand dollars and sea biscuits belong to a lineage of urchins that developed a secondary bilateral symmetry. Also, during their evolution, around 55 million years ago, the adult morphology changed in association with the occupation of sand beds; more specifically, the body flattened, the spines got shorter, the number of tube feet increased, and their feeding apparatus (lantern of Aristotle), which was absent in other adult irregular urchins, was retained into adulthood.

Since I was interested in the developmental origins of such changes in morphology I documented the embryonic, larval, and juvenile development of a sea biscuit species, Clypeaster subdepressus. After gathering all data, I compiled it into a science outreach video showing a resumé of the life cycle of this species, from fertilization to the first steps of the juveniles. Hope you enjoy it:

We collected adults from sand beds of São Sebastião Channel (São Sebastião, SP, Brazil) and induced gamete release (eggs and sperm). We did the fertilization in vitro and followed the embryonic development in the laboratory, under light microscopy. Embryos become swimming larvae, approximately 0.2 mm wide, which we fed with microalgae until metamorphosis. A diminute sea biscuit grows inside the larva. When the minuscule podia and spines are formed the larva sinks and undergoes metamorphosis. The juvenile sea biscuit reabsorbs the larval tissue and begins to explore its new habitat, between sand grains. [Numbers on the upper right corner show how much the scene was accelerated.]

The video is available to download here, feel free to reuse it and share it around! If you want further details on sea biscuit development (including images and video footage) the official description was published earlier this year.

(9 votes)

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Like more than 500 million people in the world, the Node is now on Facebook . Our foray into Facebook was slightly overshadowed by the British royal family doing exactly the same thing a few weeks earlier, but we can guarantee you that our page will contain far more developmental biology.

We’re using our Facebook page much like our Twitter account: to notify you of new Node posts, and other brief bits of community news. Have a look , “like” us, and invite your friends and labmates to do the same. (We’ll still be updating Twitter as well, so don’t worry if you’re used to seeing us on there.)

There’s a link to our new Facebook page in the left sidebar, and the eagle-eyed among you may have spotted another new thing over there. Several people have told us that they couldn’t immediately figure out what the Node was when they arrived on the page for the first time, so we’ve tried to explain it very briefly over there.

Finally, some things are better left unchanged, it seems. We asked you whether you would like a change in the format of the e-mail notifications, and as it turns out, almost half of those that took the poll were satisfied with the current format. Good to know! Needless to say, we didn’t change the e-mail format.

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The RIKEN Center for Developmental Biology has released the images for a series of postcards under a creative commons license. The images picture a wide range of both common and uncommon model organisms, all in a Japanese paper art style.

You can download the full set of high quality images, designed by Yukiko Fujiwara, as a zip file from their site. This axolotl is now my desktop background:

Earlier this year, I came across another artistic project out of Japan: the plates that were featured on the announcement posters of the SDB/JSDB joint meeting in Albuquerque were also physically present at the meeting:

The artwork on the plates, by design company TRAIS K.K., brilliantly features developmental biology images in the styles of traditional decorations from Japan and New Mexico, and was an absolutely perfect summary of that conference.

(4 votes)

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Over the past months, we’ve seen a few posts on the Node from people who spent a few months working in labs abroad. All of them were funded by a Development travelling fellowship. The next deadline for these fellowships is coming up on December 31st, and Development would like to encourage you to apply.

To qualify, you must be a graduate student or postdoc planning to work for a few months in a distant lab in 2011. Have a look at the fellowship site for the full requirements, and read these stories from previous recipients on the Node.

Tetyana (from the Ukraine) went to India:
Research Snippets from the Land of the Tiger
The Maggot Meeting 2010

Cristian (from Chile) went to Germany:
Developing Science in a Far Country: The Paradoxes of Life

Shreeharsha (from India) went to Japan:
Research in the Land of the Rising Sun

Dávid (from Hungary) went to Japan:
Nippon

Terry (from the US) is currently in Israel:
International Experience

Will your story be next? It might, if you apply for one of the travelling fellowships before December 31st. Good luck!

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Hello, I am Terry Jackson, a 6^th year PhD student in Genetics and Genomics at Duke University which is located in Durham, North Carolina, USA. I am working on my degree in the lab of Dr. Philip Benfey whose research focuses on identifying transcription factors in the root of Arabidopsis thaliana. I am pleased to have received a travel award from the journal Development for an international collaboration with Dr. Asaph Aharoni at the Weizmann Institute of Science in Israel. His work includes investigating and identifying glucosinolates, a secondary metabolite that plants produce as a defense mechanism. Together we plan to determine the glucosinolates that are produced in many of the individual cell layers within the root. We intend to use FACS to isolate each cell type using GFP-marker lines followed by LC/MS to identify these compounds.

I knew that my trip here would be an eye-opening experience and I have not been disappointed. Thus far, I have been here for six weeks and it has been quite a grand undertaking. The planning began months before my departure by deciding the length of my stay and how much we could accomplish in that time period. Everything had to be coordinated from the date of my arrival to making sure my host lab had all of the necessary materials to scheduling time on the FACS machine. It seems simple but even now we are making adjustments and revisions.

Clearly, everyone knows that no two labs operate the same but once you get settled into a lab and into the routine you tend to forget. It is surprising the number of small details that are assumed or overlooked during planning. For instance, at Duke we have technicians that run all of the FACS samples. We only have to prepare the samples and drop them off to retrieve a couple of hours later. Here, at the Weismann Institute of Technology, they do not have technicians for this purpose; the researchers are trained to run the machines themselves. I assumed that I would drop off my samples and return to pick them up and Dr. Aharoni’s group thought I already knew how to work the machine. No one asked me about it until a week before I was scheduled to arrive if I could run the machine. Suddenly, they had to schedule training sessions for me on the FACS machine so that I could do it myself. I was very nervous about this at first but it is much easier than I thought. I consider this training to be an added bonus to my skills set as a researcher and it is one of the most enjoyable aspects of the numerous tasks I must complete each week.

My original plan was to stay here for two months but, since I needed the FACS training and we’ve had to run several test experiments, I decided it’s best to extend my stay for at least one more month. Other than the glucosinolate experiments I also intend to isolate root cells that form large inclusions under low sulfur conditions and then analyze them with LC/MS to determine their composition.  This analysis will probably be the most difficult aspect of the work I am doing here since we are trying to identify and unknown material. Furthermore, it is going to be a steep learning curve for me.  I know it is very necessary that I understand the process of completely. In the end I am sure I will return to Duke with a new perspective and knowledge of  effective collaborations.

(4 votes)

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(This interview by Kathryn Senior originally appeared in Development on November 23, 2010)

Patrick Tam’s research is focused on the cellular and molecular mechanisms of body patterning during mouse development. He agreed to be interviewed by Development to talk about his interest in mouse development, new concepts in gastrulation, X-linked diseases and his dream of an African safari.

Did you always intend to have a career in developmental biology?

I was lured into science at high school as I listened to my biology teacher reminiscing about his romance with plant biochemistry during his university days. It was really no surprise that I chose biology over medicine as my degree and then headed onto postgraduate research without a second thought. It might sound incredible but there was not a proper course on developmental biology (or embryology, as it was known) in the entire Bachelor of Science curriculum of my university in those days. To fill this gap in my education, I made a definite decision to study rodent embryo development – first in Hong Kong, and later in London with Michael Snow. This was a time when research in mouse development was taking off in a big way in the UK and so the rest, as they say, is history.

What has influenced your decisions about institutions and locations?

Before I finished my PhD, I had already accepted a faculty position in the newly founded Medical School at the Chinese University in Hong Kong. Luckily, I did manage to squeeze in one year of postdoctoral training at the University of Texas at Austin. This proved to be critical for broadening my research experience and I learned a great deal more before taking on the job back home.

Joining a young institute happened to be a good decision: there were ample start-up resources and also the flexibility that I needed to be able to run the laboratory the way I wanted it. The academic appointment offered relatively stable support for my research during this formative phase of my career. The downside was coping with the demand of teaching commitments, and being the only laboratory working on mouse development made it quite hard to maintain research momentum. My next move to a research institute in Australia was a very positive one as it allowed me to develop further in a research-intensive and intellectually stimulating environment. Having access to first-rate facilities and interacting and networking with a larger community of developmental biologists enabled me to focus and move forwards much faster.

You have been a great pioneer in applying micromanipulation and embryo culture research for investigating early mouse development: how did you get into this originally?

My PhD project was to characterise the developmental fate of an active multiplying population of cells in the epiblast of the gastrulating mouse embryo. I had little idea how challenging this would turn out to be! Initially, we focused our efforts on developing a reliable whole-embryo culture method by tweaking the protocol established by Dennis New for culturing rat embryos. We then tried to apply the conventional `slash and burn’ and `cut and paste’ techniques to study cell fate and tissue differentiation. I owe Rosa Beddington an enormous debt of gratitude for introducing me to the art of embryo manipulation during my sabbatical at Oxford University in the mid 80s: my collaboration with her has had a lasting impact on my career. Ultimately, my postgraduate project evolved into a consuming exercise of fate-mapping all three germ layers and their immediate derivatives. The work took three decades but realizing that I had completed my original objective to the best of my ability was a very satisfying moment in my scientific career. (more…)

(4 votes)

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Pak1-ing a punch in lumen formation

The generation and maintenance of correct lumen size and shape is essential for the function of tubular organs. Now, Monn Monn Myat and co-workers report that p21-activated kinase (Pak1) plays a novel role during lumen formation in Drosophila embryonic salivary glands (see p. 4177). The researchers show that Pak1 regulates the size and elongation of the apical domain of individual epithelial cells in the developing gland by decreasing and increasing E-cadherin levels at adherens junctions and basolateral membranes, respectively. Pak1 mediates these effects, they report, through Rab5- and Dynamin-dependent endocytosis of E-cadherin. Moreover, constitutively active Pak1 induces the formation of multiple intercellular lumens in the gland, an effect that is dependent on Rab5 and Dynamin, and on the Pak1 substrate Merlin. Together, these results identify a crucial role for Pak1 and E-cadherin endocytosis in lumen size and shape determination in fly salivary glands, and highlight a mechanism for multiple lumen formation, a process that occurs in pathological conditions such as breast ductal carcinoma in situ.

Shh signalling out-Foxed by cilia

Sonic hedgehog (Shh) signalling controls cellular differentiation in the neural tube by regulating a poorly defined gene regulatory network. To better understand this network, James Briscoe and colleagues have undertaken a genome-wide expression screen in chick neural tube and, on p. 4271, they identify the forkhead transcription factor Foxj1 as an Shh target gene in this tissue. Foxj1, they report, is expressed in the chick and mouse neural tube in cells that constitute the floor plate (FP), a neural tube organising centre. Foxj1 expression is associated with the formation of long motile cilia in several cell types and, consistent with this, the authors show that chick and mouse FP cells produce primary cilia longer than those produced elsewhere in the neural tube. Finally, they show that Foxj1 expression in the neural tube attenuates Shh signal transduction by altering cilia structure and modifying the intracellular localisation of the Gli proteins that mediate Shh signalling. Together, these data reveal a novel cilia-dependent mechanism that modulates cellular responses to Shh signalling.

Leaves send mobile signals for size

Organ size in plants and animals is tightly controlled, and partly determined, by cell size and number. Plant leaves, for example, exhibit compensation, in which defective cell proliferation triggers increased postmitotic cell expansion. Now, Hirokazu Tsukaya and colleagues (p. 4221) identify two novel pathways coordinating cell proliferation and expansion in Arabidopsis leaves. Two Arabidopsis mutants, the loss-of-function ANGUSTIFOLIA3 (AN3, a transcriptional co-activator) mutant and the overexpressor KIP-RELATED PROTEIN2 (KRP2, a cyclin-dependent kinase inhibitor) mutant show compensation: in an3 mutant leaves, cell numbers decrease by ~70%, whereas cell size increases by 50%. Using the Cre/lox system, the authors generated leaves chimeric for AN3 and KRP2 expression, and investigated whether compensation occurs in a cell-autonomous or non-cell-autonomous manner. An3-dependent compensation, they report, is indeed non-cell-autonomous and occurs via an intercellular signal restricted to one half of leaves. Conversely, compensation caused by KRP2 overexpression occurs cell-autonomously, possibly via a mitotic cell cycling defect. Future work should shed more light on these events and identify the transmitted signal.

Ongoing Phox2 locks in neuronal differentiation

During neuronal differentiation, expression of the transcription factors that determine neuronal identity often continues after their downstream genetic program has been launched. Is this continued expression required for neuronal differentiation? On p. 4211, Jean-François Brunet and colleagues address this question by inactivating the paired-like homeobox genes Phox2a and Phox2b, which specify several classes of visceral neurons, after the developmental timepoint at which they act to initiate visceral neuron differentiation. They report that ongoing Phox2b expression is required in branchiomotor and visceromotor neuronal precursors after their initial specification to maintain their molecular signature, migration pattern and cellular differentiation. Similarly, maintenance of noradrenergic neuron differentiation during embryogenesis requires the ongoing expression of Phox2b in sympathetic ganglia and of Phox2a in the main noradrenergic centre of the developing brain. Thus, neuronal differentiation does not always unfold as a transcriptional ‘cascade’ in which downstream events are irreversibly triggered by an upstream regulator. Instead, as seen here, it sometimes requires continuous input from so-called ‘terminal selector genes’.

Hippo links growth control to tissue homeostasis

Both tissue repair and tissue homeostasis require stem cells that proliferate to replenish lost cells, but the way in which adult stem cells respond to damage and switch between homeostatic and rapid proliferative states is not well understood. In the Drosophila midgut, intestinal stem cells (ISCs) maintain homeostasis, and, in response to damage, can proliferate rapidly following activation of the Jak/Stat pathway. In this issue, two papers demonstrate that Drosophila ISC proliferation, and hence intestinal regeneration, are regulated by the Hippo (Hpo) tumour suppressor pathway, providing an exciting new link between growth control and stem cell proliferation.

On p. 4147, Nicolas Tapon and colleagues examine the effects of Hpo pathway inactivation in the midgut by overexpressing Yorkie (Yki), a progrowth target that is usually repressed by the Hpo pathway. They report that Yki overexpression in differentiated cells increases ISC proliferation non-cell-autonomously without affecting differentiation, and induces the expression of the Jak/Stat pathway ligand Unpaired. The authors also observe that Yki target genes are induced by bacterial infection, and suggest that the Hpo pathway acts to sense cellular stress within the midgut. Finally, using RNAi, they show that Yki is also required within ISCs to drive proliferation in response to bacterial-induced tissue stress. Based on their findings, they propose that the Hpo pathway is a mediator of the Drosophila midgut regenerative response.

In a second, related paper, Norbert Perrimon and co-workers (p. 4135) demonstrate that Yki overexpression in ISCs induces proliferation cell-autonomously, whereas Yki loss has no effect on ISCs during normal homeostasis. They also show that Yki activity is required in ISCs to mediate the proliferative response to tissue damage, and propose that this effect is elicited by downstream targets that are involved in proliferation and survival. Importantly, they report that, prior to tissue damage, Yki is also repressed by the atypical cadherins Fat and Dachsous, which are upstream components of the Hpo pathway. From their findings, the researchers propose that Yki is inactive under normal homeostasis but becomes activated to induce ISC proliferation when cell-contact cues, and thus Hpo signal transduction, are disrupted by tissue injury.

Also…

Germline segregation in metazoans can occur during or after embryogenesis and often involves a common set of genes. Juliano, Swartz and Wessel now propose that this gene set represents a conserved germline multipotency programme operating in germ cells and multipotent progenitors.

See the Hypothesis article on p. 4113

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Being at the end of the planet Earth and organizing an international meeting is not easy. Even harder is to prepare and hold a course intended for an international audience. But the organizing committee of the Fifth International Meeting of the Latin American Society for Developmental Biology, together with the Society for Developmental Biology, managed to make both events possible, with an outstanding response from students and researchers.

First, it was developed the short course entitled “Concepts and Model Organisms in Regenerative Biology”, in Santiago, Chile. The course was composed by theoretical and practical sessions, focused on the regenerative abilities of model organisms, and expert  researchers were invited as speakers and to show to the students about the techniques used in the model organisms of their expertise area. Some invited scientist were Brigitte Galliot, Richard Behringer, Panagiotis Tsonis, Katia del Rio-Tsonis, Alejandro Sánchez-Alvarado, José García-Arrarás and others. The enormous effort and patience of these researchers, together with the incredible amount of work of the local organizing committee (specially Juan Larraín, Miguel Concha and Miguel Allende) made possible the success of this experience.

The course was followed by the meeting in Santa Cruz, a small town in a part of Chile located in the center of the country, known by its vineyards, wine and the nice climate. The reception opening consisted in a walk by the local museum, which has interesting collections, including one of the biggest amber collection with animal and vegetal fossils preserved inside them, and fossils from the ancient fauna in Chile. After the visit to the Museum, a cocktail with chilean wine was waiting for all the students and researchers. The following was simply a success: five days of excellent talks and poster sessions. We enjoyed the presence and talks of Janet Rossant, Allan Spradling, Claudio Stern, Edward de Robertis, Carl Phillip Heisenberg, Roberto Mayor, John Wallingford, Joachim Wittbrodt, Kenneth Poss, Jonathan Slack, the speakers invited to the course and many more. The poster sessions were very exciting; the wine made easy to share and talk with the authors. Personally, the meeting was a complete success, considering that almost eight months ago, the fifth most powerful earthquake in recorded history happened in Chile (actually, Santa Cruz is located in one of the regions of Chile most affected by the earthquake, remembered also by Cristian Undurraga here at The Node, in this post), and also considering the long distance travelled by many of the attendees and the almost two weeks that some of the invited speakers (participating in the short course) stayed in Chile.

I uploaded some pictures of the meeting. It is necessary to mention that all of this success was possible with the outstanding work of many people, including Ida Chow from the SDB.  Please enjoy the pictures, and those of you that attended the meeting and/or the course, please fell free to comment and share your experience.

(3 votes)

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Science is held pretty highly in Japan. The country has produced 15 Nobel Prize winners in the science disciplines, including two in the field of chemistry this year. But perhaps a little less in the international press’ limelight is Dr. Yoshiki Sasai, winner of the Osaka Science Prize. This honor is like the Japanese version of a science-biased Oscar for local scientists and is awarded each year to a person who has made a major contribution to physical science, engineering, agriculture, biology, medicine, pharmacology or information science by helping to advance scientific understanding and developing new technology. And this year the prestigious honor has been awarded to a developmental biologist.

Sasai is a Group Director in the RIKEN Center for Developmental Biology, a visiting professor at the National Institute of Physiological Sciences and an affiliated professor at Kyoto University Graduate School of Medicine. Adding to this impressive resume, Sasai was also a visiting professor at Lund University Faculty of Medicine and a research fellow at UCLA School of Medicine.

He was awarded with the Osaka Science Prize for his work in the analysis of organizational principles in brain development. His particular interest of research lies in understanding how the complexity of the fully-formed brain arises from a nondescript clump of cells in the embryo by studying very early neurogenesis and the mechanisms of neuronal differentiation.

It is heartening to know that developmental biologists are being recognized worldwide. It can, of course, only be a good thing.

(6 votes)

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The 3rd Latin America Course on ES cells and Development will be in Cuernavaca, Mexico. It provides extensive hands-on experience and an incredible line-up of speakers. The course can take up to 8 UK PhD students, post-docs, or young investigators, and it is fully funded. Please visit:

http://www.escellslatinamerica.org/

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