Here are the highlights from the current issue of Development:

Hoxb1b gets the neural tube into shape

Hox genes are classically known for their roles in patterning the anterior-posterior axis of animals. Now, on p. 639, Mihaela Žigman, Cecilia Moens and colleagues uncover a new role for Hoxb1b in regulating cell shape, oriented divisions and microtubule dynamics in the developing zebrafish neural tube. The researchers first identify a zebrafish mutant that carries a point mutation in hoxb1b, a gene that shares ancestral functions with mammalian Hoxa1. These mutants, they report, exhibit classical homeotic transformations associated with Hoxa1 mutations in mice. Unexpectedly, however, these mutants also show defective neuroepithelial morphogenesis within the developing hindbrain neural tube. The researchers further show that the hoxb1b mutation does not affect apico-basal or adherens junction-based polarisation, nor the proliferation or differentiation rate of neural progenitors. Instead, Hoxb1b regulates mitotic spindle orientation and the shape of progenitor cells. This function is linked to a cell-non-autonomous role for Hoxb1b in regulating microtubule dynamics. The authors thus propose that, by regulating microtubule dynamics and cell shape, Hox genes can influence global tissue morphogenetic events.

A new model for bivalency

Histone H3 lysine 4 trimethylation (H3K4me3) is a universal epigenetic mark that is deposited by histone methyltransferases. This mark can be found in the context of bivalent promoters, which harbour both repressive H3K4me3 and active H3K27me3 marks and hence are thought to be poised for lineage-specific activation or repression. Here, Francis Stewart, Henk Stunnenberg and co-workers challenge this model of poising (p. 526). They first show that the H3K4 methyltransferase Mll2 is responsible for H3K4me3 on bivalent promoters in embryonic stem cells (ESCs). Accordingly, the researchers find that Mll2 is bound to bivalent promoters but also to active promoters. By contrast, another H3K4 methyltransferase, Set1C, is bound to active but not bivalent promoters. Importantly, they observe that Mll2-deficent ESCs, which lack H3K4me3 on bivalent promoters, exhibit normal transcription responsiveness, thus arguing against a model of poising. Based on these and other findings, the authors propose that Mll2 acts as a pioneer methyltransferase and that Polygroup group action on bivalent promoters blocks the establishment of active Set1C-bound promoters.

InSpired dendrite architecture

The correct architecture of dendritic trees is essential for the wiring and function of neuronal circuits. A number of cell extrinsic factors are known to regulate dendrite shape and patterning, but here Don van Meyel and co-workers show that the transcription factor Longitudinals Lacking (Lola) regulates expression of the actin nucleation protein Spire (Spir) to sculpt dendrite architecture in Drosophila (p. 650). The researchers show that Lola is expressed in dendritic arborisation (da) neurons of the Drosophila peripheral nervous system. They further demonstrate that Lola controls the number, growth and distribution of dendrite branches in da neurons. Loss of Lola also leads to increased expression of Spir, which in turn causes increased formation of abnormal and inappropriately positioned actin-rich branches. In line with this, the authors report that Spir promotes F-actin nucleation and regulates dendrite positioning. Together, these findings suggest that Lola acts to limit the expression of Spir within da neurons, thus ensuring balanced control of the actin cytoskeleton and regulated dendrite morphogenesis.

miR-335 shapes an endoderm transcription factor gradient

Morphogen and transcription factor gradients are known to pattern tissues during development, but how these gradients are established is unclear. Using mouse embryos, embryonic stem cells (ESCs) and mathematical modelling, Heiko Lickert and colleagues show that the microRNA miR-335 fine-tunes a transcription factor gradient in the endoderm (p. 514). The researchers identify miR-335 as a microRNA that is differentially regulated during mesendoderm differentiation. They further show that miR-335 is expressed and functions transiently in endoderm progenitors and later during mesoderm formation. Importantly, miR-335 targets mRNAs encoding the endoderm-determining transcription factors Foxa2 and Sox17; miR-335 overexpression blocks endoderm differentiation in ESCs and, conversely, inhibition of miR-335 activity leads to Foxa2 and Sox17 accumulation and increased endoderm formation. Finally, mathematical modelling incorporating both microRNA and protein turnover rates predicts that miR-335 can shape a gradient of Foxa2 and Sox17 in the endoderm, and this prediction is confirmed experimentally. Overall, these findings highlight that a microRNA can shape a transcription factor gradient in time and space.

Eyeing up nutrient control of stem and progenitor cells

It is known that nutrient availability affects cell proliferation, but how nutrients affect the proliferation-differentiation programme of cells is unclear. On p. 697, Nicola Love and colleagues address this issue, using the ciliary marginal zone (CMZ) of the Xenopus retina as a model. They find that nutrient deprivation (ND) reduces the proliferation, and hence the number, of committed retinal progenitors in the CMZ. By contrast, retinal stem cells at the CMZ peripheral edge are relatively insensitive to ND. Furthermore, ND prevents cells from acquiring a committed progenitor fate, suggesting the presence of a nutrient-sensitive restriction point in the retinal progenitor proliferation-differentiation programme. Finally, the authors show that this restriction point involves mTOR signalling; blocking mTOR mimics many of the effects of ND, whereas activation of mTOR stimulates differentiation. Together, these findings suggest that an mTOR-dependent restriction point in the proliferation-differentiation programme of retinal progenitors exists to couple nutrient availability to tissue growth and development, thus allowing regrowth in ND tissue when conditions of plenty return.

Jaw-dropping differences in the neural crest

Variation in jaw size has been crucial to the evolution and adaptation of vertebrates. On p. 674, Jennifer Fish, Richard Schneider and colleagues explore the mechanisms by which duck and quail achieve distinct jaw sizes, testing the hypothesis that differences in neural crest (NC) biology contribute to species-specific differences in jaw size. The researchers show that the total sizes of the pre-migratory NC progenitor populations in duck and quail are similar. However, the midbrain region, which generates jaw NC precursors, is wider and shorter in duck owing to an anterior shift in brain regionalisation. Furthermore, they report, more pre-migratory NC precursors are allocated to the midbrain in duck, which gives rise to an increased number of post-migratory NC cells within the duck mandibular arch. Finally, differences in proliferation lead to an increase in the size of the duck mandibular arch relative to that of the quail. Thus, the authors propose, the larger jaw size of duck is the result of at least three distinct developmental events.

PLUS…

How to make spinal motor neurons

All muscle movements, including breathing, walking, and fine motor skills rely on the function of spinal motor neurons. Here, Kevin Eggan and colleagues discuss how the logic of spinal motor neuron development has been applied to generate motor neurons either from pluripotent stem cells by directed differentiation and transcriptional programming, or from somatic cells by direct lineage conversion. See the Primer on p. 491

Lung development: orchestrating the generation and regeneration of a complex organ

The respiratory system, which consists of the lungs, trachea and associated vasculature, is essential for terrestrial life. In recent years, extensive progress has been made in defining the temporal progression of lung development.  This has led to exciting discoveries including the derivation of lung epithelium from stem cells and the discovery of new targets for therapeutics. Michael Herriges and Ed Morrisey highlight review these recent advances in our understanding of lung development and regeneration. See the Review on p. 502

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Here is our monthly round-up of some of the interesting content that we spotted around the internet:

News & Research:

– Nature revealed their list of 10 people that mattered in 2013, while the UK Science Council revealed its list of 100 leading UK practicing scientists.

– This Christmas saw developmental biologist Alison Woollard present the Royal Institution Christmas lectures. You can watch them on the Royal Institution website.

– Nature News & Views published a piece on the importance of senescence in embryonic development.

– And stem cells have been in the limelight, with articles featuring updates on the current controversial situation in Italy and Woo Suk Hwang, 10 years after his stem cell cloning fraud scandal.

Weird & Wonderful:

– An Australian science agency apologised to a little girl for their lack of dragon research.

– The ASCB website suggested a few uses for those old conference posters.

– If you are a scientist and a Monty Python fan you might want to check a new hashtag trending on Twitter- #MontyPythonScience.

Beautiful & Interesting images:

– If you are a PhD student you might find this list of gifs displaying 25 painful problems of graduate students (besides their thesis) highly amusing.

– We spotted several beautiful images: colourful neural stem cell images, a delicate tree that is actually a protist and a dividing cell made of fused glass.

– And we found a great photo of how a scientist protests:

What do we want? pic.twitter.com/mwyO4fyoVU

— Dr Brooke Magnanti (@bmagnanti) January 7, 2014

Videos worth watching:

– The Naked Scientists dedicated one of their recent podcasts to developmental biology.

– The Royal Institution listed their favourite science movies of 2013, which includes this beautiful video on the life cycle of sea urchins by Parafilms:

Keep up with this and other content, including all Node posts and deadlines of coming meetings, by following the Node on Twitter.

Alison’s image by Paul Wilkinson

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The Node is back on the road in 2014, and our first stop this year is the city of dreaming spires- Oxford in the UK!
 
 
Cat, the Node community manager, will be giving two talks on Monday the 13th of January:

‘How to use social media to promote and communicate your science’
2pm, Sherrington Library, Department of Physiology, Anatomy and Genetics (University of Oxford)

‘A career in publishing and science communication’
5pm, EPA seminar room, Sir William Dunn School of Pathology (University of Oxford)

Cat will also participate in the Research Career Pathways event at Oxford Brookes University on Tuesday afternoon.

Are you based in Oxford? Cat would love to meet you and hear your thoughts on the Node! Drop us an email if you would like to meet for a chat, or simply come to one of the talks! Looking forward to meet you!

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CALL FOR A GROUP LEADER POSITION AT THE DEVELOPMENTAL BIOLOGY INSTITUTE OF MARSEILLE

The Developmental Biology Institute of Marseille (IBDM) is a leading research institute in Europe, with a unique focus on the study of developmental systems with interdisciplinary approaches using a wide range of animal models (Drosophila, Xenopus, C. elegans, chick, rat and mouse).

The IBDM is composed of 18 research groups and 5 scientific core facilities and benefits from the rich scientific environment of the Luminy campus of Aix-Marseille University. The overall research activity developed at the IBDM is at the crossroads of different fields: cell biology, development, evolution, neurobiology, physiology and biophysics. The connections and complementarity between these themes result in a strong scientific coherence of the overall research developed in the IBDM.

The teams employ transversal approaches and complementary strategies to understand how the instructions encoded in the genome are interpreted and translated to build structures (cells, tissues, organs) that perform specific functions, how these processes are regulated and integrated at the level of the whole organism and how their deregulation can lead to pathologies. A priority is to favor interdisciplinarity through the integration of new and original approaches that create conceptual and technical interfaces.

Please visit our website for more information.

We are looking for outstanding candidates who will complement the existing strengths of the Institute and develop an innovative and internationally competitive research program. Scientific excellence will be given the highest priority in the selection of the successful candidate.

This is a non-teaching position and knowledge of French is not required. The candidate will support his or her research by extramural funding * such as ERC, ATIP-Avenir or ANR.

Applicants should send in a single pdf file, a curriculum vitae, a list of publications, a 2 page summary of research achievements and projects in English, and the names and contacts of three references to the IBDM Director André Le Bivic (andre.le-bivic@univamu.fr) before the 30th of January 2014.

IBDM: CNRS / AIX-MARSEILLE UNIVERSITY, FRANCE

* Note from the contributor: All of these funding mechanisms are extremely competitive and difficult to obtain. ATIP-Avenir is the combined name of nationally awarded startup packages for promising young independent researchers from the CNRS or INSERM, now joint for this purpose. It is considered prestigious within France, though the prestige wears off after a few years. But the application deadline for an award in the second half of 2014 was the end of November, 2013.

ERC funding can be sought with the assistance of offices both at Université Aix-Marseille and at the CNRS (starting grants – success rate around 9% – or for established scientists, once cited on average at 14%, but that seems high nowadays from my anecdotal experience).

The ANR is the French national funding agency and it does help to understand written French to apply, though it’s not strictly required. 2013’s calls are here: not many are applicable to developmental biology. Success rates are hard to come by but from the POV of a mid-career developmental biologist, it’s not impossible and not easy. I guesstimate around 10%, too.

There aren’t other large extramural grant programs for research in France, of which I’m aware, relevant to developmental biology. There is international funding such as the Human Frontier Science Program but only you can see if it’s relevant to your case, when applying to such an offer.

On the plus side, such a position at the IBDM has a high chance of translating ultimately into tenure as a French civil servant. On the down side, if you don’t arrive with your own operating budget, it will be difficult to get going again at the standard at which you were recruited initially from elsewhere.

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Happy new year everyone!

To wrap up 2013 we had a look at our stats to find what out which were the most popular posts of the last year. 2013 saw the usual varied mix of news, research, meeting and discussion posts, so there was a lot to read!

Most viewed posts:

1- There and back again– Kara’s account of returning to the bench after working as an editor

2- Overly honest methods– a collection of the best tweets with this popular hashtag

3- Where scientists fear to tread– Caroline’s account of how ‘alternative’ careers are perceived

4- Breakthrough Prize floors winners with sheer amount of money– Eva commented on this newly established prize

5- A website for Postdocs and PhDs– the PostPostDoc website

Best rated posts:

1- There and back again– not only the most viewed but also the best rated!

2- The end of Biology?– Thomas’ thought provoking piece discussing some of the issues of science

3- Cellular Reincarnation– A literary interpretation of cellular reprogramming

4- A day in the life of.. a zebrafish lab

5- An interview with Alejandro Sánchez Alvarado

Other highlights:

2013 was a year that saw many people writing about their research and discussing their recent papers. Some of the most popular research posts this year included Making sense of Wnt signaling and a post by the University of Chicago journal club on the limb-to-fin transition. As has been the case in the past, our image competitions, such as our stem cell image competition or those featuring images from the Woods Hole course, have been extremely popular.

This last year also saw the beginning of two new series on the Node. A day in the life provides an account of a typical day in developmental biology labs working on different model organisms, and we have already covered many of the classical model systems. Our outreach series has already provided many case studies of outreach, as well as activity suggestions that you can try in your own outreach projects. Both series are continuing in 2014, so keep an eye out for more posts! We also launched a photography competition as part of our current outreach series- do participate for a chance to win a £50 Amazon voucher!

The Node is your community blog, and could not exist without your participation. So a big thank you to all of you who wrote, commented, rated or simply read the Node posts in 2013. We look forward to another exciting year of developmental biology in 2014!

Image: Andrea Pavanello (wikimedia commons)

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Currently, more and more women delay having children because of pursuing higher educational and career aspirations, as well as changing cultural norms. Unfortunately their eggs become susceptible to chromosome mis-segregation as a consequence of maternal aging. This would generate aneuploid embryos, so causing increased and birth defects (Jones and Lane, 2013). However, the actual ways in which chromosome segregation errors occur remain elusive, due to a lack of direct observations of the events as they happen. Live-cell tracking of chromosomes would be the infertility most appropriate technique to answer these questions, however with only chromosomal histone labeling, previous studies failed to follow any detailed dynamics of individual bivalents (Chiang et al., 2010; Lister et al., 2010).

In our recently published paper in Development (Yun et al., 2014), we applied a chromosome-tracking approach to examine bivalent dynamics in oocytes of aged mice during the entire period of meiotic maturation, by labeling both the bivalents and their kinetochores. By tracking, we have managed to reduce the intensity of imaging to such an extent that we can follow the movements of individual bivalents with a temporal resolution of 2 minutes continuously over a 12-15 hour time window, without any noticeable loss in rates of meiotic maturation (Movie 1). In so doing we have been able to catalogue the movements of bivalents and kinetochores in a way not previously performed, and establish the effects of maternal aging on chromosome dynamics in the first meiotic division (MI), through to metaphase II arrest (metII). Real-time tracking of bivalents in aged oocytes would be informative in the following aspects: 1) to determine if the process of bivalent congression necessary for faithful segregation is affected by age; 2) to determine the origin of single chromatids, which are commonly observed on metII eggs.

Using measurement of bivalent non-alignment when its displacement was >4 mm from the spindle equator (Lane et al., 2012), congression of all bivalents was achieved at least 3 hours ahead of anaphase onset independent of age, suggesting no gross malfunctioning of bivalent congression with age. However, we did observe more frequent weakly-attached bivalents in live aged oocytes, which had no apparent histone signal between the two sister chromatid pairs. Intriguingly, these bivalents did not undergo premature separation, but instead remained associated together all through MI. Despite the above observations in MI, the main defect with age was premature separation of dyads during metII arrest. The event was captured during imaging and occurred around 2 hours after anaphase I, as the metII spindle was assembling (Movie 2). The newly formed single chromatids oscillated about the spindle equator, presumably because they have only a single kinetochore that fails to establish simultaneous attachment to both spindle poles.

In conclusion, these data show that although considerable cohesion loss occurs during MI, its consequences are observed during meiosis II, when centromeric cohesion is needed to maintain dyad integrity, consistent with human studies that have shown a prevalence of pre-division in eggs from older women (Kuliev et al., 2011). The present work highlights that biopsy of the first polar body alone, which would have been normal in most aged oocytes here, may not be an effective screening method for aneuploidy.

References

Chiang, T., Duncan, F. E., Schindler, K., Schultz, R. M. and Lampson, M. A. (2010). Evidence that weakened centromere cohesion is a leading cause of age-related aneuploidy in oocytes. Current biology : CB 20, 1522-1528.

Jones, K. T. and Lane, S. I. (2013). Molecular causes of aneuploidy in mammalian eggs. Development 140, 3719-3730.

Kuliev, A., Zlatopolsky, Z., Kirillova, I., Spivakova, J. and Cieslak Janzen, J. (2011). Meiosis errors in over 20,000 oocytes studied in the practice of preimplantation aneuploidy testing. Reproductive biomedicine online 22, 2-8.

Lane, S. I., Yun, Y. and Jones, K. T. (2012). Timing of anaphase-promoting complex activation in mouse oocytes is predicted by microtubule-kinetochore attachment but not by bivalent alignment or tension. Development 139, 1947-1955.

Lister, L. M., Kouznetsova, A., Hyslop, L. A., Kalleas, D., Pace, S. L., Barel, J. C., Nathan, A., Floros, V., Adelfalk, C., Watanabe, Y. et al. (2010). Age-related meiotic segregation errors in mammalian oocytes are preceded by depletion of cohesin and Sgo2. Current biology : CB 20, 1511-1521.

Yun, Y., Lane, S. I. and Jones, K. T. (2014). Premature dyad separation in meiosis II is the major segregation error with maternal age in mouse oocytes. Development 141, 199-208.

(3 votes)

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This PhD is part of the NERC funded Doctoral Training Partnership ACCE (Adapting to the Challenges of a Changing Environment). This is a partnership between the Universities of Sheffield, Liverpool, York, and the Centre for Ecology and Hydrology.

A PhD position is available in the Fraser laboratory at the University of Sheffield, Department of Animal and Plant Sciences and with co-supervisor Nathan Jeffery, Department of Musculoskeletal Biology at the University of Liverpool. The project is also in collaboration with Zerina Johanson, Department of Palaeontology, Natural History Museum, London.

Summary: The teeth of fishes and the integrated jaw apparatus are examples of extreme evolutionary modification that have responded to functional and adaptive shifts within the wider community. This novel project aims to identify shifts in biomechanical pressures on adult jaw and tooth type that is linked to changes in the development of the feeding system. Our integrative project surrounds the core question of how development contributes to novel evolutionary changes in trophic adaptation. This project will link biomechanical adaptation of morphology to novel developmental modifications of the jaw apparatus in fishes to ask whether having a novel dentition (e.g. beak-like dentition in pufferfishes) offers an adaptive advantage compared to more standard yet highly efficient dentitions e.g. Piranha. This project will utilize advanced techniques, including biomechanical computer simulations of hard-tissues built from enhanced microCT data. We will use nano-indentation analyses to observe changes of material properties in comparative groups of fishes linked to re-specification of conserved developmental genes in species with novel tooth phenotypes. The candidate will utilise developmental techniques (gene expression and manipulation) to understand how the genetic basis of tooth and jaw development and continuous tooth regeneration impact the evolution and biomechanical function of fish feeding systems.

Please visit the Department of Animal and Plant Sciences, University of Sheffield ACCE DTP website below for details of application.
http://www.sheffield.ac.uk/aps/prospectivepg/graduate-opportunities/accestudentships

The closing date for applications is January 20th 2014. For informal inquiries direct emails to Dr. Gareth Fraser: g.fraser@sheffield.ac.uk Lead Supervisor: Dr. Gareth Fraser, Dept. Animal and Plant Sciences, University of Sheffield. Co-supervisor: Dr. Nathan Jeffery, Dept. Musculoskeletal Biology, University of Liverpool. Project collaborator: Dr. Zerina Johanson, Dept. Palaeontology, Natural History Museum.

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Watching animals, with their vast diversity of complex behaviours, can never be boring. In the animals around us, ants, spiders, lizards, dogs, cats, fish, birds…, we see so many different modes of locomotion, nesting, foraging and hunting in both solitary and social forms. Peculiar moves of appendages, bobbing of heads, unique calls and colours make up elaborate courtship or aggressive rituals, and animals have the most curious parenting styles. Underlying all these behaviours is a unique nervous system in every animal and I have been interested in how nervous systems develop. I use the fruitfly, Drosophila melanogaster, to understand this because of the phenomenal genetics available in this model organism.

I work in K. VijayRaghavan’s lab at the National Centre for Biological Sciences – TIFR in India and in collaboration with Heinrich Reichert at the Biozetrum, University of Basel in Switzerland. I was studying the role of a particular gene in the development of the fly’s olfactory system when I noticed something odd. Flies mutant for this gene seemed to have some extra neurons in the olfactory circuit. Where did these neurons come from?  We had many hypotheses that we rigorously tested. We finally worked out that this gene is normally expressed in a set of neurons in the fly’s higher brain centre. When mutant, these neurons transformed completely and became olfactory neurons!  They changed the way they looked, the neurotransmitter they expressed and even their enhancer activity profile. The extent of this transformation led us to wonder if these neurons were functional in the olfactory circuit or not.  Did they make functional synapses with other olfactory neurons and respond to odour stimuli?

We teamed up with Jing Wang’s lab in UCSD, where with Deshou Cao (a postdoctoral fellow there) we decided to test this. We did two kinds of experiments together. Odour information is brought into the brain by the sensory neurons. We reasoned that if the transformed neurons do form functional synapses, they should be postsynaptic to the sensory neurons. We used a calcium sensitive activity indicator, GCaMP, to measure the activity in the transformed neurons while we stimulated the sensory neurons either electrically or by puffing odours at the sensory neurons. To our excitement, we found that in both cases, the transformed neurons responded robustly to the stimuli! This meant that the transformed neurons were functional in the olfactory circuit.

This is very exciting because it is one of very few examples where a single gene can change the identity of neurons so completely and dramatically and therefore have an impact on the assembly of functional neural circuits in the central brain. We are now writing this story up for publication.

I have the Company of Biologist to thank for making a large part of this possible.  California, with its bustling and excellent science, balmy weather and breathtaking countryside is a very exciting place to be in. But it is also extremely expensive! We would have found it very difficult to complete this story were it not for the support that the Company of Biologists’ travelling fellowship provided.  So I want to offer my sincerest thanks and gratitude to the COB, and especially to the wonderful and helpful team of people at the COB.

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In a vague sense it was a move that was planned all along. After all I did tell my friends and family when I left in 2001 for UPenn to do my PhD there that ultimately I will return. Yet when the moment and the opportunity came, suddenly the idea to move back to Budapest felt anything but a well-planned, cool-headed decision.

It would be nice to say that the country that gave George Streisinger (the godfather of zebrafish genetics) to the world, was rolling out the red carpet, to welcome freshly trained, young and enthusiastic zebrafish researchers, but that would not be quite an exact representation of reality.

Most Hungarians who dipped their toes into the waters of zebrafish research did so abroad, and the overwhelming majority stayed there. This, of course, means that most research centers and academic institutions do not really have the infrastructure to do zebrafish genetics (indeed, I know only of a single place in Hungary, where a world-class zebrafish facility is being in use), which makes the beginning of one’s effort to build and independent zebrafish research group an even more arduous and stressful task.

During our training time, we (aspiring scientists) all dream of the moment when we will finally become masters of our own, and can start following our own instincts. Yet, after the warm welcome and back patting, when the sense of novelty fades away and you find yourself in an essentially empty room, suddenly it becomes clear that you are in an anything but enviable situation. Yes, you are free to follow your instincts, but there are some big strings attached to this freedom: you need to find the ways and means to fund your pursuit of scientific truth. This is never easy, and trying to succeed in it while the Great Recession of our time is squeezing budgets across the globe is especially frustrating.

So, there I was in mid-2009, as a young faculty member at my former alma mater, the Genetics Department of the Eötvös Loránd University (ELTE), with a firm backing from the head of Department and a small return-grant to finance my short-term work. The coming months were anything but straightforward.

If your work relies on model animals, the most important thing is to house them well. As mentioned before, zebrafish wasn’t exactly the animal model of choice for previous generations of scientists at my institute, so there was no designated facility to keep them. Therefore, my new life began with a long (and sometimes desperate) scramble to find a place for my fish lines.  During this period I remembered umpteen times an anecdote that I heard at a UCL Departmental Seminar from Hitoshi Okamoto. In the early days of zebrafish research he did not have a designated fish facility so he was forced to keep his animals in tanks in the Institute’s toilet, a condition mockingly described by him as “standard lavatory conditions”.

At the beginning my own fish “facility” was not that different from Okamoto’s: half a dozen plastic tanks bought at the local pet shop, on the top of a small bench. This was a far cry from the immense and well-oiled fish facility of UCL, to which I got accustomed during my post-doc years, but I convinced myself that this was only a transitory situation. Today my group has dozens of fish lines in a separate, temperature-controlled room of our institute’s animal facility. Obviously nothing at UCL’s scale, but still, a huge change. It was a slow but steady progress to get here, all it took was patience, resolve and outside support.

But there’s the catch: as months (and ultimately years) pass by, you realize, that patience and resolve are quite subjective concepts and from a different perspective they might seem like baffling and pointless stubbornness. Things seldom work out as easily as originally imagined, and there will be times when you start to question your judgement, whether it was really a sane idea to move back and/or to start doing fish research from scratch. When all this happens to the backdrop of continuous turmoil and funding cuts in the Hungarian higher education system, one can find himself extremely nostalgic for the safety and predictibility of the post-doc years.

By my second year at ELTE, faculty meetings with the Dean and the Head of the Institute became frustratingly predictable: we were told every time that there were further cuts coming in the university budget, which was the price we had to pay in order not to lay off dozens of people, but we should have taken the opportunity and do more with less. Though there was no question that the people in higher positions (most often scientists themselves) were sincere in their belief that there were efficiency gains to be made within the school (and that was certainly true, to some extent), after a while one couldn’t help but recall David Simon’s maxim: claiming that you can do more with less is a favoured pastime of accountants, but in fact you do less with less.

While university employees were repeatedly told that the reason for the cuts is the dire situation of the budget, people started to note that funding for sports, especially football was going through the roof. This bred a lot of enmity against football, and although science funding lately stabilized somewhat even in Hungary, many people still bear a grudge against lavish stadium-building schemes.

Even without all these “vis maior” circumstances, starting a zebrafish lab at a place where people were not familiar with its advantages would have required a “build it and they will come” type of bravado. From the beginning I repeatedly told myself that there would be also advantages of being the first at something: benefits could come by collaborating with other Hungarian researchers who would like to take advantage of the zebrafish model. In the initial period this became something of an article of faith for me, and, thankfully, I was proven right. After a slow start, when I was busy building networks, the offers for collaborations did start to trickle in. So much, that in the past few months, for the first time since moving home, I started to feel that I’m reaching my limits, and taking on more tasks would be a bad idea.

Nevertheless each new collaboration took me on an exciting new scientific journey and opened up new possibilities. I learned a lot, for which I’ll be always very grateful to all the people who trusted me with their projects, and supported our common endeavours with reagents and advice. And if I’m at handing out kudos, there’s one person who should get special mention: I want to echo my former colleague, Kara, in recognising how much our former post-doc mentor, Steve Wilson supported us, even after we left his lab.

One question I (still) often get is whether I came to regret my decision to move back. This is a complicated thing, and I would have given a somewhat different answer a year ago, and most likely my answer will not be exactly the same in a year’s time. With all my current knowledge, looking back to my 2009 self, I can certainly see that I was very naive, indeed. Truth to be told, the decision to move was made primarily by non-scientific reasons, but as I explained above, there was a clear scientific silver lining as well. Nevertheless, at this particular moment, I would say that taken all together, coming back was worthy. After all Budapest is a great place to be and I’m fortunate enough to live a good life with my family in one of the best spots the city can offer. Science funding is thrifty, but, as I said above, having great collaborators and colleagues makes a huge difference (plus there’s always the hope, that the funding situation will get better, sooner or later). And the more students pass through my lab to end up working with zebrafish in other great European labs, the more I feel that I’m able to make a difference and contribute something to both science and society. Whether that is with or against the odds, will be up to others to tell.

(10 votes)

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Here are the highlights from the current issue of Development:

Peri important role for Notch

Pericytes are specialised cells that wrap around the endothelial cells of the vasculature to regulate vascular integrity, permeability and blood flow. Despite this crucial role, the molecular mechanisms that control pericyte development are not well understood. In this issue, two papers identify a requirement for Notch in pericyte development in the brain and kidney vasculature.

On p. 307, Bruce Appel and colleagues investigate the role of Notch in regulating pericyte number in the developing zebrafish brain vasculature. The authors interrogate a panel of Notch genes and identify notch3 as expressed in the developing vasculature, specifically in cells positive for pdgfrb, a known pericyte marker. Loss-of-function of Notch3 leads to disruption of the blood-brain barrier and cerebral haemorrhaging, which is likely to be due to the reduction in pericyte number. Importantly, the authors show that Notch3 is required for pericyte development and specifically for promoting proliferation and expansion of the cells. Using pdgfrb expression as a readout, the authors observe that overexpression of the Notch3 intracellular domain is associated with increased numbers of pericytes, whereas interference with Notch3 activity causes a reduction. Based on varying levels of pdgfrb expression observed throughout the study, the authors hypothesize that Notch3 may positively regulate pdgfrb in order to regulate pericyte proliferation.

The role of Notch signalling in pericyte development is also investigated by Raphael Kopan and colleagues (p. 346), who report a critical requirement for Notch during the development of the pericytes of the mammalian kidney, known as mesangial cells. These cells, along with the smooth muscle and interstitial cells of the kidney, derive from Foxd1⁺ stromal precursors; however, Notch signalling appears to be only required for the emergence of the mesangial cells. Inactivation of Notch specifically in the stromal precursors results in the formation of glomeruli that lack mesangial cells, leading to glomerular aneurism and kidney failure at birth. The authors go on to show that, in this case of pericyte development in the kidney, Notch1 and Notch2 appear to act redundantly.

Roadmap for neuronal specification

Neuronal subtype specification is regulated by the coordinated action of transcription factors. Any one factor may be expressed in multiple subtypes, but specification is achieved based on the precise combination of factors and is therefore context dependent. In this issue (p. 422), Oliver Hobert and colleagues explore neuronal differentiation in C. elegans and focus on the role of the TTX-3 LIM homeodomain transcription factor in regulating neural subtype specification. The authors find that TTX-3 is broadly required in multiple neuron classes of relatively unrelated identity, but that the interacting partners and downstream targets of TTX-3 are subtype specific. TTX-3 is required for cholinergic AIY interneuron specification, while an interaction with the POU domain protein UNC-86 leads to the specification of serotinergic NSM neurons. Furthermore, UNC-86 itself can specify cholinergic IL2 sensory and URA motoneurons via cooperation with the ARID-type transcription factor CFI-1. This detailed analysis of transcriptional cascades reveals a programming roadmap for neuronal subtype specification.

How the zebra(fish) got its stripes

The striped pattern of the zebrafish skin offers an excellent model system in which to study biological pattern formation. Previous studies have shown that the interactions between melanophores and xanthophores are crucial for pattern formation, but little is known regarding the molecular mechanisms that regulate this phenomenon. Now, on p. 318, Shigeru Kondo, Masakatsu Watanabe and colleagues uncover a role for long-range Delta/Notch signalling between the melanophore and xanthophore pigmented cell types that is crucial for proper stripe formation. The authors show that Delta/Notch signalling is required for melanophore survival, since disruption of the pathway by DAPT treatment results in loss of melanophores, while constitutive Notch activation in transgenic fish rescues this effect. The authors use targeted laser ablation to show that the source of this survival signal is the xanthophore. Interestingly, the authors observe long protrusions that originate from the melanophores and extend to the xanthophores, which might serve as a means to mediate the Delta/Notch signalling over long distances.

Neural progenitors divide and conquer

Neuronal diversity in Drosophila is generated by the temporal specification of type II neuroblasts (NBs) and their progeny, the intermediate neural progenitors (INPs). Multiple transcription factors are expressed in a birth order-dependent manner within each INP lineage, but whether this temporal patterning gives rise to discrete neuronal sets from each individual INP cell is unclear. Now, on p. 253, Tzumin Lee and colleagues describe extensive fate-mapping of individual neurons derived from specific type II NB lineages. The authors use targeted clonal labelling to specifically label neurons in individual INP clones, and by restricting the clonal induction to specific time windows they are able to generate and characterise clones of neurons that are born from two successively produced INPs. The resulting analyses demonstrate that the temporal specification of INPs does indeed translate to distinct types of neurons, suggesting that neuronal fate diversification might operate as a function of age.

Case closed: ion channels mediate dorsal closure

Dorsal closure is a morphogenic process that involves the interplay of mechanical forces as two opposing epithelial sheets come together and fuse. These forces impact cell shape and the rate of morphogenesis, but the molecular pathways that translate mechanical force into phenotype are not well understood. Now, on p. 325, Daniel Kiehart and colleagues demonstrate a role for calcium signalling via mechanically gated ion channels (MGCs) in Drosophila dorsal closure. Using UV-induced calcium release, the authors show that increased calcium levels stimulate contractility during dorsal closure, whereas treatment with a calcium-chelating agent disrupts closure. Via a series of pharmacological perturbations, the authors demonstrate that MGCs regulate actomyosin contraction that, in turn, is required for force production and successful dorsal closure. The authors support their findings by knocking down two separate MGC subunits, which also leads to a failure to generate sufficient force for dorsal closure. This study paves the way for investigating MGCs in other morphogenic processes, for example during wound repair.

PLUS…

How to make a primordial germ cell

Primordial germ cells (PGCs) are the precursors of sperm and eggs, which generate a new organism that is capable of creating endless new generations through germ cells. Here, Magnúsdóttir and Surani summarise the fundamental principles of PGC specification during early development and discuss how it is now possible to make mouse PGCs from pluripotent embryonic stem cells, and indeed somatic cells if they are first rendered pluripotent in culture. See the Primer on p. 245

Retinal neurogenesis

In their Development at a Glance article, Centanin and Wittbrodt provide an overview of retinal neurogenesis in vertebrates and discuss implications of the developmental mechanisms involved for regenerative therapy approaches. See the poster article on p. 241

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