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Wayne A Johnson - One of the best experts on this subject based on the ideXlab platform.
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from lineage to wiring specificity pou domain transcription factors control precise connections of drosophila olfactory projection neurons
Cell, 2003Co-Authors: Takaki Komiyama, Wayne A Johnson, Gregory S X E JefferisAbstract:Abstract Axonal selection of synaptic partners is generally believed to determine wiring specificity in the nervous system. However, we have recently found evidence for specific dendritic targeting in the olfactory system of Drosophila : second order olfactory neurons (Projection Neurons) from the anterodorsal (adPN) and lateral (lPN) lineages send their dendrites to stereotypical, intercalating but non-overlapping glomeruli. Here we show that POU domain transcription factors, Acj6 and Drifter, are expressed in adPNs and lPNs respectively, and are required for their dendritic targeting. Moreover, misexpression of Acj6 in lPNs, or Drifter in adPNs, results in dendritic targeting to glomeruli normally reserved for the other PN lineage. Thus, Acj6 and Drifter translate PN lineage information into distinct dendritic targeting specificity. Acj6 also controls stereotypical axon terminal arborization of PNs in a central target, suggesting that the connectivity of PN axons and dendrites in different brain centers is coordinately regulated.
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restricted patterning of vestigial expression in drosophila wing imaginal discs requires synergistic activation by both mad and the drifter pou domain transcription factor
Development, 2000Co-Authors: Kaan Certel, Angela Hudson, Sean B Carroll, Wayne A JohnsonAbstract:The Drosophila Vestigial protein has been shown to play an essential role in the regulation of cell proliferation and differentiation within the developing wing imaginal disc. Cell-specific expression of vg is controlled by two separate transcriptional enhancers. The boundary enhancer controls expression in cells near the dorsoventral (DV) boundary and is regulated by the Notch signal transduction pathway, while the quadrant enhancer responds to the Decapentaplegic and Wingless morphogen gradients emanating from cells near the anteroposterior (AP) and DV boundaries, respectively. MAD-dependent activation of the vestigial quadrant enhancer results in broad expression throughout the wing pouch but is excluded from cells near the DV boundary. This has previously been thought to be due to direct repression by a signal from the DV boundary; however, we show that this exclusion of quadrant enhancer-dependent expression from the DV boundary is due to the absence of an additional essential activator in those cells. The Drosophila POU domain transcriptional regulator, Drifter, is expressed in all cells within the wing pouch expressing a vgQ-lacZ transgene and is also excluded from the DV boundary. Viable drifter hypomorphic mutations cause defects in cell proliferation and wing vein patterning correlated with decreased quadrant enhancer-dependent expression. Drifter misexpression at the DV boundary using the GAL4/UAS system causes ectopic outgrowths at the distal wing tip due to induction of aberrant Vestigial expression, while a dominant-negative Drifter isoform represses expression of vgQ-lacZ and causes severe notching of the adult wing. In addition, we have identified an essential evolutionarily conserved sequence element bound by the Drifter protein with high affinity and located adjacent to the MAD binding site within the quadrant enhancer. Our results demonstrate that Drifter functions along with MAD as a direct activator of Vestigial expression in the wing pouch.
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function of the drosophila pou domain transcription factor drifter as an upstream regulator of breathless receptor tyrosine kinase expression in developing trachea
Development, 1996Co-Authors: Michael G Anderson, Sarah J Certel, Kaan Certel, Denise J Montell, Wayne A JohnsonAbstract:Organogenesis of the Drosophila tracheal system involves extensive directed cell migrations leading to a stereotypic series of interconnected tubules. Although numerous gene products have been shown to be essential for tracheal morphogenesis, direct functional relationships between participants have not been previously established. Both the breathless gene, encoding a Drosophila fibroblast growth factor receptor tyrosine kinase homologue, and the POU-domain transcription factor gene, drifter, are expressed in all tracheal cells and are essential for directed cell migrations. We demonstrate here that ubiquitously expressed Breathless protein under control of a heterologous heat-shock promoter is able to rescue the severely disrupted tracheal phenotype associated with drifter loss-of-function mutations. In the absence of Drifter function, breathless expression is initiated normally but transcript levels fall drastically to undetectable levels as tracheal differentiation proceeds. In addition, breathless regulatory DNA contains seven high affinity Drifter binding sites similar to previously identified Drifter recognition elements. These results suggest that the Drifter protein, which maintains its own expression through a tracheal-specific autoregulatory enhancer, is not necessary for initiation of breathless expression but functions as a direct transcriptional regulator necessary for maintenance of breathless transcripts at high levels during tracheal cell migration. This example of a mechanism for maintenance of a committed cell fate offers a model for understanding how essential gene activities can be maintained throughout organogenesis.
Pearn P. Niiler - One of the best experts on this subject based on the ideXlab platform.
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pathways of marine debris derived from trajectories of lagrangian drifters
Marine Pollution Bulletin, 2012Co-Authors: Nikolai Maximenko, Jan Hafner, Pearn P. NiilerAbstract:Abstract Global set of trajectories of satellite-tracked Lagrangian drifters is used to study the dynamics of marine debris. A probabilistic model is developed to eliminate the bias in spatial distribution of drifter data due to heterogeneous deployments. Model experiments, simulating long-term evolution of initially homogeneous drifter array, reveal five main sites of drifter aggregation, located in the subtropics and maintained by converging Ekman currents. The paper characterizes the geography and structure of the collection regions and discusses factors that determine their dynamics. A new scale R c = (4 k / |D |) 1/2 is introduced to characterize tracer distribution under competing effects of horizontal divergence D and diffusion k . Existence and locations of all five accumulation zones have been recently confirmed by direct measurements of microplastic at the sea surface.
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A state‐space model for ocean drifter motions dominated by inertial oscillations
Journal of Geophysical Research, 2005Co-Authors: Thomas Bengtsson, Ralph F. Milliff, Doug Nychka, Richard H. Jones, Pearn P. NiilerAbstract:[1] Coincident ocean drifter position and surface wind time series observed on hourly timescales are used to estimate upper ocean dissipation and atmosphere-ocean coupling coefficients in the Labrador Sea. A discrete-process model based on finite differences is used to regress ocean accelerations on ocean velocity estimates but fails because errors in the discrete approximations for the ocean velocities are biased and accumulate over time. Model identification is achieved by fitting a stochastic differential equation model based on classical upper ocean physics to the drifter data via the Kalman filter. Ocean parameters are shown to be nonidentifiable in a direct application to the Labrador Sea data when the known Coriolis parameter is not identified by the model. To address this, the ocean parameters are estimated in an empirical sequence. Data from the Ocean Storms experiment are used to estimate ocean dissipation in isolation from complexities introduced by strong and variable winds. Given a realistic estimate of the ocean dissipation, a second application in the Labrador Sea successfully estimates atmosphere-ocean coupling coefficients and reproduces the Coriolis parameter. Model assessments demonstrate the robustness of the parameter estimates. The model parameter estimates are discussed in comparison with Ekman theory and results from analyses of the global ocean surface drifter data set.
Ad J.h.m. Reniers - One of the best experts on this subject based on the ideXlab platform.
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surf zone surface retention on a rip channeled beach
Journal of Geophysical Research, 2009Co-Authors: Jamie Macmahan, Jenna Brown, Martijn Henriquez, Timothy P Stanton, Edward B. Thornton, Jeff Brown, Ad J.h.m. Reniers, Edith L. GallagherAbstract:The retention of floating matter within the surf zone on a rip-channeled beach is examined with a combination of detailed field observations obtained during the Rip Current Experiment and a three-dimensional (3-D) wave and flow model. The acoustic Doppler current profiler–observed hourly vertical cross-shore velocity structure variability over a period of 3 days with normally incident swell is well reproduced by the computations, although the strong vertical attenuation of the subsurface rip current velocities at the most offshore location outside the surf zone in 4 m water depth is not well predicted. Corresponding mean alongshore velocities are less well predicted with errors on the order of 10 cm/s for the most offshore sensors. Model calculations of very low frequency motions (VLFs) with O(10) min timescales typically explain over 60% of the observed variability, both inside and outside of the surf zone. The model calculations also match the mean rip-current surface flow field inferred from GPS-equipped drifter trajectories. Seeding the surf zone with a large number of equally spaced virtual drifters, the computed instantaneous surface velocity fields are used to calculate the hourly drifter trajectories. Collecting the hourly drifter exits, good agreement with the observed surf zone retention is obtained provided that both Stokes drift and VLF motions are accounted for in the modeling of the computed drifter trajectories. Without Stokes drift, the estimated number of virtual drifter exits is O(80)%, almost an order of magnitude larger than the O(20)% of observed exits during the drifter deployments. Conversely, when excluding the VLF motions instead, the number of calculated drifter exits is less than 5%, thus significantly underestimating the number of observed exits.
Kaan Certel - One of the best experts on this subject based on the ideXlab platform.
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restricted patterning of vestigial expression in drosophila wing imaginal discs requires synergistic activation by both mad and the drifter pou domain transcription factor
Development, 2000Co-Authors: Kaan Certel, Angela Hudson, Sean B Carroll, Wayne A JohnsonAbstract:The Drosophila Vestigial protein has been shown to play an essential role in the regulation of cell proliferation and differentiation within the developing wing imaginal disc. Cell-specific expression of vg is controlled by two separate transcriptional enhancers. The boundary enhancer controls expression in cells near the dorsoventral (DV) boundary and is regulated by the Notch signal transduction pathway, while the quadrant enhancer responds to the Decapentaplegic and Wingless morphogen gradients emanating from cells near the anteroposterior (AP) and DV boundaries, respectively. MAD-dependent activation of the vestigial quadrant enhancer results in broad expression throughout the wing pouch but is excluded from cells near the DV boundary. This has previously been thought to be due to direct repression by a signal from the DV boundary; however, we show that this exclusion of quadrant enhancer-dependent expression from the DV boundary is due to the absence of an additional essential activator in those cells. The Drosophila POU domain transcriptional regulator, Drifter, is expressed in all cells within the wing pouch expressing a vgQ-lacZ transgene and is also excluded from the DV boundary. Viable drifter hypomorphic mutations cause defects in cell proliferation and wing vein patterning correlated with decreased quadrant enhancer-dependent expression. Drifter misexpression at the DV boundary using the GAL4/UAS system causes ectopic outgrowths at the distal wing tip due to induction of aberrant Vestigial expression, while a dominant-negative Drifter isoform represses expression of vgQ-lacZ and causes severe notching of the adult wing. In addition, we have identified an essential evolutionarily conserved sequence element bound by the Drifter protein with high affinity and located adjacent to the MAD binding site within the quadrant enhancer. Our results demonstrate that Drifter functions along with MAD as a direct activator of Vestigial expression in the wing pouch.
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function of the drosophila pou domain transcription factor drifter as an upstream regulator of breathless receptor tyrosine kinase expression in developing trachea
Development, 1996Co-Authors: Michael G Anderson, Sarah J Certel, Kaan Certel, Denise J Montell, Wayne A JohnsonAbstract:Organogenesis of the Drosophila tracheal system involves extensive directed cell migrations leading to a stereotypic series of interconnected tubules. Although numerous gene products have been shown to be essential for tracheal morphogenesis, direct functional relationships between participants have not been previously established. Both the breathless gene, encoding a Drosophila fibroblast growth factor receptor tyrosine kinase homologue, and the POU-domain transcription factor gene, drifter, are expressed in all tracheal cells and are essential for directed cell migrations. We demonstrate here that ubiquitously expressed Breathless protein under control of a heterologous heat-shock promoter is able to rescue the severely disrupted tracheal phenotype associated with drifter loss-of-function mutations. In the absence of Drifter function, breathless expression is initiated normally but transcript levels fall drastically to undetectable levels as tracheal differentiation proceeds. In addition, breathless regulatory DNA contains seven high affinity Drifter binding sites similar to previously identified Drifter recognition elements. These results suggest that the Drifter protein, which maintains its own expression through a tracheal-specific autoregulatory enhancer, is not necessary for initiation of breathless expression but functions as a direct transcriptional regulator necessary for maintenance of breathless transcripts at high levels during tracheal cell migration. This example of a mechanism for maintenance of a committed cell fate offers a model for understanding how essential gene activities can be maintained throughout organogenesis.
Falk Feddersen - One of the best experts on this subject based on the ideXlab platform.
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lagrangian drifter dispersion in the surf zone directionally spread normally incident waves
Journal of Physical Oceanography, 2009Co-Authors: Matthew S Spydell, Falk FeddersenAbstract:Abstract Lagrangian drifter statistics in a surf zone wave and circulation model are examined and compared to single- and two-particle dispersion statistics observed on an alongshore uniform natural beach with small, normally incident, directionally spread waves. Drifter trajectories are modeled with a time-dependent Boussinesq wave model that resolves individual waves and parameterizes wave breaking. The model reproduces the cross-shore variation in wave statistics observed at three cross-shore locations. In addition, observed and modeled Eulerian binned (means and standard deviations) drifter velocities agree. Modeled surf zone Lagrangian statistics are similar to those observed. The single-particle (absolute) dispersion statistics are well predicted, including nondimensionalized displacement probability density functions (PDFs) and the growth of displacement variance with time. The modeled relative dispersion and scale-dependent diffusivity is consistent with the observed and indicates the presence of ...