By: Erin Sparks and Matthias Benoit

Set in the idyllic location of the Sainsbury Laboratory Cambridge University (SLCU) building adjacent to the Cambridge University Botanic Garden, the inaugural Sainsbury Lab Symposium (#SLS16 on Twitter) attracted over 100 researchers from across the world. This three-day symposium focused on the topic of Induced Plant Development and featured 18 speakers, 10 poster flash talks and 36 posters, covering a variety of research topics. Several themes emerged from this meeting that we highlight in this report.

The symposium kicked off with a Keynote Address by Sofie Goormachtig (VIB Department of Plant Systems Biology – Ghent University), discussing her elegant work on the role of Strigolactones in controlling root architecture. The importance of Strigolactone signalling was further supported by, Thomas Greb (COS – Heidelberg University) presenting his results on the role of Strigolactones in primary energy metabolism and growth regulation. The implication of hormones in induced plant development was repeatedly discussed during the symposium, including several posters emphasizing the role of Auxin, Cytokinins and Abscisic Acid signalling in the regulation of cell elongation, regeneration and differentiation.

In addition to hormones, the importance of abiotic environmental signals in controlling plant development was highlighted. The environmental cues discussed included light, water, calcium, sugar and mechanical induction. Seisuke Kimura (Kyoto Sangyo University) presented his exciting results on phenotypic plasticity and heterophylly in the herbaceous semiaquatic plant Rorippa aquatica. Discussing his latest results, Seisuke showed that leaf form in R. aquatica is also affected by light and temperature. Further, Elena Baena-González (IGC – Portugal) underlined the importance of monitoring plant carbon status by SNF1-related Protein Kinase1 (SnRK1) in the restoration of post-stress homeostasis.

Biotic regulation of plant development was another central feature of the symposium. This included the discussion of parasitic plants, insects and fungi. Of particular interest was work from Melissa Mitchum (University of Missouri) on the signalling mechanisms of cyst nematode parasitism. In the classic co-option of host mechanisms, the cyst nematode delivers CLE-like effector proteins to mimic the plant CLE peptides. The subsequent signalling through the CLE pathway is essential for the establishment of nematode feeding sites. In considering parasitic plants, Ken Shirasu (RIKEN) reported the draft genome sequence of Striga asiatica and revealed a recent whole genome duplication as a potential driving force for the adaptation to host plants. In parallel, he presented a new model for forward and reverse genetics in parasitic plants, Phtheirospermum japonicum. Recent results from his lab provide evidence for the cooption of a lateral root developmental program for haustorium (penetration structure required for host invasion) formation.

Each of these areas of induced plant development revealed the inherent problems with studying environmental influences on plant development and the need for improved technology. Several researchers presented their emerging technologies for improving plant phenotyping and environmental control. For example, Olivier Loudet (INRA) discussed his development of a high throughput phenotyping robot called the Phenoscope. This impetus for this design was the importance of controlling water content per pot and the growth room position, which are vital for his drought response studies. Along these same lines, Christian Fankhauser (University of Lausanne) also developed a phenotyping platform to analyse leaf growth and positioning with high spatial and temporal resolution. Least we forget about the belowground portion of plants, Malcolm Bennett (University of Nottingham) updated us on the progress of the Hounsfield Facility for 3D x-ray imaging of root systems. With a particular interest in how plants find and respond to water, Malcolm discussed his latest work on the molecular control of hydropatterning.

The link between fundamental sciences and agronomics has never been so tight as it was during this symposium. Many speakers have emphasized how their research can be applied to agronomics and industry. Kerry Franklin (University of Bristol) described a nice industrial partnership with a company interested in UV-B treatment of their plants undergoing shade avoidance and thermomorphogenesis problems. Christian Fankhauser (University of Lausanne) also revealed industrial interest in his research on light-induced morphogenesis and accessibility to sunlight.

It is noteworthy to mention the extreme diversity of plant species used in the topics discussed during the symposium, reflecting the vitality of the plant induced development field. From Arabidopsis thaliana to Rorippa aquatica, to the parasitic plant Striga asiatica (aka witchweed) to a variety of crops, not less than a dozen different species were represented, pushing the boundaries of plant development to new and exciting topics.

All together the inaugural Sainsbury Laboratory Symposium was a rousing success. In our humble opinion, this symposium highlighted the reason many of us attend meetings – there was stimulating discussions, new ideas, cutting edge research and a great diversity of topics. Congratulations to Dana MacGregor, postdoctoral scientist in Steve Penfield’s lab (John Innes Centre), awarded best poster of the Symposium for her work on natural variation and environmental regulators of seed dormance. The success of this symposium is due in large part to the organizer, Sebastian Schornack, who did a wonderful job and has our gratitude for the substantial effort required in organizing such an event. This symposium will definitely be included on the “must attend” list for future years.

(3 votes)

Loading...

Lei Lei and Allan Spradling

          Germ cells are unique among all metazoan cells in their ability to persist from one generation to the next. In seeking to understand how germ cells acquire and maintain immortality, a logical place to start with is the distinctive cell biological properties these cells display. For example, in many organisms, developing germ cells socially interact just before and during meiosis. In Drosophila, a founder germ cell called a cystoblast synchronously divides four times without undergoing cytokinesis to produce sixteen interconnected cells known as a germline cyst. Interconnected germ cells within ovarian cysts transport cytoplasm, organelles and RNAs to one germ cell that will survive and develop as oocyte. The rest of the fifteen sister germ cells that transfer materials, undergo apoptosis and are called nurse cells (de Cuevas et al., 1997).

          Whether mammals also nurse developing oocytes has remained unclear. In fetal mammalian ovaries, germ cells appear morphologically similar, rather than as recognizable oocytes and nurse cells. After migrating to the fetal ovary, primordial germ cells (PGCs) proliferate and the resulting cells either differentiate into primary oocytes or undergo apoptosis. In humans, PGCs proliferate into about 7 million germ cells at 20 weeks of gestation and these give rise to 1 million primary oocytes at birth (Baker, 1963). In mice, PGCs generate about 20,000 germ cells at embryonic day 14.5 (E14.5) that differentiate into about 4,000 primary oocytes in the postnatal day 4 (P4) ovary (Lei and Spradling, 2013). These germ cell losses could be explained if the distinction between nurse cell and oocyte was not difficult to recognize in mammals. In that case, the cells undergoing apoptosis would be nurse cells that had finished transferring important materials to the oocytes.

          If mammalian fetal ovaries do contain nurse cells as well as differentiating oocytes, they should be interconnected in germline cysts, like in Drosophila and many other species. Efforts to characterize mouse germline cysts began in our group in 1995 when Dr. Melissa Pepling joined the laboratory. Pepling systematically studied intercellular bridges and nest development within the fetal ovary. She found evidence that cysts form based on an increasing number of intercellular bridges, and observed multiple bridges per cell, bridges containing microtubules and with luminal mitochondria apparently moving between sister germ cells. Strikingly, she documented that synchronous germ cell mitotic divisions occur at this time, initially in groups corresponding to powers of two. These observations strengthened the case that germline cysts form between E10.5 when PGCs reach the gonad, and E14.5, when germ cells cease mitosis and enter meiosis (Pepling and Spradling, 1998). A few years later, Pepling demonstrated that the breakdown of mouse cysts by apoptosis correlated with the formation of primary oocytes and primordial follicles (Pepling and Spradling, 2001). However, it was not possible to precisely describe the structure of the starting cysts or how they broke down into oocytes. How many oocytes derived from an initial cyst remained unknown.

          Oocytes from diverse species contain a visible mass of organelles known as the Balbiani body or mitochondrial cloud at the time they are first enclosed within a follicle. Specific mRNAs that later localize within the oocyte, including in the germ plasm, associate with the Xenopus Balbiani body (Kloc and Etkin, 1995). Up until this time, mouse oocytes were reported to be symmetrically organized and to lack a Balbiani body. However, studies in Drosophila showed that the Balbiani body is built mostly from organelles that are transferred from nurse cells into the oocyte around the time of follicle formation (Cox and Spradling, 2003, 2006). This prompted Pepling et al. (2007) to reinvestigate and show that a Balbiani body does form in mouse oocytes around the time of birth (Figure 1). The existence of a mouse Balbiani body raised the question of whether it forms like in Drosophila, by the transfer of its organelles and other components from connected nurse cells.

          This was the situation when Lei Lei, a new postdoc with extensive previous experience in studying the mouse ovary, joined the lab in 2009. Clearly, the major roadblock to analyzing the behavior and function of cysts in the mouse ovary was simply the difficulty in recognizing individual cysts and their component germ cells. Since cyst cells share a common lineage, lineage-tracing methods offered a solution. Lei began to experiment with labeling only about one PGC per ovary at E10.5 when individual PGCs arrive at the fetal gonad using a general CreER-loxP system and low doses of Tamoxifen that rarely remove a blocker segment and activate yellow fluorescent protein (YFP) production. This approach, dubbed “single-cell lineage labeling,” would render the cells making up at least one cyst unambiguous in each ovary (Figure 2). Of course, using a low dose of Tamoxifen could not actually guarantee that exactly one PGC would be labeled. Some ovaries would have zero and a few would have two. However, even when two were labeled, they would usually be widely separated in the ovary, ensuring that their progeny remained separate. Lei would come to realize that this simpler paradigm could act as a key to throw open the treasure chest of mammalian oogenesis.

          By analyzing the development of 164 individual marked E10.5 PGCs in this manner (about 500 are present per ovary), many longstanding questions were resolved (Lei and Spradling, 2013). All the PGCs follow the same developmental program, undergoing a similar number of divisions and producing a similar number of primary oocytes. PGCs start by generating germline cysts, since the initial number of labeled cells produced is always a power of two, reflecting the synchronous divisions first seen by Pepling. No PGCs from the fetal ovary remained undifferentiated, generated any other cell types or gave rise to oogonial stem cells, as previously postulated by some. Overall, between E10.5 and P4, 80% of PGC daughter cells underwent apoptosis, while the surviving 20% became primary oocytes. On average, each PGC produced an initial cyst that fragmented into about 5 derived cysts by E14.5 when mitotic division ceased. All germ cells then entered meiosis and generated about 6 primary oocytes by P4. The close agreement between the number of final derived cysts and the number of oocytes suggested that after an initial period of fragmentation, each remaining derived cyst generates one oocyte.

          These experiments finally laid the groundwork for Lei to directly address the question of whether mouse cysts function like Drosophila cysts to nurse the oocyte and build the Balbiani body. First, she mapped the pattern of cellular interconnections within large, unfragmented cysts. In Drosophila cysts the oocyte always has 4 ring canals (intercellular bridges). Mouse germ cells with 3 or 4 ring canals were scattered throughout the early cysts, and this pattern may somehow presage how the initial cyst breaks into its derivatives. Lei went on to investigate whether organelles move between the interconnected cells within mouse cysts and accumulate in cells that become oocytes. She found that the Balbiani body could be used to distinguish cells transferring organelles (which lack a Balbiani body), from cells receiving organelles (which have a forming Balbiani body). By following centrosomes, mitochondria, Golgi elements and total cytoplasmic volume from E14.5 until all the cells have separated and either formed oocytes or died, she was able to prove that both organelles and cytoplasm are transferred non-randomly from the 80% of cells that later undergo apoptosis into the 20% that accumulate these materials, form a Balbiani body and become primary oocytes (Lei and Spradling, 2016). When cytoplasmic transport was blocked by inhibitors of microtubule polymerization or dynein-mediated movement, oocyte production and Balbiani body formation were greatly reduced. Concomitantly, apoptosis also declined, arguing that transfer is necessary to induce apoptosis. Thus, it is finally clear that fetal mammalian germ cells are divided into nurse cells and oocytes despite the fact that both enter meiosis and cannot easily be distinguished throughout much of fetal development by chromosomal or synaptonemal complex morphology.

          During her final Spring and Summer in Baltimore, as this work was nearing completion, problems with the “Drosophila model” of transport through the ring canals became apparent. Mouse ring canals seemed to be important only during the early cyst stages. They shrink after E14.5, detach from the membrane joining adjacent germ cells, and disappear entirely after E19.5, well before oocyte differentiation is complete. The membranes separating germ cells develop large gaps at this same time, connecting the cells directly. The number of organelles and amount of cytoplasm moving into the oocytes is so large, it seemed more likely that they moved directly through membrane discontinuities rather than through the lumens of these small bridges. Moreover, confocal microscopy and EM studies began to make it clear that the germ cells undergoing apoptosis frequently have lost most of their cytoplasm, with little more than the nucleus being excluded from transfer. This suggested that germ cell apoptosis at these stages mostly destroyed nuclei, rather than entire cells. This realization should probably not have seemed so surprising. In Drosophila, the nurse cells in full-grown follicles synchronously transfer their cytoplasm into the oocyte just prior to entering apoptosis, a process known as “nurse cell dumping.” The nurse cell nuclei are excluded and show signs of apoptotic degeneration. Thus, the process of mouse oocyte formation by cytoplasmic dumping appears to be a variation on germ cell behaviors that are widespread among oocytes across many phyla.

          These new insights require a revision of the traditional concept that mammalian oogenesis is highly inefficient. The largest single phase of germ cell loss, that occurring during oocyte differentiation, can now been seen as resulting from nurse cell apoptosis following the transfer of their cytoplasm and organelles to oocytes. Thus, “germ cell apoptosis” does not represent a waste of material, but rather a mechanism to start increasing the cytoplasmic/nuclear ratio of oocytes that will grow to be the largest cells in the mammalian body. The transfer of RNAs from nurse cells, including small RNAs, may also constitute an important part of the genome re-programming that takes place in the oocyte about this time.

          The realization that mammalian oocytes develop in cysts and are supported by nurse cells provides new evidence that mammalian oocyte development is fundamentally similar to oogenesis in other animal groups. Indeed, even plant gametophytes transfer RNAs and other components between the somatic endosperm and the oocyte, in part to aid in the control of transposable elements (Creasey and Martienssen, 2010). Our work encourages the view that many of the unique properties of germ cells in all organisms, arise from fundamentally similar mechanisms that have been extensively conserved during evolution.

References:

Baker T.G. (1963). A quantitative and cytological study of germ cells in human ovaries. Proc. R. Soc. B. 150, 417-433.

Cox R.T. and Spradling A.C. (2003). A Balbiani body and the fusome mediate mitochondrial inheritance during Drosophila oogenesis. Development. 130,1579-1590.

Cox R.T. and Spradling A.C. (2006). Milton controls the early acquisition of mitochondria by Drosophila oocytes. Development. 133,3371-3377.

Creasey K.M. and Martienssen R.A. (2010). Germline reprogramming of heterochromatin in plants. Cold Spring Harb Symp Quant Biol. 75,269-274.

de Cuevas M., Lilly M.A. and Spradling A.C. (1997). Germline cyst formation in Drosophila. Annu. Rev. Genet. 31,405-28.

Kloc M. and Etkin L.D. (1995). Two distinct pathways for the localization of RNAs at the vegetal cortex in Xenopus oocytes. Development. 121,287-297.

Lei L. and Spradling A.C. (2013). Mouse primordial germ cells produce cysts that partially fragment prior to meiosis. Development. 140, 2075-2081.

Lei L. and Spradling A.C. (2016). Mouse oocytes differentiate through organelle enrichment from sister cyst germ cells. Science. 352,95-99.

Pepling M.E. and Spradling A.C. (1998). Female mouse germ cells form synchronously dividing cysts. Development. 125,3323-3328.

Pepling M.E. and Spradling A.C. (2001). Mouse ovarian germ cell cysts undergo programmed breakdown to from primordial follicles. Dev. Biol. 234, 339-351.

Pepling M. E., Wilhelm J.E. O’Hara A.L. Gephardt G.W. and Spradling A.C. (2007). Mouse oocytes within germ cell cysts and primordial follicles contain a Balbiani body. Proc Natl Acad Sci U S A. 104,187-192.

(3 votes)

Loading...

Today, the Rockefeller University held its third annual Science Saturday in New York City, its bigger science outreach event of the year.

I had the chance to get involved for the second time and I can attest it is unbelievably fun and rewarding!! Individual research labs and the Science Outreach team from Rockefeller University set up over 25 booths where they present scientific concepts and methods through different activities to engage kids and (importantly!) their families. Children get to learn about DNA structure, brain function, model organisms and – of course – ice cream making (because… ice cream) through games, simple experiments and handcrafts. As usual, you can catch up with the action on twitter.

Bridging robots and humans @RockefellerUniv #rockedu #technology #science #nyc #scisat16 pic.twitter.com/dwA5YQVpbR

— RockEDU (@rockedu_) May 7, 2016

Had an awesome time isolating DNA from strawberries today at #SciSat16 @rockedu_ #scicomm pic.twitter.com/ku9vUDxGrP

— Clair Geary, PhD (@GirlTalkScience) May 7, 2016

Such a large event is a lot of work and requires resources, an organizing team like the university’s excellent Science Outreach program (led by the amazing Jeanne Garbarino) and the coordinated effort of tens of volunteers (from PIs to high school students), from both Rockefeller and the neighboring institutions. However, science outreach can be done at any level. Do it next time a relative asks you ‘what do you do in the lab all day?’. Do it when you’re at a party and someone asks ‘what do you exactly work on?’. Prepare a big-picture, short explanation, practice and deliver it. Bring a friend to the lab and show them around! The goal is always the same: engage non-scientists, show them that they too can understand science and make them aware of the way science actually works (and how it often doesn’t!). To boot, it will make you understand your own work better and will help you put it into context! Let’s create a more scientifically literate society that demands more and better science. Get involved!

(4 votes)

Loading...

Department/Location: Department Molecular Biology, UT Southwestern Medical Center, Dallas Texas 75390

Closing date: June 30, 2016

Position: The funds for this post are available for up to 4 years, however postdoc will be encouraged to seek independent fellowship funding.

General area of research includes regenerative medicine, developmental biology, molecular biology, stem cells, and tissue engineering. We are interested in how the vasculature develops coordinately with organs, including the kidney and pancreas. We will investigate basic mechanisms of blood vessel patterning, cell-cell interactions and tissue morphogenesis and function. In particular, we want to engineer replacement nephrons, within the framework of the NIH-NIDDK consortium (https://www.rebuildingakidney.org/collaborate.html).

For this position experience in molecular biological and biochemical techniques, basic mammalian cell and tissue culture, mouse husbandry, histology and tissue engineering is desirable. The position is based in the Cleaver laboratory and is available immediately.

The Cleaver lab is part of the Department of Molecular Biology and the Hamon Center for Regenerative Science and Medicine. It is also part of the Harold C. Simmons Comprehensive Cancer Center. The lab is located on the 8th floor of the NA building on North campus at UTSW (http://www.utsouthwestern.edu/education/medical-school/departments/molecular-biology/index.html).

Applicants should have been awarded a PhD degree or equivalent and have several years laboratory experience.

To apply for this position and to view further information, please visit: http://www.utsouthwestern.edu/labs/cleaver/ . Apply directly to Ondine.Cleaver@utsouthwestern.edu via email.

The closing date for applications is June 30 2016, but the position is available immediately.

Please provide your Curriculum Vitae (CV) including at least 3 referent contact information, as well as a cover letter in initial inquiries.

UTSW values diversity and is committed to equality of opportunity. The University has a responsibility to ensure that all employees are eligible to live and work in the USA.

(No Ratings Yet)

Loading...

The Department of Human Evolutionary Biology at Harvard University invites applications for a Postdoctoral Fellow in the Evolutionary and Developmental Genetics Laboratory of Dr. Terence D. Capellini.  The focus of the position will be to study the genetic and developmental basis of human-specific adaptations and disease.

While the lab primarily concentrates on skeletal adaptations in humans and primates, an important research focus is to identify causal genetic variants that mediate human phenotypes resulting from more recent selection. The lab uses a variety of experimental and computational tools, such as functional genomics (e.g., ATAC-seq), developmental genetics in the mouse (e.g., CRISPR-Cas9), and in vitro methods on human cells, to explore the consequences of genetic variants on human biology.

The research will take place in the Evolutionary and Developmental Genetics Laboratory directed by Dr. Capellini and located in the Peabody Museum on Harvard University’s Cambridge, Massachusetts campus.

A doctoral degree is required for this position. Desired qualifications include research in developmental genetics, functional genomics, evolutionary developmental biology, mouse developmental biology and/or human evolutionary genetics.

Please submit a letter of interest, an updated CV, and the names and email addresses of three references to Terence Capellini at tcapellini@fas.harvard.edu.  Evaluation will begin at the time this advertisement is posted and will continue until the position is filled.

The lab’s website is: http://projects.iq.harvard.edu/evolutionary_genetics/home

Harvard University is an equal opportunity employer and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, sexual identity, national origin, disability status, protected veteran status, or any other characteristic protected by law.

(No Ratings Yet)

Loading...

As you may have noticed, we have a series of new Node banners (alongside some of our old favourites). As there isn’t really space to give credit to the authors on the banner itself, we thought we would write this short post to give credit where credit is due!

Below is the list of the authors of the beautiful images decorating the Node banner:

Joseph Campanale, Aracely Lutes, and Stephanie Majkut took this awesome image of pilidium larvae of the Nemertean ribbon worm at the 2011 Woods Hole Embryology course.

Also at Woods Hole, but during the 2012 Embryology course, Eduardo Zattara (University of Maryland, College Park) took this image of the male stolon of an annelid.

The human embryo images were taken by Juan Carlos Izpisua Belmonte (The Salk Institute for Biological Studies).

The last banner image featured on the cover of Development:

This Arabidopsis thaliana stem section was taken by Truernit et al (paper here).

Thank you to all the authors for giving us permission to use their images on the Node!

(1 votes)

Loading...

I was kindly asked to shortly summarize my experience at the Career Workshop at the BSDB/BSCB Meeting at the University of Warwick.

My name is Hamze Beati and I am currently a postdoctoral researcher in the laboratory of Arno Müller in the Department of Cell and Developmental Biology in the School of Lifesciences at the University of Dundee. I am about to finish my postdoc after doing my PhD in the lab of Andreas Wodarz in Göttingen, Germany (now in Cologne). Later this year I will start my own junior research group “Nachwuchsgruppe” at the University of Kassel in Germany, which of course made the Career Workshop an interesting opportunity to learn about individual careers/career paths.

The first session was led by James Wakefield from the University of Exeter. The discussion was very interesting for me as he had chosen an academic career path, establishing his own group following up his own research interests. We have learnt that he changed the places he lived and worked frequently, also including times when he had to commute extensively. It was particularly nice to see that he managed to balance his work/life balance, also having a family with children at home. From our discussion I have learnt that a very important factor for an academic career path is to work together with PIs where one can follow up own ideas and interests to a particular extend. That covers my own experience so far as I was always able to develop my own ideas and thoughts about particular questions in Cell and Developmental contexts.

The second session I have attended was of great interest to me and was hosted by Claudia Barros, as she is working with the same model organism (Drosophila melanogaster) as I do. She was trying to establish the most important things for a successful academic career by looking back at her own career path. Similarly to James Wakefield we learnt that she had to change the places she lived and had to go through a hard time working in the US while her partner still lived in Europe. Things she pointed out were that winning awards are important for a successful career, including winning poster prizes, travel grants, etc.. These are all factors for a good CV. Both sessions agreed that the publication record is the most important determinant for a successful career, which was not surprising to me. Also, both sessions pointed out that during an academic career work in the laboratory will decrease, while work in the office is increasing drastically (University duties, paper and grant writing, etc.).

The last session I have attended was led by Anne Wiblin from Abcam. This discussion was also of big interest to me as she is working for a company and had left an academic career path. I learned that it was not very easy for her to find a job in industry coming from Lifesciences, something I was aware of before talking to many young researchers who decided to leave academia. Anne had to apply to many companies to finally get a position. We were able to ask her about the kind of work which is done once one decides to leave Lifescience, starting work in a company. She told us that the scientists in her company are quite busy testing new reagents, antibodies, etc. for their specificity, etc., which is quite nice as many people leaving Lifesciences would prefer to continue doing “benchwork”.

I really liked the Career Workshop and would highly recommend people to try and attend in the future. It also helped to network with the hosts, which sometimes is not very easy elsewhere at the conference.

(1 votes)

Loading...

Today is my last day on the Node, so this is my chance to say goodbye!  It has been 3 very busy years on the Node, but I have really enjoyed myself! When I first started on the Node I was fresh out of my PhD (actually, I was still writing my thesis) and my background was really cell biology. But I quickly discovered how wonderful the developmental biology community is, and you were all very welcoming. Thank you! The definite highlight of this job has been meeting all of you, either online or in person. I had the opportunity to chat to you about science, give career advice, discuss online communication and even, on one notable occasion, a heated but friendly argument on whether anarchy was a viable social system! So it wasn’t all just work, and I had fun as well.

During the last three years I have been involved in a lot of projects on the Node, which I hope you have enjoyed.  The most obvious change was the new look of the site and its new logo, which I hope you approve. This was also when we celebrated the Node’ s 5th anniversary, a very respectable age, and had a great time filming some of you to mark the occasion! One of the series that I launched during my time on the Node was the ‘A day in the life‘ series, on model organisms in developmental biology. This was actually an idea that I suggested at my job interview, so it was great to see it come to fruition. This year we even turned a selection of the posts into a small booklet that you can collect at conferences. Your feedback on this series has always been really positive, so this is definitely a highlight! Other highlights included designing our Node postcards, kicking off the new forgotten classics series and interviewing people at conferences. Ok, ok, and I must admit that the conference locations were one of the pluses of the job as well!

My very first conference location (ISDB in Cancun). It was a tough job, but someone had to do it!

When I started this job I often still had to explain what the Node was, and ensuring that there was a constant flow of content was one of my priorities. Three years on the Node is a household name within the community, averaging more than 1 new post a day, and boasting almost 8,000 visitors a month. This is only possible because you have embraced the Node as your community site, and have read, posted and commented, and shared the word with your colleagues. Thank you for making my job so easy! And this is also a good occasion to ask for your help again. My replacement will only start in mid June, which means that for a few weeks the Node will be without a community manager to keep things ticking at the usual pace. I hope that you will help the Node team by continuing to post and comment during this period!

At the Vienna city hall (European Evo Devo meeting)

 
I hope that this post is not a goodbye, but only a see you later! My new job is based at the University of Oxford, where I will be involved in academic online communications, although not specifically about science. While I will not be travelling to exciting conferences any more, I hope I will come across some of you in the future. If you would like to keep in touch, my twitter account is @catcvicente. Thank you and see you around!

(13 votes)

Loading...

Young Embryologists’ Network 2016

As a neglectful member of this parish over the last few months/years (insert standard academic administration/teaching workload complaints here), I have the great pleasure to come out of my slumber to drum up interest in one of the best things about being (a developmental biologist) in London:

https://www.eventbrite.co.uk/e/yen2016-8th-annual-summer-conference-tickets-24488618116

If you have been lots before, you have probably forgotten when it is (I had): this month (27th). If you have never been before, you should come because it is interesting, friendly, and all the lovely things a good conference should be. If you are a PhD student looking for a nice place to give your first talk, YEN is absolutely brilliant. A medium sized, very supportive, and very friendly audience. If you are a desperate postdoc looking to engage in much needed shameless self-promotion, it is good for that too, but you’ll need to get a move on: the abstract deadline is 5TH MAY.

See you there for science and beer (probably in that order).

(5 votes)

Loading...

This post highlights the approach and findings of a new research article published in Disease Models & Mechanisms: ‘Stem cell-specific endocytic degradation defects lead to intestinal dysplasia in Drosophila’. This feature was written by Elan Strange as part of a graduate level seminar at The University of Alabama (taught by DMM Editorial Board member, Prof. Guy Caldwell) on current topics related to use of animal and cellular model systems in studies of human disease. The course is designed to expose students to recent research in a variety of diseases, and for this assignment, students were asked to read and provide a scholarly summary of an assigned research article ‘in press’ at DMM. Elan’s summary was selected by the editorial team for publication at the Node. The text has been edited and shortened by DMM in conjunction with the author.

A useful approach to investigating the mechanisms underlying complex diseases such as cancer involves exploring common genetic mutations. Understanding the phenotypic impact of such mutations can help to identify risk, estimate prognosis and guide treatment for specific forms of cancer. For example, screening for BRCA1 and BRCA2 mutations has been shown to be effective in determining risk of developing breast and ovarian cancer (Mavaddat et al., 2013). Similarly, Marisa et al. (2013) showed that grouping colon cancer patients into subtypes based on genetic mutations can provide a better indication of prognosis. Researching genetic mutations that correlate with oncogenesis has proven to be an invaluable means of learning more about the causes of cancer and guiding the development of new chemotherapeutics.

UVRAG, the metazoan homolog of yeast Vps38, is well characterized as a regulator of autophagy (Liang et al., 2006), a conserved mechanism by which cells digest and recycle dispensable or dysfunctional organelles and cellular components. Although loss-of-function mutations in UVRAG are known to correlate with tumorigenesis (Ionov et al., 2004) and overexpression of the protein has been shown to reduce cell proliferation (Liang et al., 2006), the precise mechanisms by which UVRAG acts as a tumor suppressor have not yet been elucidated. Given that autophagy has been shown to be involved in several types of cancer (Bento et al., 2016), the most intuitive hypothesis for the role of UVRAG in tumorigenesis implicates its autophagy-regulating function. However, this hypothesis was explored  by Knævelsrud et al. (2010), who determined using qualitative and quantitative readouts for autophagy that the tumorigenicity of UVRAG mutations in colorectal cancer cell lines is independent of its role in regulating autophagy. Additionally, UVRAG has functions in DNA repair, maintenance of centrosome stability, and endocytosis (Zhao et al., 2012), all of which are implicated in cancer and could explain the role of UVRAG as a tumor suppressor. In a new study published in DMM, Nagy et al. sought to investigate the role of UVRAG as a tumor suppressor, using the fruit fly Drosophila melanogaster. Drosophila represents a powerful model for exploring the pathology and molecular mechanisms of human intestinal disorders due to the highly similar histological and cellular stress response mechanisms (specifically those involving cell proliferation and renewal) in the guts of mammals and flies.

The authors began by using RNAi silencing to study the effects of adult-onset loss of Uvrag in Drosophila intestinal stem cells (ISCs). They report that the Notch ligand Delta and Wnt ligand Wingless (Wg), two biomolecules known to be trafficked via endosomes, accumulate in intracellular compartments of ISCs lacking UVRAG, thus indicating that these cells are deficient in endosomal trafficking. They validated their RNAi silencing experiments by showing that cells expressing null alleles of Uvrag show similar patterns of Delta and Wg accumulation.

The team then analyzed the effects of Uvrag silencing on ISC proliferation and morphology. The most noteworthy observations made were an increase in ISC number and concomitant thickening of the intestinal wall, both of which are characteristics of intestinal dysplasia (a precancerous lesion, see related DMM Review). To analyze the effects of silencing Uvrag on gut function, the authors fed the flies food containing a blue dye that enabled movement through the gut to be tracked. The feces of flies with UVRAG-deficient ISCs contained less dye, indicating

that these animals retain food more efficiently. Consistent with a previous finding that proper gut function is essential for normal lifespan (Biteau et al., 2010), Nagy et al. found that the fly mutants had significantly reduced lifespan. To look at how flies with UVRAG-deficient guts respond to environmental stress, the authors treated the flies with the toxin dextran sodium sulfate (DSS), and, in a separate experiment, infected them with the pathogen Pseudomonas aeruginosa. Under both treatments, UVRAG-deficient flies were killed faster than control flies. Overall, these experiments show that UVRAG deficiency induces gut dysplasia and sensitizes the gut to external stressors.

ISCs maintain integrity of the gut by proliferating and differentiating via a process dependent on Notch, which induces differentiation by activating the well-studied kinase, target of rapamycin (TOR) (Kapuria et al., 2012). This process involves individual ISCs undergoing asymmetric cell division to produce a new ISC and an enteroblast, the latter of which can then differentiate into an enterocyte (90% of the time) or an enteroendocrine cell (Zeng et al., 2011). The authors wanted to see if Notch signaling can regulate this process in the absence of UVRAG.They report that despite the presence of Notch activity in UVRAG-deficient cells, there is a significant lack of differentiation and active TOR. Interestingly, Uvrag silencing resulted in larger and selective impairment of enteroblast differentiation into enterocytes (but not into enteroendocrine cells).

Based on a previous finding showing that JAK/STAT regulates ISC proliferation in Drosophila (Jiang et al., 2009), the authors sought to determine the activity of key proliferation/differentiation signaling pathways in UVRAG-deficient intestines. They found that while AKT and Ras-MAPK pathways were not involved, JNK activity was misregulated in UVRAG-deficient ISCs. Subsequent knockdown of the JNK homolog Basket or STAT homolog Stat92E suppressed the hyperproliferation seen in UVRAG-deficient ISCs.

The authors then looked at how Notch signaling, which has been implicated in regulating ISC differentiation (Micchelli and Perrimon, 2006),  is affected by Uvrag silencing. Silencing of both Uvrag and Notch suppressed ISC differentiation, while Notch overexpression rescued the impaired differentiation phenotype induced by Uvrag silencing. To address the question of whether or not the effects of Uvrag silencing are a consequence of autophagic defects in ISCs, the authors measured levels of the trafficked nucleoporin p62 homolog Ref(2)P. No differences in the endogenous levels of Ref(2)P in UVRAG-deficient and wild-type ISCs were detected, suggesting that autophagy is not impaired in ISCs in the absence of UVRAG.

In perhaps the most revealing experiment presented in the paper, the authors expressed a dominant-negative form of the dynamin homolog (shibire) and silenced Rab7 using RNAi (both in ISCs) to inhibit early and late endocytosis, respectively. Expression of dominant-negative shibire was lethal in young flies; however, silencing of Rab7 induced gut dysplasia in a manner that mimicked Uvrag silencing. This exciting result provides compelling evidence that intestinal dysplasia induced by knocking out Uvrag expression is a result of impaired endocytic trafficking.

The goal of this study was to learn more about the pathogenic role of loss-of-function mutation of UVRAG often observed in human colorectal cancer. The authors determined that deregulation of endocytic trafficking in ISCs, driven by loss of UVRAG, leads to intestinal dysplasia in Drosophila. Given that intestinal dysplasia is a common precancerous lesion in the human gastrointestinal tract, this finding provides important insight into the potential role of UVRAG in colorectal cancer.

References

Bento, C. F., Renna, M., Ghislat, G., Puri, C., Ashkenazi, A., Vicinanza, M., Menzies, F. M. and Rubinsztein, D. C. (2016). Mammalian Autophagy: How Does It Work? Annu. Rev. Biochem. 85, annurev–biochem–060815–014556.

Biteau, B., Karpac, J., Supoyo, S., DeGennaro, M., Lehmann, R. and Jasper, H. (2010). Lifespan extension by preserving proliferative homeostasis in Drosophila. PLoS Genet. 6, 1–15.

Ionov, Y., Nowak, N., Perucho, M., Markowitz, S. and Cowell, J. K. (2004). Manipulation of nonsense mediated decay identifies gene mutations in colon cancer Cells with microsatellite instability. Oncogene 23, 639–645.

Jiang, H., Patel, P. H., Kohlmaier, A., Grenley, M. O., McEwen, D. G. and Edgar, B. A. (2009). Cytokine/Jak/Stat Signaling Mediates Regeneration and Homeostasis in the Drosophila Midgut. Cell 137, 1343–1355.

Kapuria, S., Karpac, J., Biteau, B., Hwangbo, D. and Jasper, H. (2012). Notch-Mediated Suppression of TSC2 Expression Regulates Cell Differentiation in the Drosophila Intestinal Stem Cell Lineage. PLoS Genet. 8, 1–14.

Knævelsrud, H., Ahlquist, T., Merok, M. A., Nesbakken, A., Stenmark, H., Lothe, R. A. and Simonsen, A. (2010). UVRAG mutations associated with microsatellite unstable colon cancer do not affect autophagy. Autophagy 6, 863–870.

Li, H. and Jasper, H. (2016). Gastrointestinal stem cells in health and disease: from flies to humans. Dis. Model. Mech. 9: 487-499

Liang, C., Feng, P., Ku, B., Dotan, I., Canaani, D., Oh, B.-H. and Jung, J. U. (2006). Autophagic and tumour suppressor activity of a novel Beclin1-binding protein UVRAG. Nat. Cell Biol. 8, 688–99.

Marisa, L., de Reyniès, A., Duval, A., Selves, J., Gaub, M. P., Vescovo, L., Etienne-Grimaldi, M. C., Schiappa, R., Guenot, D., Ayadi, M., et al. (2013). Gene Expression Classification of Colon Cancer into Molecular Subtypes: Characterization, Validation, and Prognostic Value. PLoS Med. 10, 1-13.

Mavaddat, N., Peock, S., Frost, D., Ellis, S., Platte, R., Fineberg, E., Evans, D. G., Izatt, L., Eeles, R. A., Adlard, J., et al. (2013). Cancer risks for BRCA1 and BRCA2 mutation carriers: Results from prospective analysis of EMBRACE. J. Natl. Cancer Inst. 105, 812–822.

Micchelli, C. a and Perrimon, N. (2006). Evidence that stem cells reside in the adult Drosophila midgut epithelium. Nature 439, 475–9.

Nagy, P., Kovacs, L., Sandor, G. O. and Juhasz, G. (2016).  Stem cell-specific endocytic degradation defects lead to intestinal dysplasia in Drosophila. Dis. Model. Mech. 9: 501-512

Zeng, X., Chauhan, C. and Hou, S. X. (2011). Characterization of Midgut Stem Cell– and Enteroblast-Specific Gal4 Lines in Drosophila. 48, 607–611.

Zhao, Z., Oh, S., Li, D., Ni, D., Pirooz, S. D., Lee, J. H., Yang, S., Lee, J. Y., Ghozalli, I., Costanzo, V., et al. (2012). A Dual Role for UVRAG in Maintaining Chromosomal Stability Independent of Autophagy. Dev. Cell 22, 1001–1016.

(2 votes)

Loading...