BBSRC funded postdoc position in the laboratory of Natalia Sanchez-Soriano (https://sanchezlab.wordpress.com), to study the cell biology of neuronal ageing and the underlying mechanisms. The aim of the project is to understand the harmful changes that neurons undergo at the subcellular level during ageing, and unravel the cascade of events that cause them, with a focus on intracellular degradation systems and the upstream regulatory pathways. Ideally applicants should be trained in neuro- and/or in vivo cell biology, and imaging, and have experience with Drosophila.
The post is available from 1st of September 2018 until 31st of August 2021.
For full details and to apply online, please visit: https://recruit.liverpool.ac.uk
Job Ref: 009401, closing Date: 28 June 2018.
The Maehr lab (http://maehrlab.net/) is looking for a team member in the area of developmental immunology and human pluripotent stem cell-based disease models.
Envisioned projects will utilize pluripotent stem cell differentiation approaches, together with assays of thymus and T cell development, to decipher the molecular underpinnings of human immune syndromes such as thymus dysfunction-based autoimmunity and immunodeficiency. In addition to stem cell differentiation and immunological assays, the team will apply technologies such as functional genomins (e.g. CRIPSR) and single cell RNA-sequencing as well as computational approaches.
Candidates should possess a Ph.D. and have a strong background in immunology and/or developmental biology. Experience with immunological assays, stem cell differentiation, bioengineering and/or next generation sequencing assays is desirable. Excellent communication, writing, and collaboration skills are essential.
Interested candidates should email a cover letter, CV, and 3 references to Dr. René Maehr, Associate Professor of Molecular Medicine, UMass Medical School (rene.maehr@umassmed.edu).
An emerging trend in developmental biology focuses on the role of cell adhesion in modulating tissue morphogenesis. Spectacular advances have shed light on how modulation of adhesion between equivalent cells orchestrates the acquisition of forms. However, how interactions at complex interfaces between distinct neighboring cell types influence tissue growth remains to be elucidated. In a recent paper, staring mostly at a flat muscle that spreads subcutaneously and its partner motor neurons, I investigated how neuromuscular morphogenesis involves complementary activities of the Fat1 Cadherin in three interdependent cell types – myogenic cells, motor neurons, and the connective tissue through which muscles spreads.
The story started as I was transitioning from being a post-doc in the lab of Rüdiger Klein in Munich, to establishing my own group in Marseilles. At the time, I was interested in events of communication between motor neuron (MN) populations, whereby a pool of MNs influences the specification of neighbor MNs. I was looking for molecules mediating such function, and Fat1 originally came up as one of my candidate genes. Although Fat1 met many of my criteria, it was initially considered a low priority candidate for the specific question I was asking (which I won’t discuss here). However, there were also good reasons for deciding to work on Fat1, aside from the main project of my freshly established lab: (1) Fat1 was expressed in my favorite MN population (Figure 1), a group of neurons recognizable by the transcription factor they expressed, which innervates a fascinating muscle, the Cutaneous Maximus (CM), (2) there were mouse mutants available (which by chance happened to be already in my former lab), and (3) through pioneer experiments with these mutants, I had gathered preliminary data indicating that Fat1 disruption resulted in defective specification of the CM motor pool and in defective axonal arborization within the target muscle – the phenotype I was expecting.
Whatever the underlying gene function, starting a project with a robust in vivo phenotype guaranteed that an interesting story would emerge from it, even though this was not my main project. For this reason, I kept this as my own side project. I had no hypothesis, but it felt like starting a classical forward genetics approach, with the advantage that I already knew the gene identity. This is also when the field of planar cell polarity (PCP) started blooming, mostly through work in Drosophila. The Drosophila Fat Cadherin, initially regarded as a putative tumor suppressor, had been attributed the mysterious function of propagating information on cell polarity within the plane of epithelia across long distances. I was fascinated by these studies, and curious to ask if MNs could propagate some polarity information to their neighbors too. Well, the story took a completely different path!
The two first key results that I had obtained were that 1) axons of the motor neuron pool innervating my favorite muscle, the CM, were clearly shorter in Fat1-deficient embryos, when all other nerves appeared unaffected; and 2) expression of one of the markers specifically characterizing this MN population was drastically reduced. Given the fact that at that time, I had selected Fat1 because of its selective expression in subsets of MNs encompassing the CM-innervating pool (marked by Etv4 expression, Figure 1B), these data were compatible with the simplistic and straight forward hypothesis of a cell autonomous activity of Fat1 in MNs. Thus, it looked as if this project would be devoted to finding out whether specification or axonal growth was affected first, and to tackle the mechanism, keeping PCP principles in mind, possibly using a combination of genetics, in vitro, and in vitro approaches.
Figure 1: (A) Scheme representing the cervical spinal cord and the spinal nerves, which converge at the base of the limb, from which limb-innervating nerves emerge. The Etv4-expressing MN pool and its axons are highlighted in red. (B) Fat1 expression in the spinal cord (visualized using a Fat1LacZ allele or by in situ hybridization) highlights a pool of MNs expressing the transcription factor Etv4. Induction of Etv4 expression is dependent on a peripheral signal, GDNF, secreted by the target muscle of this motor pool, the Cutaneous Maximus muscle. Peripheral Fat1LacZ expression is also detected within this muscle and in surrounding connective tissue. (A, B) appeared originally as Fig5A,C, whereas (C) appeared as Fig4A, B in Helmbacher 2018.
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Prior to jumping to the conclusion that Fat1 indeed controlled MN specification and axon patterning cell autonomously, it was essential to determine whether the target muscle, the CM, had developed normally in Fat1 deficient embryos. Any muscle defect might indeed represent a potential cause – or consequence – of these MN phenotypes, or might even indicate an independent phenotype. With my team, we therefore performed the experiment that changed the course of this story. We visualized muscle development by whole mount in situ hybridization to detect MyoD RNA in myogenic progenitors. To my surprise, this experiment turned out not to yield the anticipated negative result. Instead, Fat1-deficient embryos exhibited a series of very robust muscle defects affecting morphogenesis of subsets of muscles in the face and shoulder, phenotypes that we described in our PLoS Genetics paper in 2013 [1].
When we first saw these muscle phenotypes, there was no reason a priori to dissociate our findings on the altered development of a selective group of muscles and associated defects in the corresponding motor neuron population. However, as I was reflecting on the possible significance of these results in terms of health and biomedical implications, and as, in these early days, I was also in a phase of heavy grant writing, I wondered whether these phenotypes could possibly correspond to symptoms of a rare human pathology that would not have been assigned yet any genetic culprit. I thus started exploring the human genome to see where the human FAT1 gene was located, and discovered the OMIM database (Online Mendelian Inheritance in Man). It didn’t take long to realize that the 4q35 region where FAT1 was localized was also known for being subject to chromosomal abnormalities associated with a human muscular dystrophy called Facioscapulohumeral dystrophy (FSHD) [2]. I was really amazed to learn that the muscle wasting symptoms in this disease affected a highly regionalized group of muscles, with a topography reminiscent of what we had seen in Fat1-deficient embryos. I was also intrigued by the fact that additional non-muscular symptoms of this disease, auditory and vascular retinal abnormalities, were emerging as hallmarks of defective planar cell polarity.
At that time, this was a completely unexpected finding. First, the FAT1 gene was relatively far from the true FSHD locus (where changes in the D4Z4 macrosatellite repeat array were considered to be the primary event linked to FSHD). This distance (~3Mb) was sufficiently large to guarantee unambiguous genetic mapping of a disease locus, but was small enough for a genetic linkage, and for FAT1 regulation to be affected secondarily to chromatin architecture changes occurring as a result of the FSHD abnormalities (although the concept of topologically associated domains (TADs) was not as popular then as it has become). Even though a possible deregulation/contribution of neighboring genes had been considered, FAT1 had largely been ignored or dismissed. Nothing in the literature at that time indicated any likely involvement of Fat1 in muscle biology, whereas Fat1 disruption in mice had instead been reported to result in severe kidney abnormalities [3], the latter not being part of the panoply of FSHD symptoms.
This is when I decided to radically change the topic of the lab. I therefore sought to identify potential collaborators who would help approaching the human disease link. I was lucky to turn to Nicolas Levy, who headed a department of medical genetics at La Timone Hospital in Marseilles, and was really enthusiastic about this new idea. With his help, we were later joined by Marc Bartoli, who started a group on translational myology in Marseilles, and by Julie Dumonceaux (now at UCL, London). To make a long story short, this fruitful collaboration has led to date to 3 papers exploring the possible link between FAT1 dysfunction and FSHD [1, 4, 5]. First, my team provided compelling data indicating that disrupting Fat1 in mice caused muscular and non-muscular phenotypes with an FSHD-like topography [1]. Second, we detected lowered FAT1 RNA and protein levels in affected muscles from FSHD patients with classical diagnosis, at fetal [1] and adult [5] stages. Third, we identified FSHD-like patients carrying pathogenic FAT1 variants, in absence of the traditional FSHD-causal abnormalities [1, 4]. These FAT1 variants included single nucleotide variants affecting RNA splicing or amino-acid structure [4], but also copy number variants deleting a putative cis-regulatory element in the FAT1 locus [1]. Such deletions had the potential to cause tissue-specific depletion of FAT1 expression, thus offering a logical explanation for why some phenotypes resulting from Fat1 deficiency in mice were not part of the clinical picture of FSHD symptoms in human patients.
Because the FAT1/FSHD link was so unanticipated and provocative, the road to our first publication turned into a long and emotionally agitated roller coaster ride. As a result, this paper was submitted multiple times, and went through several rounds of revisions for several journals, until it proudly landed in PLoS Genetics in 2013 [1]. As in the meantime we had produced mice with a conditional Fat1 allele, we were able to show in this first study that Fat1 deletion in the myogenic lineage reproduced in part the aberrant dispersion of myogenic cells in the limb observed in constitutive knockouts [1]. I already knew however that this only gave a partial account of the complexity of Fat1 functions. I just figured that it was unnecessarily challenging to simultaneously report the identification of a potential new genetic actor in a human pathology (even when only considered a modifier gene) and the complexity of its biology. This deserved to be studied as a developmental question per se, independently of its relevance for this disease, which somehow is still a controversial issue, despite our genetic evidence obtained with the Levy/Bartoli groups.
To approach the complexity of the Fat1-driven control of neuromuscular morphogenetic, the new study I have just published [6] gives a central position to one emblematic couple: the Cutaneous Maximus (CM) muscle, and its cognate MN pool. This MN pool can be recognized through its expression of the transcription factor Etv4, which is essential to specify the cell body position and dendritic architecture of these MNs [7]. The CM muscle emerges from the bulk of forelimb levels myogenic progenitors that undergo long range migration. Unlike other limb muscles, the CM muscle progenitors avoid entering the limb bud. Instead, they undergo a sharp caudal turn and start their subcutaneous progression. Throughout this migration phase, CM progenitors secrete Glial-cell-derived-neurotrophic-factor (GDNF), previously known for its neurotrophic activity and for its roles in motor axon guidance and in CM motor pool specification (as it induces Etv4 expression) [8]. Thus, by way of GDNF production, there is an intimate link between muscle progression and partner MN development. Among the muscles vulnerable to Fat1 deficiency, the CM muscle was also the easiest to approach quantitatively, by measuring the orientation of individual progenitor cells in our first study [1], and with simple area measurements in the new study [6]. Such an analysis illustrates how Fat1 disruption robustly interferes with expansion of the area occupied by Gdnf-expressing myogenic progenitors, by differentiating muscle fibers (Figure 2), as well as by axons of the cognate MNs.
Figure 2: Fat1 disruption robustly alters the subcutaneous expansion of the CM muscle. (A, B) Developing muscles are visualized at two successive stages (~E12.5) in control and Fat1-/- embryos owing to a transgene expressing a nuclear LacZ reporter (Mlc3f-2E) in differentiating muscle cells (driven by regulatory regions of the sarcomeric gene Mlc3f). Top images show the whole left flank of the embryo, whereas bottom images show higher magnifications of the area in the squared box, featuring the CM muscle. The area delineated with yellow, red, and white dotted lines represent respectively the area occupied by body wall (BW) muscles, by differentiated CM muscle fibers, and by CM myogenic progenitors (indicative). (C) Plots representing: (Left plot) the evolution of the CM area (red lines) with respect to the BW area; and (right plot) the ratio CM/BW normalized to the median control ratio, for each embryo (controls, blue dots; Fat1-/-, red dots). (A-C) appeared originally as Fig1A-C in Helmbacher 2018.
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Given my initial selection of Fat1 for its expression in the pool of MNs innervating the CM muscle, this was a region of non-myogenic Fat1 expression of obvious relevance to the phenotype. I was really excited by the possibility that Fat1 expression in the CM pool of MNs might represent a key driver of CM subcutaneous morphogenesis. Quantifications of morphometric parameters confirmed that MN-specific Fat1 ablation interfered with axonal growth and specification of the CM-innervating MNs. In addition, this also non-autonomously slows the subcutaneous progression of CM myogenic progenitors, hence expansion of the GDNF producing domain, without altering the rate of myogenic differentiation. However, this role turned out to be way more modest than what I initially anticipated, with an effect size considerably smaller than the phenotypes of constitutive mutants. This implied that another site of Fat1 activity had to be making a major contribution to neuromuscular morphogenesis.
An unanticipated third site of Fat1 expression that turned out to play a major role is the loose connective tissue (CT) that surrounds muscles. During their collective progression, myogenic progenitors and motor axons explore such connective tissues and select their migration trajectory. The CM progenitors in particular encounter an increasing gradient of Fat1 expression in this tissue. Furthermore, Fat1 expression appears fully preserved in mouse mutants lacking migratory muscles (Met or Pax3 mutants, in which myoblast migration is abrogated), indicating that the main site of peripheral Fat1 expression represented non-myogenic cells. To establish the contribution of CT-Fat1 to muscle morphogenesis, Fat1 activity was ablated in the lateral plate derived mesenchyme, in a domain (driven by Prx1-cre) including the limb and flank connective tissues encompassing a large part of the territory through which the CM migrates. This led to severe non-cell autonomous disruption not only of the progression of CM progenitors and subsequent myofiber elongation, but also of motor axon elongation across the same territory, and of acquisition of CM fate characteristics. Similar results were obtained with a Cre line allowing stage-controlled Tamoxifen-inducible Fat1 excision in Pdgfrα-expressing connective tissue at the time of myoblast migration, with a lesser effect size matching the lower excision efficiency. These data identify connective tissue as a tissue type in which Fat1 activity is mandatory for neuromuscular morphogenesis. They imply that Fat1 signaling activity in CT cells is necessary for them to emit proper signals promoting collective myoblast migration, myogenic differentiation, motor axon growth, and MN specification, with the exact mechanisms underlying these cell interactions remaining to be explored.
Figure 3: Fat1 ablation in the mesenchyme is sufficient to robustly delay the subcutaneous expansion of CM progenitors. (A) Myogenic progenitors of the CM muscle are visualized owing to a GdnfLacZ allele (by Salmon Gal staining) in control and Prx1-cre; Fat1Flox/Flox embryos, at E12.5. (B) Plots representing: (left plot) the evolution of the area covered by CM progenitors relative to the trunk length of control and Prx1-cre; Fat1Flox/Flox embryos, and (right plot) the CM/TL ratio normalized to controls, for each embryo (controls, blue dots; Prx1-cre; Fat1Flox/Flox, red dots). (C) Scheme explaining how the domain of Prx1-cre activity (in mesenchymal cells), in which Fat1 activity is deleted, is visualized owing to the cre-dependent R26-YFP reporter (green), in relation to the domain of GdnfLacZ expression (red, in CM progenitors). (D) The relative thickness of the CM is visualized on embryo sections by immunohistochemistry with anti-beta-galactosidase and anti-YFP antibodies, in control, Prx1-cre; R26YFP/+; GdnfLacZ/+ and Fat1Flox/Flox; Prx1-cre; R26YFP/+; GdnfLacZ/+ embryos. (A, B) appeared originally as Fig7C,D, whereas (C,D,E) appeared as part of Fig8 in Helmbacher 2018.
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In conclusion, looking back on how the story started, the loop has been closed by the identification of gene functions that underlie the phenotype which initially attracted my attention. Although my intuition that this had to be connected to the neuronal expression of this atypical Cadherin was not completely wrong after all, conditional mutagenesis nevertheless revealed that this function was modest in regard of the unexpected predominant activity in a cell type – connective tissue – that I had initially not considered. I have learned many lessons along the way of this unusual story. Above all, I learned not to fall in love with a favorite hypothesis but instead to be open to what the facts tell us: when the results of an experiment are the opposite of what you expect, this pushes you to think outside the box, and challenges you to remain unbiased in conceiving experimental plans and analyzing data. It is now time to switch scale, and start exploring what happens at the connective tissue muscle interface from a cell biologist’s point of view.
We recently published a manuscript in Cell that describes a method to image transcription factor concentration dynamics in real time, in living embryos, using a nanobody-based protein tag that we call the “LlamaTag.” We were particularly excited about these investigations because this new technology overcomes a major technical obstacle to understanding how gene-expression dynamics are regulated in development, which has held back the field for decades.
From Snapshots of Dead Embryos to Movies
Remember when you were first starting to study developmental biology? In one of your lab sections, you probably participated in that classic teaching activity where you watched the cephalic furrow form in Drosophila embryos. Maybe you were one of those students struggling to move embryos with an eyelash glued to a toothpick, and the whole time you were thinking, “I need to hurry up—this thing is gastrulating while I’m messing around here!” There’s a strong contrast between watching development unfold before your eyes and scrutinizing snapshots of FISH data from dead, fixed embryos. This contrast hinders more than budding scientific excitement: how can we truly understand dynamic processes by analyzing static data?
I was particularly struck by this conundrum as a postdoctoral researcher as my mind kept replaying a video of a gastrulating embryo. How could I bridge this gap so that developmental biologists could accurately model—and ultimately construct—dynamic systems as complex as embryos? At the simplest level, we would need to know the input and the output of each genetic circuit as it changes throughout development in order to deduce the logic gates at play. I tackled the output end first: as a postdoc, I developed a technique to quantify transcription in flies at the single-cell level by tagging a gene’s nascent mRNA molecules with fluorescent proteins. How could we accomplish the same feat with the DNA-protein interactions that constitute the input to these genetic circuits? I decided that solving this challenge would be a major driver of the research in my own lab. Jacques Bothmawas equally excited about this challenge and decided to join the project as a postdoctoral fellow.
Typically, one would quantify the concentration of a transcription factor by fusing it to a fluorescent protein. However, in flies, worms, fish, and frogs, these fluorescent take more than 40 minutes before they mature and become fluorescent. This delay is actually a major problem: the activators and repressors that drive development often exist for less than 10 minutes before they are degraded. By the time the fluorescent proteins actually became fluorescent, the action they were supposed to report on is already over!
Jacques had a great idea: instead of relying on the synthesis of fluorescent proteins, why not use the localization of already matured fluorescent proteins to report gene expression? Our Cell paper describes the engineering and implementation of this idea with LlamaTags, a technology that enables quantitation of the dynamics of transcription-factor activity without limits from the slow maturation of traditional fluorescent fusion proteins. Instead of these fusions, we employed nanobodies, which are small, highly specific, single-domain antibodies that are raised in llamas (hence LlamaTags). We fused a transcription factor of interest (we started with Hunchback) to a nanobody raised against eGFP, and expressed the construct from the endogenous locus for that transcription factor. Importantly, the embryo was engineered to contain maternally deposited eGFP, which means that eGFP is already mature before the transcription factor of interest is expressed (no waiting around for the fusion to mature!). When the transcription factor-nanobody is translated, it binds cytoplasmic eGFP within seconds, yielding a quantitative increase in nuclear fluorescence when the transcription factor moves to the nucleus to perform its regulatory function. LlamaTags therefore deliver a direct readout of the instantaneous transcription-factor concentration in a given nucleus.
Through a variety of experiments, we showed that LlamaTags serve as specific and faithful reporters of the endogenous concentration dynamics of transcription factors during development, thus capturing the input pertinent to these circuits. So, we finally had the two pieces needed to solve the puzzle of measuring input-output functions. LlamaTags made it possible to measure the input concentration of transcription factors in individual nuclei, while MS2 revealed the transcriptional activity of specific genes to these input levels.
By fusing a LlamaTag to Fushi-Tarazu (Ftz), we obtained measurements of its nuclear concentration during development, from which we extracted the in vivo degradation rate of the construct. We were pleased when our data revealed rapid fluctuations in Ftz concentration—consistent with previous reports of protein bursts that likely arise from stochastic fluctuations in mRNA concentrations. We nailed down this relationship, and uncovered exciting evidence of inter-nuclear communication within the embryo. This coupling could be a major driver of the sharp boundaries that dictate development of the fly embryo. However, our greatest satisfaction came from simultaneously visualizing input transcription-factor activity and output transcription, at the single-cell level, in real time, as stripe 2 of eve was laid down in live embryos:
Spatiotemporal evolution of the Kr protein expression pattern (green) and eve stripe 2 mRNA expression pattern (red puncta) during the course of nc14. Video S6 in the paper
A New “Microscope” for the Central Dogma in Development
Our recent work establishes a powerful pair of technologies—labeling transcription with MS2and labeling DNA-protein interactions with LlamaTags—that together constitute a “microscope” for visualizing and interrogating the activity of genetic circuits as they function. We envision that LlamaTags can be applied to quantitatively measure the flow of information along regulatory networks in any multicellular organism that is amenable to transgenic control and live imaging. LlamaTags literally light up the central dogma, in real time, as development unfolds. Importantly, we can do more than map input to output: we can quantitate the dynamics of these connections over time. That’s the difference between trying to create a stop-motion movie where you need a new actor for each frame (a dead embryo), and actually observing development unfold in real time.
Physical Biology of Living Embryos
Like many of you, we believe that in order to construct a system, we should first understand it in quantitative detail. We view this as a call for reaching a “predictive understanding” of development, through which we can calculate developmental outcomes from knowledge of the concentrations of input transcription factors and the DNA regulatory sequence. To reach this predictive understanding, we believe that a powerful dialogue is necessary in which theoretical models make predictions that are subsequently tested experimentally, with measurements fed forward into the model to generate a new cycle of experiments. Our work in Cell is a crucial early step toward enabling the biophysical dissection of developmental programs by making it possible to measure the very same input-output functions predicted by our theoretical models.
Applications are now open for this year’s Gene Regulatory Networks for Development which will be at The Marine Biological Laboratory in Woods Hole, USA from October 14- 27. The application deadline is July 20. The course is for graduate students, postdoctoral researchers, and faculty members and it focuses on using experimental data and computational modeling to analyze gene regulatory networks that are key to development in animals and plants.
This unique course is an intense and always interesting experience and has drawn rave reviews in all of its previous incarnations. Students will meet with experts in the field for an in-depth treatment of experimental and computational approaches to GRN science. Through lectures, highly interactive discussions, and group projects we will explore the GRN concept and how it can be applied to solve developmental mechanisms in various systems and contexts. Topics include structural and functional properties of networks, GRN evolution, cis-regulatory logic, experimental analysis of GRNs, examples of solved GRNs in a variety of developmental contexts, and the computational analysis of network behaviour by continuous and discrete modelling approaches.
Travel fellowships are available.
For more information about the course, go to www.mbl.edu
The 2018 GRN course faculty:
Scott Barolo, University of Michigan
James Briscoe, The Francis Crick Institute, London
Fernando Casares, Andalusian Center for Developmental Biology, Spain
Ken Cho, University of California, Irvine
Doug Erwin, Smithsonian Institution
Robb Krumlauf, Stowers Institute
Bill Longabaugh, Institute for Systems Biology, Seattle
The Karam Teixeira lab (https://karamteixeira.wixsite.com/website) at the University of Cambridge (Department of Genetics) is looking to recruit a Research Assistant to support a range of projects being carried out in our research group. We are primarily interested in germline development (stem cell regulation and genome defense mechanisms) and we use the Drosophila ovary as a model system (see Sanchez et al, Cell Stem Cell 2016; Teixeira et al., Nature 2017).
We are looking for enthusiastic and proactive candidates with expertise in standard molecular biology techniques (including genotyping, cloning, and RT-qPCR). Prior experience in fly genetics would be an advantage – although training can be provided where necessary. Candidates should have a B.Sc. or M.Sc. degree in a relevant biological subject and should possess good communication skills and the ability to work effectively as part of a team.
Qualifications: Applicants should possess a Ph.D. in a relevant field, such as Biology, Biochemistry, Genetics or another related discipline and be highly motivated, independent and organized. Successful applicants will have a record of communicating research results via publications and/or professional presentations, and be willing and able to participate in collaborative, interdisciplinary research projects. Experience in developmental biology, cell and molecular biology and avian/murine model systems is desirable. Preference will be given to applicants with a proven record in craniofacial research.
Please submit your application to Dr. Brugmann with the following information: A cover letter, a statement of research interests, and a CV with contact details for 3 referees.
Cincinnati Children’s Hospital Medical Center (CCHMC) is a premier pediatric research institution with over 900 diverse and productive faculty members. Here, researchers work collaboratively across specialties and divisions to address some of the biggest challenges we face today in improving child health. A strong network of research support services and facilities, along with institutional commitment to research, push our team of faculty, postdocs and support staff to explore the boundaries of what is possible, leading to significant breakthroughs. We are driven by our mission to improve child health and transform the delivery of care through fully integrated, globally recognized research, education and innovation.
For further information about working at CCHMC or living in Cincinnati, please contact the CCHMC Postdoc recruiter, Uma Sivaprasad, PhD, at research@cchmc.org
Applications are invited from highly motivated individuals dedicated to peruse a PhD and who are interested in nerve/tumour interactions and nervous system development.
PROJECT DESCRIPTION
During tumour progression nerves and tumours interact resulting in tumour cells using nerves as a metastatic route out of the organ, through a process called perineural invasion (PNI). While this is robustly documented at a histological level, the molecular mechanisms underling this, remain poorly understood. You will join an interdisciplinary collaborative team focusing on the signalling between nerves and tumours, leading to provocation of nerve plasticity (such as growth and remodelling) and tumour metastasis via nerves. You will engage a systematic strategy to identify these mechanisms by (i) examining how nerves form/grow/remodel and migrate normally during embryo development and (ii) pathologically in tumour models with an initial focus on pancreatic ductal adenocarcinoma (PDAC). The formal PhD qualification you will obtain is a PhD in medical science with a focus on cell biology.
LOCATION
The laboratory is located at IMB, Umeå University, Sweden. IMB is an interdisciplinary department, which focuses on questions in basic and medical sciences and provides an interactive modern environment with good core facilities within the wider university. The working ‘day to day’ language in the laboratory is English. The position is for 4 years and is fully funded.
Following our latest data release, the DMDD website (dmdd.org.uk) now contains detailed phenotype data for nearly 700 embryos from 82 different knockout mouse lines. Highlights include the identification of limb defects and cysts in Col4a2 knockouts and replication of the major features of Meckel syndrome in B9d2 knockouts.
We have begun to add immunohistochemistry image data for the brain and spinal cord of some embryos at E18.5. These images give further information about lines in which the embryos appeared morphologically normal at E14.5, but were still not viable. We have also added viability data for every line at both E9.5 and E14.5.
Together with the placental phenotype data that we hold for more than 100 knockout lines, the DMDD website is a rich resource for those investigating the effect of gene mutations on embryo development, and may provide clues about the genetic basis of rare diseases.
LIMB DEFECTS SEEN IN Col4a2 KNOCKOUTS
In humans, COL4A2 mutations have been linked to porencephaly, a rare disorder with phenotypes that include the development of intracranial cysts. In the latest DMDD data, Col4a2 knockouts have a variety of nervous system disorders in line with porencephaly. However, all four embryos also show abnormal autopod morphology and cysts between the nasal septum and the oral cavity, as well as other morphological defects.
A Col4a2 knockout embryo has a cyst between the nasal septum and oral cavity (left) and abnormal autopod morphology (right). The individual fingers don’t diverge distally and can’t be discerned from an external view.
B9d2 KNOCKOUTS MODEL MECKEL SYNDROME
In humans, mutations of the gene B9D2 have been linked to Meckel syndrome, a severe disorder caused by dysfunction of the primary cilia during the early stages of embryogenesis. Meckel syndrome is characterised by multiple kidney cysts, occipital encephalocele (where a portion of the brain protrudes through an opening in the skull) and polydactyly, but it also commonly affects the brain and spinal cord, eyes, heart, lungs and bones.
B9d2 knockout mouse embryos included in our latest data release show the major features of Meckel syndrome, including polydactyly and defects in the brain, peripheral nervous system, heart and vascular system. They also display situs defects, where the left-right asymmetry of the body did not develop as expected. The image below shows a B9d2 knockout embryo with left pulmonary isomerism and symmetric branching of the principle bronchi from the trachea.
A B9d2 embryo showing situs defects (left). A magnified view (right) shows that both lungs have developed with a single-lobe structure. In mice the left lung usually has one lobe, while the right lung has four. In addition, the principle bronchi (red arrows) have branched symmetrically from the trachea. This branching would normally have a distinct asymmetry.
NEURAL IMAGE DATA NOW AVAILABLE
In around 20% of embryonic lethal lines, embryos appear morphologically normal at E14.5 but still go on to die before or shortly after birth. To understand more about why these embryos were not viable, DMDD colleagues Professor Corinne Houart and Dr Ihssane Bouybayoune at Kings College London analysed the lines at E18.5 – when embryo development is almost complete. They used immunohistochemistry to identify abnormalities in the brain and spinal cord that could not be picked up in our standard, whole-embryo morphological analyses. This data is now available for the line Trappc9, and additional lines will be added in future data releases.
Immunohistochemistry analysis of the brains of two Trappc9 knockout mice. The calretinin (green) + neurofilament (red) combined stain highlights interneurons and axons, while Hoechst (blue) is a nuclear stain.
Neural images are available as 20-micron sections through the brain and spinal cord, and the images from different embryos can be compared side by side using the stack viewer. A separate Nissl stain was used to highlight neural death and these images can also be explored online.
Development is pleased to welcome submissions for an upcoming special issue on ‘Development at the single cell level’. This special issue aims to showcase the best research in stem cell and developmental biology, building on the rapidly evolving tools of single cell analysis. The issue will be guest-edited by Allon Klein and Barbara Treutlein, working alongside our team of academic editors.
Embryonic development and stem cell differentiation are inherently multicellular phenomena, and every cell can have an important story to tell. The analysis of developmental and stem cell biology at single cell resolution has a long and distinguished history, for example in tracing the lineage of tissues, defining concepts such as commitment, and revealing the existence of adult stem cells. More recently, innovations in single cell transcriptomic, genomic, live imaging and quantitative approaches have opened up new questions about the nature of developmental and stem cell hierarchies, the repertoire of differentiating cell types in tissues and the functional and mechanistic basis of cell types. These new analytical tools are rapidly evolving. They include not just descriptive methods but also fate-tracing and perturbative approaches. They hold promise not just in providing a deeper understanding of cell fate specification and commitment in a native context, but also for understanding and controlling differentiation, de-differentiation and trans-differentiation in vitro and in disease contexts.
Development is the natural home for papers applying single cell analytical and perturbative methods to gain insights into developmental biology and stem cells. We invite you to showcase your breakthrough research that has either been driven by the creative application of single cell approaches; or has created a novel single cell methodology for developmental and stem cell systems.
We also welcome proposals for review-type articles for this special issue. Please send us a short synopsis detailing the scope and structure of the proposed article, and including key references. The deadline for submission of proposals is August 15th and reviews must be submitted by October 31st.
The issue will be published in mid-2019 (note that, in our new ‘continuous publication‘ model, we will be able to publish your article as soon as it is accepted; you will not have to wait for the rest of the issue to be ready) and the deadline for submission of articles is October 31st*. This special issue will be widely promoted online and at key global conferences – guaranteeing maximum exposure for your work. Please refer to our author guidelines for information on preparing your manuscript for Development, and submit via our online submission system. Please highlight in your cover letter that the submission is to be considered for this special issue. Prospective authors are welcome to send presubmission enquiries, or direct any queries, to dev.specialissue@biologists.com
*Please note that not all articles accepted for publication will be included in the special issue; they may instead by published in earlier or later issues of the journal.
Why choose Development?
Submissions handled by expert academic Editors
Competitive decision speeds and rapid publication
Format-free submission
Strong commitment at first decision – over 95% of invited revisions accepted
Free to publish – no page or colour charges, no hidden fees