RESUMEN
Jeune asphyxiating thoracic dystrophy, an autosomal recessive chondrodysplasia, often leads to death in infancy because of a severely constricted thoracic cage and respiratory insufficiency; retinal degeneration, cystic renal disease and polydactyly may be complicating features. We show that IFT80 mutations underlie a subset of Jeune asphyxiating thoracic dystrophy cases, establishing the first association of a defective intraflagellar transport (IFT) protein with human disease. Knockdown of ift80 in zebrafish resulted in cystic kidneys, and knockdown in Tetrahymena thermophila produced shortened or absent cilia.
Asunto(s)
Asfixia/genética , Enfermedades del Desarrollo Óseo/genética , Proteínas Portadoras/genética , Enfermedades Renales Quísticas/genética , Mutación/genética , Tetrahymena thermophila/genética , Enfermedades Torácicas/genética , Pez Cebra/genética , Animales , Femenino , Humanos , Recién Nacido , Masculino , Linaje , Polidactilia/genética , Tetrahymena thermophila/crecimiento & desarrollo , Pez Cebra/crecimiento & desarrolloRESUMEN
The evolutionarily conserved planar cell polarity (PCP) pathway (or noncanonical Wnt pathway) drives several important cellular processes, including epithelial cell polarization, cell migration and mitotic spindle orientation. In vertebrates, PCP genes have a vital role in polarized convergent extension movements during gastrulation and neurulation. Here we show that mice with mutations in genes involved in Bardet-Biedl syndrome (BBS), a disorder associated with ciliary dysfunction, share phenotypes with PCP mutants including open eyelids, neural tube defects and disrupted cochlear stereociliary bundles. Furthermore, we identify genetic interactions between BBS genes and a PCP gene in both mouse (Ltap, also called Vangl2) and zebrafish (vangl2). In zebrafish, the augmented phenotype results from enhanced defective convergent extension movements. We also show that Vangl2 localizes to the basal body and axoneme of ciliated cells, a pattern reminiscent of that of the BBS proteins. These data suggest that cilia are intrinsically involved in PCP processes.
Asunto(s)
Síndrome de Bardet-Biedl/patología , Proteínas Asociadas a Microtúbulos/genética , Chaperonas Moleculares/genética , Proteínas del Tejido Nervioso/metabolismo , Animales , Síndrome de Bardet-Biedl/genética , Polaridad Celular/genética , Cilios/química , Cóclea/patología , Células Epiteliales/química , Párpados/fisiopatología , Chaperoninas del Grupo II , Ratones , Ratones Mutantes , Mutación , Proteínas del Tejido Nervioso/análisis , Defectos del Tubo Neural/patología , Pez Cebra/genética , Pez Cebra/metabolismoRESUMEN
BACKGROUND: The cardiac progenitor cells for the outflow tract (OFT) reside in the visceral mesoderm and mesodermal core of the pharyngeal region, which are defined as the secondary and anterior heart fields (SHF and AHF), respectively. RESULTS: Using chick embryos, we injected fluorescent-dye into the SHF or AHF at stage 14, and the destinations of the labeled cells were examined at stage 31. Labeled cells from the right SHF were found in the myocardium on the left dorsal side of the OFT, and cells from the left SHF were detected on the right ventral side of the OFT. Labeled cells from the right and left AHF migrated to regions of the ventral wall of the OFT close to the aortic and pulmonary valves, respectively. CONCLUSION: These observations indicate that myocardial progenitors from the SHF and AHF contribute to distinct conotruncal regions and that cells from the SHF migrate rotationally while cells from the AHF migrate in a non-rotational manner.
Asunto(s)
Movimiento Celular , Mioblastos Cardíacos/fisiología , Miocardio , Faringe/embriología , Animales , Embrión de Pollo , Cardiopatías Congénitas/embriología , Faringe/citologíaRESUMEN
Laterality defects such as situs inversus are not uncommonly encountered in humans, either in isolation or as part of another syndrome, but can have devastating developmental consequences. The events that break symmetry during early embryogenesis are highly conserved amongst vertebrates and involve the establishment of unidirectional flow by cilia within an organising centre such as the node in mammals or Kupffer's vesicle (KV) in teleosts. Disruption of this flow can lead to the failure to successfully establish left-right asymmetry. The correct apical-posterior cellular position of each node/KV cilium is critical for its optimal radial movement which serves to sweep fluid (and morphogens) in the same direction as its neighbours. Planar cell polarity (PCP) is an important conserved process that governs ciliary position and posterior tilt; however the underlying mechanism by which this occurs remains unclear. Here we show that Bbs8, a ciliary/basal body protein important for intraciliary/flagellar transport and the core PCP protein Vangl2 interact and are required for establishment and maintenance of left-right asymmetry during early embryogenesis in zebrafish. We discovered that loss of bbs8 and vangl2 results in laterality defects due to cilia disruption at the KV. We showed that perturbation of cell polarity following abrogation of vangl2 causes nuclear mislocalisation, implying defective centrosome/basal body migration and apical docking. Moreover, upon loss of bbs8 and vangl2, we observed defective actin organisation. These data suggest that bbs8 and vangl2 act synergistically on cell polarization to establish and maintain the appropriate length and number of cilia in the KV and thereby facilitate correct LR asymmetry.
Asunto(s)
Tipificación del Cuerpo , Polaridad Celular/fisiología , Proteínas de la Membrana/metabolismo , Proteínas de Pez Cebra/metabolismo , Pez Cebra/embriología , Animales , Cilios/metabolismo , Embrión no Mamífero/metabolismo , Proteínas de la Membrana/genética , Proteínas de Pez Cebra/genéticaRESUMEN
The brachial plexus is an important nervous structure from which all major nerves to the upper limb arise. It typically originates from the anterior rami of the C5-T1 spinal nerves. As it passes laterally, the roots are successively organized into three trunks, six divisions, and three cords. The BP is susceptible to injury during the perinatal and postnatal periods, as well as in adulthood. Its structure can show considerable variation, and there is a wealth of literature describing its variations, providing indispensable information to neurosurgeons. Here, we report a novel unilateral variant of the brachial plexus found in an adult Japanese male cadaver. In this case, the middle trunk arose from the C7 and C8 spinal nerves, and the inferior trunk continued from the T1 alone. At the interscalene triangle, the subclavian artery was situated between the C8 and T1 nerves. The posterior cord arose from the posterior divisions of the superior and middle trunks, while the root from the T1 nerve/inferior trunk was absent. The anterior division of the middle trunk gave independent roots to the musculocutaneous and median nerves, without completely establishing the lateral cord. A communicating branch arose from the musculocutaneous nerve to join the median nerve. Some branches from the roots and cords also deviated from typical configurations. This case represents a rare combination of variations in the trunks, divisions, cords, and the median nerve and offers a valuable addition to the literature regarding variations in the brachial plexus.
Asunto(s)
Variación Anatómica , Plexo Braquial/anatomía & histología , Nervios Espinales/anatomía & histología , Extremidad Superior/inervación , Anciano de 80 o más Años , Cadáver , Humanos , Masculino , Nervio Mediano/anatomía & histología , Arteria Subclavia/anatomía & histologíaRESUMEN
Paraxial protocadherin (PAPC) has been shown to be involved in gastrulation cell movements during early embryogenesis. It is first expressed in the dorsal marginal zone at the early gastrula stage and subsequently restricted to the paraxial mesoderm in Xenopus and zebrafish. Using Xenopus embryos, we found that PAPC is also regulated at the protein level and is degraded and excluded from the plasma membrane in the axial mesoderm by the late gastrula stage. Regulation of PAPC requires poly-ubiquitination that is dependent on phosphorylation. PAPC is phosphorylated by GKS3 in the evolutionarily conserved cytoplasmic domain, and this in turn is necessary for poly-ubiquitination by an E3 ubiquitin ligase ß-TrCP. We also show that precise control of PAPC by phosphorylation/ubiquitination is essential for normal Xenopus gastrulation cell movements. Taken together, our findings unveil a novel mechanism of regulation of a cell adhesion protein and show that this system plays a crucial role in vertebrate embryogenesis.
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Cadherinas/metabolismo , Movimiento Celular/fisiología , Gastrulación/fisiología , Ubiquitinación/fisiología , Proteínas de Xenopus/metabolismo , Animales , Regulación hacia Abajo , Glucógeno Sintasa Quinasa 3/metabolismo , Fosforilación/fisiología , Protocadherinas , XenopusRESUMEN
In Xenopus, injection of S-adenosylmethionine decarboxylase (SAMDC) mRNA into fertilized eggs or 2-cell stage embryos induces massive cell dissociation and embryo-lysis at the early gastrula stage due to activation of the maternal program of apoptosis. We injected SAMDC mRNA into only one of the animal side blastomeres of embryos at different stages of cleavage, and examined the timing of the onset of the apoptotic reaction. In the injection at 4- and 8-cell stages, a considerable number of embryos developed into tadpoles and in the injection at 16- and 32-cell stages, all the embryos became tadpoles, although tadpoles obtained were sometimes abnormal. However, using GFP as a lineage tracer, we found that descendant cells of the blastomere injected with SAMDC mRNA at 8- to 32-cell stages are confined within the blastocoel at the early gastrula stage and undergo apoptotic cell death within the blastocoel, in spite of the continued development of the injected embryos. These results indicate that cells overexpressed with SAMDC undergo apoptotic cell death consistently at the early gastrula stage, irrespective of the timing of the mRNA injection. We assume that apoptosis is executed in Xenopus early gastrulae as a "fail-safe" mechanism to eliminate physiologically-severely damaged cells to save the rest of the embryo.
Asunto(s)
Adenosilmetionina Descarboxilasa/metabolismo , Apoptosis/fisiología , Embrión no Mamífero/metabolismo , Adenosilmetionina Descarboxilasa/genética , Animales , Blástula/efectos de los fármacos , Blástula/fisiología , Blástula/ultraestructura , División Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Embrión no Mamífero/ultraestructura , Desarrollo Embrionario , Regulación del Desarrollo de la Expresión Génica , Regulación Enzimológica de la Expresión Génica , Proteínas Fluorescentes Verdes , Humanos , Larva/citología , Larva/efectos de los fármacos , Larva/fisiología , Proteínas Luminiscentes/genética , Proteínas Luminiscentes/metabolismo , Microscopía Electrónica , Modelos Biológicos , ARN Mensajero/administración & dosificación , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factores de Tiempo , XenopusRESUMEN
The epicardium, which is derived from the proepicardial organ (PE) as the third epithelial layer of the developing heart, is crucial for ventricular morphogenesis. An epicardial deficiency leads to a thin compact layer for the developing ventricle; however, the mechanisms leading to the impaired development of the compact layer are not well understood. Using chick embryonic hearts, we produced epicardium-deficient hearts by surgical ablation or blockade of the migration of PE and examined the mechanisms underlying a thin compact myocardium. Sarcomeric maturation (distance between Z-lines) and cardiomyocyte growth (size) were affected in the thin compact myocardium of epicardium-deficient ventricles, in which the amounts of phospho-smad2 and phospho-ERK as well as expression of transforming growth factor (TGF)ß2 and fibroblast growth factor (FGF)2 were reduced. TGFß and FGF were required for the maturation of sarcomeres and growth of cardiomyocytes in cultured ventricles. In ovo co-transfection of dominant negative (dN)-Alk5 (dN-TGFß receptor I) and dN-FGF receptor 1 to ventricles caused a thin compact myocardium. Our results suggest that immature sarcomeres and small cardiomyocytes are the causative architectures of an epicardium-deficient thin compact layer and also that epicardium-dependent signaling mediated by TGFß and FGF plays a role in the development of the ventricular compact layer before the onset of coronary circulation.
Asunto(s)
Vasos Coronarios/embriología , Factores de Crecimiento de Fibroblastos/fisiología , Ventrículos Cardíacos/citología , Miocitos Cardíacos/fisiología , Pericardio/fisiología , Factor de Crecimiento Transformador beta/fisiología , Animales , Proteínas Aviares/metabolismo , Aumento de la Célula , Proliferación Celular , Embrión de Pollo , Vasos Coronarios/fisiología , Proteínas Serina-Treonina Quinasas/metabolismo , Receptor Tipo 1 de Factor de Crecimiento de Fibroblastos/metabolismo , Receptor Tipo I de Factor de Crecimiento Transformador beta , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Flujo Sanguíneo Regional , Sarcómeros/fisiología , Técnicas de Cultivo de TejidosRESUMEN
Planar cell polarity is a fundamental concept to understanding the coordination of cell movements in the plane of a tissue. Since the planar cell polarity pathway was discovered in mesenchymal tissues involving cell interaction during vertebrate gastrulation, there is an emerging evidence that a variety of mesenchymal and epithelial cells utilize this genetic pathway to mediate the coordination of cells in directed movements. In this review, we focus on how the planar cell polarity pathway is mediated by migrating cells to communicate with one another in different developmental processes.
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Comunicación Celular , Movimiento Celular , Polaridad Celular , Regulación del Desarrollo de la Expresión Génica , Animales , Adhesión Celular , División Celular , Inhibición de Contacto , Drosophila/citología , Drosophila/embriología , Drosophila/genética , Drosophila/metabolismo , Células Epiteliales/citología , Células Epiteliales/metabolismo , Gastrulación , Ratones , Defectos del Tubo Neural/metabolismo , Defectos del Tubo Neural/patología , Vía de Señalización Wnt , Xenopus/embriología , Xenopus/genética , Xenopus/metabolismoAsunto(s)
Movimiento Celular/genética , Polaridad Celular/genética , Inducción Embrionaria/genética , Gástrula , Péptidos y Proteínas de Señalización Intercelular/fisiología , Vertebrados/embriología , Animales , Proteínas de Drosophila/fisiología , Drosophila melanogaster , Embrión no Mamífero , Gástrula/citología , Regulación del Desarrollo de la Expresión Génica , Péptidos y Proteínas de Señalización Intercelular/genética , Transducción de Señal/genética , Transducción de Señal/fisiología , Proteínas Wnt , Xenopus laevis , Pez Cebra , Proteínas de Pez Cebra/fisiologíaRESUMEN
The branch of the Wnt pathway, related to planar cell polarity signaling in Drosophila, is fundamental not only to the establishment of tissue polarity but also to a variety of morphogenetic processes in vertebrates. The genetic pathway has been noted for its similarity as well as divergence of between vertebrates and Drosophila. This review focuses on issues related to the complexity of the output of the planar cell polarity pathway during gastrulation in zebrafish and Xenopus and, to a lesser extent, during gastrulation/neurulation in mice.
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Gastrulación , Transducción de Señal , Proteínas Wnt/metabolismo , Animales , Polaridad Celular , Drosophila , Ratones , Pez CebraRESUMEN
During vertebrate gastrulation, cells forming the prechordal plate undergo directed migration as a cohesive cluster. Recent studies revealed that E-cadherin-mediated coherence between these cells plays an important role in effective anterior migration, and that platelet-derived growth factor (Pdgf) appears to act as a guidance cue in this process. However, the mechanisms underlying this process at the individual cell level remain poorly understood. We have identified miles apart (mil) as a suppressor of defective anterior migration of the prospective prechordal plate in silberblick (slb)/wnt11 mutant embryos, in which E-cadherin-mediated coherence of cell movement is reduced. mil encodes Edg5, a sphingosine-1-phosphate (S1P) receptor belonging to a family of five G-protein-coupled receptors (S1PRs). S1P is a lipid signalling molecule that has been implicated in regulating cytoskeletal rearrangements, cell motility and cell adhesion in a variety of cell types. We examined the roles of Mil in anterior migration of prechordal plate progenitor cells and found that, in slb embryos injected with mil-MO, cells migrate with increased motility but decreased directionality, without restoring the coherence of cell migration. This indicates that prechordal plate progenitor cells can migrate effectively as individuals, as well as in a coherent cluster of cells. Moreover, we demonstrate that Mil regulates cell motility and polarisation through Pdgf and its intracellular effecter PI3K, but modulates cell coherence independently of the Pdgf/PI3K pathway, thus co-ordinating cell motility and coherence. These results suggest that the net migration of prechordal plate progenitors is determined by different parameters, including motility, persistence and coherence.
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Movimiento Celular/fisiología , Gastrulación , Receptores de Lisoesfingolípidos/metabolismo , Células Madre/metabolismo , Pez Cebra/metabolismo , Animales , Embrión no Mamífero , Modelos Biológicos , Pez Cebra/embriología , Proteínas de Pez Cebra/metabolismoRESUMEN
The genomes of 28 bacterial strains, including mycobacterial species Mycobacterium tuberculosis and Mycobacterium bovis, were analyzed for the presence of a special class of microsatellite, that of trinucleotide repeat sequences (TRS). Results of a search of all 10 possible TRS motifs (i.e., CCT, CGG, CTG, GAA, GAT, GTA, GTC, GTG, GTT, and TAT) with five or more repeating units showed that (CGG)(5) was highly represented within the genomic DNA of M. tuberculosis and M. bovis. Most of the (CGG)(5) repeats in the genome were within the open reading frames of two large gene families encoding PE_PGRS and PPE proteins that have the motifs Pro-Glu (PE) and Pro-Pro-Glu (PPE). (CGG)(5)-probed Southern hybridization showed that some mycobacterial species, such as Mycobacterium marinum, Mycobacterium kansasii, and Mycobacterium szulgai, possess many copies of (CGG)(5) in their genomes. Analysis of clinical isolates obtained from Tokyo and Warsaw with both IS6110 and (CGG)(5) probes showed that there is an association between the fingerprinting patterns and the geographic origin of the isolates and that (CGG)(5) fingerprinting patterns were relatively more stable than IS6110 patterns. The (CGG)(5) repeat is a unique sequence for some mycobacterial species, and (CGG)(5) fingerprinting can be used as an epidemiologic method for these species as well as IS6110 fingerprinting can. If these two fingerprinting methods are used together, the precise analysis of M. tuberculosis isolates will be accomplished. (CGG)(5)-based fingerprinting is particularly useful for M. tuberculosis isolates with few or no insertion elements and for the identification of other mycobacterial species when informative probes are lacking.
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Mycobacterium tuberculosis/clasificación , Mycobacterium tuberculosis/genética , Mycobacterium/genética , Polimorfismo de Longitud del Fragmento de Restricción , Repeticiones de Trinucleótidos/genética , Secuencia de Bases , ADN Bacteriano/genética , ADN Bacteriano/aislamiento & purificación , Humanos , Repeticiones de Microsatélite , Mycobacterium/clasificación , Mycobacterium/aislamiento & purificación , Mycobacterium tuberculosis/aislamiento & purificación , FilogeniaRESUMEN
We previously demonstrated that overexpression of S-adenosylmethionine decarboxylase (SAMDC) in Xenopus early embryos induces execution of maternal program of apoptosis shortly after midblastula transition, which likely serves as a fail-safe mechanism of early development to eliminate physiologically damaged cells before they entering the gastrula stage. To determine how caspases are involved in this process, we microinjected peptide inhibitors and "dominant-negative forms" of caspase-9 and -1 into Xenopus fertilized eggs, and found that inhibitors of caspase-9, but not caspase-1, completely suppress SAMDC-induced apoptosis. The lysate of SAMDC-overexpressing late blastulae contained activity to cleave in vitro-synthesized [(35)S]procaspase-9, but not [(35)S]procaspase-1, and mRNA for caspase-9, but not caspase-1, occurred abundantly in the unfertilized egg as maternal mRNA. We also found that overexpression of caspase-9 and -1 equally executes the apoptosis, but the apoptosis executed by these mRNAs was only partially rescued by Bcl-2 and rescued embryos did not develop beyond neurula stage. These results indicate that activation of caspase-9 is a key step for execution of the maternally preset program of apoptosis in Xenopus early embryos.