Ve-ptp modulates vascular integrity by promoting adherens junction maturation

Background: Endothelial cell junctions control blood vessel permeability. Altered permeability can be associated with vascular fragility that leads to vessel weakness and haemorrhage formation. In vivo studies on the function of genes involved in the maintenance of vascular integrity are essential to better understand the molecular basis of diseases linked to permeability defects. Ve-ptp (Vascular Endothelial-Protein Tyrosine Phosphatase) is a transmembrane protein present at endothelial adherens junctions (AJs). Methodology/Principal Findings: We investigated the role of Ve-ptp in AJ maturation/stability and in the modulation of endothelial permeability using zebrafish (Danio rerio). Whole-mount in situ hybridizations revealed zve-ptp expression exclusively in the developing vascular system. Generation of altered zve-ptp transcripts, induced separately by two different splicing morpholinos, resulted in permeability defects closely linked to vascular wall fragility. The ultrastructural analysis revealed a statistically significant reduction of junction complexes and the presence of immature AJs in zve-ptp morphants but not in control embryos. Conclusions/Significance: Here we show the first in vivo evidence of a potentially critical role played by Ve-ptp in AJ maturation, an important event for permeability modulation and for the development of a functional vascular system

X-ray microscopy of living multicellular organisms with the Prague Asterix Iodine Laser System

Soft X-ray contact microscopy (SXCM) experiments have been performed using the Prague Asterix Iodine Laser System (PALS). Laser wavelength and pulse duration were λ = 1.314 μm and τ (FWHM) = 450 ps, respectively. Pulsed X rays were generated using teflon, gold, and molybdenum targets with laser intensities I ≥ 1014 W/cm2. Experiments have been performed on the nematodes Caenorhabditis elegans. Images were recorded on PMMA photo resists and analyzed using an atomic force microscope operating in contact mode. Our preliminary results indicate the suitability of the SXCM for multicellular specimens

Oocyte development and egg envelope formation in Oreochromis niloticus, a mouth-brooding cichlid fish

The development of the oocyte and of its associated follicle cells in the Nile tilapia, Oreochromis niloticus, has been examined by optical and transmission electron microscopy. During oocyte development the female gamete of Orochromis niloticus increases in size because of the accumulation of yolk in its cytoplasm. As the accumulation of yolk proceeds, the organization of cortex of the oocyte becomes very complex; all of the cytoplasmic organelles and several populations of vesicles can be found. On the other hand follicle cells also undergo a series of modifications: they first become cuboidal then cylindrical and their cytoplasm become densely populated with organelles. The mature egg of Oreochromis niloticus is surrounded by a thin acellular envelope (chorion) assembled during oocyte development. Biochemical analysis of isolated and purified chorions from mature females was also performed. SDS-PAGE under reducing conditions showed a reproducible pattern of three major polypeptides (121, 66 and 50 kD), most of which being glycosylated. The pattern of synthesis and assembly of the egg envelope in Oreochromis niloticus, a mouth-brooding cichlid fish, is also discussed

LOCALIZATION AND DISTRIBUTION OF ACTIN IN MAMMALIAN SPERM HEADS

Actin was identified in boar and mole spermatozoa by utilizing indirect immunofiuorescence, immunoelectron microscopy, and SDS-PAGE, followed by blot and screening with an anti-actin monoclonal antibody. Actin was detected in two places in the sperm head: the equatorial segment of the acrosome and the postacrosomal region. The protein was present in a nonfilamentous form and was localized under the plasma membrane. A small amount of actin was also detected in the sperm tail. The function of actin in the sperm head is discussed. \ua9 1986

Identification and expression pattern of mago nashi during zebrafish development

In a search for zebrafish genes expressed during early stages of development, we have identified two ESTs encoding proteins related to Drosophila mago nashi. Zebrafish mago nashi codes for a small protein with no clearly identified functional domains, and which is highly conserved during evolution. This paper describes the identification and a detailed gene expression analysis of zebrafish mago nashi during development. Our results demonstrate that mago nashi encodes a maternal transcript detected in both blastomeres and yolk cell at the 1\u20132 cell stages, and in the blastoderm during segmentation. We show that a putative microtubule-mediated transport of mago nashi mRNA from the vegetal hemisphere into animal blastomeres determines the localization of the transcript in the animal pole, immediately after fertilization. Furthermore, the microtubule array contained into the yolk cell seems to be responsible for the high level of mago nashi transcript detected in the central blastomeres at the 8\u201316 cell stages. Zygotic mago nashi is expressed into the dorsal-marginal region during gastrulation, and starting from somitogenesis to 24 hpf, the expression domain becomes progressively restricted to the developing neural tube and paraxial structures, and ventrally to the pronephric ducts. q 2004 Elsevier B.V. All rights reserved

Neurogenic role of prox1 in the CNS and lateral line development

In teleost, the lateral line is a sensory organ composed of neuromasts containing hair cells, expressing athl, and surrounded by supporting cells, expressing notch3. notch3 signalling seems to limit the number of cells that are allowed to adopt the hair cell fate while failure of notch3 signal generates an overproduction of athl expressing hair cells in the middle of the neuromast. In this report we analyze the role of prox1 in zebrafish (z-prox1) on neural and proneural genes in the neuromasts of the posterior lateral line. We have examinated the z-prox1 interaction with ath1 and notch3 in the lateral line system of zebrafish by both z-prox1 morpholino-mediated inactivation and z-prox1 mRNA overexpression. This gene is expressed in the migrating primordium, and its inactivation results in a reduced number of neuromasts at 48 hpf but does not affect the primordium migration. In particular, lack of prox1 inhibits the differentiation of ath1 expressing hair cells, while enhances the number of the supporting cells, expressing notch3. Injection of prox1 synthetic mRNA generates the opposite phenotype: the number of the pre-determined ath1 expressing hair cells is increased, while notch3 expression in the supporting cells is reduced. Moreover prox1 could have a role in timing regulation of the neuromasts development because morphant embryos rigenerate neuromasts after 48 hpf

Myogenic determination in Zebrafish is entirely dependent upon myf5 and myod but can be rescued by exogenous mrf4

Muscle regulatory factors activate myogenesis in all vertebrates, but their role has been studied in great detail only in the mouse embryo, where all but myogenin \u2013 Myod, Myf5 and Mrf4 \u2013 are sufficient to activate (albeit not completely) skeletal myogenesis. In the zebrafish embryo, myod and myf5 are required for induction of myogenesis because their simultaneous ablation prevents muscle development. Here we show that mrf4 but not myog can fully rescue myogenesis in the myod/myf5 double morphant via a selective and robust activation of myod, in keeping with its chromatin remodelling function in vitro. Rescue does not happen spontaneously, because the gene, unlike that in the mouse embryo, is expressed only at the onset of muscle differentiation, Moreover, because of the transient nature of morpholino inhibition, we were able to investigate how myogenesis occurs in the absence of a myotome. We report that in the complete absence of a myotome, subsequent myogenesis is abolished, whereas myogenesis does proceed, albeit abnormally, when the morpholino inhibition was not complete. Therefore our data also show that the early myotome is essential for subsequent skeletal muscle differentiation and patterning in the zebrafish