scholarly journals The hook shape of growing leaves results from an active regulatory process

2020 ◽  
Vol 71 (20) ◽  
pp. 6408-6417 ◽  
Author(s):  
Mathieu Rivière ◽  
Yoann Corre ◽  
Alexis Peaucelle ◽  
Julien Derr ◽  
Stéphane Douady
Keyword(s):  
Spatial Organization ◽  
Mechanical Test ◽  
Mechanical Strain ◽  
Intrinsic Curvature ◽  
Differential Growth ◽  
Regulatory Processes ◽  
Mechanical Investigation ◽  
Constant Distance ◽  
Shed Light ◽  
Hook Curvature

Abstract The rachis of most growing compound leaves observed in nature exhibits a stereotypical hook shape. In this study, we focus on the canonical case of Averrhoa carambola. Combining kinematics and mechanical investigation, we characterize this hook shape and shed light on its establishment and maintenance. We show quantitatively that the hook shape is a conserved bent zone propagating at constant velocity and constant distance from the apex throughout development. A simple mechanical test reveals non-zero intrinsic curvature profiles for the rachis during its growth, indicating that the hook shape is actively regulated. We show a robust spatial organization of growth, curvature, rigidity, and lignification, and their interplay. Regulatory processes appear to be specifically localized: in particular, differential growth occurs where the elongation rate drops. Finally, impairing the graviception of the leaf on a clinostat led to reduced hook curvature but not to its loss. Altogether, our results suggest a role for proprioception in the regulation of the leaf hook shape, likely mediated via mechanical strain.

scholarly journals Hook shape of growing leaves results from an active regulation

2020 ◽  
Author(s):  
Mathieu Rivière ◽  
Yoann Corre ◽  
Alexis Peaucelle ◽  
Julien Derr ◽  
Stéphane Douady
Keyword(s):  
Spatial Organization ◽  
Mechanical Test ◽  
Mechanical Strain ◽  
Elongation Rate ◽  
Spontaneous Curvature ◽  
Differential Growth ◽  
Active Regulation ◽  
Mechanical Investigation ◽  
Constant Distance ◽  
Shed Light

The rachis of most growing compound leaves observed in nature exhibit a stereotyped hook shape. In this study, we focus on the canonical case of Averrhoa carambola. Combining kinematics and mechanical investigation, we characterize this hook shape and shed light on its establishment and maintenance. We show quantitatively that the hook shape is a conserved bent zone propagating at constant velocity and constant distance from the apex throughout development. A simple mechanical test first reveals non-zero spontaneous curvature profiles for the growing leaves, indicating that the hook shape is actively regulated. It then evidences the robust spatial organization of growth, curvature, rigidity and lignification and their interplay. Regulation processes appear to be specifically localized: in particular, differential growth occurs where the elongation rate drops. Finally, impairing the graviception of the leaf on a clinostat led to reduced hook curvatures but not to its loss. Altogether our results suggest a role for proprioception in the regulation of the apical hook, likely mediated via mechanical strain.

scholarly journals Spatial Organization of Chromatin: Emergence of Chromatin Structure During Development

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Rajarshi P. Ghosh ◽  
Barbara J. Meyer
Keyword(s):  
Single Molecule ◽  
Genome Organization ◽  
Spatial Organization ◽  
Super Resolution ◽  
Annual Review ◽  
Publication Date ◽  
Cellular Processes ◽  
Regulatory Processes ◽  
Genome Wide ◽  
Resolution Imaging

Nuclei are central hubs for information processing in eukaryotic cells. The need to fit large genomes into small nuclei imposes severe restrictions on genome organization and the mechanisms that drive genome-wide regulatory processes. How a disordered polymer such as chromatin, which has vast heterogeneity in its DNA and histone modification profiles, folds into discernibly consistent patterns is a fundamental question in biology. Outstanding questions include how genomes are spatially and temporally organized to regulate cellular processes with high precision and whether genome organization is causally linked to transcription regulation. The advent of next-generation sequencing, super-resolution imaging, multiplexed fluorescent in situ hybridization, and single-molecule imaging in individual living cells has caused a resurgence in efforts to understand the spatiotemporal organization of the genome. In this review, we discuss structural and mechanistic properties of genome organization at different length scales and examine changes in higher-order chromatin organization during important developmental transitions. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals Lysosomal Storage Disorders Shed Light on Lysosomal Dysfunction in Parkinson’s Disease

2020 ◽  
Vol 21 (14) ◽  
pp. 4966 ◽  
Author(s):  
Shani Blumenreich ◽  
Or B. Barav ◽  
Bethan J. Jenkins ◽  
Anthony H. Futerman
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Neurological Diseases ◽  
Critical Role ◽  
Lysosomal Storage ◽  
Loss Of Function ◽  
Regulatory Processes ◽  
Lysosomal Dysfunction ◽  
The Brain ◽  
Shed Light

The lysosome is a central player in the cell, acting as a clearing house for macromolecular degradation, but also plays a critical role in a variety of additional metabolic and regulatory processes. The lysosome has recently attracted the attention of neurobiologists and neurologists since a number of neurological diseases involve a lysosomal component. Among these is Parkinson’s disease (PD). While heterozygous and homozygous mutations in GBA1 are the highest genetic risk factor for PD, studies performed over the past decade have suggested that lysosomal loss of function is likely involved in PD pathology, since a significant percent of PD patients have a mutation in one or more genes that cause a lysosomal storage disease (LSD). Although the mechanistic connection between the lysosome and PD remains somewhat enigmatic, significant evidence is accumulating that lysosomal dysfunction plays a central role in PD pathophysiology. Thus, lysosomal dysfunction, resulting from mutations in lysosomal genes, may enhance the accumulation of α-synuclein in the brain, which may result in the earlier development of PD.

scholarly journals Quantifying the Biophysical Impact of Budding Cell Division on the Spatial Organization of Growing Yeast Colonies

2020 ◽  
Vol 10 (17) ◽  
pp. 5780
Author(s):  
Mikahl Banwarth-Kuhn ◽  
Jordan Collignon ◽  
Suzanne Sindi
Keyword(s):  
Cell Division ◽  
Nutrient Limitation ◽  
Large Scale ◽  
Daughter Cell ◽  
Spatial Organization ◽  
Experimental Studies ◽  
Differential Growth ◽  
Yeast Saccharomyces Cerevisiae ◽  
Scale Properties ◽  
The Impact

Spatial patterns in microbial colonies are the consequence of cell-division dynamics coupled with cell-cell interactions on a physical media. Agent-based models (ABMs) are a powerful tool for understanding the emergence of large scale structure from these individual cell processes. However, most ABMs have focused on fission, a process by which cells split symmetrically into two daughters. The yeast, Saccharomyces cerevisiae, is a model eukaryote which commonly undergoes an asymmetric division process called budding. The resulting mother and daughter cells have unequal sizes and the daughter cell does not inherit the replicative age of the mother. In this work, we develop and analyze an ABM to study the impact of budding cell division and nutrient limitation on yeast colony structure. We find that while budding division does not impact large-scale properties of the colony (such as shape and size), local spatial organization of cells with respect to spatial layout of mother-daughter cell pairs and connectivity of subcolonies is greatly impacted. In addition, we find that nutrient limitation further promotes local spatial organization of cells and changes global colony organization by driving variation in subcolony sizes. Moreover, resulting differences in spatial organization, coupled with differential growth rates from nutrient limitation, create distinct sectoring patterns within growing yeast colonies. Our findings offer novel insights into mechanisms driving experimentally observed sectored yeast colony phenotypes. Furthermore, our work illustrates the need to include relevant biophysical mechanisms when using ABMs to compare to experimental studies.

scholarly journals Adsorption of semiflexible polymers in crowded environments

2021 ◽  
Author(s):  
Gaurav Chauhan ◽  
Michael L. Simpson ◽  
Steven M. Abel
Keyword(s):  
Computer Simulations ◽  
Spatial Organization ◽  
Volume Fraction ◽  
Bending Stiffness ◽  
Radius Of Gyration ◽  
Semiflexible Polymers ◽  
Size And Shape ◽  
Crowded Environments ◽  
Shed Light ◽  
Induced Adsorption

Macromolecular crowding is a feature of cellular and cell-free systems that, through depletion effects, can impact the interactions of semiflexible biopolymers with surfaces. In this work, we use computer simulations to study crowding-induced adsorption of semiflexible polymers on otherwise repulsive surfaces. Crowding particles are modeled explicitly, and we investigate the interplay between the bending stiffness of the polymer and the volume fraction and size of crowding particles. Adsorption is promoted by stiffer polymers, smaller crowding particles, and larger volume fractions of crowders. We characterize transitions from non-adsorbed to partially and strongly adsorbed states as a function of the bending stiffness. The crowding-induced transitions occur at smaller values of the bending stiffness as the volume fraction of crowders increases. Concomitant effects on the size and shape of the polymer are reflected by crowding- and stiffness-dependent changes to the radius of gyration. We also demonstrate that curvature of the confining surface can induce desorption when the bending stiffness is sufficiently large. The results of our simulations shed light on the interplay of crowding and bending stiffness on the spatial organization of biopolymers in encapsulated cellular and cell-free systems.

scholarly journals Hat törvényhatósági jogú város székházépítési pályázata •

2021 ◽  
Author(s):  
Megyeri-Pálffi Zoltán ◽  
Marótzy Katalin
Keyword(s):  
Spatial Organization ◽  
Large City ◽  
Specific System ◽  
Large Cities ◽  
City Hall ◽  
Design Competition ◽  
New Perspective ◽  
Space Requirements ◽  
The City ◽  
Shed Light

A magyar nagyvárosok városházái – amelyek többsége a magyar historizmus legszebb építészeti emlékei közé tartozik – jól reprezentálják azt a robbanásszerű polgárosodást és modernizációt, amely az Osztrák– Magyar Monarchia (1867) létrejöttével bekövetkező változások velejárója volt. Tanulmányunkban a korszak építészeti tendenciáinak megismeréséhez kívánunk egy új szempontot adni: a nagy városházák térszervezetét vizsgáljuk meg a közigazgatási struktúra történeti alakulásának fényében. Ezzel az elemzéssel egyúttal az adminisztráció és az építészet sajátos viszonyrendszerét is megvilágítjuk. A vizsgálat alapját a dualizmus korának magyar építészeti szaksajtójában közölt hat törvényhatósági jogú város részletesebb pályázati dokumentációja adja, amely látványosan tükrözi a korszak városháza- építészeti tendenciáit. Győr (1893–1894), Pécs (1902–1903), Marosvásárhely (1905), Szabadka (1906), Pozsony (1907) és Kolozsvár (1910) városi székházainak tervpályázati anyagát dolgoztuk fel, aminek köszönhetően a városháza mint jelentős közigazgatási épülettípust elemeztük az építészeti funkció és a hely igény relációjában. Így – a legnagyobb városházák pályázatain keresztül – a kor városházáinak mint adminisztratív épületeknek – ismert építészeti reprezentativitása mellett – alaprajzi rendszerükben, helyiség struktúrájukban megfigyelhető speciális vonásait rajzolhatjuk fel. The city halls of the Hungarian large cities – most of which are among the most beautiful architectural monuments of Hungarian historicism – well represent the explosive civilization and modernization that accompanied the changes that took place with the establishment of the Austro–Hungarian Monarchy (1867). In our study, we want to give a new perspective to get to know the architectural tendencies of the period: we examine the spatial organization of large city halls in the light of the historical development of the administrative structure. With this analysis, we also shed light on the specific system of relations between administration and architecture. The study is based on the more detailed tender documentation of six cities with municipal rights published in the Hungarian architectural press of the age of dualism, which spectacularly reflects the city hall architectural tendencies of the period. We wrote up the design competition material of the city headquarters of Győr (1893–1894), Pécs (1902– 1903), Târgu Mureş (1905), Subotica (1906), Bratislava (1907) and Cluj-Napoca (1910), thanks to which we analyzed the city hall as a significant administrative building type in relation to architectural function and space requirements. Thus, through the tenders of the largest city halls, we can draw the special features of the city halls of the age as administrative buildings, in addition to their well-known architectural representativeness, in their floor plan system and room structure.

scholarly journals CPAP promotes angiogenesis and metastasis by enhancing STAT3 activity

2019 ◽  
Vol 27 (4) ◽  
pp. 1259-1273 ◽  
Author(s):  
Ruo-Yu Chen ◽  
Chia-Jui Yen ◽  
Yao-Wen Liu ◽  
Chun-Guo Guo ◽  
Chieh-Yu Weng ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Target Gene ◽  
Target Genes ◽  
Ex Vivo ◽  
Functional Characterization ◽  
Migration And Invasion ◽  
Transcriptional Coactivator ◽  
Mechanical Investigation ◽  
Shed Light

Abstract Centrosomal P4.1-associated protein (CPAP) is overexpressed in hepatocellular carcinoma (HCC) and positively correlated with recurrence and vascular invasion. Here, we found that CPAP plays an important role in HCC malignancies. Functional characterization indicated that CPAP overexpression increases tumor growth, angiogenesis, and metastasis ex vivo and in vivo. In addition, overexpressed CPAP contributes to sorafenib resistance. Mechanical investigation showed that the expression level of CPAP is positively correlated with activated STAT3 in HCC. CPAP acts as a transcriptional coactivator of STAT3 by directly binding with STAT3. Interrupting the interaction between CPAP and STAT3 attenuates STAT3-mediated tumor growth and angiogenesis. Overexpression of CPAP upregulates several STAT3 target genes such as IL-8 and CD44 that are involved in angiogenesis, and CPAP mRNA expression is positively correlated with the levels of both mRNAs in HCC. Knocked-down expression of CPAP impairs IL-6-mediated STAT3 activation, target gene expression, cell migration, and invasion abilities. IL-6/STAT3-mediated angiogenesis is significantly increased by CPAP overexpression and can be blocked by decreased expression of IL-8. Our findings not only shed light on the importance of CPAP in HCC malignancies, but also provide potential therapeutic strategies for inhibiting the angiogenesis pathway and treating metastatic HCC.

Central Nervous System Embryogenesis and Its Failures

2002 ◽  
Vol 5 (5) ◽  
pp. 425-447 ◽  
Author(s):  
Felicitas L. Lacbawan ◽  
Maximilian Muenke
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Neuronal Migration ◽  
Intracellular Signaling ◽  
Spatial Organization ◽  
Molecular Mechanisms ◽  
Synapse Formation ◽  
Proper Function ◽  
Stages Of Development ◽  
Regulatory Processes

The well-orchestrated development of the central nervous system (CNS) requires highly integrated regulatory processes to ensure its precise spatial organization that provides the foundation for proper function. As emphasized in this review, the type, timing, and location of regulatory molecules influence the different stages of development from neuronal induction, regional specification, neuronal specification, and neuronal migration to axonal growth and guidance, neuronal survival, and synapse formation. The known molecular mechanisms are summarized from studies of invertebrates and lower vertebrates, in which we have learned more about the different ligands, receptors, transcription factors, and the intracellular signaling pathways that play specific roles in the different stages of development. Despite known molecular mechanisms of some disturbances, most of the clinical entities that arise from failures of CNS embryogenesis remain unexplained. As more novel genes and their functions are discovered, existing mechanisms will be refined and tenable explanations will be made. With these limitations, two specific clinical entities that have been relatively well studied, holoprosen-cephaly and neuronal migration defects, are discussed in more detail to illustrate the complexity of regulatory mechanisms that govern well-defined stages of CNS development.

Computational Micrograph Registration with Sieve Processes

1996 ◽  
Vol 54 ◽  
pp. 440-441
Author(s):  
P.J. Phillips ◽  
J. Huang ◽  
S. M. Dunn
Keyword(s):  
Planar Graph ◽  
Efficient Algorithm ◽  
Spatial Organization ◽  
Spatial Arrangement ◽  
Stereo Image ◽  
Image Model ◽  
Geometric Invariants ◽  
Point Set

In this paper we present an efficient algorithm for automatically finding the correspondence between pairs of stereo micrographs, the key step in forming a stereo image. The computation burden in this problem is solving for the optimal mapping and transformation between the two micrographs. In this paper, we present a sieve algorithm for efficiently estimating the transformation and correspondence.In a sieve algorithm, a sequence of stages gradually reduce the number of transformations and correspondences that need to be examined, i.e., the analogy of sieving through the set of mappings with gradually finer meshes until the answer is found. The set of sieves is derived from an image model, here a planar graph that encodes the spatial organization of the features. In the sieve algorithm, the graph represents the spatial arrangement of objects in the image. The algorithm for finding the correspondence restricts its attention to the graph, with the correspondence being found by a combination of graph matchings, point set matching and geometric invariants.

Caveolin-1, galectin-3 and lipid raft domains in cancer cell signalling

2015 ◽  
Vol 57 ◽  
pp. 189-201 ◽  
Author(s):  
Jay Shankar ◽  
Cecile Boscher ◽  
Ivan R. Nabi
Keyword(s):  
Plasma Membrane ◽  
Lipid Rafts ◽  
Cancer Cell ◽  
Cellular Response ◽  
Spatial Organization ◽  
Essential Feature ◽  
Cell Signalling ◽  
Coated Pits ◽  
Signalling Molecules ◽  
Raft Domains

Spatial organization of the plasma membrane is an essential feature of the cellular response to external stimuli. Receptor organization at the cell surface mediates transmission of extracellular stimuli to intracellular signalling molecules and effectors that impact various cellular processes including cell differentiation, metabolism, growth, migration and apoptosis. Membrane domains include morphologically distinct plasma membrane invaginations such as clathrin-coated pits and caveolae, but also less well-defined domains such as lipid rafts and the galectin lattice. In the present chapter, we will discuss interaction between caveolae, lipid rafts and the galectin lattice in the control of cancer cell signalling.

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