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2012 Seminars

Special Christmas CABD Seminar December 19 @ 12:30 pm

Dr. Óscar Marín
Instituto de Neurociencias de Alicante, Spain
CABD Seminar November 30 @ 12:30 pm
From eye field to optic vesicle: morphogenetic mechanisms involved in vertebrate eye formation
Dr. Florencia Cavodeassi
CBMSO, Madrid

Summary: During neural tube morphogenesis, the primordium of the eyes, the eye field, evaginates from the lateral walls of the forebrain to give rise to the optic vesicles. This morphogenetic transformation is unique to the eye field, since cells in surrounding neural tissues converge towards the midline to form the neural tube, while eye field cells move away from the midline to form the optic vesicles. The current model for eye field morphogenesis in teleosts proposes that eye field cells actively migrate during evagination. Indeed, eye field cells bear characteristics of highly motile cells, although it is unclear whether they migrate as individual cells or coordinated as a group. I will present here recent work in which we use high-resolution 4D confocal imaging to analyse some of the key cellular events and behaviours that underlie optic vesicle evagination in zebrafish. Our results not only describe the changes in cell shape, polarity and organisation that accompany optic vesicle evagination with a high level of resolution, but also provide us with exciting insights into the understanding of the driving forces promoting the evagination of an embryonic tissue.
CABD Seminar November 23 @ noon
Lipoproteins and signaling lipids in the Hedgehog pathway
Dr. Suzanne Eaton
Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany

Summary: Hedgehog proteins, critical regulators of tissue development and homeostasis, are covalently modified by lipids and can be released from cells in association with lipoproteins. Hh signals through its receptor, Patched, which is thought to modulate the availability of small lipophilic inhibitors of Smoothened, a 7-pass transmembrane protein. Lipoproteins are important in vivo sources of Hh signaling inhibitors, in both mammals and Drosophila. Lipoprotein associated forms of Hedgehog prevent utilization of lipoproteins for Smoothened repression. I will present our work on the purification and identification lipoprotein-derived signaling lipids that repress the Hedgehog pathway.
CABD Seminar November 16 @ noon
Molecular abnormalities of chaperones and their pathogenic potential
Dr Alberto Macario
Department of Microbiology and Immunology, School of Medicine, University of Maryland at Baltimore, and IEMET, Columbus Center, Baltimore, MD, USA; and Istituto Euro-Mediterraneo di Scienza e Tecnologia (IEMEST), Palermo, Italy

Summary: The chaperonopathies are diseases associated with abnormalities in molecular chaperones. These pathological conditions, many of which have been known for years, have been grouped in a coherent nosological group only recently. They are varied and widespread and constitute a new, large, field of Medicine that intersects various organ systems. Typically, the basis of a chaperonopathy is a structural abnormality of the chaperone molecule, affecting one of its functional domains. The abnormality can be genetic (e.g., mutation) or acquired (e.g., post-translational modification) and can manifest itself in the loss or decrease, or in gain of a function of the chaperone. In addition, other chaperonopathies are characterized by quantitative changes, e.g., increase or decrease in concentration, which may or may not be associated with qualitative changes due to structural alterations. The quantitative chaperonopathies may be due to dysregulation of the affected chaperone gene or of a regulatory gene. In any case, the result is a quantitative abnormality of the chaperone protein. While any given chaperonopathy affects predominantly one system, e.g., the central nervous system, there are chaperonopathies for any system, one might say. Thus diseases of the brain, peripheral nerves, muscle, heart, blood vessels, airways, digestive tract, bones and joints, etc. may be associated with chaperone abnormality. Chaperones display what have been called canonical or typical functions, all connected with maintenance of protein homeostasis, including polypeptide folding, refolding, translocation through membranes, assembly, prevention of aggregation, dissolution of aggregates, facilitation of degradation of damaged proteins by the ubiquitin-proteasome system, and participation in regulated autophagy. Beyond these, chaperones can play other roles unrelated to protein quality control, for instance as signals for the immune system. Because this is a new field of Medicine and very large, the presentation will consist of an overview of its scope and contents (i.e., the diseases that can be considered chaperonopathies) as a way of introduction, with only sporadic and brief descriptions of molecular, pathological, or clinical details.
CABD Seminar November 15 @ noon
Tissue-specific proteome remodeling by alternative splicing
Dr Manuel Irimia
Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Canada.

Summary: One of the most striking findings of the first high-throughput RNA sequencing analyses was that ~95% of human multiexonic genes undergo differential processing of their introns and exons by alternative splicing. However, despite the huge potential of this vastly expanded proteome complexity, little is yet known about how much of this molecular diversity is regulated in time and space, and, more importantly, to what extent alternative exons play important biological roles. Here, I will discuss recent efforts to answer these questions using large-scale analyses on transcriptomes and proteomes. Hundreds of exons are being found to be coregulated in different tissues and cell lines by specific splicing factors, particularly in neural and muscular tissues. In addition to several individual case examples of alternative splicing impacting protein domain function, we found that at least a third of neural-specific exons are involved in modulating protein-protein interactions. We have also described a network of exons that are differentially regulated in embryonic stem cells compared to differentiated tissues and cell lines, and found that at least half of these exons are negatively regulated by Muscleblind-like proteins (Mbnl), providing an extra regulatory layer for the control of pluripotency and differentiation. In summary, these studies show that regulated alternative splicing further contributes to establish cell type-specific proteomes during development and adulthood.
CABD Seminar November 9 @ 11 am
Deciphering the regulatory architecture of the mouse genome
Dr. Francois Spitz
Developmental Biology Unit EMBL Heidelberg

Summary: Vertebrate genomes are characterized by the substantial role of remote cis-regulatory elements, located hundreds of kilobases away from the genes they control. The dramatic consequences of some human genomic rearrangements suggest that the specific organization of the genome is not random, and that the mechanisms that control enhancer-promoter interactions depends tightly on a higher-order organization. To determine functionally the underlying regulatory architecture of the genome and identify elements and genomic parameters that could determine it, we have developed an in vivo approach, building on the controlled mobilization of a Sleeping Beauty transposon to distribute a regulatory sensor throughout the mouse genome (Ruf et al. Nature Genetics, 2011). The properties of Sleeping Beauty allows investigation of the whole genome, but also mapping of the fine-scale structure of loci of interests. The large collection of insertions we have generated not only highlight the unexpected complexity of the genome regulatory architecture, but also reveals some principles governing it. It also provides a very useful resource to model and understand the consequences of human structural variants found associated with pathological conditions.
CABD Seminar October 26 @ 11 am
Epigenome: a manual for genome function and utilization
Dr. Henk Stunnenberg
Dept. of Molecular Biology, NCMLS, Nijmegen, The Netherlands

Summary: Deciphering the human genome sequence has provided critical insight in genome function in relation to biological processes in health and diseases. Recent technological improvements have opened up the analysis of the epigenetic regulation of the information embedded in the genome. Epigenetic regulation takes place at many levels including histone modifications, positioning of histone variants, nucleosome remodeling and DNA accessibility. Together with DNA modifications, transcription factors and other DNA-binding proteins this information provides an epigenetic blueprint. The epigenetic features of each cell type in the body (>250) are distinct and once established during development and differentiation need to be maintained. Hence, the study of epigenetic processes go beyond DNA-stored information and provide essential insight in the manual of the genome, in deciphering derailed processes in disease.
CABD Seminar October 19 @ noon
Regulation and function of the Drosophila Iroquois complex genes
Dr Sonsoles Campuzano
CMBSO, Madrid

Summary:The Iroquois (Iro) homeodomain transcription factors (Irx in vertebrates) play several roles during normal development, ranging from territorial specification to pattern formation and cell fate specification. The different roles played by these genes, some of them evolutionarily conserved, correlate with their complex expression patterns that are controlled by position specific enhancers. We are characterizing the enhancers that drive expression in the imaginal discs and act as integrative devices for several signalling pathways. The three Drosophila Iroquois genes araucan, caupolican and mirror, are arranged in a complex, the Iroquois-complex. araucan and caupolican show similar pattern of expression while that of mirror is different in most of the tissues. This is most likely due to the expression of araucan and caupolican depending on the use of shared enhancers, unable to act on mirror promoter. We have identified a CTCF-associated insulator element that could contribute to the differential expression of ara/caup from that of mirr. Generation of a novel set of Iroquois-complex deficiencies has uncovered a role of the Iro genes in cell proliferation in the imaginal discs independent of their involvement in the generation of organising boundaries. Deregulation of the Iro-C genes affects passage through the G1 phase of the cell cycle. Unexpectedly for a transcription factor, Caupolican does not appear to control cell proliferation by transcriptional regulation of target genes but by binding to and inactivation of the Cyclin E/CDK2 complex. The association of loss-of-function of Irx genes with development of multiple types of cancer have classified them as putative tumour suppressor genes. This appears to be the case in Drosophila since we have found that reduction of the activity of any one of the Iro-C genes increased tumour growth in several established Drosophila tumour models while, conversely, over expression of caup resulted in decreased tumour size.
CABD Seminar October 5 @ noon
The mechanism of translational regulation during pattern formation in the Drosophila oocyte
Dr. Ilan Daviss
Department of Biochemistry, University of Oxford, UK

Summary: The primary embryonic axes in flies, frogs and fish are formed through translational regulation of localized transcripts before fertilization. In Drosophila, the primary body axes are established through the transport and translational regulation of gurken (grk), bicoid (bcd) and oskar (osk) messenger RNA (mRNA) in the oocyte and embryo. bcd and grk mRNA are both transported in a translationally silent state from the nurse cells into the oocyte and are subsequently localized within the oocyte through transport along microtubules by cytoplasmic Dynein. On the one hand, grk mRNA is translated in the dorso-anterior corner of the oocyte into a TGF-alpha signal that assigns dorsal identity to the overlying somatic follicle cells. On the other hand, bcd mRNA encodes a transcription factor that acts as a morphogen when it is first translated in the embryo. The mechanism that causes grk and bcd to be translated at distinct times was not known. In my talk I will focus on our recent work, in press, showing that the key regulatory step is the differential association of the two transcripts with EM dense bodies known as processing bodies (P bodies) containing translational repressors and lacking ribosomes. We show that while grk mRNA becomes docked on the outside of P bodies and becomes translationally active, bcd mRNA enters the interior of the P bodies which are devoid of ribosomes. We also show that an excess of grk mRNA produced either from transgenes or by injection enters the interior of the P bodies, suggesting a mechanism for suppressing the translation of excess grk mRNA. We propose a general principle for regulation of translation of factors that specify embryonic axes involving differential association of localised transcripts with the translationally active exterior and translationally silent interior of P bodies. In the second part of my talk I will describe mostly unpublished work showing that at least some of the factors that bind the grk mRNA localisation signal in the oocyte, also play a role in localised translational regulation in the larval neuromuscular junction.
CABD Seminar September 24 @ noon
Chromatin insulators and nuclear organization
Dr. Victor G. Corces
Emory University, Atlanta, USA
CABD Seminar September 14 @ 12:30 pm
Hormonal coordination of developmentally-induced behaviors
Dr. Pierre Leópold
Institute of Biology Valrose (iBV), Nice, France

Summary:
Modeling the homeostatic control of feeding behavior in flies.
We are interested in identifying the molecular and neuro-anatomical characteristics of the pathways controlling feeding behavior in the Drosophila larva. The regulation of food intake is a highly controlled process where a quantitative and qualitative evaluation of the food is coordinated with internal nutrient stores in order to fulfill nutritional requirements. In addition, the rewarding value of a palatable food triggers a motivational control of feeding, which in some instances can override the nutritional needs [51]. One specific aspect of feeding behavior concerns the necessity to provide essential nutrients that cannot be synthesized or stored. Metazoans have lost the ability to synthesize all amino acids, and Essential Amino Acids (EAAs) need to be provided by the food. Earlier experiments have demonstrated that animals rapidly evaluate the lack of EAAs in the food and translate this evaluation into drastic changes in behavioral strategies [52]. Less than twenty minutes after being exposed to an EAA Deficiency (EAAD, one missing EAA in an otherwise complete food), rodents present a specific sequence of behaviors starting with developing an aversion towards the imbalanced diet. This aversion is followed by foraging for an alternative food source and finally developing adaptive long term responses like a learned aversion to EAA-deficient food as well as a memory for the taste, the smell and the place associated with non-deficient food [52]. The complexity of the vertebrate brain represents a considerable barrier to understanding the molecular mechanisms of such behavior and a possible alternative is to carry this analysis in a simpler, genetically tractable organism like the fruit fly Drosophila.

Hormonal coordination of developmentally-induced behaviors.
We have an interest in the function of a peptidic hormone called the Prothoracicotropic Hormone (PTTH). Previous work in other holometabolous insects has demonstrated that the PTTH is required for the activation of ecdysteroid biosynthesis at the end of larval development [15, 16]. Therefore, this hormone serves an important timer function for a major developmental transition marking the completion of larval growth period, entry into maturation, metamorphosis and transition to adulthood. PTTH is produced in two neurons in each lobes of the larval brain, which project axons towards the ecdysone-producing gland called the Prothoracic gland. PTTH acts through a conserver receptor tyrosine kinase called Torso, whose activation is required for the biosynthesis of ecdysteroids in this tissue. Nevertheless, an important gap in the mechanism is lacking, which is the process that leads to the induction of the PTTH gene at the end of larval development. This is crucial for the coordination between growth and developmental timing, since it is believed that in Drosophila, PTTH induction is the first step in the hormonal cascade leading to pupariation. We have started investigating the function of this hormone and in particular the mechanisms responsible for its developmental induction at the larval/pupal transition. In the course of this work we have discovered that the two pairs of neurons in the larval brain that express the PTTH gene are identical to two neurons called NP0394 neurons, recently described for the control of light preference. Drosophila larvae have a strong light avoidance behavior, which is believed to be abolished just before metamorphosis. It is also believed that this alleviation allows larvae to move out of the food and find a spot to pupariate. PTTH is one of the main players controlling developmental timing, but its connection with larval light response was unexpected. Our current work demonstrates that a hormonal system relying on PTTH coordinates light preference and the time of pupariation, and that the “where and when to pupariate” decisions rely on the same molecule, PTTH, acting on separate target organs. This work is carried out through an ongoing collaboration with the group of Michael O’Connor in Minneapolis. We are currently studying the role of PTTH/Torso signaling in controlling/enhancing light avoidance in the NP neurons. We also work on the elucidation of the complete light sensing circuitry that is controlled through the PTTH/Torso signal in the larval brain.
CABD Seminar September 7 @ noon
Genetic and epigenetic networks in intellectual disabilities.
Prof. Dr. Hans van Bokhoven
Department of Human Genetics, Molecular Neurogenetics Unit, Radboud University Nijmegen Medical Centre, Box 9101, 6500 HB Nijmegen, The Netherlands

Summary: Intellectual disabilities (ID) comprise a highly diverse group of cognitive disorders. Gene defects account for about half of all patients and mutations causative for impaired cognition have been identified in more than 400 genes. While there are numerous genetic defects underlying ID, a more limited number of pathways is emerging whose disruption appears to be shared by groups of ID genes. One of these common pathways is composed of ID genes that encode regulators of chromatin structure and of chromatin-mediated transcription regulation. Already more than 20 “epigenetic ID genes” have been identified and this number is likely to increase in the coming years. A prominent example is the EHMT1 gene, encoding euchromatin histone methyltransferase 1, which carries heterozygous mutations in 25% of patients with a recognizeable ID disorder, denoted Kleefstra syndrome (KS). We hypothesized that the remaining ‘‘EHMT1-negative’’ KS individuals have mutations in genes that share a biological function with EHMT1. Indeed, next generation sequencing in a cohort of such patients identified de novo mutations in four genes, MBD5, MLL3, SMARCB1, and NR1I3, all of which encode epigenetic regulators. Using Drosophila, we demonstrate that MBD5, MLL3, and NR1I3 cooperate with EHMT1, whereas SMARCB1 is known to directly interact with MLL3. Our results reveal a chromatin-modification module that underlies a recognizable form of ID. We propose a highly conserved epigenetic network that underlies cognition. Our current research aims to gain more insight into patterns of altered chromatin modifications that are caused by epigenetic gene mutations and how these will disrupt the brain-specific expression of target genes. In-depth knowledge about this network should allow the design of rational strategies to treat the growing group of ID pathologies that are caused by epigenetic defects.
CABD Seminar July 16 @ noon
Sex, flies and video tapes: how to get rid of a segment in Drosophila
Dr. Ernesto Sánchez-Herrero
CBMSO, Madrid

Summary: Many species display sexually dimorphic characters in specific regions of their body. In Drosophila melanogaster, a striking difference between males and females is the development of the seventh abdominal segment (A7), absent in males. In this talk I would present some efforts aiming to understand why the male A7 segment is eliminated. We have found that in the first 30h of pupal development, proliferation in the male A7 is reduced as compared to that of other abdominal segments, resulting in a small primordium. The Epidermal growth factor receptor pathway, which is in part responsible for this reduction, is down-regulated in male A7 cells, and if the activity of the pathway is increased there is a small seventh segment in the adult male. In later stages of pupal development, the remaining cells of the male A7 invaginate and die, and this requires the activity of myosin regulated by the gene extramacrochetae. Extramacrochetae levels of expression are increased in the male, but not female, A7 cells, suggesting that the sex determination pathway regulates the sexual difference (absence or not of the A7) by governing this gene. The Hox gene Abdominal-B, required to specify the posterior abdominal segments, controls both down-regulation of the Epidermal growth factor receptor pathway and extrusion, the latter partly through the regulation of the transcription of doublesex, a key gene in the sex determination pathway. Since the elimination of posterior segments is characteristic of more advanced Diptera, the study of the mechanisms implementing A7 elimination in males is important for understanding both development and evolution.
CABD Seminar July 13 @ noon
Molecular and behavioural circadian rhythms in C. elegans.
Dr. Maria Olmedo
Institute of Medical Psychology, University of Munich, Germany.

Summary: Circadian clocks are present in most organisms from cyanobacteria to humans. Circadian rhythms have a period of about 24 hours in constant conditions and are entrained to the 24‑ hours day by environmental signals (zeitgebers). In entrainment, clocks organize gene expression and metabolism to anticipate the daily changes of the environment. C. elegans lives in the dark (soil) and may experience only muted daily environmental cycles leading to speculation that it may dispense with the daily clock. However, previous protocols have shown circadian rhythms in behaviours (e.g. locomotor activity, defecation and pharyngeal pumping rate) or metabolism (e.g.resistance to osmotic stress), or rhythms in the expression of hundreds of genes. These data sets suggest that the nematode has a circadian system but it is not clear how it relates to those of other animals. We have used a protocol based on the ecology of nematodes (low amplitude temperature cycles) that reveals entrained and free-running rhythms in an olfactory behaviour and in the abundance of a protein, GRK-2 (G protein-coupled receptor kinase), that is involved in circadian regulation of olfaction in Drosophila. Furthermore, we have shown rhythms in the oscillation of the oxidized form on PRX (Peroxiredoxin), a universal marker for circadian rhythms in all domains of life. Our work emphasizes the importance of daily rhythms in sensory functions that will have consequences on fitness and population structure.
CABD Seminar July 6 @ noon
Growth, Patterning, Morphogenesis and the Evolution of Form in Insect Wings
Dr. Robert Ray
University of Sussex, UK

Summary: In multi-cellular eukaryotes, form arises from the interplay between cell proliferation and growth, patterning, and morphogenesis, and understanding the molecular basis of how these different systems are integrated is fundamental to understanding how developmental processes work and how form evolves. While studies in a variety of model systems have identified many of the genes and pathways intrinsic to these systems, the interconnections between them, for instance, how patterning genes direct cell proliferation or cell shape changes, remain less well understood. Furthermore, it is not yet clear whether shape (i.e. form independent of size) is a direct result of this interconnectedness or of some higher regulatory feature that has not been discovered. Finally, comparison of homologous structures between species show that evolution can act on these elements independently, for example, changing size but not pattern or pattern but not shape, or coordinately, and we know very little of how these changes come about and whether they target specific components of these systems or involve multiple adjustments over the entire process. These issues are at the fore of current studies in development and evolution and are key to understanding how these processes operate. The wings of insects provide a uniquely tractable model system to address these issues. It is a simple system consisting of a small number of cell types arranged in relatively simple patterns that can readily be compared between species. Moreover, the wing is, in effect, a two-dimensional structure that can be readily analyzed at the cellular and tissue level. In my talk, I will address three related issues that concern different levels of wing development. I will first address the cellular basis for morphogenesis in the developing Drosophila wing. I will show how each of the cell types in the wing behave during wing development, and how these behaviors are coordinated to produce the final structure in the adult. In the second part of my talk I will address one molecular mechanism that is involved in translating the activities of patterning genes into these distinct cellular morphologies. Finally, using interspecific comparisons, I will discuss how the Drosophila wing pattern has arisen from the ancestral state and how issues of size and shape are regulated in other species.
CABD Seminar June 29 @ noon
LINE-1 activity in stem cells
Dr. Jose Luis García Pérez
Universidad de Granada - Junta de Andalucía Centre for Genomics and Oncological Research (GENYO), Granada

Summary: Long INterspersed Element class 1 (LINE-1 or L1) retrotransposons comprise a fifth of the human genome and their ongoing activity continues to impact the genome. Heritable LINE-1 retrotransposition events must occur in cell types that ensure their transmission to newborns. Previous reports have detected LINE-1 expression and activity of engineered elements in cultured human cells that mimic an early embryo. These include human embryonic stem cells (hESCs), human embryonic carcinoma cells (hECs) and induced pluripotent stem cells (iPSCs). Additionally, recent reports have revealed the expression and mobilization of LINE-1 elements in selected somatic human cells including Neuronal Progenitor Cells (NPCs). Here, we used a panel of pluripotent and differentiated cell cultures to inspect the expression and retrotransposition levels of engineered LINE-1 retrotransposons. Remarkably, we observed that LINE-1s are expressed in pluripotent neuronal and embryonic cell types, although expression is higher in embryonic cell types. Additionally, we recapitulated engineered LINE-1 retrotransposition in pluripotent neuronal and embryonic cell types, but observed that retrotransposition rates can vary more than 200-fold among different pluripotent cell types. Indeed, under our experimental conditions, the highest rate of engineered LINE-1 retrotransposition is observed in neuronal cell types. These data suggest that the main load of LINE-1 retrotransposition in humans may occur in selected somatic cells and that most mobilization events will not be transmitted to newborns.
CABD Seminar June 22 @ noon
Gene-environment interactions: Influence on C. elegans physiology and life span
Dr Roxani Gatsi
Friedrich Miescher Institute for Biomedical Researc, Basel, Switzerland

Summary: The genetic makeup of an organism can define various aspects of its physiology. However, environmental cues can also influence physiology and lead to complex gene-environment interactions. Contributing to this complexity is the nature of the environmental cue, such an environmental cue is food. For example, food levels and food types have differential effects on an animal’s physiology. In C. elegans, food intake levels can determine its growth rate. However, I will describe how feeding rate and growth rate can be uncoupled by inositol 1,4,5-trisphosphate (IP3) signalling and specifically by its receptor, IP3R. In addition, I will present the results of an RNAi screen that identified interacting genes involved in the regulation of growth. Apart from food levels, the type of food an organism consumes can also have an influence on its physiology. In C. elegans different types of food can have distinct effects on the animal’s life span and reproduction and I will present how different neuropeptide receptors of the neuromedin U receptor (NMUR) family can play distinct roles in these processes.
CABD Seminar June 19 @ noon
Deconstructing leukemia in vivo: An AML1-ETO-driven mouse model recapitulates human core binding factor AML and provides detailed mechanistic insight into the disease.
Dr Ernesto Bockamp
Clinical School of the Johannes Gutenberg-University Mainz Division of Experimental and Translational Oncology Mainz, Germany

Summary: Chimeric transcription factors arising from chromosomal translocations are important regulators of leukemia. Although the AML1-ETO (AE) translocation is a consitent hallmark of core binding factor (CBF) acute myeloid leukemia (AML), the implications of aberrant AE expression are only parially understood and we are lacking an appropriate experimentel in vivo model. Using a novel conditional mouse system, which faithfully recapitulates the main features of human CBF-AML disease, we demonstrate that AE acts as a lineage instructor that initially promotes the expansion of the myeloid compartment and finally leads to the onset of ouvert AML. Furthermore, we show that both AE-expressing hematopoietic stem cells (HSC/MPPs) as well as committed myeloid progenitors (GMPs) independently function as cancer stem cells (CSCs). The existence of two immuno-phenotypic distinct cancer stem cell populations clearly indicates that leukemic stemness can be acquired independently of lineage maturation boundaries. High-throughput RNA deep sequencing (RNA-seq) established a functional link between disease progression and whole transcriptome alterations and revealed that unlimited proliferation and self-renewal of leukemic cells is sustained by elevated telomerase activity and the corruption of anti-apoptotic fail safe mechanisms. Using murine RNA-seq correlation analysis, we were able to establish a molecular signature that unambigously distinguishes human AML-CBF patient expression profiles from those of healthy donors. Furthermore, bioinformatic correlation computing identified a "drugable" and differentially expressed serine/threonine kinase as a potential novel therapeutic target for treating CBF AML. Finally, we provide for the first time direct in vivo evidence that loss of AE function can be beneficial for reversing leukemia. These results strongly suggest that CBF AML patients will equally benefit from therapeutic inactivation of AE function.
CABD Seminar June 8 @ noon
Building a fly leg: lessons from morphogenes and transcription factors
Dr. Carlos Estella
CBMSO, Madrid

Summary: Limb formation is a great model to study cell specification, tissue growth and cell differentiation during animal development. In many animal phyla the expression in embryos of the homeodomain containing gene Dll marks the field where the appendages will form. Here we describe how Dll expression is controlled by a group of cis-regulatory elements that account for its expression during leg development. Moreover, the identification of these enhancers allow us to subdivide the leg primordia in three mutually exclusive domains with different fates: the coxopodite or the extension of the body wall, the telopodite that will give rise to the true appendage, and the progenitors of the Keilin Organs (KO), a larval sensory structure associated with the leg disc. We also elucidate the signals that control the expression of all these enhancers and how this information is integrated at the molecular level in the cis-regulatory element. Lastly we analyzed the function of two sister genes of the Sp family of transcription factors, btd and Sp1, that act as the ventral selector genes restricting Dll expression to the leg. Vertebrate Sp8, the ortholog of fly Sp1, can rescue many of the functions of the Drosophila Sp genes, arguing that these activities have been conserved, despite more than 500 million years of independent evolution.
CABD Seminar June 6 @ 3pm
Genetic studies of schizophrenia in the Costa Rican Population
Dr. Henriette Raventós
Centro de Investigación en Biología Celular y Molecular (CIBCM) de la Universidad de Costa Rica

Summary: Although it is clear that genes play a role in the causation of bipolar disorder and schizophrenia, the identification of these has remained elusive. For the past 15 years, our group has been working on the identification of genes for complex neuropsychiatric disorders including migraine, schizophrenia, bipolar disorder, Alzheimer dementia and schizoaffective disorder. Using a set of standardized diagnostic instruments, neurocognitive tests and a best estimate process, subjects have been categorized according to DSMIV criteria. We have conducted whole genome scans on these subjects and identified genetic variants associated to some of these disorders, which are not being further characterized. In this lecture, I will review the studies we have conducted in Costa Rica on schizophrenia, loci with significant results in our population, additional evidence for the participation of NRG1, TGIF and MSRA, and mention other ancillary studies underway.
CABD Seminar June 1 @ noon
Metabolomic Tools for Actinomycete Synthetic Biology
Dr Rainer Breitling
Institute of Molecular, Cell and Systems Biology, University of Glasgow, UK

Summary: Metabolomics, the comprehensive global quantification of small molecules in biological systems, is becoming increasingly important as a diagnostic tool for engineered microbes. We have developed a computational pipeline for the analysis of metabolomics data obtained from high-resolution mass spectrometry measurements, and have applied these to study the metabolomic response of actinomycetes to a variety of experimental perturbations. Current developments focus on the incorporation of stable-isotope labeling information and the combination of metabolic flux measurements with genome-scale metabolic modelling.
CABD Seminar June 1 @ 10am
Synthetic Biology of Antibiotic Production: rewiring bacterial gene clusters.
Dr E Takano
Department of Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands

Summary: Streptomyces bacteria are well known for their ability to produce an immense diversity of secondary metabolites, including many antibiotics. The underlying biosynthetic machinery is a particularly interesting target for synthetic biology, due to its inherent modularity at multiple levels. A treasure trove of antibiotic biosynthesis gene clusters has been identified by genome sequencing, typically 20–50 per genome. We can use synthetic biology to re-engineer the bacterial genomes to awaken this multitude of cryptic antibiotic clusters. We have already demonstrated the potential of this strategy by awakening the cryptic/orphan CPK gene cluster, which produces a novel antibacterial compound. Generalizing this approach using standardized molecular modules will become a central tool for discovering new bioactive compounds, ranging from anti-cancer drugs to antibiotics.
CABD Seminar May 25 @ noon
Molecular pathways in adrenal and gonad development
Dr. Amanda Swain
The Institute of Cancer Research
CABD Seminar May 18 @ noon
The Science of Ageing: from melecules to hormesis
Prof. Suresh Rattan
University of Aarhus. Denmark

Summary: Biogerontology is a highly advanced field of research, which has developed a deep understanding of the biological basis of ageing and longevity. Ageing is not caused by any specific gerontogenes or by a genetic programme. Ageing happens due to the imperfections of the maintenance and repair systems and due to the shrinkage of the protective homeodynamic space. Accumulation of molecular damage is the ultimate reason for ageing. Interventions in ageing can either be piecemeal therapies using natural and synthetic compounds, food components, stem cells, and tissue and organ transplants, or interventions can be preventive measures for slowing down ageing. A promising rational strategy for ageing intervention is that of strengthening the homeodynamics by mild stress-induced hormesis. Exercise is an example of hormesis-inducing hormetin with wide ranging beneficial effects. Other physical, nutritional and mental hormetins can be developed to modulate ageing, to prevent or delay the onset of age-related diseases, and to extend health-span.
CABD Seminar May 16 @ noon
Immunity and Ageing - human immunosenescence
Dr. Graham Pawelec
Center for Medical Research, University of Tübingen Medical School, Tübingen, Germany

Summary: The immune system defends against infection, but older people paradoxically suffer both from failing immunity resulting in increased susceptibility to infections, and decreased responsiveness to vaccination, and at the same time increased immunopathology accompanying immune responses. Interventions to reduce such immunopathology while enhancing protective immunity are challenging but need to be confronted if we are to deal successfully with the increasing numbers of elderly and frail people in modern societies. To do this, we need to define and understand the mechanisms responsible for age-associated alterations and identify reliable biomarkers for monitoring clinically-relevant immune status in the elderly. This means performing longitudinal as well as cross-sectional studies assessing innate and adaptive immune parameters and correlating these with morbidity and mortality at follow-up. The assembly of large-scale databases including psychosocial, nutritional, genetic and health information in different populations will be required to dissect out the multitude of interactions affecting immunity throughout the lifespan. Limited longitudinal studies have begun to reveal biomarkers of immune ageing increasingly recognized as an “immune risk profile” (IRP) predicting mortality in the very elderly. Hallmark parameters of the IRP may also be associated with poorer responses to vaccination. Perhaps surprisingly, usually asymptomatic infection with the widespread persistent β-herpesvirus HHV5 (Cytomegalovirus, CMV) has an enormous impact on these immune biomarkers. This is probably because, for reasons not fully understood, a large proportion of available human immune resources is committed to controlling CMV in infected individuals. The prevalence of CMV infection in the population increases with age, and within individuals, the degree of immune commitment also increases with age. This may cause pathology by maintaining higher systemic levels of inflammatory mediators and decreasing the “immunological space” available for immune cells with other specificities. Interventions to prevent or reverse immunosenescence may therefore need to include targeting infectious agents such as CMV.
CABD Seminar May 11 @ noon
Decoding the Notch response
Dr. Sarah Bray
Gurdon Institute, Cambridge, UK

Summary: Signalling through the Notch receptor controls many different decisions in development, contributes to the maintenance of tissues in the adult and is associated with a number of diseases, including cancers. Despite its simple transduction pathway, Notch activation elicits different consequences in these different contexts, for example sometimes causing proliferation, sometimes cell-death. Our goal is to understand the molecular basis for this diversity. Through a combination of genomic and genetic approaches, primarily using Drosophila as our model, we have been investigating the transcriptional responses to Notch in several cell types and the mechanisms that cause different types of target-genes to be activated in different contexts.
CABD Seminar May 3 @ noon
Understanding a complex system. Exome sequencing of patients with intellectual disability to catalogue the genes that shape the brain
Dr. Han G.Brunner
Radboud University Nijmegen Medical Center Department of Human Genetics, Nijmegen, the Netherlands
CABD Seminar April 20 @ noon
Histone H3K4 methylation and genome stability in the C. elegans germline
Dr. Francesca Palladino
Laboratory of Molecular and Cellular Biology, CNRS, Université de Lyon, Ecole Normale Supérieure, 69364 Lyon Cedex 07, France

Summary: Repressed or active transcription states of developmental genes are maintained by epigenetic mechanisms, including the reversible covalent modification of histones. H3K4 methylation is closely associated with transcriptionally active chromatin and is deposited by the highly conserved SET1/MLL family of histone methyltransferases (HMTs). In mammalian cells, six SET1/MLL family members have been characterized, suggesting that these may have distinct tissue specific and developmentally regulated roles. The presence of multiple complexes has emphasized the need to study the function of individual subunits in a developmental context. We have shown that SET-2, the C. elegans SET1 homologue, and absent, small, or homeotic discs 2 (ASH-2) are differentially required for tri- and dimethylation of H3K4 (H3K4me3 and -me2) in embryos and adult germ cells. In embryos, whereas efficient H3K4me3 requires both SET-2 and ASH-2, H3K4me2 relies mostly on ASH-2. In adult germ cells by contrast, SET-2 serves a major role whereas ASH-2 is mostly dispensable. Loss of SET-2 results in progressive sterility over several generations, and genome instability accompanied by increased sensitivity to DNA damage and apoptosis. This study demonstrates that individual subunits of SET1-related complexes can show tissue specificity and developmental regulation, and points to an important role for H3K4 methylation in germline genome stability.
CABD Seminar April 19 @ noon
Microbiology's platypus, a journey to the origin of the eukaryotic cell
Dr. Damien Devos
Structural Bioinformatics EMBL, Meyerhofstrasse 1, D-69117 Heidelberg, Germany

Summary: The origin of the eukaryotic cell is one of the most fundamental and fascinating question in Biology. We study little characterised bacteria of Planctomycete phylum which have been suggested to bear clues to this question. We use a combination of computational, molecular, cell biology, and microscopy to decipher the biology of the Planctomycetes and understand their contribution to eukaryotic origin and evolution. Recently, we have have shown that members of the Planctomycetes have eukaryotic membrane coat-like proteins that were involved in the maintenance or organization of the bacteria endomembrane system. In addition, we have contributed to demonstrate that those proteins are involved in the phenomenon of endocytosis recently described in this bacteria. Reviewing the various eukaryotic or archaeal characteristics found in this bacteria, we have suggested a new hypothesis for the origin of the archaea and eukaryotes where the last common ancestor of eukaryotes and archaea was a sister group of the last Planctomycetes ancestor.
CABD Seminar April 13 @ noon
A novel genetic switch for an alternative path to epithelial-to-mesenchymal transitions
Dr. Jordi Casanova
IRB Barcelona

Summary: The epithelial-to-mesenchymal transition (EMT) converts cells from static epithelial to migratory mesenchymal states. All EMTs studied to date have been shown to rely on the activity of e-cad transcriptional repressors. In contrast we have found that EMT in the Drosophila endoderm is dependent on the GATA-factor Serpent (Srp) through a downregulation of junctional dE-Cadherin (dE-Cad) protein, without a block in its transcription. Moreover, the relocalisation of dE-Cad is achieved through the direct repression of crumbs (crb) by Srp. These results reveal a new mechanism for EMT induction through the modulation of apicobasal polarity complexes; loss of polarity in turn destabilizes the intercellular adhesion machinery. In addition, both Srp and hGATA-6, a human ortholog of Srp, act as potent triggers for this transition when activated ectopically. Similar to Srp, hGATA-6 acts through the downregulation of junctional E-Cad, without blocking its transcription, and induces the repression of a Crumbs ortholog, crb2. Together, these results identify a set of GATA factors as a conserved alternative trigger to repress epithelial characteristics and confer migratory capabilities on epithelial cells in development and pathogenesis.
CABD Seminar March 28 @ noon
CONTROL OF HOX TRANSCRIPTION FACTOR ACTIVITY: INSIGHTS FROM GENETIC AND STRUCTURAL APPROACHES
Dr. Y. Graba
IBDML, CNRS/AMU. Marseille. France

Summary: Protein function is encoded within protein sequence and protein domains. However, how protein domains inter-cooperate to modulate overall activity and how this impacts on functional diversification at the molecular and organism levels remains largely unaddressed. Focusing on three domains of the central class Drosophila Hox transcription factor AbdominalA (AbdA), we used combinatorial domain mutations and most known AbdA developmental functions to investigate how protein domains collectively shape protein activity. Results uncover intrinsic features shaping Hox protein activity, which account for robustness of Hox-controlled morphogenetic programs in development and evolution. The work also highlights an orchestrating role for a structurally-plastic C-terminal extension of the homeodomain (HD), which provides a topologically constrained contact with the Hox cofactor Extradenticle. This contact impacts on the subtle positioning of the HD recognition helix within the DNA major groove, ultimately defining base specific DNA recognition. The conservation of similarly structurally organized C-terminal sequences in other HD-containing proteins further suggests that the mechanism uncovered may broadly contribute to specify the DNA binding properties of HD containing proteins in general.
CABD Seminar March 9 @ 12:30pm
Diagnosis of neuromuscular diseases through computerized image analysis
Dr. Luisma Escudero
IBIS, Sevilla

Summary: I am interested in the concept of quantification of the tissue organization. To this end, we developed a method using Drosophila and Chicken epithelial images. We applied network theory at the scale of individual cells to uncover patterns in cell-to-cell contacts that govern epithelial organization. The approach permits characterization, quantification and classification of normal and perturbed epithelia. This initial method has been the base for the development of INDICIA, a new tool for the study of neuromuscular diseases. A very important clue for the diagnosis of neuromuscular diseases is the histological characterization of biopsy samples. However, the morphological analyses of muscle biopsies are mostly subjective and hard to quantify. We have developed an image analysis method that captures the maximum information contained in a muscle biopsy using networks science. INDICIA characterize muscular tissues by representing each image as a network with cells as nodes and cell contacts as links. This representation incorporates information about the type of cells (fast or slow fibres) and the content of collagen in the image. The analysis of the different characteristics of the image produces a defining signature that permits quantification and classification of normal and affected muscular samples.
CABD Seminar March 2 @ noon
The development of hair cells and otic neurons: Sox2, Notch and Atoh1 play a trio
Dr. Fernando Giráldez
CEXS, Universitat Pompeu Fabra, PRBB, Barcelona

Summary: The functional unit of the inner ear consists of three elements of neural origin: the mechano-transducing hair cells, the supporting cells, and the primary afferent neurons. These cell types derive from progenitor cells located in the neurosensory competent domain of the otic placode. The specification of neuronal and hair cell fates depend on the proneural genes Neurog1 and Atoh1, respectively, and Notch and Sox2 are upstream factors that regulate neurosensory competence and the expression of proneural genes. However, the mechanisms responsible for this regulation are largely unknown. I shall discuss recent work showing that the interplay between Jag1-dependent Notch activity, Sox2 and proneural gene expression is instrumental for the specification of hair cells and neurons. By a mechanism of lateral induction, Jag1 generates coherent domains of Notch activity that result in the maintenance of Sox2 expression within discrete domains of the developing inner ear. Sox2 is necessary and sufficient for Atoh1 induction and sensory development. However, Sox2 shows a seemingly contradictory function and it also prevents hair cell formation when over-expressed in sensory precursors. We show that Sox2 is sufficient to induce Atoh1 transcription by the direct binding to a conserved 3’ Atoh1 enhancer, but it promotes also the expression of Helix-Loop-Helix (HLH) proteins that inhibit Atoh1. As a result of this incoherent response, Sox2 induces sensory competence, but it procrastinates sensory differentiation. Sox2 also regulates neurogenic genes and the dual regulation of proneural genes by Sox2 provides a simple mechanism for the establishment of neurosensory competence, and for the sequential generation of neurons and hair cells in the inner ear.
CABD Seminar February 24 @ noon
Generation of Hematopoeitic Stem Cells in the mouse embryo
Dr. Anna Bigas
IMIM (Institut de Recerca Hospital del Mar, Parc de Recerca Biomedica de Barcelona

Summary: Understanding how Hematopoietic Stem Cells (HSC) are generated is crucial for further applications in regenerative medicine which require their in vitro production. There is now evidence that in vivo HSC are only generated during the embryonic period in the Aorta/Gonad/Mesonephros region. Our lab is studying the regulatory signals that determine the hematopoietic program in the mouse embryo and are required to generate “de novo” HSC. These signals include the Notch and Wnt, which are a well-conserved signalling pathways and their function is crucial during HSC generation.
CABD Seminar February 17 @ noon
Breaking the symmetry in Drosophila: on kinesins, transport and stirring
Dr. Isabel Palacios
Department of Zoology, University of Cambridge Downing Street CB2 3EJ Cambridge UK

Summary: A fundamental aspect in the development of an organism is the establishment of cell polarity, which relies on the asymmetric organisation of cellular components. We are interested in understanding the function of motor proteins and their associated cytoskeletons in setting up these asymmetries. We study two types of motion that depend on motors: cytoplasmic streaming and the transport of material along the cytoskeleton. In my talk I will mainly discuss how motors are Nature’s microfluidic stirres. One context in which streaming occurs is the establishment of /Drosophila/ body axes, when the motor Kinesin transports the axes determinants and drives ooplasmic streaming. Although Kinesin is essential for flows, neither the mechanism by which this motor induces streaming nor the impact of these flows on transport are known. In order to answer these key questions, we are using an interdisciplinary approach to decipher the biophysical behavior of streaming as the oocyte polarizes. I will also discuss our recent advances on how Kinesin coordinates its function as a stirrer and as a transporter.
CABD Seminar February 10 @ noon
A live imaging of Notch regulation by Numb in Drosophila
Dr François Schweisguth
Institut Pasteur, Paris, France

Summary:Cell fate diversity can be generated by the unequal segregation of the Notch regulator Numb during asymmetric cell divisions in both vertebrates and invertebrates. While the mechanisms underlying Numb unequal inheritance are understood, how Numb antagonizes Notch has remained unsolved. Here, we studied the dynamics of Notch signalling and its regulation by Numb in Drosophila Sensory Organ Precursor cells (SOPs) using a functional GFP-tagged Notch. Real-time in vivo imaging revealed that Notch localizes at the interface between SOP daughter cells at cytokinesis and that nuclear Notch is detected soon after cytokinesis in the daughter cell that does not inherit Numb. This early onset of directional Notch signalling is regulated by Numb and Sanpodo. We propose a general model whereby unequal segregation of Numb results in an early asymmetry of Notch at the cytokinetic furrow, hence directional signalling and binary fate choice.
CABD Seminar February 3 @ noon
The interface of genome expression and duplication with epigenetics
Dr Crisanto Gutierrez
CBMSO, Madrid

Summary:Development of multicellular organisms depends on a strict balance between cell proliferation and differentiation, where highly regulated gene expression patterns are established. Contrary to animals, plant development is an undeterminate and postembryonic process that frequently relies on endoreplication cycles. In addition, various differentiated cell types retain the capacity to dedifferentiate, proliferate again and take a variety of morphogenetic patterns. We are interested in understanding how these processes crosstalk by studying cell division, DNA replication control and gene expression, as well as the involvement of chromatin dynamics. To that end, we use the model plant Arabidopsis thaliana that allow us to use molecular, cellular, genetic and genomic approaches. I will discuss our recent advances in defining the features of DNA replication origins and the possible links with gene expression control and epigenetic marks. In this context we are also interested in understanding histone H3 dynamics during the cell cycle, differentiation and development.
CABD Seminar January 20 @ noon
Cell behaviours during morphogenesis of the adult abdominal epidermis of Drosophila
Dr. Marcus Bischoff
Department of Zoology, University of Cambridge, UK

Summary:Animal development is the result of the complex interplay of multiple cell behaviours, such as cell migrations, cell divisions, and cell shape changes. How cells integrate all the information necessary to shape organs and tissues remains mysterious. During the formation of the adult abdominal epidermis of Drosophila, the adult histoblasts replace the larval epithelial cells (LECs). While the histoblasts divide and migrate towards the midline, the LECs constrict apically, delaminate and die. I use 4D microscopy to study the coordination of cell behaviours during this morphogenetic event. 4D microscopy allows me to track each individual cell and analyse cell behaviours in great detail, e.g. by evaluating parameters such as the path a cell has moved and the speed of migration. I will show how different behaviours of both histoblasts and LECs contribute to morphogenesis. Cell migration appears to be most relevant to the positioning of the histoblasts. Also the LECs undergo coordinated migrations, which are propelled by apical lamellipodia-like protrusions. I will discuss how these migrations are regulated and coordinated and how they might drive abdominal closure.