Genes controlling cellular polarity in Drosophila

Development ◽  
1993 ◽  
Vol 119 (Supplement) ◽  
pp. 269-277 ◽  
Author(s):  
David Gubb
Keyword(s):  
Signal Transduction ◽  
Cell Membrane ◽  
Mirror Image ◽  
Fine Scale ◽  
Embryonic Cells ◽  
Cellular Polarity ◽  
Spatial Organisation ◽  
Large Numbers ◽  
Transmission Of Information ◽  
Segment Polarity

The control of cellular polarity is one of the least understood aspects of development. Genes have been identified in Drosophila that affect the polarity of embryonic cells in all three axes, apical-hasal, proximodistal and dorsoventral. Mutations that affect adult polarity are also known and mutant flies show several types of pattern alteration, including rotations and mirror-image duplications. Imaginal discs are much greater in size, however, than the embryo, and adult structures contain very large numbers of cells, many of which are not visibly differentiated with respect to their immediate neighbours. In regions where neighbouring cells are similar to each other, the imaginal polarity mutants alter the orientation of bristles and hairs but do not change cellular fate. Other regions, such as the tarsal segments of the legs, the ommatidia of the eye and the bracted bristle sockets on the tibia, behave as discrete fields. Within these fields, fine-scale mirror-image reversals and pattern duplications are observed, analogous to those caused by the embryonic segment polarity mutants. Thus, the polarised transmission of information can affect either orientation or fate depending on whether cells are differentiated from their immediate neighbours. Cellular polarity will be critically dependent on both the internal cytoskeletal architecture and the spatial organisation of signal transduction molecules within the cell membrane.

Structure of the chloroplast and its DNA in chloromonadophycean algae

1981 ◽  
Vol 49 (1) ◽  
pp. 401-409
Author(s):  
A.W. Coleman ◽  
P. Heywood
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Membrane ◽  
Nuclear Envelope ◽  
Chloroplast Dna ◽  
Single Layer ◽  
Longitudinal Axis ◽  
Chloroplast Envelope ◽  
Large Numbers ◽  
Gonyostomum Semen ◽  
Chloroplast Stroma

The arrangement and ultrastructure of chloroplasts is described for the Chloromonadophycean algae gonyostomum semen Diesing and Vacuolaria virescens Cienkowsky. The chloroplasts are present in large numbers and are discoid structures approximately 3–4 micrometer in length by 2–3 micrometer in width. In Gonyostomum semen the chloroplasts form a single layer immediately interior to the cell membrane; frequently their longitudinal axis parallels the longitudinal axis of the cell. The chloroplasts in Vacuolaria virescens are more than I layer deep and do not appear to be preferentially oriented. In both organisms, chloroplast bands usually consist of 3 apposed thylakoids, although fusion and interconnections between adjacent bands frequently occur. External to the girdle band (the outermost thylakoids) is the chloroplast envelope. This is bounded by endoplasmic reticulum but there is no immediately apparent continuity between this endoplasmic reticulum and the nuclear envelope. Electron-dense spheres in the chloroplast stroma are thought to be lipid food reserve. Ring-shaped electron-translucent regions in the chloroplast contain chloroplast DNA. The DNA is distributed along this ring in an uneven fashion and, when stained, resembles a string of beads. Each plastid has I ring, and the ring is unbroken in the intact plastid.

The Culture of Small Aggregates of Amphibian Embryonic Cells in vitro

Development ◽  
1963 ◽  
Vol 11 (1) ◽  
pp. 135-154
Author(s):  
K. W. Jones ◽  
T. R. Elsdale
Keyword(s):  
Pigment Cells ◽  
Two Dimensional ◽  
Embryonic Cells ◽  
Common Procedure ◽  
Large Numbers ◽  
Organ Type ◽  
Typical Cell ◽  
Primary Explant ◽  
Migration Of Cells

A Common procedure in amphibian embryology has been to remove portions from embryos and culture these under conditions in which the large numbers of cells retain a close-knit association, favourable to the differentiation of primitive organs in the explant. It has not, in general, been the aim to employ the primary explant as a source of a two-dimensional outgrowth of cells on the substrate, as in typical cell culture procedures. Because of their inherent migratory tendencies, however, outgrowths of pigment cells are readily obtained from explants of the amphibian neural crest, and these have stimulated the interest of a number of investigators (see Wilde, 1961). Holtfreter (1938, 1946) and Finnegan (1953) have also observed the migration of cells from explants of Urodele embryos. Several investigators have employed cell cultures as opposed to organ type cultures in induction studies, Niu & Twitty (1953), Niu (1958), Barth & Barth (1959) and Becker, Tiedemann & Tiedemann (1959).

Dose-dependent regulation of pair-rule stripes by gap proteins and the initiation of segment polarity

Development ◽  
1990 ◽  
Vol 110 (3) ◽  
pp. 759-767 ◽  
Author(s):  
R. Warrior ◽  
M. Levine
Keyword(s):  
Expression Patterns ◽  
Gene Products ◽  
Embryonic Cells ◽  
Periodic Patterns ◽  
Threshold Response ◽  
Gap Gene ◽  
Relative Placement ◽  
Segment Polarity ◽  
Pair Rule Gene ◽  
Pair Rule

A key step in Drosophila segmentation is the establishment of periodic patterns of pair-rule gene expression in response to gap gene products. From an examination of the distribution of gap and pair-rule proteins in various mutants, we conclude that the on/off periodicity of pair-rule stripes depends on both the exact concentrations and combinations of gap proteins expressed in different embryonic cells. It has been suggested that the distribution of gap gene products depends on cross-regulatory interactions among these genes. Here we provide evidence that autoregulation also plays an important role in this process since there is a reduction in the levels of Kruppel (Kr) RNA and protein in a Kr null mutant. Once initiated by the gap genes each pair-rule stripe is bell shaped and has ill-defined margins. By the end of the fourteenth nuclear division cycle, the stripes of the pair-rule gene even-skipped (eve) sharpen and polarize, a process that is essential for the precisely localized expression of segment polarity genes. This sharpening process appears to depend on a threshold response of the eve promoter to the combinatorial action of eve and a second pair-rule gene hairy. The eve and hairy expression patterns overlap but are out of register and the cells of maximal overlap form the anterior margin of the polarized eve stripe. We propose that the relative placement of the eve and hairy stripes may be an important factor in the initiation of segment polarity.

Intracellular signalling

2010 ◽  
pp. 169-176
Author(s):  
R. Andres Floto
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Intracellular Signalling ◽  
Cell Surface Receptors ◽  
Surface Receptors ◽  
Transmission Of Information ◽  
Effective Transmission

This section outlines the general principles of intracellular signalling. Focusing on cell surface receptors, the requirements for effective transmission of information across the plasma membrane are outlined. The principal mechanisms utilized in mammalian signal transduction are described. For each, the pathological consequences of aberrant signalling and means by which pathways can be pharmacologically targeted are described in molecular terms....

Intracellular signalling

2020 ◽  
pp. 256-265
Author(s):  
R. Andres Floto
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Intracellular Signalling ◽  
Signalling Pathways ◽  
Molecular Processes ◽  
Surface Receptors ◽  
Intracellular Signalling Pathways ◽  
Transmission Of Information ◽  
Effective Transmission

This chapter outlines the general principles of intracellular signalling. Focusing on cell surface receptors, the requirements for effective transmission of information across the plasma membrane are outlined. The principal mechanisms utilized in mammalian signal transduction are described. For each, the pathological consequences of aberrant signalling and means by which pathways can be pharmacologically targeted are described in molecular terms. Intracellular signalling pathways permit the transmission and integration of information within cells. Mammalian receptor signalling relies on only a small number of distinct molecular processes which interact to determine cellular responses. Rapid advances in our knowledge of the mechanisms of intracellular signalling has greatly increased understanding of how cells function physiologically, how they malfunction pathologically, and how their behaviour might be manipulated therapeutically.

scholarly journals Spatial Turing-type Pattern Formation in a Model of Signal Transduction Involving Membrane-based Receptors Coupled by G Proteins

2006 ◽  
Vol 2 ◽  
pp. 117693510600200
Author(s):  
Chontita Rattanakul ◽  
Yongwimon Lenbury ◽  
Jonathan Bell ◽  
Varanuj Chatsudthipong ◽  
Wannapong Triampo ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Cell Membrane ◽  
G Proteins ◽  
Surface Membrane ◽  
Reaction Diffusion ◽  
Nonlinear Stability Analysis ◽  
Functional Responses ◽  
Weakly Nonlinear ◽  
Messenger Molecules ◽  
Type Pattern

In this paper, a model of signaling pathways involving G proteins is investigated. The model incorporates reaction-diffusion mechanisms in which various reactants participate inside and on the extra-cellular surface membrane. The messenger molecules may diffuse over the surface of the cell membrane and signal transduction across the cell membrane is mediated by membrane receptor bound proteins which connect the genetically controlled biochemical intra-cellular reactions to the production of the second messenger, leading to desired functional responses. Dynamic and steady-state properties of the model are then investigated through weakly nonlinear stability analysis. Turing-type patterns are shown to form robustly under different delineating conditions on the system parameters. The theoretical predictions are then discussed in the context of some recently reported experimental evidence.

scholarly journals Dexamethasone Modulates Nonvisual Opsins, Glucocorticoid Receptor, and Clock Genes inDanio rerioZEM-2S Cells

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Jennifer Caroline Sousa ◽  
Keila Karoline Magalhães-Marques ◽  
Sanseray da Silveira Cruz-Machado ◽  
Maria Nathalia Moraes ◽  
Ana Maria de Lauro Castrucci
Keyword(s):  
Cell Membrane ◽  
Glucocorticoid Receptor ◽  
Nuclear Localization ◽  
Clock Genes ◽  
Clock Synchronization ◽  
Cellular Distribution ◽  
Embryonic Cells ◽  
Light Conditions ◽  
Peripheral Clocks ◽  
First Time

Here we report, for the first time, the differential cellular distribution of two melanopsins (Opn4m1 and Opn4m2) and the effects of GR agonist, dexamethasone, on the expression of these opsins and clock genes, in the photosensitiveD. rerioZEM-2S embryonic cells. Immunopositive labeling for Opn4m1 was detected in the cell membrane whereas Opn4m2 labeling shows nuclear localization, which did not change in response to light.opn4m1,opn4m2,gr,per1b,andcry1bpresented an oscillatory profile of expression in LD condition. In both DD and LD condition, dexamethasone (DEX) treatment shifted the peak expression ofper1bandcry1btranscripts to ZT16, which corresponds to the highestopn4m1expression. Interestingly, DEX promoted an increase ofper1bexpression when applied in LD condition but a decrease when the cells were kept under DD condition. Although DEX effects are divergent with different light conditions, the response resulted in clock synchronization in all cases. Taken together, these data demonstrate thatD. rerioZEM-2S cells possess a photosensitive system due to melanopsin expression which results in an oscillatory profile of clock genes in response to LD cycle. Moreover, we provide evidence that glucocorticoid acts as a circadian regulator ofD. rerioperipheral clocks.

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