Excitatory Motor Neurons are Local Central Pattern Generators in an Anatomically Compressed Motor Circuit for Reverse Locomotion [preprint]

Central pattern generators are cell- or network-driven oscillators that underlie motor rhythmicity. The existence and identity of C. elegans CPGs remain unknown. Through cell ablation, electrophysiology, and calcium imaging, we identified oscillators for reverse locomotion. We show that the cholinergic and excitatory class A motor neurons exhibit intrinsic and oscillatory activity, and such an activity can drive reverse locomotion without premotor interneurons. Regulation of their oscillatory activity, either through effecting an endogenous constituent of oscillation, the P/Q/N high voltage-activated calcium channel UNC-2, or, via dual regulation, inhibition and activation, by the descending premotor interneurons AVA, determines the propensity, velocity, and sustention of reverse locomotion. Thus, the reversal motor executors themselves serve as oscillators; regulation of their intrinsic activity controls the reversal motor state. These findings exemplify anatomic and functional compression: motor executors integrate the role of rhythm generation in a locomotor network that is constrained by small cell numbers

Excitatory motor neurons are local oscillators for backward locomotion

Cell- or network-driven oscillators underlie motor rhythmicity. The identity of C. elegans oscillators remains unknown. Through cell ablation, electrophysiology, and calcium imaging, we show: (1) forward and backward locomotion is driven by different oscillators; (2) the cholinergic and excitatory A-class motor neurons exhibit intrinsic and oscillatory activity that is sufficient to drive backward locomotion in the absence of premotor interneurons; (3) the UNC-2 P/Q/N high-voltage-activated calcium current underlies A motor neuron\u27s oscillation; (4) descending premotor interneurons AVA, via an evolutionarily conserved, mixed gap junction and chemical synapse configuration, exert state-dependent inhibition and potentiation of A motor neuron\u27s intrinsic activity to regulate backward locomotion. Thus, motor neurons themselves derive rhythms, which are dually regulated by the descending interneurons to control the reversal motor state. These and previous findings exemplify compression: essential circuit properties are conserved but executed by fewer numbers and layers of neurons in a small locomotor network

A Genetically Encoded Tag for Correlated Light and Electron Microscopy of Intact Cells, Tissues, and Organisms

Electron microscopy (EM) achieves the highest spatial resolution in protein localization, but specific protein EM labeling has lacked generally applicable genetically encoded tags for in situ visualization in cells and tissues. Here we introduce “miniSOG” (for mini Singlet Oxygen Generator), a fluorescent flavoprotein engineered from Arabidopsis phototropin 2. MiniSOG contains 106 amino acids, less than half the size of Green Fluorescent Protein. Illumination of miniSOG generates sufficient singlet oxygen to locally catalyze the polymerization of diaminobenzidine into an osmiophilic reaction product resolvable by EM. MiniSOG fusions to many well-characterized proteins localize correctly in mammalian cells, intact nematodes, and rodents, enabling correlated fluorescence and EM from large volumes of tissue after strong aldehyde fixation, without the need for exogenous ligands, probes, or destructive permeabilizing detergents. MiniSOG permits high quality ultrastructural preservation and 3-dimensional protein localization via electron tomography or serial section block face scanning electron microscopy. EM shows that miniSOG-tagged SynCAM1 is presynaptic in cultured cortical neurons, whereas miniSOG-tagged SynCAM2 is postsynaptic in culture and in intact mice. Thus SynCAM1 and SynCAM2 could be heterophilic partners. MiniSOG may do for EM what Green Fluorescent Protein did for fluorescence microscopy

Familial t(1;11) translocation is associated with disruption of white matter structural integrity and oligodendrocyte–myelin dysfunction

Although the underlying neurobiology of major mental illness (MMI) remains unknown, emerging evidence implicates a role for oligodendrocyte–myelin abnormalities. Here, we took advantage of a large family carrying a balanced t(1;11) translocation, which substantially increases risk of MMI, to undertake both diffusion tensor imaging and cellular studies to evaluate the consequences of the t(1;11) translocation on white matter structural integrity and oligodendrocyte–myelin biology. This translocation disrupts among others the DISC1 gene which plays a crucial role in brain development. We show that translocation-carrying patients display significant disruption of white matter integrity compared with familial controls. At a cellular level, we observe dysregulation of key pathways controlling oligodendrocyte development and morphogenesis in induced pluripotent stem cell (iPSC) derived case oligodendrocytes. This is associated with reduced proliferation and a stunted morphology in vitro. Further, myelin internodes in a humanized mouse model that recapitulates the human translocation as well as after transplantation of t(1;11) oligodendrocyte progenitors were significantly reduced when compared with controls. Thus we provide evidence that the t(1;11) translocation has biological effects at both the systems and cellular level that together suggest oligodendrocyte–myelin dysfunction

Building stereotypic connectivity: mechanistic insights into structural plasticity from C. elegans

The ability of neurons to modify or remodel their synaptic connectivity is critical for the function of neural circuitry throughout the life of an animal. Understanding the mechanisms underlying neuronal structural changes is central to our knowledge of how the nervous system is shaped for complex behaviors and how it further adapts to developmental and environmental demands. Caenorhabditis elegans provides a powerful model for examining developmental processes and for discovering mechanisms controlling neural plasticity. Recent findings have identified conserved themes underlying neural plasticity in development and under environmental stress

Real Time Screening and Trajectory Optimization of UAVs in Cluster Based on Improved Particle Swarm Optimization Algorithm

To solve the problem of selecting drones for passive positioning within unmanned aerial vehicle (UAV) swarm and optimizing corresponding trajectories. This article constructs a method for determining and optimizing the trajectory of UAVs based on an improved particle swarm optimization (PSO) algorithm. Firstly, the time difference of arrival (TDOA) positioning principle was introduced and corresponding algorithm models were organized. Afterwards, the objective function and constraint conditions for selecting drones and optimizing flight paths were designed. The correlation between the optimal solutions of the continuous time optimization problem is used to determine the UAV for positioning. This paper constructs the UAV determination process based on similarity screening. At the same time, combined with the characteristics of the problem to be optimized, the Particle Swarm Optimization (PSO) is improved from three aspects: updating the initial position of particles, improving the iteration formula and setting the adaptive termination condition. This paper further constructs the track optimization process based on improved particle swarm optimization. Through simulation experiments and algorithm comparison, it can be seen that the method constructed in this article can determine the drone used for positioning in real-time and optimize its spatial position. Compared to the selected drones and mainstream passive positioning methods, the method in this article reduces errors by more than 60% and 45%

Implications of CRNDE in prognosis, tumor immunity, and therapeutic sensitivity in low grade glioma patients

Abstract Background Colorectal tumor differentially expressed (CRNDE) is specifically expressed in human brains and is the most highly expressed lncRNA in gliomas. Nevertheless, its implications in low grade glioma (LGG) are still indistinct. This study presented systematic analyses of CRNDE in LGG biology. Methods We retrospectively retrieved TCGA, CGGC and GSE16011 LGG cohorts. Survival analysis was conducted for evaluating the prognostic significance of CRNDE in LGG. A CRNDE-based nomogram was established, and its predictive performance was verified. Signaling pathways underlying CRNDE were analyzed through ssGSEA and GSEA approaches. The abundance of immune cells and activity of cancer-immunity cycle were estimated with ssGSEA approach. Immune checkpoints, HLAs, chemokines, and immunotherapeutic response indicators (TIDE, and TMB) was quantified. U251 and SW1088 cells were transfected with specific shRNAs of CRNDE, and flow cytometry (apoptosis) and western blot (β-catenin and Wnt5a) assays were conducted. Results Up-regulated CRNDE was found in LGG, and was linked to unfavorable clinical outcomes. The CRNDE-based nomogram enabled to accurately predict patients’ prognosis. High CRNDE expression was linked to more genomic variations, activity of tumorigenic pathways, tumor immunity (increase in infiltration of immune cells, expression of immune checkpoints, HLAs and chemokines, and cancer-immunity cycle), and therapeutic sensitivity. CRNDE knockdown mitigated malignant phenotypes of LGG cells. Conclusions Our study determined CRNDE as a novel predictor for patient prognosis, tumor immunity and therapeutic response in LGG. Assessment of CRNDE expression is a promising approach for predicting the therapeutic benefits of LGG patients

A Tet/Q Hybrid System for Robust and Versatile Control of Transgene Expression in C. elegans

Summary: Binary gene regulatory tools such as the Tetracycline (Tet)-controlled transcription system have revolutionized genetic research in multiple organisms, but their applications to the worm remain very limited. Here we report that the canonical Tet system is largely inactive in the worm but can be adapted for the worm by introducing multiple modifications, a crucial one being the use of the transcription activation domain from the fungal Q binary system. The resultant Tet/Q hybrid system proves more robust and flexible than either of its precursors, enabling elaborate modes of transgene manipulation previously hard to achieve in the worm, including inducible intersectional regulation and, in combination with the Q system, independent control of distinct transgenes within the same cells. Furthermore, we demonstrated, as an example of its applications, that the hybrid system can tightly and efficiently control Cre expression. This study establishes Tet/Q as a premier binary system for worm genetic research. : Genetics; Techniques in Genetics; Model Organism Subject Areas: Genetics, Techniques in Genetics, Model Organis