Types Of Neurons Research Articles

Effect of electroacupuncture stimulation of "Sibai"(ST2) and "Quanliao"(SI18) on excitatory neurons of sensorimotor cortex in mice.

To observe the activation state and neuronal types of somatosensory cortex and the primary motor cortex induced by electroacupuncture (EA) stimulation of "Sibai" (ST2) and "Quanliao" (SI18) acupoints in mice. Male C57BL/6J mice were randomly divided into blank control and EA groups, with 6 mice in each group. Rats of the EA group received EA stimulation (2 Hz, 0.6 mA) at ST2 and SI18 for 30 minutes. Samples were collected after EA intervention, and immunofluorescence staining was performed to quantify the expression of the c-Fos gene (proportion of c-Fos positive cells) in the somatosensory cortex and primary motor cortex. The co-labelled cells of calcium/calmodulin-dependent protein kinase Ⅱ (CaMKⅡ) and gamma-aminobutyric acid (GABA) in the somatosensory cortex and primary motor cortex were observed and counted by using microscope after immunofluorescence staining. Another 10 mice were used to detect the calcium activity of excitatory neurons in the somatosensory cortex and primary motor cortex by fiber photometry. In comparison with the blank control group, the number of c-Fos positive cells, and the proportion of c-Fos and CaMKⅡ co-labelled cells in both the somatosensory cortex and primary motor cortex were significantly increased after EA stimulation (P<0.05). No significant changes were found in the proportion of c-Fos and GABA co-labeled cells in both the somatosensory cortex and primary motor cortex after EA. Results of fiber optic calcium imaging technology showed that the spontaneous calcium activity of excitatory neurons in both somatosensory cortex and primary motor cortex were obviously increased during EA compared with that before EA (P<0.01), and strikingly reduced after cessation of EA compared with that during EA (P<0.05). Under physiological conditions, EA of ST2 and SI18 can effectively activate excitatory neurons in the somatosensory cortex and primary motor cortex.

TASK-3, two-pore potassium channels, contribute to circadian rhythms in the electrical properties of the suprachiasmatic nucleus and play a role in driving stable behavioural photic entrainment.

Stable and entrainable physiological circadian rhythms are crucial for overall health and well-being. The suprachiasmatic nucleus (SCN), the primary circadian pacemaker in mammals, consists of diverse neuron types that collectively generate a circadian profile of electrical activity. However, the mechanisms underlying the regulation of endogenous neuronal excitability in the SCN remain unclear. Two-pore domain potassium channels (K2P), including TASK-3, are known to play a significant role in maintaining SCN diurnal homeostasis by inhibiting neuronal activity at night. In this study, we investigated the role of TASK-3 in SCN circadian neuronal regulation and behavioural photoentrainment using a TASK-3 global knockout mouse model. Our findings demonstrate the importance of TASK-3 in maintaining SCN hyperpolarization during the night and establishing SCN sensitivity to glutamate. Specifically, we observed that TASK-3 knockout mice lacked diurnal variation in resting membrane potential and exhibited altered glutamate sensitivity both in vivo and in vitro. Interestingly, despite these changes, the mice lacking TASK-3 were still able to maintain relatively normal circadian behaviour.

A strong direct link from the layer 3/4 border to layer 6 of cat primary visual cortex.

The cat primary visual cortex (V1) is a cortical area for which we have one of the most detailed estimates of the connection 'weights' (expressed as number of synapses) between different neural populations in different layers (Binzegger et al in J Neurosci 24:8441-8453, 2004). Nevertheless, the majority of excitatory input sources to layer 6, the deepest layer in a local translaminar excitatory feedforward loop, was not accounted for by the known neuron types used to generate the quantitative Binzegger diagram. We aimed to fill this gap by using a retrograde tracer that would label neural cell bodies in and outside V1 that directly connect to layer 6 of V1. We found that more than 80% of labeled neurons projecting to layer 6 were within V1 itself. Our data indicate that a substantial fraction of the missing input is provided by a previously unidentified population of layer 3/4 border neurons, laterally distributed and connecting more strongly to layer 6 than the typical superficial layer pyramidal neurons considered by Binzegger et al. (Binzegger et al in J Neurosci 24:8441-8453, 2004). This layer 3/4 to layer 6 connection may be a parallel route to the layer 3 - layer 5 - layer 6 feedforward pathway, be associated with the fast-conducting, movement-related Y pathway and provide convergent input from distant (5-10 degrees) regions of the visual field.

The neuronal ceroid lipofuscinosis type 2 – associated variants: An analysis of alterations in the TPP1 gene and genotype–phenotype correlation in Ukraine

The neuronal ceroid lipofuscinosis type 2 – associated variants: An analysis of alterations in the <i>TPP1</i> gene and genotype–phenotype correlation in Ukraine

Sex differences in neuronal activation in the cortex and midbrain during quinine-adulterated alcohol intake.

Continued alcohol consumption despite negative consequences is a core symptom of alcohol use disorder. This is modeled in mice by pairing negative stimuli with alcohol, such as adulterating alcohol solution with quinine. Mice consuming alcohol under these conditions are considered to be engaging in aversion-resistant intake. Previously, we have observed sex differences in this behavior, with females more readily expressing aversion-resistant consumption. We also identified three brain regions that exhibited sex differences in neuronal activation during quinine-alcohol drinking: ventromedial prefrontal cortex (vmPFC), posterior insular cortex (PIC), and ventral tegmental area (VTA). Specifically, male mice showed increased activation in vmPFC and PIC, while females exhibited increased activation in VTA. In this study, we aimed to identify what specific type of neurons are activated in these regions during quinine-alcohol drinking. We assessed quinine-adulterated alcohol intake using the two-bottle choice procedure. We also utilized RNAscope in situ hybridization in the three brain regions that previously exhibited a sex difference to examine colocalization of Fos, glutamate, GABA, and dopamine. Females showed increased aversion-resistant alcohol consumption compared to males. We also found that males had higher colocalization of glutamate and Fos in vmPFC and PIC, while females had greater dopamine and Fos colocalization in the VTA. Collectively, these experiments suggest that glutamatergic output from the vmPFC and PIC may have a role in suppressing, and dopaminergic activity in the VTA may promote, aversion-resistant alcohol consumption. Future experiments will examine neuronal circuits that contribute to sex differences in aversion resistant consumption.

A conserved molecular logic for neurogenesis to gliogenesis switch in the cerebral cortex

During development, neural stem cells in the cerebral cortex, also known as radial glial cells (RGCs), generate excitatory neurons, followed by production of cortical macroglia and inhibitory neurons that migrate to the olfactory bulb (OB). Understanding the mechanisms for this lineage switch is fundamental for unraveling how proper numbers of diverse neuronal and glial cell types are controlled. We and others recently showed that Sonic Hedgehog (Shh) signaling promotes the cortical RGC lineage switch to generate cortical oligodendrocytes and OB interneurons. During this process, cortical RGCs generate intermediate progenitor cells that express critical gliogenesis genes Ascl1, Egfr, and Olig2. The increased Ascl1 expression and appearance of Egfr+ and Olig2+ cortical progenitors are concurrent with the switch from excitatory neurogenesis to gliogenesis and OB interneuron neurogenesis in the cortex. While Shh signaling promotes Olig2 expression in the developing spinal cord, the exact mechanism for this transcriptional regulation is not known. Furthermore, the transcriptional regulation of Olig2 and Egfr has not been explored. Here, we show that in cortical progenitor cells, multiple regulatory programs, including Pax6 and Gli3, prevent precocious expression of Olig2, a gene essential for production of cortical oligodendrocytes and astrocytes. We identify multiple enhancers that control Olig2 expression in cortical progenitors and show that the mechanisms for regulating Olig2 expression are conserved between the mouse and human. Our study reveals evolutionarily conserved regulatory logic controlling the lineage switch of cortical neural stem cells.

Activation of feedforward wiring in adult hippocampal neurons by the basic-helix-loop-helix transcription factor Ascl4.

Although evidence indicates that the adult brain retains a considerable capacity for circuit formation, adult wiring has not been broadly considered and remains poorly understood. In this study, we investigate wiring activation in adult neurons. We show that the basic-helix-loop-helix transcription factor Ascl4 can induce wiring in different types of hippocampal neurons of adult mice. The new axons are mainly feedforward and reconfigure synaptic weights in the circuit. Mice with the Ascl4-induced circuits do not display signs of pathology and solve spatial problems equally well as controls. Our results demonstrate reprogrammed connectivity by a single transcriptional factor and provide insights into the regulation of brain wiring in adults.

Conserved expression of the zebrafish syt4 gene in GABAergic neurons in the cerebellum of adult fishes revealed by mammalian SYT4 immunoreactive-like signals

Synaptotagmin 4 (syt4) belongs to the synaptotagmin protein family, which has 17 and 28 family members in human and zebrafish, respectively. In zebrafish and rodents, syt4 is known to express abundantly in the entire central nervous system in the early developmental stages. In adult rodents, the gene expression shifts to be predominant in the cerebellum, mostly in Purkinje cells, a type of GABAergic neurons. However, there is no report of the expression pattern of syt4 in the adult zebrafish brain. Therefore, we hypothesize that the expression of syt4 is conserved in adult zebrafish and is specific to the GABAergic neurons, likely Purkinje cells, in the cerebellum. To examine the hypothesis, we first show that only one copy of syt4 gene remains in the zebrafish genome, and it is orthologous to the gene in other vertebrates. We further observe mammalian SYT4 antibody immunoreactive-like (mSYT4-ir) signals in several structures in the hindbrain including the medial divisions of the valvula cerebelli and the corpus cerebelli. In addition, our observations indicate the presence of mSYT4-ir signals in GABAergic neurons, most notably in the Purkinje cell layer of the molecular layer in the aforementioned structures. Conversely, mSYT4-ir signals are not observed in glutamatergic or cholinergic neurons. Therefore, we deduce that the syt4 gene in zebrafish exhibits a homologous expression pattern to those of previously studied vertebrate species, which is revealed by the positive immunoreactive-like signals of mammalian SYT4 antibodies.

Genome sequence analyses identify novel risk loci for multiple system atrophy.

Multiple system atrophy (MSA) is an adult-onset, sporadic synucleinopathy characterized by parkinsonism, cerebellar ataxia, and dysautonomia. The genetic architecture of MSA is poorly understood, and treatments are limited to supportive measures. Here, we performed a comprehensive analysis of whole genome sequence data from 888 European-ancestry MSA cases and 7,128 controls to systematically investigate the genetic underpinnings of this understudied neurodegenerative disease. We identified four significantly associated risk loci using a genome-wide association study approach. Transcriptome-wide association analyses prioritized USP38-DT, KCTD7, and lnc-KCTD7-2 as novel susceptibility genes for MSA within these loci, and single-nucleus RNA sequence analysis found that the associated variants acted as cis-expression quantitative trait loci for multiple genes across neuronal and glial cell types. In conclusion, this study highlights the role of genetic determinants in the pathogenesis of MSA, and the publicly available data from this study represent a valuable resource for investigating synucleinopathies.

Nucleus accumbens neuronal ensembles vary with cocaine reinforcement in male and female rats.

Neuronal ensembles in the medial prefrontal cortex mediate cocaine self-administration via projections to the nucleus accumbens. We have recently shown that neuronal ensembles in the prelimbic cortex form rapidly to mediate cocaine self-administration. However, the role of neuronal ensembles within the nucleus accumbens in initial cocaine-seeking behaviour remains unknown. Here, we sought to expand the current literature by testing the necessity of the cocaine self-administration ensemble in the nucleus accumbens core (NAcCore) 1 day after male and female rats acquire cocaine self-administration by using the Daun02 inactivation procedure. We found that disrupting the NAcCore ensembles after a no-cocaine reward-seeking test increased subsequent cocaine seeking, while disrupting NAcCore ensembles following a cocaine self-administration session decreased subsequent cocaine seeking. We then characterized neuronal cell type in the NAcCore using RNAscope in situ hybridization. In the no-cocaine session, we saw reduced dopamine D1 type neuronal activation, while in the cocaine self-administration session, we found preferential dopamine D1 type neuronal activity in the NAcCore.

A needle in a haystack? The impact of a targeted epilepsy gene panel in the identification of a treatable but rapidly progressive metabolic epilepsy: CLN2 disease.

Neuronal ceroid lipofuscinoses (NCL) are a group of autosomal recessive, inherited, lysosomal, and neurodegenerative diseases that causes progressive dementia, seizures, movement disorders, language delay/regression, progressive visual failure, and early death. Neuronal ceroid lipofuscinosis type 2 (CLN2), caused by biallelic pathogenic variants of the TPP1 gene, is the only NCL with an approved targeted therapy. The laboratory diagnosis of CLN2 is established through highly specific tests, leading to diagnostic delays and eventually hampering the provision of specific treatment for patients with CLN2. Epilepsy is a common and clinically-identifiable feature among NCLs, and seizure onset is the main driver for families to seek medical care. To evaluate the results of the Latin America Epilepsy and Genetics Program, an epilepsy gene panel, as a comprehensive tool for the investigation of CLN2 among other genetic causes of epilepsy. A total of 1,284 patients with epilepsy without a specific cause who had at least 1 symptom associated with CLN2 were screened for variants in 160 genes associated with epilepsy or metabolic disorders presenting with epilepsy through an epilepsy gene panel. Variants of the TPP1 gene were identified in 25 individuals (1.9%), 21 of them with 2 variants. The 2 most frequently reported variants were p.Arg208* and p.Asp276Val, and 2 novel variants were detected in the present study: p.Leu308Pro and c.89 + 3G > C Intron 2. The results suggest that these genetic panels can be very useful tools to confirm or exclude CLN2 diagnosis and, if confirmed, provide disease-specific treatment for the patients.

Nr4a1 regulates cell-specific transcriptional programs in inhibitory GABAergic interneurons.

The patterns of synaptic connectivity and physiological properties of diverse neuron types are shaped by distinct gene sets. Our study demonstrates that, in the mouse forebrain, the transcriptional profiles of inhibitory GABAergic interneurons are regulated by Nr4a1, an orphan nuclear receptor whose expression is transiently induced by sensory experiences and is required for normal learning. Nr4a1 exerts contrasting effects on the local axonal wiring of parvalbumin- and somatostatin-positive interneurons, which innervate different subcellular domains of their postsynaptic partners. The loss of Nr4a1 activity in these interneurons results in bidirectional, cell-type-specific transcriptional switches across multiple gene families, including those involved in surface adhesion and repulsion. Our findings reveal that combinatorial synaptic organizing codes are surprisingly flexible and highlight a mechanism by which inducible transcription factors can influence neural circuit structure and function.

Subregion preference in the long-range connectome of pyramidal neurons in the medial prefrontal cortex

BackgroundThe medial prefrontal cortex (mPFC) is involved in complex functions containing multiple types of neurons in distinct subregions with preferential roles. The pyramidal neurons had wide-range projections to cortical and subcortical regions with subregional preferences. Using a combination of viral tracing and fluorescence micro-optical sectioning tomography (fMOST) in transgenic mice, we systematically dissected the whole-brain connectomes of intratelencephalic (IT) and pyramidal tract (PT) neurons in four mPFC subregions.ResultsIT and PT neurons of the same subregion projected to different target areas while receiving inputs from similar upstream regions with quantitative differences. IT and PT neurons all project to the amygdala and basal forebrain, but their axons target different subregions. Compared to subregions in the prelimbic area (PL) which have more connections with sensorimotor-related regions, the infralimbic area (ILA) has stronger connections with limbic regions. The connection pattern of the mPFC subregions along the anterior–posterior axis showed a corresponding topological pattern with the isocortex and amygdala but an opposite orientation correspondence with the thalamus.ConclusionsBy using transgenic mice and fMOST imaging, we obtained the subregional preference whole-brain connectomes of IT and pyramidal tract PT neurons in the mPFC four subregions. These results provide a comprehensive resource for directing research into the complex functions of the mPFC by offering anatomical dissections of the different subregions.

Protein phosphatases regulate the formation of Müller glia-derived progenitor cells in the chick retina

Different kinase-dependent cell signaling pathways are known to play important roles in glia-mediated neuroprotection and reprogramming of Müller glia (MG) into Müller glia-derived progenitor cells (MGPCs) in the retina. However, very little is known about the phosphatases that regulate kinase-dependent signaling in MG. Using single-cell RNA-sequencing (scRNA-seq) databases, we investigated patterns of expression of Dual Specificity Phosphatases (DUSP1/6) and other protein phosphatases in normal and damaged chick retinas. We found that DUSP1, DUSP6, PPP3CB, PPP3R1 and PPPM1A/B/D/E/G are widely expressed by many types of retinal neurons and are dynamically expressed by MG and MGPCs in retinas during the process of reprogramming. We find that inhibition of DUSP1/6 and PP2C phosphatases enhances the formation of proliferating MGPCs in damaged retinas and in retinas treated with insulin and FGF2 in the absence of damage. By contrast, inhibition of PP2B phosphatases suppressed the formation of proliferating MGPCs, but increased numbers of proliferating MGPCs in undamaged retinas treated with insulin and FGF2. In damaged retinas, inhibition of DUSP1/6 increased levels of pERK1/2 and cFos in MG whereas inhibition of PP2B's decreased levels of pStat3 and pS6 in MG. Analyses of scRNA-seq libraries identified numerous differentially activated gene modules in MG in damaged retinas versus MG in retinas treated with insulin+FGF2 suggesting significant differences in kinase-dependent signaling pathways that converge on the formation of MGPCs. Inhibition of phosphatases had no significant effects upon numbers of dying cells in damaged retinas. We conclude that the activity of different protein phosphatases acting through retinal neurons and MG “fine-tune” the cell signaling responses of MG in damaged retinas and during the reprogramming of MG into MGPCs.

Synaptic proteomics decode novel molecular landscape in the brain.

Synapses play a pivotal role in forming neural circuits, with critical implications for brain functions such as learning, memory, and emotions. Several advances in synaptic research have demonstrated the diversity of synaptic structure and function, which can form thousands of connections depending on the neuronal cell types. Moreover, synapses not only interconnect neurons but also establish connections with glial cells such as astrocytes, which play a key role in the architecture and function of neuronal circuits in the brain. Emerging evidence suggests that dysfunction of synaptic proteins contributes to a variety of neurological and psychiatric disorders. Therefore, it is crucial to determine the molecular networks within synapses in various neuronal cell types to gain a deeper understanding of how the nervous system regulates brain function. Recent advances in synaptic proteome approaches, such as fluorescence-activated synaptosome sorting (FASS) and proximity labeling, have allowed for a detailed and spatial analysis of many cell-type-specific synaptic molecules in vivo. In this brief review, we highlight these novel spatial proteomic approaches and discuss the regulation of synaptic formation and function in the brain. This knowledge of molecular networks provides new insight into the understanding of many neurological and psychiatric disorders.

Whole-cortex in situ sequencing reveals input-dependent area identity.

The cerebral cortex is composed of neuronal types with diverse gene expression that are organized into specialized cortical areas. These areas, each with characteristic cytoarchitecture1,2, connectivity3,4 and neuronal activity5,6, are wired into modular networks3,4,7. However, it remains unclear whether these spatial organizations are reflected in neuronal transcriptomic signatures and how such signatures are established in development. Here we used BARseq, a high-throughput in situ sequencing technique, to interrogate the expression of 104 cell-type marker genes in 10.3 million cells, including 4,194,658 cortical neurons over nine mouse forebrain hemispheres, at cellular resolution. De novo clustering of gene expression in single neurons revealed transcriptomic types consistent with previous single-cell RNA sequencing studies8,9. The composition of transcriptomic types is highly predictive of cortical area identity. Moreover, areas with similar compositions of transcriptomic types, which we defined as cortical modules, overlap with areas that are highly connected, suggesting that the same modular organization is reflected in both transcriptomic signatures and connectivity. To explore how the transcriptomic profiles of cortical neurons depend on development, we assessed cell-type distributions after neonatal binocular enucleation. Notably, binocular enucleation caused the shifting of the cell-type compositional profiles of visual areas towards neighbouring cortical areas within the same module, suggesting that peripheral inputs sharpen the distinct transcriptomic identities of areas within cortical modules. Enabled by the high throughput, low cost and reproducibility of BARseq, our study provides a proof of principle for the use of large-scale in situ sequencing to bothreveal brain-wide molecular architecture and understand its development.

Spatiotemporal expression of thyroid hormone transporter MCT8 and THRA mRNA in human cerebral organoids recapitulating first trimester cortex development

Thyroid hormones (TH) play critical roles during nervous system development and patients carrying coding variants of MCT8 (monocarboxylate transporter 8) or THRA (thyroid hormone receptor alpha) present a spectrum of neurological phenotypes resulting from perturbed local TH action during early brain development. Recently, human cerebral organoids (hCOs) emerged as powerful in vitro tools for disease modelling recapitulating key aspects of early human cortex development. To begin exploring prospects of this model for thyroid research, we performed a detailed characterization of the spatiotemporal expression of MCT8 and THRA in developing hCOs. Immunostaining showed MCT8 membrane expression in neuronal progenitor cell types including early neuroepithelial cells, radial glia cells (RGCs), intermediate progenitors and outer RGCs. In addition, we detected robust MCT8 protein expression in deep layer and upper layer neurons. Spatiotemporal SLC16A2 mRNA expression, detected by fluorescent in situ hybridization (FISH), was highly concordant with MCT8 protein expression across cortical cell layers. FISH detected THRA mRNA expression already in neuroepithelium before the onset of neurogenesis. THRA mRNA expression remained low in the ventricular zone, increased in the subventricular zone whereas strong THRA expression was observed in excitatory neurons. In combination with a robust up-regulation of known T3 response genes following T3 treatment, these observations show that hCOs provide a promising and experimentally tractable model to probe local TH action during human cortical neurogenesis and eventually to model the consequences of impaired TH function for early cortex development.

Wallerian Degeneration and Clearance of Olfactory Receptor Neuron Axons following Drosophila Antennal Transection.

Neurons extend their axons and dendrites over long distances and rely on evolutionarily conserved mechanisms to maintain the cellular structure and function of neurites at a distance from their cell body. Neurites that lose connection with their cell body following damage or stressors to their cytoskeleton undergo a programmed self-destruction process akin to apoptosis but using different cellular machinery, termed Wallerian degeneration. While first described for vertebrate axons by Augustus Waller in 1850, key discoveries of the enzymes that regulate Wallerian degeneration were made through forward genetic screens in Drosophila melanogaster Powerful techniques for genetic manipulation and visualization of single neurons combined with simple methods for introducing axotomy (neuron severing) to certain neuron types in Drosophila have enabled the discovery and study of the cellular machinery responsible for Wallerian degeneration, in addition to mechanisms that enable clearance of the resulting debris. This protocol describes how to study the degeneration and clearance of axons from olfactory receptor neurons (ORNs). These peripheral neurons reside in the antennae and project axons to olfactory glomeruli of the anterior brain. Simple and nonlethal removal of antennae from adult flies causes axotomy of ORNs, and the fate of the injured axons can be readily visualized in a whole-mount dissected brain. This assay takes advantage of well-characterized genetic methods to robustly and specifically label subsets of ORNs. This method of neurite labeling and axotomy was the first axon injury paradigm to be developed in flies and is still regularly used due to its simplicity to perform, dissect, image, and analyze.

Extensive long-range polycomb interactions and weak compartmentalization are hallmarks of human neuronal 3D genome.

Chromatin architecture regulates gene expression and shapes cellular identity, particularly in neuronal cells. Specifically, polycomb group (PcG) proteins enable establishment and maintenance of neuronal cell type by reorganizing chromatin into repressive domains that limit the expression of fate-determining genes and sustain distinct gene expression patterns in neurons. Here, we map the 3D genome architecture in neuronal and non-neuronal cells isolated from the Wernicke's area of four human brains and comprehensively analyze neuron-specific aspects of chromatin organization. We find that genome segregation into active and inactive compartments is greatly reduced in neurons compared to other brain cells. Furthermore, neuronal Hi-C maps reveal strong long-range interactions, forming a specific network of PcG-mediated contacts in neurons that is nearly absent in other brain cells. These interacting loci contain developmental transcription factors with repressed expression in neurons and other mature brain cells. But only in neurons, they are rich in bivalent promoters occupied by H3K4me3 histone modification together with H3K27me3, which points to a possible functional role of PcG contacts in neurons. Importantly, other layers of chromatin organization also exhibit a distinct structure in neurons, characterized by an increase in short-range interactions and a decrease in long-range ones.

The gut microbiome promotes locomotion of Drosophila larvae via octopamine signaling.

The gut microbiome is a key partner of animals, influencing various aspects of their physiology and behaviors. Among the diverse behaviors regulated by the gut microbiome, locomotion is vital for survival and reproduction, although the underlying mechanisms remain unclear. Here, we reveal that the gut microbiome modulates the locomotor behavior of Drosophila larvae via a specific neuronal type in the brain. The crawling speed of germ-free (GF) larvae was significantly reduced compared to the conventionally reared larvae, while feeding and excretion behaviors were unaffected. Recolonization with Acetobacter and Lactobacillus can fully and partially rescue the locomotor defects in GF larvae, respectively, probably due to the highest abundance of Acetobacter as a symbiotic bacterium in the larval gut, followed by Lactobacillus. Moreover, the gut microbiome promoted larval locomotion, not by nutrition, but rather by enhancing the brain levels of tyrosine decarboxylase 2 (Tdc2), which is an enzyme that synthesizes octopamine (OA). Overexpression of Tdc2 rescued locomotion ability in GF larvae. These findings together demonstrate that the gut microbiome specifically modulates larval locomotor behavior through the OA signaling pathway, revealing a new mechanism underlying larval locomotion regulated by the gut microbiome.