Hi I’m Steve and I work in the Sensory Development lab at the RIKEN Center for Developmental Biology in Kobe, Japan. We study the development of the chick inner ear. I haven’t always been in a chick lab – during my Ph.D. at The University of York I used Xenopus, so it was really nice to read Gary’s post. Looking back, I miss those slimy yet serene critters. Although at the time (as a poor PhD student) I would often get pretty jealous of all the care, attention, and, in particular, premium food they used to get. Especially when I was tucking into my staple Ph.D. meal, the supernoodle sandwich™. Anyway, enough of the reminiscing!
 

Chick-en you believe it?

The chick is a brilliant and beautiful model system for studying the embryonic development, and in our case more specifically, the inner ear. Embryo husbandry could not be simpler, because the hen is thoughtful enough to pack everything the embryo needs to develop inside the egg. We simply buy fertilized eggs from a local farm, incubate them at 37°C, and hey presto, the embryos develop!
 

It takes 21 days for chicks to hatch, but luckily we don’t have to wait that long if we need chicks, because we can also order 20 day-old fertilized eggs that arrive ready to hatch. When hatching, the chick cuts through the top of the shell using its “egg tooth” and then shimmies out. This takes a lot of work, so the chicks are pretty exhausted afterwards and they often take a little nap. But once they recover they are soon up and at ‘em, hopping around and pecking for food.

Our hatched chicks reside in a special bird room where they live in large temperature controlled incubators complete with sawdust and shredded paper bedding, fresh clean water, and mix of cereal and seed for food. They get fresh bedding, food and water every day, and we are lucky to have a very attentive technician (she calls herself “Mama Hen”) who takes care great of them.

Access all areas.

Because chick embryos develop ex-utero, we have easy access to them from the very earliest stages of development. We put a small strip of sellotape along the shell, cut a window through it, and can access the embryo through this window as it develops on the surface of the yolk. This unlimited access is fantastic for us, because the inner ear is specified very early in development. To understand how these events occur, we need to be able to manipulate the system at these early stages. The chick system makes it easy to do so.
 

Spot the difference.

Mice are the kings when it comes to using a model system close to humans. So why bother using other systems at all? Well, one reason is that the differences between species can be just as important as the similarities. Birds, unlike mammals, can regenerate the hair cells of their inner ear, so for our lab this makes them a great system to use for researching the mechanisms that govern regeneration. We use hatched chicks up to around 3 weeks old to study regeneration. By focusing on the differences as well as they similarities between species we can gain an insight into what exactly are the key mechanisms that coordinate the regenerative process.
 

An egg-sample day – the morning.

Ok, no more puns, I promise. The first thing I do when I arrive in the morning is check the embryos already incubating from previous day’s experiments. It is important to keep the incubator as clean as possible, so we keep a keen eye out for any signs of infection and remove the offending eggs.

Next I will check to see if any fresh fertilized eggs have arrived for me. If so, I put them in a 14°C fridge. This arrests the embryos’ development, and allows me to have a better idea of their developmental time course when I come to incubate them at 37°C. Accurate timing is everything because we don’t have near limitless supplies of eggs. We receive egg deliveries twice a week, and you have to order your eggs a week in advance, so forward planning is critical. If you miss the stage you want, you have to wait until next weeks eggs arrive to start again.

After this, I usually start some electroporation experiments. I like to do these in the morning, for two reasons. Firstly, I am usually electroporating something that is GFP or RFP tagged, so a morning session means I can check for fluorescence just before I go home in the evening. Secondly, the ever-approaching lunchtime serves as good motivation to work quickly.

Our electroporation set up is in the main area of our lab, near to a gargantuan egg incubator and a darkroom for fluorescent microscopy. A common and somewhat surreal result of this set up is that I often find myself chatting with someone who has their head (and often most of their upper body) inside the incubator as they check their eggs. To increase the surreal stakes further, what appears to be a dismembered head will often join the conversation when someone who is working in the dark room sticks their head around the curtain to get involved. And of course I’m trying to talk with a mouth pipette for the electroporations in my mouth. Despite (or maybe because of) this, it is one of my favourite areas of the lab.
 

The afternoon

The afternoons are spent doing a variety of things, depending on what stage of the project I am at and what the priorities are. Often I am finishing up ongoing experiments, – doing some immunohistochemistry, some confocal microscopy, analyzing data, administering drug treatments, fixing samples, or doing some in situ hybridisations. Actually, on the subject of in situ’s, we have an “in situ robot”, which runs through most of the protocol autonomously, leaving us with the job of overseeing the final colour reaction. I’m pretty skeptical about this robot – something about which the rest of the lab enjoy mercilessly taking the mickey out of me. But I’ve seen the Terminator movies, and I know what happens when robots get too smart. This one hasn’t done anything other than produce beautiful gene expression patterns yet, but it is only a matter of time.

The day ends incubating some more eggs for the next set of experiments. This is probably the most dangerous time of the day for me. The fridge and the incubator are at opposite ends of the lab, so I run a nightly gauntlet from one to the other, precariously tippy toeing through the busy lab with trays of eggs in my hands. Each tray carries 24 eggs, and when you drop one (as I have many times over the years) it really sucks!

This post is part of a series on a day in the life of developmental biology labs working on different model organisms. You can read the introduction to the series here and read other posts in this series here.

(13 votes)

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Ever wondered how cells communicate with each other during brain development? What happens to cells which the body doesn’t need any longer? And how do scientists study the events that are going on inside the brain?

In the upcoming ELLS Webinar, EMBL group leader Francesca Peri looks at the brain’s phagocyting cells – the microglia – and explores how the newest imaging techniques help scientists to understand how the developing brain is protected from damage and injury.

To read more, watch the Webinar teaser and register for the FREE event, please follow this link.

27th November 2013, 4:00 – 5:00 pm CET

Topic: “Neuronal cell death goes live: microglia as the guardians of the developing brain”

Speaker: Francesca Peri, EMBL Group Leader

Organised by the European Learning Laboratory for the Life Sciences

(2 votes)

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Using Drosophila melanogaster, researchers at IRB Barcelona discover that during multiple cell migrations a single cell can act as leader, dragging the others with it.
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The migration of groups of cells in order to form tissues is common during the development of an organism. Discovering how these multiple movements are achieved is not only crucial to understand the basic principles of development but provides new information and insights for further research into processes associated with the spread of cancer.

Jordi Casanova, head of the “Morphogenesis in Drosophila” lab at IRB Barcelona and CSIC research professor, and Gaëlle Lebreton, postdoctoral fellow in the same group, have published a study performed using Drosophila melanogaster in the Journal of Cell Science. This work reveals that in a multiple movement, a single cell can act as the leader and can drag the rest with it. The scientists have studied the tracheal development of Drosophila in vivo and describe the morphological characteristics of the leading cell and provide molecular details about how it drives the movement.

“Cancer researchers are keen to know how cells are organized to achieve migration and to form new capillaries to feed an expanding cancerous tumor,” explains Gaëlle Lebreton, first author of the article. “Our study gives new data about how angiogenesis might arise,” comments the French scientist at IRB Barcelona. Angiogenesis or the formation of new blood vessels is a critical process in the context of cancer because it is one of the steps that mark the transformation of a benign tumour into a malignant one. The formation of new blood vessels involves the synchronized movements of groups of cells. In this regard, understanding how these groups work will open up new research lines on angiogenesis.

Over seven hours, the scientists tracked a group of seven cells that form one of the tracheal branches of the fly Drosophila melanogaster in its first hours of development. The leading cell is the only one that has receptors for the growth factor FGF. The FGF signal stimulates a cascade of reactions in this cell in order to generate sufficient energy and to turn it into the promoter of motility.

“This is a novel piece of work because we monitored the entire process in vivo and because it is the first time we have seen, in an experimental context, that a single cell can lead this multiple migration,” says Casanova.

It is important to note that the development of trachea in the Drosophila fly is similar to that of bronchia in humans. Consequently, this development is also of biomedical interest in order to unravel the basic processes involved in the formation of new tissue.

Reference article:

Specification of leading and trailing cell features during collective migration in the Drosophila trachea
Lebreton G, Casanova J.
J Cell Sci. 2013 Nov 8. [Epub ahead of print]

 
 
This article was first published on the 20th of November 2013 in the news section of the IRBBarcelona website.
 
 

(2 votes)

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

News

– Developmental biologist Jim Smith, director of MRC National Institute for Medical Research, has been announced as the new MRC Deputy Chief Executive and Chief of Strategy.

– Elena Cattaneo is the winner of 2013 Stem Cell Person of the Year Award run by the Knoepfler lab stem cell blog. f you are interested in Elena’s work, you can read a Node post about one of her papers.

– If you are a member of the Society for Developmental Biology, nominations are now open for the 2014 SDB awards.

– And the shortlist for the 2013 Royal Society Winton Prize for Science Books has been announced. You can read the review of one of the shortlisted books, ‘Cells to Civilizations’, on this Node post.

Weird & Wonderful

– Halloween is the season for pumpkin carving, and twitter was full of science-themed pumpkins! We even carved our own Node Halloween pumpkin! And if you use stats in your research, you might also like this Halloween statistics cartoon.

– We spotted some stunning science cakes as part of a CRUK initiative, including this amazing cake representing a scientist hard at work in the lab.

– And if you were ever frustrated by how scientists in movies never seem to be able to pipette correctly, then this website is for you (scroll to the bottom for some of the best picks).

Beautiful and interesting images

– The winners of the Nikon Small World 2013 competition have been announced. Check out their website to see the stunning winning images!

– Ever wondered what a banana flower looks like in an MRI? Check this website for the answer– very beautiful!

– And check out this great trick of mimicry in nature!

Videos worth watching

– The finalists of the 2013 Dance your PhD competition have been announced. You can vote for your favourite dance here.

– This year marks the 100 years of the death of Alfred Wallace, and the New York Times released this nice animation of his life and legacy:
 

As usual, you can keep up with this and other content, including all Node posts and deadlines of coming meetings, by following the Node on Twitter.

(3 votes)

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Here are the highlights from the new issue of Development:

Broken-hearted over Hippo

Mammalian cardiac regeneration is greatly impeded by the massive loss of cardiomyocytes that occurs following acute injury. The failure of the remaining cells to proliferate is a considerable challenge for the field, but the molecular mechanisms that control cardiomyocyte proliferation in the adult heart are largely unknown. Now, on p. 4683, James Martin and colleagues demonstrate a role for Hippo signalling in suppressing adult and postnatal murine cardiomyocyte proliferation. Using conditional knockouts, the authors show that removal of Hippo pathway members Salv or Lats1 and Lats2 from normal adult cardiomyocytes results in increased proliferation, as these cells are able to re-enter the cell cycle and undergo cytokinesis. Moreover, removal of Salv from cardiomyocytes in vivo results in improved cardiac regeneration after adult myocardial infarction, a time when regeneration is usually severely impaired. Here, the authors observed reduced scarring and full restoration of cardiac function. This elegant study suggests that Hippo signalling is a repressor of adult cardiomyocyte renewal and regeneration.

Osr2 PAX a punch in palate formation

Precise orchestration of palate formation involves the complex interaction of signalling cascades and transcriptional networks in the developing craniofacial region. Pax9 and Osr2 have previously been implicated in palate formation, but little is known about how these molecular components interact within the greater regulatory network. Now, on p. 4709, Rulang Jiang and colleagues report a crucial role for Pax9 in patterning the anterior-posterior axis as well as outgrowth of the developing palatal shelves. The authors show that Pax9 regulates mesenchyme-epithelium interactions during pattern formation and that the expression of several key genes involved in palate development, such as Shh, Bmp4, Fgf10, Msx1 and Osr2, is reduced in Pax9 mutant mice. Interestingly, expression of Osr2 from the Pax9 locus was able to rescue the posterior, but not anterior, palate formation defect in the absence of Pax9 function. These data place Pax9 upstream of transcription factor Osr2 and signalling molecules Bmp4, Fgf10 and Shh in the molecular network that regulates palate development.

Par3 makes contact in migrating mesenchyme

Contact inhibition of locomotion (CIL) is a fundamental regulatory mechanism that ensures correct cell movement and migration. During CIL, cells form transient contacts but the molecular nature of such contacts is unknown. In this issue, Roberto Mayor and colleagues (p. 4763) investigate the role of the cell polarity protein Par3 in microtubule collapse and reorganisation during CIL in migrating neural crest cells. Using antisense morpholinos to Par3 in Xenopus and zebrafish, the authors show that loss of Par3 has a dramatic effect on migration and is essential for CIL both in vitro and in vivo. Par3 knockdowns fail to exhibit microtubule collapse at the cell-cell contact; however, this can be rescued by injection of an antisense morpholino to Trio, implicating the Rac-GEF Trio in migrating neural crest CIL. The authors propose a model in which CIL requires the local destabilisation of microtubules at the cell-cell contacts, which is controlled in a Par3/Trio-dependent manner.

Designer flies: accelerated genome editing in Drosophila

The immense power of Drosophila genetics has allowed invaluable insight into developmental biology. Despite these advances, a significant limitation has always been the lack of an efficient method for modifying select genetic loci. Now, on p. 4818, Jean-Paul Vincent and colleagues report high-efficiency homologous recombination in Drosophila with a novel gene-targeting vector. This can be achieved via a two-generation crossing scheme or via direct embryo injection. Importantly, both approaches yield few false-positives due to efficient negative selection, while readily detectable markers aid in the rapid identification of correctly targeted flies. The efficiency can be further increased by co-injecting the sequence-specific endonuclease CRISPR/Cas9. The investigators also report a series of vectors that can be used to insert different genetic elements into the targeted loci, such as mutated or tagged cDNAs and additional reporter genes. Their approach will enable genetic modification in a wide range of contexts, including in postmitotic cells. These tools will be a valuable resource for the Drosophila community.

Puffyeye regulates Myc-mediated cell growth

Proper control of cell size is vital to ensure the correct growth and development of any organism. The Myc family of proteins are key regulators of growth, but the mechanisms that control Myc protein levels are complex. Now, on p. 4776, Robert Eisenman and colleagues identify Drosophila Puffyeye (Puf), an orthologue of mammalian USP34, as a novel ubiquitin-specific protease (USP) regulating dMyc-dependant cell growth at the post-translational level. Using genetic interaction experiments, the authors demonstrate that puf opposes the activity of the ubiquitin ligase archipelago (ago) and that Puf acts to stabilise dMyc protein levels. Overexpression of puf in the eye and wing phenocopies dMyc overexpression, while expression of a catalytically inactive form of Puf had no effect, demonstrating the requirement of the Puf USP catalytic domain. Interestingly, the authors demonstrated that Puf can also regulate Ago and Cyclin E protein levels. These data reveal a new mechanism by which dMyc levels can be regulated by USPs in order to fine-tune cell growth.

GDF5 determines dendrite growth

Dendrite complexity determines the functional properties of neurons and the overall connectivity of neuronal circuits. The bone morphogenetic protein (BMP) family is known to regulate a myriad of developmental processes, but the extent to which different members of the family are involved in dendrite growth remains unclear. In this issue (p. 4751), Alun Davies and colleagues identify growth differentiation factor 5 (GDF5), a member of the BMP family, as a key regulator of dendrite growth and complexity in the pyramidal neurons of the developing hippocampus. Mice harbouring a mutation in Gdf5 showed dramatically reduced dendrite size and complexity. In vitro, exogenous GDF5 treatment was sufficient to increase elongation of the dendrites, but not the axons, of pyramidal cells derived from the developing mouse hippocampus. The authors further demonstrated that GDF5-mediated dendrite growth acts via the Smad signalling pathway and that GDF5-regulated HES5 expression is both necessary and sufficient for enhanced dendritic growth and complexity.

PLUS…

Nutritional regulation of stem and progenitor cells in Drosophila

Stem cells and their progenitors are maintained within a microenvironment, termed the niche, but it is known that systemic signals originating outside the niche also affect stem cell and progenitor behavior. Here, Utpal Banerjee and colleagues review recent studies of nutritional effects on stem and progenitor cell maintenance and proliferation in Drosophila. See the Review article on p. 4647

Cell-intrinsic drivers of dendrite morphogenesis

The proper formation and morphogenesis of dendrites is fundamental to the establishment of neural circuits in the brain. In this issue, Sidharth Puram and Azad Bonni review cell-intrinsic drivers of dendrite patterning and discuss how the characterization of such regulators advances our understanding of normal brain development and pathogenesis of diverse cognitive disorders. See the Review on p. 4657

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Endoreplication (endoreduplication or endomitosis) is the process by which a cell undergoes successive rounds of DNA replication without an intervening mitosis and its accompanying cytokinesis. Developmentally programmed endoreplication causes differentiating cells, such as TGCs and megakaryocytes (MKCs), to become highly polyploid. Our recent study published in Development (Sakaue-Sawano et al., 2013) comparatively characterized endoreduplication (TGCs) and endomitosis (MKCs) using Fucci (Fluorescent Ubiquitination-based Cell Cycle Indicator) technology. Our long-term imaging experiments also enabled monitoring of endoreplication for weeks, which revealed that the transition from endoG2 to endoG1 in MKCs varied with the polyploidy level.

The Fucci technology harnesses the cell cycle dependent proteolysis of two ubiquitin oscillators, human Cdt1 and Geminin, which are the direct substrates of the SCF^Skp2 and APC^Cdh1 E3 ubiquitin ligase complexes, respectively (Sakaue-Sawano et al., 2008).

The image shown above is a comprehensive perspective view of cell-cycle progression in a mouse fetal-placental unit (embryonic day 11.5) that was fixed with 4% formaldehyde and then optically cleared by the Scale technique (Hama et al., 2011). The fluorescent cell cycle indicator Fucci was expressed ubiquitously in the tissues. Green and red signals indicate the presence of FucciS/G2/M (mAG-hGem(1/110)) and FucciG1(G0) (mKO2-hCdt1(30/120)) probes, and signify cell proliferation and differentiation, respectively. The developing heart inside the fetus is most clearly illuminated. Remarkably, the enormous nuclei of endoreplicating trophoblast giant cells (TGCs) scattered in the placenta are highlighted in green and red, indicating endoS/G2 and endoG1 phases, respectively.

We would like to express our concern about the inaccurate usage of Fucci terminology in recent literature. While an increasing number of papers report cell cycle dynamics by use of the Fucci technology, the two Fucci probes, mKO2-hCdt1(30/120) and mAG-hGem(1/110), are often called mKO2-Cdt1 and mAG-Geminin, respectively, without annotation. However, this terminology misleads readers into believing that the Fucci probe contains the entire Cdt1 or Geminin protein. In fact, quite a few researchers are wondering whether such probes perturb the cell cycle regulation in recipient cells. In our original study of Fucci (Sakaue-Sawano et al. 2008), we made considerable effort to extract the regulatory domains (ubiquitination domains) from Cdt1 and Geminin. After performing long-term time-lapse imaging of numerous constructs, we demonstrated that amino acid residues 30-120 of human Cdt1 (hCdt1(30/120)) and amino acid residues 1-110 of human Geminin (hGem(1/110)) are both necessary and sufficient for this purpose. We would like to request that future studies using Fucci technology should include the full names of the probes, mKO2-hCdt1(30/120) and mAG-hGem(1/110), in the methods.

Hama, H., Kurokawa, H., Kawano, H., Ando, R., Shimogori, T., Noda, H., Fukami, K., Sakaue-Sawano, A. and Miyawaki, A. (2011). ‘Scale: a chemical approach for fluorescence imaging and reconstruction of transparent mouse brain’, Nat. Neurosci. 14: 1481-1488.

Sakaue-Sawano, A., Kurokawa, H., Morimura, T., Hanyu, A., Hama, H., Osawa, H., Kashiwagi, S., Fukami, K., Miyata, T., Miyoshi, H., Imamura, T., Ogawa, M., Masai, H. And Miyawaki, A. (2008). ‘Visualizing spatiotemporal dynamics of multicellular cell-cycle progression’, Cell 132: 487-498.

Sakaue-Sawano, A,. Hoshida, T., Yo, M., Takahashi, R., Ohtawa, K., Arai, T., Takahashi, E., Miyoshi, H. and Miyawaki, A. (2013) ‘Visualizing developmentally programmed endoreplication in mammals using ubiquitin oscillators’, Development.  140:4624-4632.

(5 votes)

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Earlier this year, Development launched Stem Cells & Regeneration: a website dedicated to hosting all of the journal’s stem cell and regeneration content. This online home means that you can now receive email alerts that contain only the Stem Cells & Regeneration content from Development. So if this is your main interest, sign up for email alerts now.

More than just an outlet for the latest research, Development’s Stem Cells & Regeneration page is also a home for the community. With regular posts on stem cell news, events, awards and meetings, the website will keep you up to date and in the loop of the stem cell scene.

There’s also a Stem Cells & Regeneration Image Gallery page, which shows how truly beautiful this area of science can be. Visit the Image Gallery and submit your own!

The website contains all of Development’s latest research papers covering the stem cell and regeneration fields, as well as new techniques and resources for the community. The site also offers the latest review articles, plus coverage of key community meetings such this year’s EMBO/EMBL Cardiac Biology: From Development to Regeneration report, as well as a report on the Cambridge Stem Cell Institute’s recent Physical Biology of Stem Cells meeting.

For a trip down memory lane, don’t miss the Highlighted Articles section, where we mine the archives for some truly classic Development papers, like this one from the Rossant lab in 1990.

There also a handy tool for searching particular areas within Development’s Stem Cell & Regeneration content. Or you can customise your own search here.

The launch of the website coincides with a new research section within Development, entitled “Stem Cells And Regeneration”. By doing this, Development is reaching out to the stem cell and regeneration communities,with the aim of highlighting the fundamental importance of developmental principles in these research areas. For more on why Development feels that this is important, click here.

So sign up and stay tuned as Stem Cells & Regeneration brings you the latest Development papers in the field. Engage with us and become part of your community.

(2 votes)

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Following the publication in Nucleic Acids Research of my new database that I developed in Olivier Pourquié’s lab, I would like to introduce you to Manteia http://manteia.igbmc.fr/. This database contains a lot of information (genomic, regulation, interaction, phenotype, disease etc …) for animal models (mouse, chicken, zebrafish) and man. These data are all formatted so they can be used together. In a same species, this makes it possible to ask complex questions by combining different types of data, but you can also use data from different species in order to supplement them or make predictions.

Mining huge complex datasets usually requires computer skills that few biologists have. However the user interface available for most public databases is too basic to really give a biologist the freedom to study all these data as a whole and make new discoveries. This is why I have developed new easy to use data mining and visualization tools for Manteia. One of these tools is called Refine. It allows to break down a complex biological question into multiple simple queries. For example, to identify candidate genes potentially involved in human muscle diseases using mouse phenotype data while taking into account a linkage analysis, one will select the genes corresponding to the chromosome region of interest using a tool called “chromosome location”, then from the result page one will search for their mouse orthologs using the “orthology” tool to finally find the genes involved in muscle phenotypes using “phenotype” or involved in myogenesis using “gene ontology “. The whole process takes a few seconds and gives the researchers the freedom to test different strategies to refine their list of candidates.

Another search tool is called “Query Builder “. This tool uses a simple interface to create complex queries such as: “I am looking for genes belonging to the Wnt signaling pathway and involved in somitogenesis but not in myogenesis” using Boolean operators (and, or, not). Several independent queries can be addressed at the same time. This is particularly useful when one is looking for genes that could explain a patient’s clinical features. In this case a query will be designed for each feature and the system will order the genes by relevance without discarding those that do not correspond to all of the symptoms. Every datasets can be used together to create a query. Whether to make predictions, test hypotheses or analyze experimental results.

Manteia is not limited to the selection of genes based on their annotation. Datasets can be analyzed statistically to see if they tend to be involved in the same biological functions, in the same signaling pathways, if they come from the same chromosomal regions etc. … this is particularly useful for analyzing deregulated genes from microarray or RNA seq experiments. These statistical tools can also be used to see which annotations are correlated to check, for example, if the genes involved in a biological process or a disease belong to the same signaling pathway.

There are a lot more things you can do with this system. Feel free to read the article (http://nar.oxfordjournals.org/cgi/content/full/gkt807?ijkey=8NMUhzVEjkVGdGw&keytype=ref) and watch our tutorial videos to learn more about Manteia. The release of the paper is not the end but the beginning of the project. Feel free to give your impressions on this database, make suggestions to improve the user experience or suggest new data to be entered in the system.

Enjoy. http://manteia.igbmc.fr/

A few examples of data visualization tools from Manteia

(8 votes)

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I am James Lloyd and have just finished my PhD at the University of Leeds, UK working with Prof Brendan Davies (plant developmental biologist) and Dr Andrew Cuming (moss biologist).

Moss is a plant, a fact that some people I eat lunch with refuse to believe. It is sometimes called primitive. While moss does look like plants that exist in the fossil records and lived hundred of millions of years ago, it has been evolving during this time, so what is true for modern moss might not have been true of ancient plants. But moss is very useful in comparative studies, allowing us to gain an insight into the evolution of developmental processes and assess how ancient they are.

To keep moss happy in the lab, we grow it on agar plates with a defined medium in a room with continuous light at 25 ^oC. Here, a whole plant (often called a colony) will grow from a single haploid spore or a ‘spot’ of moss tissue. Any part of a moss plant can regenerate to form a new moss plant on standard media, making it easy to routinely subculture moss. The main body of the plant is haploid, in contrast to animals and vascular plants, in which most tissues are diploid.

A moss plant consists of filamentous tissue (protonemata), which are great for studying polar tip growth in plants. These filaments branch and eventually some of these branches become leafy shoot-like structures called gametophores (see photos). At the base of these gametophores, filaments called rhizoids grow and anchor it in the agar.

Photo of moss by James Lloyd University of Leeds

Moss can take months to go through the full life-cycle but only takes about three weeks to produce fully expanded colonies with large gametophores, which can be studied. If you are brave enough to go through the whole life-cycle (as moss will regenerate any tissue, you do not always need to bother unless you want to phenotype the diploid tissue), you can grow moss in short day conditions (8 hours light, 16 hours dark) while being cooled to 16 ^oC stimulates production of the reproductive organs at the apex of gametophores. A few drops of water will then allow the water-dependent sperm to swim and fertilise egg cells resulting in the appearance of a small diploid structure at the apex of a gametophore. Inside this ‘sporophyte’, meiosis will occur and many new haploid spores will be produced.

Moss is a user-friendly model plant. It mostly sits there on a Petri dish, photosynthesising. Moss could almost be thought of as the yeast of the plant kingdom because it is grown on defined media but can also have genes knocked out at will using homologous recombination.

While most plant researchers wanting to study mutants of their favourite gene need to make RNAi knockdown lines or hope someone has randomly hit that gene with a point mutation or transposons/T-DNA insertion, moss researchers can ‘easily’ make their own knockout mutant lines. Flowering plants have to low a rate of homologous recombination to make this feasible, but it would greatly improve GM strategies. You could even knock-in tags or mutations in to your favourite genes, in case a full deletion isn’t appropriate. Just clone around one kilobase of DNA from upstream and downstream of the gene you want to knock around an antibiotic selection gene and you are away.

A day in the life of a moss researcher can vary a lot depending on if you are transforming moss with your knockout construct you have just made or if you are sub-culturing it or simply pulling the plant apart to phenotype. Generally moss is happy to be left alone for a while and can be easily manipulated in a molecular lab. To collect filamentous tissue for phenotyping or transformation, moss can be homogenized or blended (click in the photo below for a bigger image).

Moss is a useful model to understand how plant development has evolved over the last few hundred million years and the basic mechanisms underlining some growth forms such as polar tip growth could be better understood. Moss also has its uses in better understanding processes common to all plants. Animal researchers have used multiple, evolutionarily distant model organisms for years, which has helped better understanding in many processes as different models have their own advantages and disadvantages. Moss has many advantages over the flowering plant model Arabidopsis thaliana, such as easy to generate gene knockouts and easy of propagation of tissue. Studying moss can reveal insights about basic pathways (such as RNA decay) in plants that were not apparent from studying A. thaliana alone. Sometimes what is true for moss is true of rice, but not of A. thaliana.

How to homogenise moss by Dr Andrew Cuming University of Leeds

Thanks to Dr Barry Causier for proof reading and Dr Andrew Cuming for moss homogenising photo.

This post is part of a series on a day in the life of developmental biology labs working on different model organisms. You can read the introduction to the series here and read other posts in this series here.

(8 votes)

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