To uncover the mysteries of development, developmental biologists use an amazingly wide range of systems – from cells in culture to live mouse embryos, and from classical model organisms to unusual critters.

We read the papers and listen to the talks about the work using these organisms, but we only really know the details of the model we work with. So what does an axolotl eat? How do you get a frog to lay eggs? How do you make a transgenic Arabidopsis? Why do fly researchers always talk about collecting virgins?

‘A day in the life of…’ is a new series of posts that will aim to answer these and other questions by giving you an insider’s view of what is like to do developmental biology using different organisms. Our first post is a day in the life of a Xenopus lab, where postdoc Gary reveals the mysteries of doing research on frogs. In the next few months we hope to feature posts on ‘a day in the life of’ many other lab organisms, and we already have a few exciting articles lined up. However, with so many different organisms being used in labs around the world, we need your help! If you are interested in writing about what is like to do developmental biology in your model organism, why not drop us an email? It would be great to have your participation!

We hope you will enjoy this series! You can read all the posts so far here.

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September was a little bit more quiet than usual, but we still had many interesting posts. Here are the highlights!

Research

– Gary examines a recent Science paper on the titration of replication factors in the Midblastula transition in Xenopus.

– Karuna followed up on a previous Node post by writing about her recent paper on identifying a protein that controls the positioning of squint RNA in the zebrafish embryo

– Nadia discussed her group’s recent paper on the role of fluid forces in epicardium morphogenesis.

– and Christele continued her Stem Cell Beauty blog by writing about a recent paper on the importance of insulin signalling in the development of ovarian stem cell niches.

Spotlight on the Woods Hole embryology course

– This year marks the 120th anniversary of the Woods Hole course, so we interviewed Professor Alejandro Sánchez Alvarado, one of the current co-directors of the course.

– September also saw an exciting update on the Woods Hole competitions here on the Node, as this year’s last round featured 4 beautiful movies taken at the course. Many of you voted, and the big winner was the ascidian metamorphosis movie!

Books

– Development‘s Associate Reviews Editor (stem cells), Caroline Hendry, interviewed author and researcher Paul Knoepfler on his new book ‘Stem cells- an Insider’s Guide’.

– while Teisha presented her new book  ‘Biology Bytes: Digestible Essays on Stem Cells and Modern Medicine’.

Also on the Node
– Once again we summarised our best spots on science and (developmental) biology from around the internet in one post.

Happy Reading!

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Here are the highlights from the new issue of Development:

Coordinating stem cell and niche development

The Drosophila ovary provides an accessible system for analysing the interactions between stem cells and their supporting niche. The Insulin-like receptor (InR) and Target of rapamycin (Tor) pathways affect germline stem cell activity in the adult fly, but their roles during ovary formation are poorly understood. On p. 4145, Dana Gancz and Lilach Gilboa investigate the consequences of manipulating InR and Tor signalling in germline and gonadal somatic tissues. They find that both pathways are required cell-autonomously in primordial germ cells (PGCs) to promote their proliferation, while disrupting either pathway in the soma affects both precursor cell proliferation and niche differentiation. InR activity in somatic cells also promotes PGC differentiation non-autonomously. Importantly, these experiments reveal that the PGC-to-cyst transition is a two-step process, only the first of which is insulin regulated. Together, these data demonstrate that InR and Tor act to coordinate development of ovarian stem cells and somatic cells, helping to ensure the formation of functional niche-stem cell units.

How to grow a heart

During heart development, proliferation of cardiomyocytes (CMs) must be tightly controlled to determine organ size, and different regions of the heart show differential proliferation rates. How is CM proliferation regulated in space and time, and how might the mechanisms regulating tissue growth be harnessed for clinical applications? Ibrahim Domian and co-workers investigate the role of Wnt/β-catenin signalling in regulating CM proliferation, using in vitro stem cell culture and in vivo approaches (p. 4165). They find that canonical Wnt signalling promotes proliferation of CMs derived from mouse embryonic stem cells (ESCs) or from induced pluripotent stem cells, and, importantly, of human ESC-derived CMs. Furthermore, they show that differential Wnt pathway activity likely underlies the differential proliferation rates of trabecular versus compact myocardium in the developing mouse heart in vivo. The effects of Wnt signalling on CM proliferation provides a potential method for generating large numbers of CMs in culture, which could be used for drug screening or regenerative therapy approaches.

Chromatin regulation: KIS and tell

The chromatin-modifying Polycomb and trithorax group proteins are crucial for the establishment of key transcriptional networks during development. Kismet (KIS), a member of the trithorax group of proteins, promotes gene expression via transcriptional elongation as well as by antagonizing Polycomb-mediated repression; however, it is not understood how closely these two processes are linked and the molecular mechanisms that underpin them. In this issue (p. 4182), Kristel Dorighi and John Tamkun provide evidence for two distinct mechanisms of KIS-mediated gene regulation in Drosophila, separating the processes of transcriptional elongation and antagonism of Polycomb repression. The authors find that KIS recruits ASH1 to regulate levels of H3K27me3, but that ASH1 is dispensable for transcriptional elongation. Conversely, inhibition of transcriptional elongation does not affect ASH1 chromosome localization or H3K27me3 levels. Thus, the authors show that these two processes are independent and that, in addition to a general role in promoting transcriptional elongation, KIS has a separate specific role in recruiting ASH1, which regulates H3K27me3 levels and antagonizes Polycomb repression.

MYB in multiciliogenesis

The airways of the lung are lined with multiciliated cells (MCCs), the coordinated beating of which generates fluid flow to remove particles from the lungs. Generation of MCCs requires massive amplification of centriole numbers to form the basal bodies of each cilium. How are MCCs specified and how do they differentiate? Here (p. 4277), Mark Krasnow and co-workers uncover a role for the cell cycle regulator MYB in promoting multiciliogenesis. MYB is expressed in newly postmitotic cells of the mouse airway epithelium (as well as other multiciliated cells), and mutants lacking MYB show defects in centriole amplification during MCC formation – particularly at earlier stages of development. They further show that MYB promotes the expression of the key late MCC regulator FOXJ1, while MYB itself is regulated by Notch signalling and the nuclear protein multicilin. As MYB is better known as an S-phase regulator, they propose that it may control multiciliogenesis by promoting an S-phase-like state in which centrioles are synthesized but DNA is not.

Eph-icient cell packing in the lens

The lens of the eye is a unique tissue in that its key function, transmitting and focusing light, crucially depends on the refractive index of the tissue, and hence on the packing and alignment of lens fibre cells. Lens opacity, or cataracts, can result from defects in this precise tissue organisation. Recently, mutations in EphA2 and ephrin A5 have been associated with cataracts in both mice and humans. Here (p. 4237), Xiaohua Gong and colleagues analyse the mechanisms by which Eph/ephrin signalling regulates lens cell organisation in mice. The authors find that EphA2 regulates the subcellular localisation of adhesion and cytoskeletal proteins such as cortactin, F-actin and E-cadherin. These effects are likely mediated – at least in part – by Src kinase, the localisation of which is also dependent upon EphA2. Cell shape and packing are disrupted in Epha2 and Src mutants, suggesting that Eph/ephrin signalling via Src plays a key role in regulating cytoskeletal organisation in lens fibre cells and their arrangement in the tissue.

APC: Assuring Proper Centrosome separation

The adenomatous polyposis coli (APC) tumour suppressor is best known as a Wnt signalling regulator, but it also plays cytoskeletal roles, including during mitosis. APC mutant cells show enhanced chromosomal instability, while in early Drosophila embryos undergoing syncytial mitoses, APC2 mutants show enhanced ‘nuclear fallout’ – whereby nuclei that have undergone defective division are removed from the cortex. To understand the mechanisms underlying the mitotic function of APC, Mark Peifer and colleagues (p. 4226) have analysed the mitotic defects in APC2 mutant Drosophila embryos in detail. Their data suggest that APC2 is not essential for mitosis, but does promote mitotic fidelity. The primary consequence of APC2 loss appears to be a defect in centrosome separation; when this fails, the mitotic spindle can still form, but ectopic cleavage furrows appear and disrupt chromosome segregation. Moreover, the APC-binding partner Axin is also involved in this process. These data suggest a key role for APC family proteins in promoting centrosome separation during mitosis; this may also be relevant for its tumour suppressor activity.

PLUS…

Sox proteins: regulators of cell fate specification and differentiation

Sox transcription factors play widespread roles during development. Here, Kamachi and Kondoh provide an mechanistic overview of how Sox family proteins function and how they can thus regulate diverse processes during development. See the Primer on p. 4129

Studies of morphogens: keep calm and carry on

The recent EMBO Workshop on ‘Morphogen gradients’, which took place in Oxford, UK in June 2013, centered on the formation and interpretation of  morphogen gradients during development. Here, Angelike Stathopoulos and Dagmar Iber provide a brief overview of the talks and discussion at the meeting. See the Meeting Review on p. 4119

Getting the measure of things: the physical biology of stem cells

In July 2013, the diverse fields of biology, physics and mathematics converged to discuss ‘The Physical Biology of Stem Cells’, the subject of the third annual symposium of the Cambridge Stem Cell Institute, UK. Here, Sally Lowell reviews the meeting and the themes that emerged from it. See the Meeting Review on p. 4125

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Stuck! Here I was trapped in this valley with no way out. And it was crowded here, with all of my fibers I sensed numerous peers condemned to a similar fate. The wonderful scenes that could be reached from the top of Mt. Waddington had been illusionary. Was this my reward: being trapped in Fibrocity, the slum of existence? Ignorant of the adventure yet to come, I cursed my fate.

It all got started when “Zygote Enterprises” organized this foolish competition, a race that can be best compared with an obstacle course in the swamp. The countless contestants, including me, were lured by the “Carte Blanche” awaiting the winner. Before the start, we were boasting like little Titans, judging each other’s fitness and calculating our odds. Suddenly, we were launched and hyperactively we raced towards our goal. I realized that my chances to win were next to zero. Then we arrived at a junction and in a lucky burst of inspiration, I directed my nearest competitors to go left, after which most of them unsuspectingly raced off in the wrong direction and I reached the target before the others could. Immediately after I crawled through the opening located in the curved transparent wall it closed, shutting my rivals outside. Unable to avert my eyes, I could see through the wall how the losers perished out there in the damp and hot wilderness, some of them fruitlessly banging the wall with their extremities. Despite the horrific sight, victory tasted good.

Exhausted, but filled with anticipation, I was taken to the top of Mt. Waddington where my triumph would be celebrated and the prize awarded. An employee of “Zygote Enterprises” who introduced herself as OCT4 told me that I would get the blank check in due time, but that she would first show me the view from the top. “It’s marvelous”, she said, “You’ll love it”. She guided me to the edge of Mt. Waddington’s summit, and indeed the view was awesome. “It feels as if I am on top of the world looking down on creation” I told her in a mellow voice.

“From here you have a panoramic view into “Les Trois Vallées’” OCT4 told me. “The three large valleys you can see from here are named “Outer Valley”, “Middle Valley”, and “Most Proximal Valley”. OCT4 continued. “If you look carefully, you can see all wonderful places that you can reach from each of these valleys. At the edge of Outer valley you can see Neuronburg and Schwann Lake. Deep down there at the bottom of Middle Valley are Kidney Harbor and Leydig. And there, at the far end of Most Proximal Valley lies Hepatocity with Salivaryg Land’s river glistening beyond”. Dizzied by the dazzling view of unlimited possibilities I grabbed hold of OCT4, afraid I would fall down into the deep. I had hardly steadied myself when OCT4 pushed me hard over the edge. As a marble I started rolling downhill, oblivious of my fate. Had I known where I wanted to go I might have been able to steer myself in the right direction. Faltering, I passed the bifurcation and while contemplating my passivity I entirely missed the second, resulting in the wrong choices at the third and the fourth. In the meantime I had gained so much momentum that all further decisions were pure random. My roller coaster ride came to a sudden halt when I bumped into this non-descript individual. “Welcome to Fibrocity, for those who like to connect”, he said unconvincingly.

It took me a long time to accept my fate in Fibrocity. Finally, I adopted a zen-like state that may be best described as total apathy to cope with my situation, unresponsive to my immediate surroundings. I have no idea for how long I had been in this impassive condition, but I know that it was long enough that I initially failed to notice things were slowly changing around me. Gradually it dawned on me that some of my neighbors had disappeared and I was able to move more freely, a feeling I had not had in ages. Slowly I recovered from the passive state I had been. One by one, all the connections I had with my neighbors were lost. A character that was vaguely familiar to me approached me from a distance. “Hello”, she said “we have met before, remember”. “OCT4” I muttered, while I indeed remembered how she pushed me from the mountain. “Please” she continued, “don’t be angry with me, my intentions are good. Follow me and I will have a surprise for you”. Reluctantly I followed her, cautious for any foul new tricks she would play on me. When I saw where we were heading I was astonished. To my disbelief we drew near a seemingly endless gondola lift going up on the slopes of Mt. Waddington. The lift was brand new, built in Kyoto Japan and signs on the posts read “Takahashi Yamanaka Unlimited”. OCT4 guided me to the small station where the rail cars that come down are sent up again. Just as we entered, a rail car opened its doors. OCT4 stepped inside and intrigued I followed her. She took a seat and pulled me next to her. Immediately the doors closed and the rail car jumped into motion. It was a long journey during which I felt increasingly better at ease. Finally we reached the top of Mt Waddington and the doors swung open. “Go on”, OCT4 said, “It is time for you to collect your prize”. Speechless, I carefully stepped outside. At the exit station a sign read “Welcome to Tir nan-Og, The Land of the Ever Young”. Reborn, I walked to the edge of the mountain top unafraid that OCT4 would push me over again, grateful for the lesson she taught me. In the future, I would carefully choose my next destination, but for the time being I enjoyed the scenery.

(18 votes)

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This year’s last Woods Hole competition had an exciting development- instead of choosing from 4 images, we asked the Node readers to choose from 4 stunning movies. It was probably hard to choose who to vote for, but in the end the beautiful movie of the ascidian metamorphosis was the big winner. The following collection of stills from the movie will be in the cover of a future issue of Development, while the movie itself will feature in the homepage of the journal.

 
 
Congratulations to Matthew Clark, from the University of Oregon, for the winning movie.

The runners-up to this competition were Marina Venero Galanternik (University of Utah), Rodrigo G. Arzate-Mejía (Universidad Nacional Autonoma de Mexico), Jennifer McKey (Universite Montpellier) and William Munoz (The University of Texas MD Anderson Cancer Center) for their movie of Drosophila embryogenesis; Daniela Di Bella (Fundacion Instituto Leloir), Joyce Pieretti (University of Chicago), Saori Tani (Kobe University) and Manuela Truebano (Plymouth University) for their movie of cell divisions in C.elegans; Eduardo Zattara (University of Maryland, College Park) for his movie of zebrafish lateral line migration.

(2 votes)

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I recently had the pleasure of interviewing Associate Professor and dedicated stem cell blogger Dr. Paul Knoepfler about his upcoming book “Stem Cells: An Insider’s Guide”. The book covers everything from defining stem cells and their clinical applications to stem cell regulation and even some stem cell urban legends. Here, Paul chats about his book, his own thoughts on the stem cell field, and possible approaches for cloning John Lennon…

Congratulations on your book, it’s a real stem cell tour-de-force. Can you tell me what motivated you to start writing this?

I’d been working on my stem cell blog for about three years and finding it really rewarding as an additional element to my professional life. It occurred to me that I could probably expand the audience further by putting some of my thoughts down in the context of an actual book. One of the things I did was to go on Amazon and look at the different books that were out there on stem cells. I found that there is this big gap: some are probably over-simplified, but most of them are way too scientifically dense, half a sentence on half a page, that sort of thing. I couldn’t really find the kind of book that I would have liked to read, or that a friend of mine who is not a scientist but is interested in stem cells would want to read. I tried to write that book, and hopefully I was successful.

So your book is aimed at both scientists and non-scientists?

I’m hoping to have a book that scientists will enjoy but also a wider audience can comfortably read and understand. I also want to challenge people to think, but I don’t want people to feel like they are reading a textbook. I aim to be in the middle, where people are challenged, but not overwhelmed.

I think you do challenge people, partially because you present many different views, not just your own.

I went into this project trying to write a book that has a unique voice. Like you said, I do try to include other people’s opinions, but I didn’t shy away from including my own. And so that is a little different, or actually really different, from what we are formally taught in science. I intentionally said in the book that these are actual opinions, not necessarily facts. I think that’s helpful because it gets people’s attention, even if they don’t necessarily agree with me. Maybe it makes them think in a new way, makes them talk about it and gets a discussion going. I also wanted to get some humour in there, because even if it is a little edgy or risky, it’s also kind of fun.

You are also a cancer survivor. Was there a more personal motivation for demystifying the stem cell hype? 

Yeah, that definitely played a role in all of this. Having cancer has really opened my eyes to the fact that there is another side to this: the patient side. I think for me, having been a patient, it helped me to empathize and connect more with patients in the stem cell arena, because they are very vulnerable. They are often facing very devastating diseases and injuries and they don’t feel like conventional medicine has anything to offer them. So I try, by my own experience as a cancer patient, and also as a stem cell scientist, to help them in whatever way I can. But also I empathize with the situation they are in, because often times they’re willing to take more risks than I am comfortable with. They have a different perspective and I try to respect that. I try to take that patient perspective with me and put it into the book. I don’t think it is good to just write a book about stem cells without including things that are important for the patient. Having been a patient myself, it helps me to be more conscious of those issues.

You talk in the book about stem cell tourism and the problems it creates for patients and for the field. Whose responsibility do you think it is to crack down on stem cell tourism? 

That’s a great question, and I don’t necessarily have all the answers. I don’t know if people are aware but there is a sort of ad hoc group of stem cell scientists and bioethicists around the world who have been activists on this issue. And I include myself in that group, because we as individuals are putting ourselves at risk, promoting evidence-based medicine in the stem cell field and encouraging patients to ask more questions before jumping into a risky situation. Many of us, including myself, have experienced being threatened with litigation and serious retaliation in other ways. So I don’t think that model is really going to work in the long run because it puts too much risk and responsibility on individuals as human beings. And I am not saying that there isn’t a role for individuals, but I think that somehow we need to have a higher level response to stem cell tourism. While down here in the trenches there isn’t a whole lot of concrete data on stem cell tourism, there is definitely a feeling that the problem is accelerating, so I don’t think that just a group of ad hoc individuals is going to be able manage it. The FDA, at least in the jurisdiction of the US, has a responsibility to work on these issues. But it starts becoming very complicated when you are dealing with international companies, because the FDA doesn’t have jurisdiction outside the US.

So then it really comes down to education. You’ve clearly tried to address this with your book, but is there a greater need to educate not just patients but doctors as well?

That is definitely something that I have advocated for. I proposed earlier this year for medical schools to start having a formal stem cell training program for physicians (see http://www.ncbi.nlm.nih.gov/pubmed/23477401). If you have a gastrointestinal problem, you want someone who has years of training dealing with gastrointestinal problems. It’s the same kind of thing with stem cells. I want patients to raise their expectations and to ask more questions. So I think you’re totally right, education might be in the long run the most effective way to go, so that patients and potential patients who think that they might want to get a stem cell transplant actually have resources that they can easily obtain. So that they can think “Ok, I should be asking this question, I should be asking that question, I should be skeptical about this” and so on. I am a real believer in outreach and education.

In your book you list over 10 different diseases that may be amenable to stem cell therapies. How close do you think we are to any one of those?

I don’t think we are as close as I would hope we are, and I don’t think we are as close as many other people hope we are. I wish it were different but the unfortunate reality is that if you want to do this kind of science properly, and I really think we need to do that, it’s a relatively slow process. You have to accept that there are going to be setbacks, and some things aren’t going to work, and other things will work. I am cautiously optimistic that within a decade, macular degeneration might be one of the first diseases where we see a substantial impact in a significant number of patients using stem cell technology. I have some optimism, and to me the basic idea behind that approach seems very straightforward and logical. And so I would say I am pretty hopeful on that. I think we are going to see some progress on diabetes too. I definitely wouldn’t use anything close to the word ‘cure’, but then again I think that you can see a pathway to helping patients via stem cell technology. It might take a decade, but you can see a roadmap where you can regenerate either endogenous beta cells that were dormant, or put in a new mini-pancreas from stem cell-derived beta cells. I believe there are definitely reasons for hope.

You also encourage us to “get your geek on” and think about far-out applications of stem cells. Of all the ones that you discuss in your book, which would you most like to see happen?

I would love to see whole organs becoming available. Because nowadays, for example, if you get really serious liver disease, in the end there is a very good chance that is going to kill you even if the rest of your body is healthy. So I think this idea that you can just go get a new liver, or a new pancreas, or regrow your hand; I think that’s both really cool and practically speaking could have a spectacular impact on human health. I also like space related stuff. I was surprised to find that NASA actually funds a lot of research for stem cells in space. That is one of my own stem cell geeky fascinations. I think that is kind of cool.

I would like to see dinosaurs…

I have mixed feelings on cloning, I have actually come out against some of that stuff. I think it is going to be a tough one technologically speaking, but it’s very fascinating and it does capture peoples’ imagination that they might see a woolly mammoth. I am not so sure about human cloning: some guy recently bought John Lennon’s old tooth, because he wanted to clone John Lennon. I guess he was hoping to get some DNA or something. There are a lot of weird, potentially dangerous, yet fascinating ideas out there.

You have been named one of the Top 50 most influential people in the stem cell field. Where do you think the influence comes from, and how do you intend to use it?

When I started my career I would have hoped that my influence was purely scientific, but I think realistically that ranking in the top 50 must have had a lot to do with my blog and me being somehow a leader in stem cell social media. I know from the people who confidentially contact me that a lot of the other top 50 and other stem cell bigwigs do read my blog very regularly. It doesn’t mean that they agree with me, and they may even think I am totally crazy on some topics, but they come and read it so I think that is where that influence comes from in a large part.

My hope is to use my influence in a positive way: one of my biggest goals is to get people communicating more, people who wouldn’t normally talk to each other. And also to get patients connected up with resources. And I have definitely encouraged patients to try to find researchers’ emails in articles: the researcher may not respond to you, but then they might. That is my biggest goal, to get people more interconnected and educated.

Stem Cells: An Insider’s Guide is available now via World Scientific and Amazon.com 

(7 votes)

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A team at IRB Barcelona identifies an essential protein for embryonic viability during the first cell divisions in the fly Drosophila.

This protein, called dBigH1, which is a variant of histone 1, could also be associated with fertility issues.

A zygote is the first cell of a new individual that comes about as the result of the fusion of an ovule with a spermatozoid. The DNA of the zygote holds all the information required to generate an adult organism. However, in the first stages of life, during the so-called embryogenesis, the genome of this zygote is repressed and does not exert any activity.

In the fly Drosophila melanogaster, the genomes of the zygote are repressed until the thirteenth division, after which the embryo starts to express its own genes. Headed by Ferran Azorín, also CSIC Research professor, the Chromatin Structure and Function group at the IRB Barcelona has identified a protein in Drosophila that keeps the zygotic genome inactive until the correct moment. This function is vital for embryo life because without dBigH1 the genome is switched on too early and the embryos die. The results are published in Developmental Cell, the most important journal of the Cell group devoted to development.

This is the first time that scientists have described a specific function of histone 1 during embryogenesis. Although this protein is present in the first embryonic stages of humans and mice, nothing is known about its function.

“The fact that now we have also detected this protein in Drosophila has allowed us to study its vital activity during early stages of embryonic development more quickly and efficiently,” explains Salvador Pérez-Montero, PhD student and first author of the study, and Albert Carbonell, postdoctoral researcher who joined the project a year ago. “If this same function is conserved in humans, its alteration could be related to gestational disorders or early miscarriage,” says the head of the group Ferran Azorín.

The scientist goes on to explain that “they are not disorders —in the true sense— that are commonly treated and, in fact, problems during gestation can arise for many different reasons.”
 
 
Future studies on infertility

The protein dBigH1 could also be related to male and female fertility. In this study the scientists have revealed that this molecule plays a fundamental role in fly embryogenesis, but they are now focusing on defining the function of this protein in germinal cells.

The so-called germline comprises the sex cells, namely the cells that give rise to ovules and spermatozoids, and thus the very cells responsible for passing down genetic information from one generation to another. In the Drosophila embryo, even in the first divisions about 40 germline cells separate and differentiate and all of them express the protein dBigH1.

The scientists already have the first functional results, which point to dBigH1 regulating sperm production in males and ovule production in females. “When this gene is removed, this process is totally disrupted,” explain the researchers.

The next paper is expected to reveal whether there is indeed a relationship between the protein dBigH1 and individual fertility, and if so, the potential biomedical applications of this new discovery.
 
 
Reference article:

The Embryonic Linker Histone H1 Variant of Drosophila, dBigH1, Regulates Zygotic Genome Activation Salvador Pérez-Montero, Albert Carbonell, Tomás Morán, Alejandro Vaquero, and Fernando Azorín.
Developmental Cell (2013),

This article was first published on the 30th of September 2013 in the news section of the IRB Barcelona website
 
 

(1 votes)

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I recently published a book, called Biology Bytes: Digestible Essays on Stem Cells and Modern Medicine, which is on stem cells and other medical-related topics, and thought it would be of interest to readers at The Node. A large part of the book is just on stem cells — specifically, an entire chapter (74 pages) is on the many different stem cell types and relevant cutting-edge research (including a general introduction to stem cells), and another chapter is dedicated to bioengineering organs, regeneration in the salamander, and the amazing life-cycle of the jellyfish Turritopsis nutricula. The book is geared towards the general public, so it is perfect for introducing someone to these fields.

Here are some more details on the book:
“In Biology Bytes: Digestible Essays on Stem Cells and Modern Medicine, author Dr. Teisha J. Rowland discusses the history and latest scientific advancements in these fields of science, and many more. With a specific focus on issues that we increasingly encounter in the modern world around us, Dr. Rowland explores cutting-edge science through essays that can be easily digested: complex scientific concepts are broken down into key points based on the latest discoveries, technical jargon is clearly explained, and the impacts of these discoveries on our lives are explored. This book includes comprehensible explorations of a wide range of topics, including different types of stem cells and treatments they may be used in, the development and impact of in vitro fertilization (a technique responsible for over 1% of U.S. births today), how and why GMOs are made, the creation of vaccines to fight cancer, and fascinating food science behind delectable drinks such as beer, wine, and tea.”

The book is available as a Kindle eBook or paperback at Amazon.com. Feel free to spread the word to anyone you think may be interested.

Also, for those who may be interested, I recently published a second similar book that is focused on animals, called Biology Bytes: Digestible Essays on Animals Both Commonplace and Bizarre, which is also available through Amazon.com.

(1 votes)

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Stem cell beauty…yes they are so beautiful, they have amazing properties, they bring a lot of hope for future therapies…well, yes they are the stars!

However, like in everyday life, “the star” is not the only one to be the key of its own success, success is teamwork! And for stem cells, the supportive team is the stem cell niche, also called microenvironment.

Studying stem cell niches is key to understanding stem cell biology since the niche directly influences stem cell fate choices, such as proliferation and/or differentiation.

Several factors regulate stem cells within the niche: interactions between stem cells and their neighboring cells but also interactions between stem cells and the surrounding matrix components or nutritional inputs (growth factors for example).  In addition, the physiochemical surrounding (pH, temperature,…) is very important within the niche.

This month in Development , Gancz and Gilboa show that the nutritional input conveyed by the insulin signalling pathway plays key roles in the development of the ovarian niche-stem cell units in Drosophila melanogaster. In this picture, we can observe Drosophila melanogaster ovaries at LL3 stage of development. When the insulin receptor is overexpressed (on the right panel), the ovary is much bigger than normal (on the left). Also, there are more terminal filaments cells (in pink), a major component of the germ stem cell niche.

Interestingly, their study shows that in addition of strongly influencing the development of the germ stem cell niche (terminal filament cells and intermingled cells), insulin signalling also regulates the number of germ stem cell precursors (ancestors of mature ovarian stem cells, in blue in the picture). So, insulin signalling contributes to ensure that germ stem cells and their niche develop coordinately.

Extensively describing niche components and understanding how they influence stem cell decisions is a major challenge in stem cell biology. Indeed, reproducing stem cell-niche interactions in petri dishes would give scientists the keys to instruct stem cells in the directions they are interested in!

D. Gancz, L. Gilboa, Insulin and Target of rapamycin signaling orchestrate the development of ovarian niche-stem cell units in Drosophila. Development,  (Sep 11, 2013). doi:10.1242/dev.093773

(2 votes)

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Here are the highlights from the new issue of Development:

Roadmap for human trophoblast model

Correct trophoblast development is essential for placenta function and embryogenesis. In humans, the early stages of this process can only be modelled in vitro using embryonic stem cells (ESCs); however, owing to the failure to identify the stepwise progression that occurs during differentiation, the identity of the resulting cells is not clear. Now, on p. 3965, Mana Parast and colleagues narrow this gap by directly comparing various stages of in vitro trophoblast differentiation with in vivo cell types in the human placenta. The authors find that in vitro BMP4-driven trophoblast differentiation progresses through a p63⁺/KRT7⁺ stage that is akin to cytotrophoblast (CTB) cells in vivo. The CTB cells are the precursors of the terminally differentiated syncytiotrophoblast (STB) and extravillous trophoblast (EVT) cells. As expected, ESC-derived CTB-like cells can be differentiated further into functionally mature KLF4⁺ STB and HLA-G⁺ EVT cells. The authors propose that BMP4-driven differentiation of human ESCs is an accurate and informative model of human trophoblast development.

Plant germ cells count on chromatin

Unlike animals, plants do not set aside germ cells during embryogenesis. Instead, the precursors of these cells, called spore mother cells (SMCs), are generated via a somatic-to-reproductive transition that occurs later in life. Although epigenetic remodelling has been largely studied in the post-meiotic phase of germline development, it is unknown whether pre-meiotic events contribute to cellular reprogramming in the reproductive lineage. Now, on p. 4008, Célia Baroux and colleagues investigate these dynamic changes and uncover widespread chromatin reprogramming during the slow meiotic S-phase that accompanies specification of the female Arabidopsis SMC. As in animal primordial germ cells, the authors observe increased nuclear size, reduction in heterochromatin, depletion of linker histones, chromatin decondensation, changes in histone modifications and core histone variants in the female SMCs. The authors propose a bi-phasic chromatin reprogramming process that is necessary for proper somatic-to-reproductive cell fate transition and thus competency to establish the pluripotent, female gametophyte.

Vascular remodelling goes with the flow

Mechanical forces such as blood flow play a key role in regulating vascular remodelling and angiogenesis. Vessel diameter must be tightly controlled to establish correct hierarchical vascular architecture, but how this is achieved is unclear. Now, on p. 4041, Mary Dickinson and colleagues report that vessel diameter in the mouse embryonic yolk sac is regulated by blood flow via two distinct mechanisms: vessel fusion and endothelial cell migration. Using live confocal imaging of dual Flk1-reporting whole embryos, the authors observe that vessel fusion only occurs in areas of relatively high flow, and that this leads to a rapid increase in vessel diameter. In addition, high flow also facilitates the preferential recruitment of endothelial cells from smaller capillaries, which further increases vessel diameter. Analyses using the Mlc2a mutant, in which blood flow is compromised, supports these findings. This study highlights the importance of mechanical forces in regulating individual cell behaviour as well as more complex processes such as the establishment of correct vascular architecture.

Mechanical forces fly high in wing morphogenesis

Mechanical forces regulate cellular behaviour to guide correct tissue size and shape. Distribution of stress can affect individual cell morphology, but how global forces are balanced across the whole tissue is largely unknown. In this issue, two papers examine how mechanical stress influences cell shape, and how these forces converge to regulate tissue morphogenesis in the developing Drosophila wing.

On p. 4051, Thomas Lecuit and colleagues investigate the global pattern of stress in the developing wing disc. They find that cell shape is governed by stretching at the periphery and compression at the interior, which may arise from increased proliferation at the centre of the wing. Cells at the periphery counteract this stress by polarising Myosin II tangent to the wing pouch, and by switching their cell division axis to align with the direction of stress. To support these findings, the authors inactivate Hippo signalling to mimic the effect of overproliferation. They observe a loss of the directionally dependent stress effect and a reduced apical surface in the mutant clones compared with their wild-type counterparts, which results in distortion of the bordering cells. These results suggest that the pressure exerted by proliferating cells influences global mechanical stress, which in turn regulates tissue morphogenesis at the periphery of the wing.

The role of mechanical stress in regulating cell shape and tissue morphogenesis is further examined by Shuji Ishihara and Kaoru Sugimura (p. 4091), who investigate the formation of hexagonal cell geometry in the phase II pupal wing. The authors use live imaging and Bayesian inference to map global mechanical forces in response to defined perturbations. They show that the direction of stress originates primarily from the attachment site to the wing hinge, and that this results in a redistribution of myosin, which enables greater tension at the cell junction as a means to resist tissue stretch. This in turn provides directional information for the cells, which ultimately results in the hexagonal configuration and a structurally balanced wing.

Distinct SCL isoforms regulate HSC emergence

The emergence of haematopoietic stem cells (HSCs) from the aorta-gonad-mesenephros (AGM) region requires the coordinated activity of multiple transcriptional networks. The transcription factor stem cell leukemia (SCL) is necessary for this process; however, multiple scl isoforms exist and the exact stage at which each is required is unknown. In this issue (p. 3977), Zilong Wen and colleagues deconstruct the stage-specific requirement of scl isoforms scl-α and scl-β during the emergence of HSCs from the ventral wall of the dorsal aorta in zebrafish, which is equivalent to the AGM. Using dual fluorescent reporters coupled with in vivo time-lapse imaging, the authors show that scl-β is expressed in the haemogenic endothelial cells, whereas scl-α is expressed after the endothelial-to-haematopoietic transition has occurred. In loss-of-function studies, the authors show that scl–β is necessary for the specification of the haemogenic endothelial cells, whereas scl-α acts to maintain the newly born HSCs. This study represents an important step in teasing apart the transcriptional complexity that governs HSC development.

PLUS:

The developmental origins of adipose tissue

The formation and maintenance of adipose tissue is essential to many biological processes and when perturbed leads to significant diseases. Here, Jon Graff and colleagues highlight recent efforts to unveil adipose developmental cues, adipose stem cell biology and the regulators of adipose tissue homeostasis and dynamism. See the Review on p. 3939

The regulation of Hox gene expression during animal development

Hox genes encode a family of transcriptional regulators that elicit distinct developmental programmes along the head-to-tail axis of animals. Here, Mallo and Alonso examine the spectrum of molecular mechanisms that control Hox gene expression in model vertebrates and invertebrates.  See the Review article on p. 3951

Developing insights into cardiac regeneration

The recent EMBO/EMBL-sponsored symposium ‘Cardiac Biology: From Development to Regeneration’ gathered cardiovascular scientists from across the globe to discuss the latest advances in our understanding of the development and growth of the heart, and application of these advances to improving the limited innate regenerative capacity of the mammalian heart. Christoffels and Pu summarize some of the exciting results and themes that emerged from the meeting. See the Meeting Review on p. 3933

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