Project description:Neural circuits in the spinal cord have a critical role in integrating sensory information and descending commands to coordinate body movements. Defining the functional diversity of spinal neurons is therefore essential for understanding the mechanisms underlying motor control. In this study, by combining anatomical, molecular, and functional analyses in mice, we identified and characterized a subtype of ascending spinal neurons belonging to the V0g family. We found that V0g ascending neurons are integrated in lumbar sensorimotor circuits and their function is specifically required for the execution of precise limb movements necessary for skilled locomotion. This work advances our understanding of the functional organization of V0 neurons and highlights a previously unappreciated role in adjusting body movements to the more demanding needs of skilled locomotor tasks
Project description:The flexibility of motor actions is ingrained in the diversity of neurons and how they are organized into functional circuit modules, yet our knowledge of the molecular underpinning of motor circuit modularity remains limited. Locomotion is a motor behavior characterized by sudden changes in speed and strength enabled by the coordinated recruitment of different motoneuron subtypes. Here we use adult zebrafish to link the molecular diversity of motoneurons and the rhythm-generating V2a interneurons with their modular circuit organization that is responsible for changes in locomotor speed. We show that the molecular diversity of motoneurons and V2a interneurons reflects their functional segregation into slow, intermediate or fast subtypes. Furthermore, we reveal shared molecular signatures between V2a interneurons and motoneurons of the three speed circuit modules. Overall, by characterizing how the molecular diversity of motoneurons and V2a interneurons relates to their function, connectivity and behavior, our study provides important insights not only into the molecular mechanisms for neuronal and circuit diversity for locomotor flexibility but also for charting circuits for motor actions in general.
Project description:Electrical stimulation can augment or modify neuronal function and can have therapeutic benefits for certain neurological disorders. There is evidence that enhancing spinal excitability with either epidural or transcutaneous stimulation can restore some volitional motor output after spinal cord injury (SCI). Lumbosacral epidural stimulation temporarily improves locomotor and autonomic function in both rodents and humans with SCI. When combined with overground locomotor training enabled by a weight-supporting device, epidural electrical stimulation (EES) promotes extensive reorganization of residual neural pathways that improves locomotion after stopping stimulation. However, the exact mechanism underlying the reconstruction of spinal cord neural circuits with electrical stimulation is not yet known. Thus, we developed a epidural electrical and muscle stimulation(EEMS) system at the interface of the spinal cord and muscle to mimic feedforward and feedback electrical signals in spinal sensorimotor circuits. Using methods of motor function evaluation, neural circuit tracing and neural signal recording, we discovered a unique stimulus frequency of 10-20 Hz under EEMS conditions that was required for structural and functional reconstruction of spinal sensorimotor circuits. Single-cell transcriptome analysis of EEMS activated motoneurons characterized molecular networks involved in spinal sensorimotor circuit reconstruction. This study provides insights into neural signal decoding during spinal sensorimotor circuit reconstruction, and indicates a technological approach for the clinical treatment of SCI.
Project description:This SuperSeries is composed of the following subset Series: GSE36241: Identification of a FOXO3/IRF7 circuit that limits inflammatory sequelae of antiviral responses (ChIP-Seq) GSE37051: Identification of a FOXO3/IRF7 circuit that limits inflammatory sequelae of antiviral responses (expression) Refer to individual Series
Project description:Astrocytes, the most abundant cells in the central nervous system, promote synapse formation and help refine neural connectivity. Although they are allocated to spatially distinct regional domains during development, it is unknown whether region-restricted astrocytes are functionally heterogeneous. Here we show that postnatal spinal cord astrocytes express several region-specific genes, and that ventral astrocyte-encoded Semaphorin3a (Sema3a) is required for proper motor neuron and sensory neuron circuit organization. Loss of astrocyte-encoded Sema3a led to dysregulated α−motor neuron axon initial segment orientation, markedly abnormal synaptic inputs, and selective death of α−but not of adjacent γ−motor neurons. Additionally, a subset of TrkA+ sensory afferents projected to ectopic ventral positions. These findings demonstrate that stable maintenance of a positional cue by developing astrocytes influences multiple aspects of sensorimotor circuit formation. More generally, they suggest that regional astrocyte heterogeneity may help to coordinate postnatal neural circuit refinement. 12 total samples consisting of three biological replicates each of flow sorted postnatal day 7 dorsal spinal cord astrocytes, ventral spinal cord astrocytes, dorsal SC non astrocytes, and ventral SC non astrocytes
Project description:Human iPSC-derived thoracic spinal cord organoids were transplanted into spinal cord injury mice, and spinal cord tissue was collected after 7 weeks. The transplantation resulted in functional recovery and neural circuit remodeling in the injured mice.
Project description:The fidelity of motor control requires the precise positional arrangement of motor pools and the establishment of synaptic connections between these pools. In the developing spinal cord, motor nerves project to specific target muscles and receive proprioceptive input from the muscles via the sensorimotor circuit. LIM-homeodomain transcription factors are known to successively restrict specific motor neuronal fates during neural development; however, it remains unclear to what extent they contribute to limb-based motor pools and locomotor circuits. Here, we showed in mice that deletion of Isl2 resulted in scattered motor pools, primarily in the median motor column and lateral LMC (LMCl) populations, and lacked Pea3 expression in the hindlimb motor pools, accompanied by reduced terminal axon branching and disorganized neuromuscular junctions. Transcriptomic analysis of Isl2-deficient spinal cords revealed that a variety of genes involved in motor neuron differentiation, axon development, and synapse organization were downregulated in hindlimb motor pools. Moreover, the loss of Isl2 impaired sensorimotor connectivity and hindlimb locomotion. Together, our studies indicate that Isl2 plays a critical role in organizing motor pool position and sensorimotor circuits in hindlimb motor pools.
Project description:We have previously shown that Il1a-knockout (KO) mice exhibit rapid (at day 1) and persistent improvements in locomotion associated with reduced lesion volume compared with Il1b-KO mice and C57BL/6 controls after traumatic spinal cord injury (SCI). To investigate the mechanism by which Il1a mediates its detrimental effect, we analyzed the transcriptome of the injured spinal cord of Il1a-KO, Il1b-KO and C57BL/6 mice at 24 hours after SCI using GeneChip microarrays. Il1a-KO, Il1b-KO and C57BL/6 mice were subjected to a 50-kdyn SCI and a 6-mm spinal cord segment centered over the site of contusion extracted for RNA isolation and microarray analysis.
Project description:Identification of the neuronal types that form the specialized circuits controlling distinct behaviors has benefited greatly from the simplicity offered by zebrafish. Electrophysiological studies have shown that additional to connectivity, understanding of circuitry requires identification of functional specializations among individual circuit components, such as those that regulate levels of transmitter release and neuronal excitability. In this study we use single cell RNAseq (scRNAseq) to identify molecular distinctions causal to the unique physiology of primary motoneuron (PMn) function, as well as associated specialized interneurons that are tailored specifically for mediation of the powerful escape response. Generating scRNA-seq datasets that provide both a wide overview of the cellular populations of the spinal cord and a granular view of the zebrafish motor neurons.