Axo-axonic synaptic input drives homeostatic plasticity by tuning the axon initial segment structurally and functionally.

Homeostatic plasticity maintains the stability of functional brain networks. The axon initial segment (AIS), where action potentials start, undergoes dynamic adjustment to exert powerful control over neuronal firing properties in response to network activity changes. However, it is poorly understood whether this plasticity involves direct synaptic input to the AIS. Here we show that changes of GABAergic synaptic input from chandelier cells (ChCs) drive homeostatic tuning of the AIS of principal neurons (PNs) in the prelimbic (PL) region, while those from parvalbumin-positive basket cells do not. This tuning is evident in AIS morphology, voltage-gated sodium channel expression, and PN excitability. Moreover, the impact of this homeostatic plasticity can be reflected in animal behavior. Social behavior, inversely linked to PL PN activity, shows time-dependent alterations tightly coupled to changes in AIS plasticity and PN excitability. Thus, AIS-originated homeostatic plasticity in PNs may counteract deficits elicited by imbalanced ChC presynaptic input at cellular and behavioral levels. Teaser: Axon initial segment dynamically responds to changes in local input from chandelier cells to prevent abnormal neuronal functions.

Light-induced giant enhancement of nonreciprocal transport at KTaO3-based interfaces.

Nonlinear transport is a unique functionality of noncentrosymmetric systems, which reflects profound physics, such as spin-orbit interaction, superconductivity and band geometry. However, it remains highly challenging to enhance the nonreciprocal transport for promising rectification devices. Here, we observe a light-induced giant enhancement of nonreciprocal transport at the superconducting and epitaxial CaZrO3/KTaO3 (111) interfaces. The nonreciprocal transport coefficient undergoes a giant increase with three orders of magnitude up to 105 A-1 T-1. Furthermore, a strong Rashba spin-orbit coupling effective field of 14.7 T is achieved with abundant high-mobility photocarriers under ultraviolet illumination, which accounts for the giant enhancement of nonreciprocal transport coefficient. Our first-principles calculations further disclose the stronger Rashba spin-orbit coupling strength and the longer relaxation time in the photocarrier excitation process, bridging the light-property quantitative relationship. Our work provides an alternative pathway to boost nonreciprocal transport in noncentrosymmetric systems and facilitates the promising applications in opto-rectification devices and spin-orbitronic devices.

Whole-brain in vivo base editing reverses behavioral changes in Mef2c-mutant mice.

Whole-brain genome editing to correct single-base mutations and reduce or reverse behavioral changes in animal models of autism spectrum disorder (ASD) has not yet been achieved. We developed an apolipoprotein B messenger RNA-editing enzyme, catalytic polypeptide-embedded cytosine base editor (AeCBE) system for converting C·G to T·A base pairs. We demonstrate its effectiveness by targeting AeCBE to an ASD-associated mutation of the MEF2C gene (c.104T>C, p.L35P) in vivo in mice. We first constructed Mef2cL35P heterozygous mice. Male heterozygous mice exhibited hyperactivity, repetitive behavior and social abnormalities. We then programmed AeCBE to edit the mutated C·G base pairs of Mef2c in the mouse brain through the intravenous injection of blood-brain barrier-crossing adeno-associated virus. This treatment successfully restored Mef2c protein levels in several brain regions and reversed the behavioral abnormalities in Mef2c-mutant mice. Our work presents an in vivo base-editing paradigm that could potentially correct single-base genetic mutations in the brain.

Anisotropic Amorphization and Phase Transition in Na2 Ti3 O7 Anode Caused by Electron Beam Irradiation.

Na2 Ti3 O7 is considered one of the most promising anode materials for sodium ion batteries due to its superior safety, environmental friendliness, and low manufacturing cost. However, its structural stability and reaction mechanism still have not been fully explored. As the electron beam irradiation introduces a similar impact on the Na2 Ti3 O7 anode as the extraction of Na+ ions during the battery discharge process, the microstructure evolution of the materials is investigated by advanced electron microscopy techniques at the atomic scale. Anisotropic amorphization is successfully observed. Through the integrated differential phase contrast-scanning transmission electron microscopy technique and density functional theory calculation, a phase transition pathway involving a new phase, Na2 Ti24 O49 , is proposed with the reduction of Na atoms. Additionally, it is found that the amorphization is dominated by the surface energy and electron dose rate. These findings will deepen the understanding of structural stability and deintercalation mechanism of the Na2 Ti3 O7 anode, providing new insight into exploring the failure mechanism of electrode materials.

Controlled synthesis of transition metal oxide multi-shell structures andin situstudy of the energy storage mechanism.

Multi-shell transition metal oxide hollow spheres show great potential for applications in energy storage because of their unique multilayered hollow structure with large specific surface area, short electron and charge transport paths, and structural stability. In this paper, the controlled synthesis of NiCo2O4, MnCo2O4, NiMn2O4multi-shell layer structures was achieved by using the solvothermal method. As the anode materials for Li-ion batteries, the three multi-shell structures maintained good stability after 650 long cycles in the cyclic charge/discharge test. Thein situtransmisssion electron microscope characterization combined with cyclic voltammetry tests demonstrated that the three anode materials NiCo2O4, MnCo2O4and NiMn2O4have similar charge/discharge transition mechanisms, and the multi-shell structure can effectively buffer the volume expansion and structural collapse during lithium embedding/delithiation to ensure the stability of the electrode structure and cycling performance. The research results can provide effective guidance for the synathesis and charging/discharging mechanism of multi-shell metal oxide lithium-ion battery anode materials.

Projection-Specific Heterogeneity of the Axon Initial Segment of Pyramidal Neurons in the Prelimbic Cortex.

The axon initial segment (AIS) is a highly specialized axonal compartment where the action potential is initiated. The heterogeneity of AISs has been suggested to occur between interneurons and pyramidal neurons (PyNs), which likely contributes to their unique spiking properties. However, whether the various characteristics of AISs can be linked to specific PyN subtypes remains unknown. Here, we report that in the prelimbic cortex (PL) of the mouse, two types of PyNs with axon projections either to the contralateral PL or to the ipsilateral basal lateral amygdala, possess distinct AIS properties reflected by morphology, ion channel expression, action potential initiation, and axo-axonic synaptic inputs from chandelier cells. Furthermore, projection-specific AIS diversity is more prominent in the superficial layer than in the deep layer. Thus, our study reveals the cortical layer- and axon projection-specific heterogeneity of PyN AISs, which may endow the spiking of various PyN types with exquisite modulation.

TadA reprogramming to generate potent miniature base editors with high precision.

Although miniature CRISPR-Cas12f systems were recently developed, the editing efficacy and targeting range of derived miniature cytosine and adenine base editors (miniCBEs and miniABEs) have not been comprehensively addressed. Moreover, functional miniCBEs have not yet be established. Here we generate various Cas12f-derived miniCBEs and miniABEs with improved editing activities and diversified targeting scopes. We reveal that miniCBEs generated with traditional cytidine deaminases exhibit wide editing windows and high off-targeting effects. To improve the editing signatures of classical CBEs and derived miniCBEs, we engineer TadA deaminase with mutagenesis screening to generate potent miniCBEs with high precision and minimized off-target effects. We show that newly designed miniCBEs and miniABEs are able to correct pathogenic mutations in cell lines and introduce genetic mutations efficiently via adeno-associated virus delivery in the brain in vivo. Together, this study provides alternative strategies for CBE development, expands the toolkits of miniCBEs and miniABEs and offers promising therapeutic tools for clinical applications.

Distinct recruitment dynamics of chandelier cells and basket cells by thalamocortical inputs.

Diverse types of GABAergic interneurons tend to specialize in their inhibitory control of various aspects of cortical circuit operations. Among the most distinctive interneuron types, chandelier cells (i.e., axo-axonic cells) are a bona fide cell type that specifically innervates pyramidal cells at the axon initial segment, the site of action potential initiation. Chandelier cells have been speculated to exert ultimate inhibitory control over pyramidal cell spiking. Thus, chandelier cells appear to share multiple similarities with basket cells, not only in firing pattern (fast spiking) and molecular components, but also in potentially perisomatic inhibitory control. Unlike basket cells, however, synaptic recruitment of chandelier cells is little known yet. Here, we examined the mediodorsal thalamocortical input to both chandelier cells and basket cells in medial prefrontal cortex, through combining mouse genetic, optogenetic and electrophysiological approaches. We demonstrated that this thalamocortical input produced initially weak, but facilitated synaptic responses at chandelier cells, which enabled chandelier cells to spike persistently. In contrast, this thalamocortical input evoked initially strong, but rapidly depressed synaptic responses at basket cells, and basket cells only fired at the initiation of input. Overall, the distinct synaptic recruitment dynamics further underscores the differences between chandelier cells and basket cells, suggesting that these two types of fast spiking interneurons play different roles in cortical circuit processing and physiological operation.

Transcardiac Perfusion of the Mouse for Brain Tissue Dissection and Fixation.

Transcardiac perfusion with saline followed by 4% paraformaldehyde (PFA) is widely used to clear blood and preserve brain for immunostaining or in situ hybridization. PFA breaks into formaldehyde in solution, which cross-link protein and DNA molecules to preserve tissue and cell structure. Here we provide a step by step guide for performing this procedure in mouse.

Oligophrenin-1 moderates behavioral responses to stress by regulating parvalbumin interneuron activity in the medial prefrontal cortex.

Ample evidence indicates that individuals with intellectual disability (ID) are at increased risk of developing stress-related behavioral problems and mood disorders, yet a mechanistic explanation for such a link remains largely elusive. Here, we focused on characterizing the syndromic ID gene oligophrenin-1 (OPHN1). We find that Ophn1 deficiency in mice markedly enhances helpless/depressive-like behavior in the face of repeated/uncontrollable stress. Strikingly, Ophn1 deletion exclusively in parvalbumin (PV) interneurons in the prelimbic medial prefrontal cortex (PL-mPFC) is sufficient to induce helplessness. This behavioral phenotype is mediated by a diminished excitatory drive onto Ophn1-deficient PL-mPFC PV interneurons, leading to hyperactivity in this region. Importantly, suppressing neuronal activity or RhoA/Rho-kinase signaling in the PL-mPFC reverses helpless behavior. Our results identify OPHN1 as a critical regulator of adaptive behavioral responses to stress and shed light onto the mechanistic links among OPHN1 genetic deficits, mPFC circuit dysfunction, and abnormalities in stress-related behaviors.

Axo-axonic Innervation of Neocortical Pyramidal Neurons by GABAergic Chandelier Cells Requires AnkyrinG-Associated L1CAM.

Among the diverse interneuron subtypes in the neocortex, chandelier cells (ChCs) are the only population that selectively innervate pyramidal neurons (PyNs) at their axon initial segment (AIS), the site of action potential initiation, allowing them to exert powerful control over PyN output. Yet, mechanisms underlying their subcellular innervation of PyN AISs are unknown. To identify molecular determinants of ChC/PyN AIS innervation, we performed an in vivo RNAi screen of PyN-expressed axonal cell adhesion molecules (CAMs) and select Ephs/ephrins. Strikingly, we found the L1 family member L1CAM to be the only molecule required for ChC/PyN AIS innervation. Further, we show that L1CAM is required during both the establishment and maintenance of innervation, and that selective innervation of PyN AISs by ChCs requires AIS anchoring of L1CAM by the cytoskeletal ankyrin-G/ßIV-spectrin complex. Thus, our findings identify PyN-expressed L1CAM as a critical CAM required for innervation of neocortical PyN AISs by ChCs. VIDEO ABSTRACT.

Dual role for DOCK7 in tangential migration of interneuron precursors in the postnatal forebrain.

Throughout life, stem cells in the ventricular-subventricular zone generate neuroblasts that migrate via the rostral migratory stream (RMS) to the olfactory bulb, where they differentiate into local interneurons. Although progress has been made toward identifying extracellular factors that guide the migration of these cells, little is known about the intracellular mechanisms that govern the dynamic reshaping of the neuroblasts' morphology required for their migration along the RMS. In this study, we identify DOCK7, a member of the DOCK180-family, as a molecule essential for tangential neuroblast migration in the postnatal mouse forebrain. DOCK7 regulates the migration of these cells by controlling both leading process (LP) extension and somal translocation via distinct pathways. It controls LP stability/growth via a Rac-dependent pathway, likely by modulating microtubule networks while also regulating F-actin remodeling at the cell rear to promote somal translocation via a previously unrecognized myosin phosphatase-RhoA-interacting protein-dependent pathway. The coordinated action of both pathways is required to ensure efficient neuroblast migration along the RMS.

TRPC Channels in Health and Disease.

This chapter offers a brief introduction of the functions of TRPC channels in non-neuronal systems. We focus on three major organs of which the research on TRPC channels have been most focused on: kidney, heart, and lung. The chapter highlights on cellular functions and signaling pathways mediated by TRPC channels. It also summarizes several inherited diseases in humans that are related to or caused by TRPC channel mutations and malfunction. A better understanding of TRPC channels functions and the importance of TRPC channels in health and disease should lead to new insights and discovery of new therapeutic approaches for intractable disease.

TRPC Channels and Neuron Development, Plasticity, and Activities.

In this chapter, we mainly focus on the functions of TRPC channels in brain development, including neural progenitor proliferation, neurogenesis, neuron survival, axon guidance, dendritic morphology, synaptogenesis, and neural plasticity. We also notice emerging advances in understanding the functions of TRPC channels in periphery, especially their functions in sensation and nociception in dorsal root ganglion (DRG). Because TRPC channels are expressed in all major types of glial cells, which account for at least half of total cells in the brain, TRPC channels may act as modulators for glial functions as well. The future challenges for studying these channels could be (1) the detailed protein structures of these channels, (2) their cell type-specific functions, (3) requirement for their specific blockers or activators, and (4) change in the channel conformation in the brain.

TGF-ß/Smad signaling through DOCK4 facilitates lung adenocarcinoma metastasis.

The mechanisms by which TGF-ß promotes lung adenocarcinoma (ADC) metastasis are largely unknown. Here, we report that in lung ADC cells, TGF-ß potently induces expression of DOCK4, but not other DOCK family members, via the Smad pathway and that DOCK4 induction mediates TGF-ß's prometastatic effects by enhancing tumor cell extravasation. TGF-ß-induced DOCK4 stimulates lung ADC cell protrusion, motility, and invasion without affecting epithelial-to-mesenchymal transition. These processes, which are fundamental to tumor cell extravasation, are driven by DOCK4-mediated Rac1 activation, unveiling a novel link between TGF-ß and Rac1. Thus, our findings uncover the atypical Rac1 activator DOCK4 as a key component of the TGF-ß/Smad pathway that promotes lung ADC cell extravasation and metastasis.

The X-linked mental retardation protein OPHN1 interacts with Homer1b/c to control spine endocytic zone positioning and expression of synaptic potentiation.

At glutamatergic synapses, local endocytic recycling of AMPA receptors (AMPARs) is important for the supply of a mobile pool of AMPARs required for synaptic potentiation. This local recycling of AMPARs critically relies on the presence of an endocytic zone (EZ) near the postsynaptic density (PSD). The precise mechanisms that couple the EZ to the PSD still remain largely elusive, with the large GTPase Dynamin-3 and the multimeric PSD adaptor protein Homer1 as the two main players identified. Here, we demonstrate that a physical interaction between the X-linked mental retardation protein oligophrenin-1 (OPHN1) and Homer1b/c is crucial for the positioning of the EZ adjacent to the PSD, and present evidence that this interaction is important for OPHN1's role in controlling activity-dependent strengthening of excitatory synapses in the rat hippocampus. Disruption of the OPHN1-Homer1b/c interaction causes a displacement of EZs from the PSD, along with impaired AMPAR recycling and reduced AMPAR accumulation at synapses, in both basal conditions and conditions that can induce synaptic potentiation. Together, our findings unveil a novel role for OPHN1 as an interaction partner of Homer1b/c in spine EZ positioning, and provide new mechanistic insight into how genetic deficits in OPHN1 can lead to impaired synapse maturation and plasticity.

Regulation of chandelier cell cartridge and bouton development via DOCK7-mediated ErbB4 activation.

Chandelier cells (ChCs), typified by their unique axonal morphology, are the most distinct interneurons present in cortical circuits. Via their distinctive axonal terminals, called cartridges, these cells selectively target the axon initial segment of pyramidal cells and control action potential initiation; however, the mechanisms that govern the characteristic ChC axonal structure have remained elusive. Here, by employing an in utero electroporation-based method that enables genetic labeling and manipulation of ChCs in vivo, we identify DOCK7, a member of the DOCK180 family, as a molecule essential for ChC cartridge and bouton development. Furthermore, we present evidence that DOCK7 functions as a cytoplasmic activator of the schizophrenia-associated ErbB4 receptor tyrosine kinase and that DOCK7 modulates ErbB4 activity to control ChC cartridge and bouton development. Thus, our findings define DOCK7 and ErbB4 as key components of a pathway that controls the morphological differentiation of ChCs, with implications for the pathogenesis of schizophrenia.

Canonical transient receptor potential 3 channels regulate mitochondrial calcium uptake.

Mitochondrial Ca(2+) homeostasis is fundamental to regulation of mitochondrial membrane potential, ATP production, and cellular Ca(2+) homeostasis. It has been known for decades that isolated mitochondria can take up Ca(2+) from the extramitochondrial solution, but the molecular identity of the Ca(2+) channels involved in this action is largely unknown. Here, we show that a fraction of canonical transient receptor potential 3 (TRPC3) channels is localized to mitochondria, a significant fraction of mitochondrial Ca(2+) uptake that relies on extramitochondrial Ca(2+) concentration is TRPC3-dependent, and the up- and down-regulation of TRPC3 expression in the cell influences the mitochondrial membrane potential. Our findings suggest that TRPC3 channels contribute to mitochondrial Ca(2+) uptake. We anticipate our observations may provide insights into the mechanisms of mitochondrial Ca(2+) uptake and advance understanding of the physiological role of TRPC3.

Flufenamic acid promotes angiogenesis through AMPK activation.

Angiogenesis plays critical roles in development, tumor growth and metastasis. Flufenamic acid (FFA) is an anti-inflammatory agent known to alter ion fluxes across the plasma membrane. Its role in angiogenesis has not been fully addressed to date. Here, we report that FFA treatment promotes angiogenesis both in vitro and in vivo. Applying FFA for 12 h promoted tube formation of human umbilical vein endothelial cells (HUVECs) without affecting cell proliferation. Three angiogenesis-related genes, VEGF, e-NOS and AAMP, were analyzed by RT-PCR. A significant difference was found between the FFA group and the control; the FFA group had significantly higher mRNA accumulation levels of all the three genes (p<0.05). Moreover, in the chick embryo chorioallantoic membrane (CAM) assay, FFA promoted the formation of macroscopic blood vessels. Finally, western blotting showed that the FFA-treated group had significantly higher phosphorylated AMPK levels, compared with the control (p<0.05). These results suggest that FFA promotes angiogenesis both in vitro and in vivo likely via promoting tube formation through AMPK activation.

TRPC5 channel is the mediator of neurotrophin-3 in regulating dendritic growth via CaMKIIα in rat hippocampal neurons.

Neurotrophin-3 (NT-3) plays numerous important roles in the CNS and the elevation of intracellular Ca(2+) ([Ca(2+)](i)) is critical for these functions of NT-3. However, the mechanism by which NT-3 induces [Ca(2+)](i) elevation remains largely unknown. Here, we found that transient receptor potential canonical (TRPC) 5 protein and TrkC, the NT-3 receptor, exhibited a similar temporal expression in rat hippocampus and cellular colocalization in hippocampal neurons. Stimulation of the neurons by NT-3 induced a nonselective cation conductance and PLCγ-dependent [Ca(2+)](i) elevation, which were both blocked when TRPC5, but not TRPC6 channels, were inhibited. Moreover, the Ca(2+) influx through TRPC5 induced by NT-3 inhibited the neuronal dendritic growth through activation of calmodulin-dependent kinase (CaMK) IIα. In contrast, the Ca(2+) influx through TRPC6 induced by NT-4 promoted the dendritic growth. Thus, TRPC5 acts as a novel and specific mediator for NT-3 to regulate dendrite development through CaMKIIα.