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Luis Alberto Baena-Lopez, Lewis Arthurton, Marcus Bischoff, Jean-Paul Vincent, Cyrille Alexandre, Reuben McGregor
The caspase-mediated regulation of many cellular processes, including apoptosis, justifies the substantial interest in understanding all of the biological features of these enzymes. To complement functional assays, it is critical to identify caspase-activating cells in live tissues. Our work describes novel initiator caspase-reporters that, for the first time, provide direct information concerning the initial steps of the caspase activation cascade in Drosophila tissues. One of our caspase-sensors has capitalized on the rapid subcellular localization change of a fluorescent marker to uncover novel cellular apoptotic events...
November 9, 2018: Development
Salome Stierli, Ilaria Napoli, Ian J White, Anne-Laure Cattin, Anthony Monteza Cabrejos, Noelia Garcia Calavia, Liza Malong, Sara Ribeiro, Julie Nihouarn, Richard Williams, Kaylene M Young, William D Richardson, Alison C Lloyd
Peripheral nerves are highly regenerative in contrast to the poor regenerative capabilities of the CNS. Here we show that adult peripheral nerve is a more quiescent tissue than the CNS, yet all cell-types within a peripheral nerve proliferate efficiently following injury. Moreover, whereas oligodendrocytes are produced throughout life from a precursor pool, we find that the corresponding cell of the PNS, the myelinating Schwann cell (mSC) does not turnover in the adult. However, following injury, all mSCs can dedifferentiate to the proliferating progenitor-like SCs that orchestrate the regenerative response...
November 9, 2018: Development
Konstantin Doubrovinski, Joel Tchoufag, Kranthi Mandadapu
Understanding how forces and material properties give rise to tissue shapes is a fundamental question in developmental biology. Although Drosophila gastrulation is a major system for investigating tissue morphogenesis, there does not exist a consensus mechanical model that explains all the key features of this process. One key feature of Drosophila gastrulation is its anisotropy - the mesoderm constricts much more along one axis than along the other. Previous explanations have involved graded stress, anisotropic stresses or material properties, or mechanosensitive feedback...
November 6, 2018: Development
Amelia Felipo-Benavent, Cristina Úrbez, Noel Blanco-Touriñán, Antonio Serrano-Mislata, Nicolas Baumberger, Patrick Achard, Javier Agustí, Miguel A Blázquez, David Alabadí
The thickening of plant organs is supported by secondary growth, a process by which new vascular tissues (xylem and phloem) are produced. Xylem is composed of several cell types, including xylary fibers, parenchyma and vessel elements. In Arabidopsis, it has been shown that fibers are promoted by the class-I KNOX gene KNAT1 and the plant hormones gibberellins, and repressed by a small set of receptor-like kinases, but we lack a mechanistic framework to integrate their relative contributions. Here we show that DELLAs, negative elements of the gibberellin signaling pathway, physically interact with KNAT1 and impair its binding to KNAT1 binding sites...
November 2, 2018: Development
Nina Faye Sampilo, Nadezda A Stepicheva, Syed Aun Murtaza Zaidi, Lingyu Wang, Wei Wu, Athula Wikramanayake, Jia L Song
MicroRNAs (miRNAs) are highly conserved, small non-coding RNAs that regulate gene expressions by binding to the 3'untranslated region (UTR) of target mRNAs and silence translation. Some miRNAs are key regulators of the Wnt signaling pathways which impact developmental processes. This study investigates miRNA regulation of different isoforms of Dishevelled (Dvl/Dsh) , a key component in the Wnt signaling pathway. The sea urchin Dvl mRNA isoforms have similar spatial distribution in early development, but one isoform is distinctively expressed in the larval ciliary band...
November 2, 2018: Development
Akiko Suzuki, Ryohei Minamide, Junichi Iwata
Skeletal muscle development is controlled by a series of multiple orchestrated regulatory pathways. WNT/β-catenin is one of the most important pathways for myogenesis; however, it remains unclear how this signaling pathway regulates myogenesis in a temporal- and spatial-specific manner. Here we show that WNT/β-catenin signaling is crucial for myoblast fusion through regulation of the Nephrin ( Nphs1 ) gene in the Myog-Cre -expressing myoblast population. Mice deficient for the β-catenin gene in Myog-Cre -expressing myoblasts ( Ctnnb1 F/F ;Myog-Cre mice) displayed myoblast fusion defects, but not migration or cell proliferation defects...
November 2, 2018: Development
Ferenc Jankovics, Melinda Bence, Rita Sinka, Anikó Faragó, László Bodai, Aladár Pettkó-Szandtner, Karam Ibrahim, Zsanett Takács, Alexandra Brigitta Szarka-Kovács, Miklós Erdélyi
Self-renewal and differentiation of stem cells is one of the fundamental biological phenomena relying on proper chromatin organisation. In our study, we describe a novel chromatin regulator encoded by the Drosophila small ovary (sov) gene. We demonstrate that sov is required in both the germline stem cells (GSCs) and the surrounding somatic niche cells to ensure GSC survival and differentiation. Sov maintains niche integrity and function by repressing transposon mobility, not only in the germline, but also in the soma...
November 2, 2018: Development
Rebecca P Kim-Yip, Todd G Nystul
Adult stem cell niche boundaries must be precisely maintained to facilitate segregation of stem cell and daughter cell fates. However, the mechanisms that govern this process in epithelial tissues are not fully understood. In this study, we investigated the relationship between two signals, Wnt and EGFR, that are necessary for self-renewal of the epithelial follicle stem cells (FSCs) in the Drosophila ovary, but must be downregulated in cells that have exited the niche to allow for differentiation. We found that wingless produced by inner germarial sheath (IGS) cells acts over a short distance to activate Wnt signaling in FSCs, and that movement across the FSC niche boundary is limited...
November 2, 2018: Development
Stefan Kircher, Peter Schopfer
The molecular mechanism underlying the periodic induction of lateral roots, a paradigmatic example of clock-driven organ formation in plant development, is presently a matter of ongoing, controversial debate. Here we provide experimental evidence that this clock is frequency-modulated by light and that auxin serves as a mediator for translating continuous light signals into discontinuous gene activation signals preceding the initiation of lateral roots in Arabidopsis seedlings. Based on this evidence, we propose a molecular model of an ultradian biological clock involving auxin-dependent degradation of an AUX/IAA-type transcription repressor as a flexible, frequency-controlling delay element...
November 2, 2018: Development
Sergio Garrido-Jimenez, Angel-Carlos Roman, Alberto Alvarez-Barrientos, Jose Maria Carvajal-Gonzalez
In vertebrates, planar polarization of ciliary basal bodies has been associated with actin polymerization that acts downstream of the Frizzled-planar cell polarity (Fz-PCP) pathway. In Drosophila wing epithelial cells, which do not have cilia, centrioles also polarize in a Fz-PCP dependent manner, although the relationship with actin polymerization remains unknown. By combining existing and new quantitative methods, we unexpectedly found that known PCP effectors linked to actin polymerization phenotypes affect neither final centriole polarization nor apical centriole distribution...
November 2, 2018: Development
Jumana AlHaj Abed, Elnaz Ghotbi, Piao Ye, Alexander Frolov, Judith Benes, Richard S Jones
Polycomb-group (PcG)-mediated transcriptional repression of target genes can be delineated into two phases. First, following initial repression of target genes by gene-specific transcription factors, PcG proteins recognize the repressed state and assume control of the genes' repression. Once the silenced state is established, PcG proteins may maintain repression through an indefinite number of cell cycles. Little is understood about how PcG proteins initially recognize the repressed state of target genes and the steps leading to de novo establishment of PcG-mediated repression...
November 2, 2018: Development
Anshula Samarajeewa, Danielle R Lenz, Lihong Xie, Hao Chiang, Rory Kirchner, Joanna F Mulvaney, Albert S B Edge, Alain Dabdoub
Lack of sensory hair cell (HC) regeneration in mammalian adults is a major contributor to hearing loss. In contrast, the neonatal mouse cochlea retains a transient capacity for regeneration, and forced Wnt activation in neonatal stages promotes supporting cell (SC) proliferation and induction of ectopic HCs. We currently know little about the temporal pattern and underlying mechanism of this age-dependent regenerative response. Using an in vitro model, we show that Wnt activation promotes SC proliferation following birth, but prior to postnatal day (P) 5...
November 2, 2018: Development
Andre G Wallace, Hamidah Raduwan, John Carlet, Martha C Soto
During embryonic morphogenesis, cells and tissues undergo dramatic movements under the control of F-actin regulators. Our studies of epidermal cell migrations in developing C. elegans embryos have identified multiple plasma membrane signals that regulate the Rac GTPase, thus regulating WAVE and Arp2/3 complexes, to promote branched F-actin formation and polarized enrichment. We describe here a pathway that acts in parallel to Rac to transduce membrane signals to control epidermal F-actin through the GTPase RHO-1/RhoA...
November 2, 2018: Development
Shashwati Bhattacharya, Domenic Gargiulo, M Kathryn Iovine
The correct positioning of joints in the vertebrate skeleton is not well understood. Mutations in connexin43 (cx43) cause the short segment phenotype of the zebrafish short fin ( sof b123 ) mutant. We have shown that Cx43 suppresses evx1 expression, a transcription factor required for joint formation. Here, we provide novel insights into how Cx43 influences evx1 transcription. First, we find that Simplet (Smp) knockdown recapitulates the sof b123 phenotypes of reduced regenerate length and reduced segment length, and we find evidence for synergy between cx43 and smp Moreover, knockdown of Smp increases the evx1 expression, similar to cx43 knockdown...
October 30, 2018: Development
Saurabh S Kulkarni, Mustafa K Khokha
Congenital heart disease (CHD) is a major cause of infant mortality and morbidity, yet the genetic causes and mechanisms remain opaque. In a patient with CHD and heterotaxy, a disorder of left-right (LR) patterning, a de novo mutation was identified in the chromatin modifier, WDR5. WDR5 acts as a scaffolding protein in the H3K4 methyltransferase complex, but a role in LR patterning is unknown. Here, we show that Wdr5 depletion leads to LR patterning defects in Xenopus via its role in ciliogenesis. Unexpectedly, we find a dual role for WDR5 in LR patterning...
October 30, 2018: Development
Vinh Ngoc Pham, Xiaosa Xu, Enamul Huq
The transition from skotomorphogenesis to photomorphogenesis is regulated in part by COP1/SPA complex and PIFs in Arabidopsis The constitutive photomorphogenic (cop) phenotypes of the cop1 and spaQ mutants were shown to be due to a high abundance of the positively acting transcription factors. Here we show that the four major PIF proteins are unstable in cop1 mutant, and an overexpression of PIF1, PIF3, PIF4 and PIF5 suppresses the cop1 phenotypes in the dark. A comparison of the transcriptome data among cop1 , spaQ and pifQ reveals remarkably overlapping gene expression profiles with a preferential regulation of the PIF direct target genes...
October 30, 2018: Development
Natalie Gibb, Savo Lazic, Xuefei Yuan, Ashish R Deshwar, Meaghan Leslie, Michael D Wilson, Ian C Scott
A key event in heart development is the timely addition of cardiac progenitor cells, defects in which can lead to congenital heart defects. However, how the balance and proportion of progenitor proliferation versus addition to the heart is regulated remains poorly understood. Here we demonstrate that Hey2 functions to regulate the dynamics of cardiac progenitor addition to the zebrafish heart. We found that the previously noted increase in myocardial cell number found in the absence of Hey2 function was due to a pronounced expansion in the size of the cardiac progenitor pool...
October 24, 2018: Development
Liam Campbell, J Peter Etchells, Matthew Cooper, Manoj Kumar, Simon R Turner
Division of the cambial cells and their subsequent differentiation into xylem and phloem drives radial expansion of the hypocotyl. Following the transition to reproductive growth, a phase change occurs in the Arabidopsis hypocotyl. During this second phase, the relative rate of xylem production is dramatically increased compared to that of phloem and xylem fibres containing thick secondary cell walls also form. Using two different genetic backgrounds and different environmental conditions, we identified a set of core transcriptional changes associated with the switch to the second phase of growth in the hypocotyl...
October 24, 2018: Development
E Negreiros, S Herszterg, K Hwa, A Câmara, W B Dias, K Carneiro, E Bier, A Todeschini, H Araujo
Disorders of N-linked glycosylation are increasingly reported in the literature. However, targets responsible for the associated developmental and physiological defects are largely unknown. Bone Morphogenetic Proteins (BMPs) act as highly dynamic complexes to regulate several functions during development. The range and strength of BMP activity depend on interactions with glycosylated protein complexes in the extracellular milieu. Here we investigate the role of glycosylation for the function of the conserved extracellular BMP antagonist Short gastrulation (Sog)...
October 24, 2018: Development
Alicia Pérez Saturnino, Katharina Lust, Joachim Wittbrodt
Patterning of a continuously growing naive field in the context of a life-long growing organ such as the teleost eye is of highest functional relevance. Intrinsic and extrinsic signals were proposed to regulate lineage specification in progenitors that exit the stem cell niche in the ciliary marginal zone (CMZ). The proper cell type composition arising from those progenitors is prerequisite for retinal function. Our findings in the teleost medaka ( Oryzias latipes ) uncover that the Notch-Atoh7 axis continuously patterns the CMZ...
October 18, 2018: Development
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