Direction Selectivity in Drosophila Proprioceptors Requires the Mechanosensory Channel Tmc

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An Asymmetry in Monolayer Tension Regulates Lipid Droplet Budding Direction

Cells store excess energy in the form of neutral lipids that are synthesized and encapsulated within the endoplasmic reticulum intermonolayer space. The lipids next demix to form lipid droplets (LDs), which, surprisingly, bud off mostly toward the cytosol. This directional LD formation is critical to energy metabolism, but its mechanism remains poorly understood. Here, we reconstituted the LD formation topology by embedding artificial LDs into the intermonolayer space of bilayer vesicles. We provide experimental evidence that the droplet behavior in the membrane is recapitulated by the physics of three-phase wetting systems, dictated by the equilibrium of surface tensions. We thereupon determined that slight tension asymmetries between the membrane monolayers regulate the droplet budding side. A differential regulation of lipid or protein composition around a forming LD can generate a monolayer tension asymmetry that will determine the LD budding side. Our results offer, to our knowledge, new insights on how the proteins might regulate LD formation side by generating a monolayer tension asymmetry.     

Potency of Transgenic Effectors for Neurogenetic Manipulation in Drosophila Larvae

Genetic manipulations of neuronal activity are a cornerstone of studies aimed to identify the functional impact of defined neurons for animal behavior. With its small nervous system, rapid life cycle, and genetic amenability, the fruit fly Drosophila melanogaster provides an attractive model system to study neuronal circuit function. In the past two decades, a large repertoire of elegant genetic tools has been developed to manipulate and study neural circuits in the fruit fly. Current techniques allow genetic ablation, constitutive silencing, or hyperactivation of neuronal activity and also include conditional thermogenetic or optogenetic activation or inhibition. As for all genetic techniques, the choice of the proper transgenic tool is essential for behavioral studies. Potency and impact of effectors may vary in distinct neuron types or distinct types of behavior. We here systematically test genetic effectors for their potency to alter the behavior of Drosophila larvae, using two distinct behavioral paradigms: general locomotor activity and directed, visually guided navigation. Our results show largely similar but not equal effects with different effector lines in both assays. Interestingly, differences in the magnitude of induced behavioral alterations between different effector lines remain largely consistent between the two behavioral assays. The observed potencies of the effector lines in aminergic and cholinergic neurons assessed here may help researchers to choose the best-suited genetic tools to dissect neuronal networks underlying the behavior of larval fruit flies.     

A Plastic Visual Pathway Regulates Cooperative Behavior in Drosophila Larvae

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FUS Regulates Activity of MicroRNA-Mediated Gene Silencing

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Allatostatin-C/AstC-R2 Is a Novel Pathway to Modulate the Circadian Activity Pattern in Drosophila

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Mechanical Model of Nuclei Ordering in Drosophila Embryos Reveals Dilution of Stochastic Forces

During the initial development of syncytial embryos, nuclei go through cycles of nuclear division and spatial rearrangement. The arising spatial pattern of nuclei is important for subsequent cellularization and morphing of the embryo. Although nuclei are contained within a common cytoplasm, cytoskeletal proteins are nonuniformly packaged into regions around every nucleus. In fact, cytoskeletal elements like microtubules and their associated motor proteins exert stochastic forces between nuclei, actively driving their rearrangement. Yet, it is unknown how the stochastic forces are balanced to maintain nuclear order in light of increased nuclear density upon every round of divisions. Here, we investigate the nuclear arrangements in Drosophila melanogaster over the course of several nuclear divisions starting from interphase 11. We develop a theoretical model in which we distinguish long-ranged passive forces due to the nuclei as inclusions in the elastic matrix, namely the cytoplasm, and active, stochastic forces arising from the cytoskeletal dynamics mediated by motor proteins. We perform computer simulations and quantify the observed degree of orientational and spatial order of nuclei. Solely doubling the nuclear density upon nuclear division, the model predicts a decrease in nuclear order. Comparing results to experimental recordings of tracked nuclei, we make contradictory observations, finding an increase in nuclear order upon nuclear divisions. Our analysis of model parameters resulting from this comparison suggests that overall motor protein density as well as relative active-force amplitude has to decrease by a factor of about two upon nuclear division to match experimental observations. We therefore expect a dilution of cytoskeletal motors during the rapid nuclear division to account for the increase in nuclear order during syncytial embryo development. Experimental measurements of kinesin-5 cluster lifetimes support this theoretical finding.     

Simulation of Cell Patterning Triggered by Cell Death and Differential Adhesion in Drosophila Wing

The Drosophila wing exhibits a well-ordered cell pattern, especially along the posterior margin, where hair cells are arranged in a zigzag pattern in the lateral view. Based on an experimental result observed during metamorphosis of Drosophila, we considered that a pattern of initial cells autonomously develops to the zigzag pattern through cell differentiation, intercellular communication, and cell death (apoptosis) and performed computer simulations of a cell-based model of vertex dynamics for tissues. The model describes the epithelial tissue as a monolayer cell sheet of polyhedral cells. Their vertices move according to equations of motion, minimizing the sum total of the interfacial and elastic energies of cells. The interfacial energy densities between cells are introduced consistently with an ideal zigzag cell pattern, extracted from the experimental result. The apoptosis of cells is modeled by gradually reducing their equilibrium volume to zero and by assuming that the hair cells prohibit neighboring cells from undergoing apoptosis. Based on experimental observations, we also assumed wing elongation along the proximal-distal axis. Starting with an initial cell pattern similar to the micrograph experimentally obtained just before apoptosis, we carried out the simulations according to the model mentioned above and successfully reproduced the ideal zigzag cell pattern. This elucidates a physical mechanism of patterning triggered by cell apoptosis theoretically and exemplifies, to our knowledge, a new framework to study apoptosis-induced patterning. We conclude that the zigzag cell pattern is formed by an autonomous communicative process among the participant cells.     

TwoLumps Ascending Neurons Mediate Touch-Evoked Reversal of Walking Direction in Drosophila

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Serotonergic Modulation of Walking in Drosophila

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CDK5-mediated phosphorylation of CP190 may regulate locomotor activity in adult female Drosophila

正The three-dimensional organization of the genome plays a crucial role in regulating gene expression patterns in metazoans(Ong and Corces,2014).The nuclear architectural proteins are known to facilitate the formation of topological domains within the genome through mediating inter-and intra-chromosomal interactions.In vertebrate,CCCTC-binding factor(CTCF)is the main     

Network-Specific Synchronization of Electrical Slow-Wave Oscillations Regulates Sleep Drive in Drosophila

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Locomotion in caterpillars

Most species of caterpillar move around by inching or crawling. Their ability to navigate in branching three‐dimensional structures makes them particularly interesting biomechanical subjects. The mechanism of inching has not been investigated in detail, but crawling is now well understood from studies on caterpillar neural activity, dynamics and structural mechanics. Early papers describe caterpillar crawling as legged peristalsis, but recent work suggests that caterpillars use a tension‐based mechanism that helps them to exploit arboreal niches. Caterpillars are not obligate hydrostats but instead use their strong grip to the substrate to transmit forces, in effect using their environment as a skeleton. In addition, the gut which accounts for a substantial part of the caterpillar's weight, moves independently of the body wall during locomotion and may contribute to crawling dynamics. Work‐loop analysis of caterpillar muscles shows that they are likely to act both as actuators and energy dissipaters during crawling. Because caterpillar tissues are pseudo‐elastic, and locomotion involves large body deformations, moving is energetically inefficient. Possession of a soft body benefits caterpillars by allowing them to grow quickly and to access remote food sources safely.     

Locomotion in elongate fishes: A contact sport

Despite the physical differences between water and air, a number of fish lineages are known to make terrestrial excursions on land. Many of these fishes exhibit an elongate body plan. Elongation of the body can occur in several ways, the most common of which is increasing the number of vertebrae in one or both regions of the axial skeleton – precaudal and/or caudal. Elongate species are often found in three-dimensionally complex habitats. It has been hypothesized that elongate fishes use this structure to their locomotor advantage. In this study, we consider how elongation and differences in vertebral regionalization correspond with the use of wooden pegs, which are provided as analogs to vertically oriented substrate, structures that protrude above the ground. We compare aquatic and terrestrial locomotor behaviors of Polypterus senegalus, Erpetoichthys calabaricus, and Gymnallabes typus as they move through a peg array. When considering axial elongation we find that the highly elongate species, E. calabaricus and G. typus, contact more pegs but on average move slower in both environments than P. senegalus. When considering axial regionalization, we find that the precaudally elongate species, P. senegalus and E. calabaricus, differ in the patterns of peg contact between the two environments whereas the caudally elongate species, G. typus, exhibits similar peg contact between the two environments. Our study highlights the importance of incorporating body shape and vertebral regionalization to understand how elongate fishes move in water and on land.