Coupling dynamics of 2D Notch-Delta signalling

Understanding pattern formation driven by cell–cell interactions has been a significant theme in cellular biology for many years. In particular, due to their implications within many biological contexts, lateral-inhibition mechanisms present in the Notch-Delta signalling pathway led to an extensive discussion between biologists and mathematicians. Deterministic and stochastic models have been developed as a consequence of this discussion, some of which address long-range signalling by considering cell protrusions reaching non-neighbouring cells. The dynamics of such signalling systems reveal intricate properties of the coupling terms involved in these models. In this work, we investigate the advantages and drawbacks of a single-parameter long-range signalling model across diverse scenarios. By employing linear and multi-scale analyses, we discover that pattern selection is not only partially explained but also depends on nonlinear effects that extend beyond the scope of these analytical techniques

Updated Perspectives On Vascular Cell Specification And Pluripotent Stem Cell-Derived Vascular Organoids For Studying Vasculopathies.

Vasculopathy is a pathological process occurring in the blood vessel wall, which could affect the haemostasis and physiological functions of all the vital tissues/organs and is one of the main underlying causes for a variety of human diseases including cardiovascular diseases. Current pharmacological interventions aiming to either delay or stop progression of vasculopathies are suboptimal, thus searching novel, targeted, risk-reducing therapeutic agents, or vascular grafts with full regenerative potential for patients with vascular abnormalities are urgently needed. Since first reported, pluripotent stem cells (PSCs), particularly human induced pluripotent stem cells, have open new avenue in all research disciplines including cardiovascular regenerative medicine and disease remodelling. Assisting with recent technological breakthroughs in tissue engineering, in vitro construction of tissue organoid made a tremendous stride in the past decade. In this review, we provide an update of the main signal pathways involved in vascular cell differentiation from human PSCs and an extensive overview of PSC-derived tissue organoids, highlighting the most recent discoveries in the field of blood vessel organoids as well as vascularization of other complex tissue organoids, with the aim of discussing the key cellular and molecular players in generating vascular organoids

Dynamic properties of noise and Her6 levels are optimized by miR-9, allowing the decoding of the Her6 oscillator

This work was supported by a Wellcome Trust Senior Research Fellowship to NP (106185/Z/14/Z).Noise is prevalent in biology and has been widely quantified using snapshot measurements. This static view obscures our understanding of dynamic noise properties and how these affect gene expression and cell state transitions. Using a CRISPR/Cas9 Zebrafish her6::Venus reporter combined with mathematical and in vivo experimentation, we explore how noise affects the protein dynamics of Her6, a basic helix‐loop‐helix transcriptional repressor. During neurogenesis, Her6 expression transitions from fluctuating to oscillatory at single‐cell level. We identify that absence of miR‐9 input generates high‐frequency noise in Her6 traces, inhibits the transition to oscillatory protein expression and prevents the downregulation of Her6. Together, these impair the upregulation of downstream targets and cells accumulate in a normally transitory state where progenitor and early differentiation markers are co‐expressed. Computational modelling and double smFISH of her6 and the early neurogenesis marker, elavl3, suggest that the change in Her6 dynamics precedes the downregulation in Her6 levels. This sheds light onto the order of events at the moment of cell state transition and how this is influenced by the dynamic properties of noise. Our results suggest that Her/Hes oscillations, facilitated by dynamic noise optimization by miR‐9, endow progenitor cells with the ability to make a cell state transition.Publisher PDFPeer reviewe

Epigenetic regulation of neuronal maturation : the effect of MeCP2 and MicroRNAs on the maturation of hippocampal neurons

Dendrites and the dendritic spines of neurons play key roles in the connectivity of the brain and have been recognized as the locus of long-term synaptic plasticity, which is correlated with learning and memory. The development of dendrites and spines in the mammalian central nervous system is a complex process that requires specific molecular events over a period of time. It has been shown that specific molecules are needed not only at the spines point of contact, but also at a distance, providing signals that initiate a cascade of events leading to synapse formation. The specific molecules that act to signal neuronal differentiation, dendritic morphology, and synaptogenesis are tightly regulated by genetic and epigenetic programs. It has been shown that the dendritic spine structure and distribution are altered in many diseases, including many forms of mental retardation (MR) such as Rett syndrome, and can also be potentiated by neuronal activities and an enriched environment. Because dendritic spine pathologies are found in many types of MR, it has been proposed that an inability to form normal spines leads to the cognitive and motor deficits that are characteristic of MR. Epigenetic mechanisms, including DNA methylation, chromatin remodeling, and the noncoding RNA-mediated process, have profound regulatory roles in mammalian gene expression. My dissertation research focused on two aspects of epigenetic mechanisms, Mecp2-DNA methylation pathway and noncoding microRNAs that regulate the development and maturation of dendrites and spines. It is well known that Rett Syndrome, a severe postnatal childhood neurological disorder is mostly caused by mutations in the MECP2 gene. My studies focused on the role of MeCP2-mediated epigenetic regulation in postnatal brain development in a Mecp2-deficient mouse model. I found that, while Mecp2 was not critical for the production of immature neurons in the dentate gyrus (DG) of the hippocampus, the newly generated neurons exhibited profound deficits in neuronal maturation, including delayed transition into a more mature stage, altered expression of presynaptic proteins, and reduced dendritic spine density. Furthermore, I found that cultured neurons and brains lacking Mecp2 exhibited altered expression of microRNAs. My studies demonstrate that one brain-enriched microRNA, miR-137, has a significant role in regulating neuronal maturation by translational regulation of Mind bomb1. Despite extensive efforts to understand the molecular regulation of dendrite and spine development, epigenetic and non-coding RNA pathways have only recently been considered. In this thesis, I will first summarize the literature on epigenetic mechanisms that regulate the development and maturation of dendrites and spines, and discuss some general methodologies as well as recent technological advances in biology and neurosciences. I will then present my own data to show how epigenetic alterations could result in the morphological and phenotypic abnormalities that are a fundamental characteristic MR, such as Rett syndrome

Sox10 regulates enteric neural crest cell migration in the developing gut

Concurrent Sessions 1: 1.3 - Organs to organisms: Models of Human Diseases: abstract no. 1417th ISDB 2013 cum 72nd Annual Meeting of the Society for Developmental Biology, VII Latin American Society of Developmental Biology Meeting and XI Congreso de la Sociedad Mexicana de Biologia del Desarrollo. The Conference's web site is located at http://www.inb.unam.mx/isdb/Sox10 is a HMG-domain containing transcription factor which plays important roles in neural crest cell survival and differentiation. Mutations of Sox10 have been identified in patients with Waardenburg-Hirschsprung syndrome, who suffer from deafness, pigmentation defects and intestinal aganglionosis. Enteric neural crest cells (ENCCs) with Sox10 mutation undergo premature differentiation and fail to colonize the distal hindgut. It is unclear, however, whether Sox10 plays a role in the migration of ENCCs. To visualize the migration behaviour of mutant ENCCs, we generated a Sox10NGFP mouse model where EGFP is fused to the N-terminal domain of Sox10. Using time-lapse imaging, we found that ENCCs in Sox10NGFP/+ mutants displays lower migration speed and altered trajectories compared to normal controls. This behaviour was cell-autonomous, as shown by organotypic grafting of Sox10NGFP/+ gut segments onto control guts and vice versa. ENCCs encounter different extracellular matrix (ECM) molecules along the developing gut. We performed gut explant culture on various ECM and found that Sox10NGFP/+ ENCCs tend to form aggregates, particularly on fibronectin. Time-lapse imaging of single cells in gut explant culture indicated that the tightly-packed Sox10 mutant cells failed to exhibit contact inhibition of locomotion. We determined the expression of adhesion molecule families by qPCR analysis, and found integrin expression unaffected while L1-cam and selected cadherins were altered, suggesting that Sox10 mutation affects cell adhesion properties of ENCCs. Our findings identify a de novo role of Sox10 in regulating the migration behaviour of ENCCs, which has important implications for the treatment of Hirschsprung disease.postprin

Analysis of craniofacial defects in Six1/Eya1-associated Branchio-Oto-Renal Syndrome

Poster Session I - Morphogenesis: 205/B10117th ISDB 2013 cum 72nd Annual Meeting of the Society for Developmental Biology, 7th Latin American Society of Developmental Biology Meeting and 11th Congreso de la Sociedad Mexicana de Biologia del Desarrollo.Branchio-Oto-Renal (BOR) syndrome patients exhibit craniofacial and renal anomalies as well as deafness. BOR syndrome is caused by mutations in Six1 or Eya1, both of which regulate cell proliferation and differentiation. The molecular mechanism underlying the craniofacial and branchial arch (BA) defects in BOR syndrome is unclear. We have found that Hoxb3 is up-regulated in the second branchial arch (BA2) of Six1-/- mutants. Moreover, Hoxb3 over-expression in transgenic mice leads to BA abnormalities which are similar to the BA defects in Six1-/- or Eya1-/- mutants, suggesting a regulatory relationship among Six1, Eya1 and Hoxb3 genes. The aim of this study is to investigate the molecular mechanism underlying abnormal BA development in BOR syndrome using Six1 and Eya1 mutant mice. Two potential Six1 binding sites were identified on the Hoxb3 gene. In vitro and in vivo Chromatin IP assays showed that Six1 could directly bind to one of the sites specifically. Furthermore, using a chick in ovo luciferase assay we showed that Six1 could suppress gene expression through one of the specific binding sites. On the other hand, in Six1-/- mutants, we found that the Notch ligand Jag1 was up-regulated in BA2. Similarly, in Hoxb3 transgenic mice, ectopic expression of Jag1 could be also detected in BA2. To investigate the activation of Notch signaling pathway, we found that Notch intracellular domain (NICD), a direct indicator of Notch pathway activation, was up-regulated in BAs of Six1-/-; Eya1-/- double mutants. Our results indicate that Hoxb3 and Notch signaling pathway are involved in mediating the craniofacial defects of Six1/Eya1-associated Branchio-Oto-Renal Syndrome.postprin

Tumor Angiogenesis

Tumor angiogenesis is the main process responsible for the formation of new blood vessels that promote tumor growth and metastasis. This process is driven by potent pro-angiogenic factors that are predominant in the tumor environment and are produced by both malignant cells and the host cells recruited to the tumor site. Tumor environment is characterized by the imbalance between pro-angiogenic and anti-angiogenic factors, which drives the construction of numerous but structurally defective vessels. These poorly perfused and abnormal vessels significantly contribute to the tumor pathology not only by supporting the expansion of the tumor mass but also by promoting chronic inflammation, enhancing thrombosis, impeding drug delivery, and disseminating tumor cells. These problems associated with tumor vasculature continue to attract great attention of scientists and clinicians interested in advancing the understanding of tumor biology and development of new drugs. This book complies a series of reviews that cover a broad spectrum of current topics related to the pathology of tumor blood vessels including mechanisms inducing new vessels, identification of new targets for inhibition of tumor angiogenesis, and potential clinical use of known and novel anti-angiogenic therapies. The book provides an update on tumor angiogenesis that could be useful for oncologists, cancer researchers and biologists with interests in vascular and endothelial cell behavior in the context of cancer

Xenopus

This book focuses on the amphibian, Xenopus, one of the most commonly used model animals in the biological sciences. Over the past 50 years, the use of Xenopus has made possible many fundamental contributions to our knowledge in cell biology, developmental biology, molecular biology, and neurobiology. In recent years, with the completion of the genome sequence of the main two species and the application of genome editing techniques, Xenopus has emerged as a powerful system to study fundamental disease mechanisms and test treatment possibilities. Xenopus has proven an essential vertebrate model system for understanding fundamental cell and developmental biological mechanisms, for applying fundamental knowledge to pathological processes, for deciphering the function of human disease genes, and for understanding genome evolution. Key Features Provides historical context of the contributions of the model system Includes contributions from an international team of leading scholars Presents topics spanning cell biology, developmental biology, genomics, and disease model Describes recent experimental advances Incorporates richly illustrated diagrams and color images Related Titles Green, S. L. The Laboratory Xenopus sp. (ISBN 978-1-4200-9109-0) Faber, J. & P. D. Nieuwkoop. Normal Table of Xenopus laevis (Daudin): A Systematical & Chronological Survey of the Development from the Fertilized Egg till the End of Metamorphosis (ISBN 978-0-8153-1896-5) Jarret, R. L. & K. McCluskey. The Biological Resources of Model Organisms (ISBN 978-1-0320-9095-5

Post-transcriptional Regulation of the Drosophila Anterior Determinant, Bicoid

In a wide variety of biological contexts, messenger RNA (mRNA) is known to have a complex and dynamic life cycle. In particular, the localization and translational control of mRNA are essential for proper development in eukaryotes. The fly Drosophila melanogaster is an excellent model for studying these processes. During D. melanogaster oogenesis, several mRNAs are trafficked and localized within the developing egg chamber, and regulated at the translational level to enable embryo patterning. One such mRNA, bicoid, is localized at the anterior of the oocyte and translated in the early embryo, where its encoded protein directs formation of the fly\u27s head and thoracic segments. In this thesis, we investigated several aspects of bicoid\u27s post-transcriptional regulation that may impact its stability and translational timing. First, we demonstrate that bicoid mRNA is present in Processing Bodies (P-bodies), cytoplasmic organelles implicated in mRNA storage and decay. Perturbing P-body formation/structure, via manipulation of the mRNA decay pathway, affects the levels of bicoid and additional maternal transcripts. We next explored the possibility that the microRNA (miRNA) pathway regulates the translational timing of bicoid. We find that in cell culture experiments, a bicoid reporter gene is translationally repressed by miR-305; we also demonstrate that miR-305 is expressed in ovaries. However, loss of miR-305 is not sufficient to alter ectopic bicoid mRNA translation in the egg chamber. To determine if any genes are singly required for bicoid translational repression in the egg chamber, we used GFP-tagged transgenes to express bicoid mRNA in vivo. Although we do not yet identity any candidate genes in this small screen, we show that overexpression of bicoid mRNA results in its translation in the egg chamber, suggesting that one or more factors normally act in its translational repression. Overall, our work points to several plausible avenues of investigation into processes that regulate the translational timing of bicoid mRNA during oogenesis. Moreover, our findings are also relevant to a general understanding of the complex, multifaceted problems surrounding mRNA post-transcriptional regulation