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Scribble (Scrib) is a conserved polarity protein acting as a scaffold involved in multiple cellular and developmental processes. Recent evidence from our group indicates that Scrib is also essential for brain development as early global deletion of Scrib in the dorsal telencephalon induced cortical thickness reduction and alteration of interhemispheric connectivity. In addition, Scrib conditional knockout (cKO) mice have behavioral deficits such as locomotor activity impairment and memory alterations. Given Scrib broad expression in multiple cell types in the brain, we decided to determine the neuronal contribution of Scrib for these phenotypes. In the present study, we further investigate the function of Scrib specifically in excitatory neurons on the forebrain formation and the control of locomotor behavior. To do so, we generated a novel neuronal glutamatergic specific Scrib cKO mouse line called Nex -Scrib −/− cKO. Remarkably, cortical layering and commissures were impaired in these mice and reproduced to some extent the previously described phenotype in global Scrib cKO. In addition and in contrast to our previous results using Emx1-Scrib −/− cKO, the Nex-Scrib −/− cKO mutant mice exhibited significantly reduced locomotion. Altogether, the novel cKO model described in this study further highlights an essential role for Scrib in forebrain development and locomotor behavior. [ABSTRACT FROM AUTHOR]

The development of the neuromuscular junction (NMJ) requires dynamic trans-synaptic coordination orchestrated by secreted factors, including Wnt family morphogens. To investigate how these synaptic cues in NMJ development are transduced, particularly in the regulation of acetylcholine receptor (AChR) accumulation in the postsynaptic membrane, we explored the function of Van Gogh–like protein 2 (Vangl2), a core component of Wnt planar cell polarity signaling. We found that conditional, muscle-specific ablation of Vangl2 in mice reproduced the NMJ differentiation defects seen in mice with global Vangl2 deletion. These alterations persisted into adulthood and led to NMJ disassembly, impaired neurotransmission, and deficits in motor function. Vangl2 and the muscle-specific receptor tyrosine kinase MuSK were functionally associated in Wnt signaling in the muscle. Vangl2 bound to and promoted the signaling activity of MuSK in response to Wnt11. The loss of Vangl2 impaired RhoA activation in cultured mouse myotubes and caused dispersed, rather than clustered, organization of AChRs at the postsynaptic or muscle cell side of NMJs in vivo. Our results identify Vangl2 as a key player of the core complex of molecules shaping neuromuscular synapses and thus shed light on the molecular mechanisms underlying NMJ assembly. Brawn over brains at neuromuscular synapses: The neuromuscular junction (NMJ) is a tricellular synapse among motor neurons, glial Schwann cells, and skeletal muscle fibers that controls movement. Using tissue-specific knockout mice, Boex et al. found that the cell polarity protein Vangl2 in the muscle—not in motor neurons—was critical for the functional formation of NMJs in development and for their maintenance in adulthood. Vangl2 bound to the muscle-specific kinase MuSK to mediate Wnt signaling that promoted synaptic clustering of acetylcholine receptors in the muscle and cultured myotubes. Loss of muscle Vangl2 impaired neuromuscular transmission and led to progressive deficits in the motor function of the hindlimbs and diaphragm in mice. The findings reveal a role for muscle-specific cell polarity signaling in the molecular organization of the NMJ. [ABSTRACT FROM AUTHOR]

Social behavior is a basic domain affected by several neurodevelopmental disorders, including ASD and a heterogeneous set of neuropsychiatric disorders. The SCRIB gene that codes for the polarity protein SCRIBBLE has been identified as a risk gene for spina bifida, the most common type of neural tube defect, found at high frequencies in autistic patients, as well as other congenital anomalies. The deletions and mutations of the 8q24.3 region encompassing SCRIB are also associated with multisyndromic and rare disorders. Nonetheless, the potential link between SCRIB and relevant social phenotypes has not been fully investigated. Hence, we show that Scribcrc/+ mice, carrying a mutated version of Scrib, displayed reduced social motivation behavior and social habituation, while other behavioral domains were unaltered. Social deficits were associated with the upregulation of ERK phosphorylation, together with increased c-Fos activity. Importantly, the social alterations were rescued by both direct and indirect pERK inhibition. These results support a link between polarity genes, social behaviors and hippocampal functionality and suggest a role for SCRIB in the etiopathology of neurodevelopmental disorders. Furthermore, our data demonstrate the crucial role of the MAPK/ERK signaling pathway in underlying social motivation behavior, thus supporting its relevance as a therapeutic target. [ABSTRACT FROM AUTHOR]

Understanding the developmental steps that shape formation of the neuromuscular junction (NMJ) connecting motoneurons to skeletal muscle fibers is crucial. Wnt morphogens are key players in the formation of this specialized peripheral synapse, but their individual and collaborative functions and downstream pathways remain poorly understood at the NMJ. Here, we demonstrate through Wnt4 and Wnt11 gain-of-function studies in cell culture or in mice that Wnts enhance acetylcholine receptor (AChR) clustering and motor axon outgrowth. By contrast, loss of Wnt11 or Wnt-dependent signaling in vivo decreases AChR clustering and motor nerve terminal branching. Both Wnt4 and Wnt11 stimulate AChR mRNA levels and AChR clustering downstreamof activation of the β-catenin pathway. Strikingly, Wnt4 and Wnt11 co-immunoprecipitate with Vangl2, a core component of the planar cell polarity (PCP) pathway, which accumulates at embryonic NMJs. Moreover, mice bearing a Vangl2 loss-of-function mutation (loop-tail) exhibit fewer AChR clusters and overgrowth of motor axons bypassing AChR clusters. Together, our results provide genetic and biochemical evidence that Wnt4 and Wnt11 cooperatively contribute to mammalian NMJ formation through activation of both the canonical and Vangl2-dependent core PCP pathways. [ABSTRACT FROM AUTHOR]

Extensive evidence suggests that long term dietary n-3 polyunsaturated fatty acids (PUFAs) deficiency results in altered emotional behaviour. We have recently demonstrated that n-3 PUFAs deficiency induces emotional alterations through abnormal corticosterone secretion which leads to altered dendritic arborisation in the prefrontal cortex (PFC). Here we show that hypothalamic-pituitary-adrenal (HPA) axis feedback inhibition was not compromised in n-3 deficient mice. Rather, glucocorticoid receptor (GR) signaling pathway was inactivated in the PFC but not in the hippocampus of n-3 deficient mice. Consequently, only dendritic arborisation in PFC was affected by dietary n-3 PUFAs deficiency. In addition, occlusion experiment with GR blockade altered GR signaling in the PFC of control mice, with no further alterations in n-3 deficient mice. In conclusion, n-3 PUFAs deficiency compromised PFC, leading to dendritic atrophy, but did not change hippocampal GR function and dendritic arborisation. We argue that this GR sensitivity contributes to n-3 PUFAs deficiency-related emotional behaviour deficits. [ABSTRACT FROM AUTHOR]

The article focuses on a study related to investigation of changes induced in learning and memory processes due to glutamatergic mechanisms of neuroinflammation. Topics discussed include activation of microglia as early common feature of brain diseases, regulation of neuroplasticity and promotion of learning by immune mechanisms and conduction of Western blot analyses and protein extraction during the study.

Hypersensitivity in response to sensory stimuli and neocortical hyperexcitability are prominent features of Fragile X Syndrome (FXS) and autism spectrum disorders, but little is known about the dendritic mechanisms underlying these phenomena. We found that the primary somatosensory neocortex (S1) was hyperexcited in response to tactile sensory stimulation in Fmr1−/y mice. This correlated with neuronal and dendritic hyperexcitability of S1 pyramidal neurons, which affect all major aspects of neuronal computation, from the integration of synaptic input to the generation of action potential output. Using dendritic electrophysiological recordings, calcium imaging, pharmacology, biochemistry and a computer model, we found that this defect was, at least in part, attributable to the reduction and dysfunction of dendritic h- and BKCa channels. We pharmacologically rescued several core hyperexcitability phenomena by targeting BKCa channels. Our results provide strong evidence pointing to the utility of BKCa channel openers for the treatment of the sensory hypersensitivity aspects of FXS. [ABSTRACT FROM AUTHOR]

Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. There are three distinct subtypes of ionotropic glutamate receptors (GluRs) that have been identified including 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid receptors (AMPARs), N-methyl-D-aspartate receptors (NMDARs) and kainate receptors. The most common GluRs in mature synapses are AMPARs that mediate the fast excitatory neurotransmission and NMDARs that mediate the slow excitatory neurotransmission. There have been large numbers of recent reports studying how a single neuron regulates synaptic numbers and types of AMPARs and NMDARs. Our current research is centered primarily on NMDARs and, therefore, we will focus in this review on recent knowledge of molecular mechanisms occurring (1) early in the biosynthetic pathway of NMDARs, (2) in the transport of NMDARs after their release from the endoplasmic reticulum (ER); and (3) at the plasma membrane including excitatory synapses. Because a growing body of evidence also indicates that abnormalities in NMDAR functioning are associated with a number of human psychiatric and neurological diseases, this review together with other chapters in this issue may help to enhance research and to gain further knowledge of normal synaptic physiology as well as of the etiology of many human brain diseases. [ABSTRACT FROM AUTHOR]

In ciliated mammalian cells, the precise migration of the primary cilium at the apical surface of the cells, also referred to as translational polarity, defines planar cell polarity (PCP) in very early stages. Recent research has revealed a co-dependence between planar polarization of some cell types and cilium positioning at the surface of cells. This important role of the primary cilium in mammalian cells is in contrast with its absence from Drosophila melanogaster PCP establishment. Here, we show that deletion of GTP-binding protein alpha-i subunit 3 (Gαi3) and mammalian Partner of inscuteable (mPins) disrupts the migration of the kinocilium at the surface of cochlear hair cells and affects hair bundle orientation and shape. Inhibition of G-protein function in vitro leads to kinocilium migration defects, PCP phenotype and abnormal hair bundle morphology. We show that Gαi3/mPins are expressed in an apical and distal asymmetrical domain, which is opposite and complementary to an aPKC/Par-3/Par-6b expression domain, and non-overlapping with the core PCP protein Vangl2. Thus G-protein-dependent signalling controls the migration of the cilium cell autonomously, whereas core PCP signalling controls long-range tissue PCP. [ABSTRACT FROM AUTHOR]

Vangl2 is one of the central proteins controlling the establishment of planar cell polarity in multiple tissues of different species. Previous studies suggest that the localization of the Vangl2 protein to specific intracellular microdomains is crucial for its function. However, the molecular mechanisms that control Vangl2 trafficking within a cell are largely unknown. Here, we identify Gipc1 (GAIP C-terminus interacting protein 1) as a new interactor for Vangl2, and we show that a myosin VI-Gipc1 protein complex can regulate Vangl2 traffic in heterologous cells. Furthermore, we show that in the cochlea of MyoVI mutant mice, Vangl2 presence at the membrane is increased, and that a disruption of Gipc1 function in hair cells leads to maturation defects, including defects in hair bundle orientation and integrity. Finally, stimulated emission depletion microscopy and overexpression of GFP-Vangl2 show an enrichment of Vangl2 on the supporting cell side, adjacent to the proximal membrane of hair cells. Altogether, these results indicate a broad role for Gipc1 in the development of both stereociliary bundles and cell polarization, and suggest that the strong asymmetry of Vangl2 observed in early postnatal cochlear epithelium is mostly a 'tissue' polarity readout. [ABSTRACT FROM AUTHOR]

Scribble (Scrib) is a key regulator of apicobasal polarity, presynaptic architecture, and short-term synaptic plasticity in Drosophila. In mammals, its homolog Scrib1 has been implicated in cancer, neural tube closure, and planar cell polarity (PCP), but its specific role in the developing and adult nervous system is unclear. Here, we used the circletail mutant, a mouse model for PCP defects, to show that Scrib1 is located in spines where it influences actin cytoskeleton and spine morphing. In the hippocampus of these mutants, we observed an increased synapse pruning associated with an increased number of enlarged spines and postsynaptic density, and a decreased number of perforated synapses. This phenotype was associated with a mislocalization of the signaling pathway downstream of Scrib1, leading to an overall activation of Rac1 and defects in actin dynamic reorganization. Finally, Scrib1-deficient mice exhibit enhanced learning and memory abilities and impaired social behavior, two features relevant to autistic spectrum disorders. Our data identify Scrib1 as a crucial regulator of brain development and spine morphology, and suggest that Scrib1crc/+ mice might be a model for studying synaptic dysfunction and human psychiatric disorders. [ABSTRACT FROM AUTHOR]

The NMDA receptor is an important component of excitatory synapses in the CNS. In addition to its synaptic localization, the NMDA receptor is also present at extrasynaptic sites where it may have functions distinct from those at the synapse. Little is known about how the number, composition, and localization of extrasynaptic receptors are regulated. We identified a novel NMDA receptor-interacting protein, GIPC (GAIP-interacting protein, C terminus), that associates with surface as well as internalized NMDA receptors when expressed in heterologous cells. In neurons, GIPC colocalizes with a population of NMDA receptors on the cell surface, and changes in GIPC expression alter the number of surface receptors. GIPC is mainly excluded from the synapse, and changes in GIPC expression do not change the total number of synaptic receptors. Our results suggest that GIPC may be preferentially associated with extrasynaptic NMDA receptors and may play a role in the organization and trafficking of this population of receptors. [ABSTRACT FROM AUTHOR]

Planar cell polarity (PCP) is a process in which cells develop with uniform orientation within the plane of an epithelium. To begin to elucidate the mechanisms of PCP in vertebrates, the localization of the protein Vangl2 (Van Gogh-like) was determined during the development of the mammalian cochlea. Results indicate that Vangl2 becomes asymmetrically localized to specific cell- cell boundaries along the axis of polarization and that this asymmetry is lost in PCP mutants. In addition, PDZ2 (postsynaptic density/Discs large/zona occludens 1), PDZ3, and PDZ4 of the PCP protein Scrb1 (Scribble) are shown to bind to the C-terminal PDZ binding domain of Vangl2, suggesting that Scrb1 plays a direct role in asymmetric targeting of Vangl2. Finally, Fz3 (Frizzled), a newly demonstrated mediator of PCP, is also asymmetrically localized in a pattern that matches that of Vangl2. The presence and asymmetry of Fz3 at the membrane is shown to be dependent on Vangl2. This result suggests a role for Vangl2 in the targeting or anchoring of Fz3, a hypothesis strengthened by the existence of a physical interaction between the two proteins. Together, our data support the idea that protein asymmetry plays an important role in the development of PCP, but the colocalization and interaction of Fz3 and Vangl2 suggests that novel PCP mechanisms exist in vertebrates. [ABSTRACT FROM AUTHOR]

Appropriate trafficking and targeting of glutamate receptors (GluRs) to the postsynaptic density is crucial for synaptic function. We show that mPins (mammalian homologue of Drosophila melanogaster partner of inscuteable) interacts with SAP102 and PSD-95 (two PDZ proteins present in neurons), and functions in the formation of the NMDAR–MAGUK (N-methyl-D-aspartate receptor–membrane-associated guanylate kinase) complex. mPins enhances trafficking of SAP102 and NMDARs to the plasma membrane in neurons. Expression of dominant–negative constructs and short-interfering RNA (siRNA)-mediated knockdown of mPins decreases SAP102 in dendrites and modifies surface expression of NMDARs. mPins changes the number and morphology of dendritic spines and these effects depend on its Gαi interaction domain, thus implicating G-protein signalling in the regulation of postsynaptic structure and trafficking of GluRs. [ABSTRACT FROM AUTHOR]

The number and type of receptors present at the postsynaptic membrane determine the response to the neurotransmitter released from the presynaptic terminal. Because most neurons receive multiple and distinct synaptic inputs and contain several different subtypes of receptors stimulated by the same neurotransmitter, the assembly and trafficking of receptors in neurons is a complex process involving many levels of regulation. To investigate the mechanism that neurons use to regulate the assembly of receptor subunits, we studied a GluR2 knock-out mouse. GluR2 is a critical subunit that controls calcium permeability of AMPA receptors and is present in most native AMPA receptors. Our data indicate that in the absence of GluR2, aberrant receptor complexes composed of GluR1 and GluR3 are formed in the hippocampus, and that there is an increased number of homomeric GluR1 and GluR3 receptors. We also show that these homomeric and heteromeric receptors are less efficiently expressed at the synapse. Our results show that GluR2 plays a critical role in controlling the assembly of AMPA receptors, and that the assembly of subunits may reflect the affinity of one subunit for another or the stability of intermediates in the assembly process. Therefore, GluR1 may have a greater preference for GluR2 than it does for GluR3. [ABSTRACT FROM AUTHOR]

NMDA (N-methyl-D-aspartate) receptors (NMDARs) are targeted to dendrites and anchored at the post-synaptic density (PSD) through interactions with PDZ proteins. However, little is known about how these receptors are sorted from the endoplasmic reticulum and Golgi apparatus to the synapse. Here, we find that synapse-associated protein 102 (SAP102) interacts with the PDZ-binding domain of Sec8, a member of the exocyst complex. Our results show that interactions between SAP102 and Sec8 are involved in the delivery of NMDARs to the cell surface in heterologous cells and neurons. Furthermore, they suggest that an exocyst-SAP102-NMDAR complex is an important component of NMDAR trafficking. [ABSTRACT FROM AUTHOR]

The NMDA receptor (NMDAR) plays a central role in the function of excitatory synapses. Recent studies have provided interesting insights into several aspects of the trafficking of this receptor in neurons. The NMDAR is not a static resident of the synapse. Rather, the number and composition of synaptic NMDARs can be modulated by several factors. The interaction of PDZ proteins, generally thought to occur at the synapse, appears to occur early in the secretory pathway; this interaction may play a role in the assembly of the receptor complex and its exit from the endoplasmic reticulum. This review addresses recent advances in our understanding of NMDAR trafficking and its synaptic delivery and maintenance. [ABSTRACT FROM AUTHOR]

Mutations in GPSM2 cause Chudley-McCullough syndrome (CMCS), an autosomal recessive neurological disorder characterized by early-onset sensorineural deafness and brain anomalies. Here, we show that mutation of the mouse orthologue of GPSM2 affects actin-rich stereocilia elongation in auditory and vestibular hair cells, causing deafness and balance defects. The G-protein subunit Gαi3, a well-documented partner of Gpsm2, participates in the elongation process, and its absence also causes hearing deficits. We show that Gpsm2 defines an ∼200 nm nanodomain at the tips of stereocilia and this localization requires the presence of Gαi3, myosin 15 and whirlin. Using single-molecule tracking, we report that loss of Gpsm2 leads to decreased outgrowth and a disruption of actin dynamics in neuronal growth cones. Our results elucidate the aetiology of CMCS and highlight a new molecular role for Gpsm2/Gαi3 in the regulation of actin dynamics in epithelial and neuronal tissues. [ABSTRACT FROM AUTHOR]

Summary: The NMDA receptor (NMDAR) is a component of excitatory synapses and a key participant in synaptic plasticity. We investigated the role of two domains in the C terminus of the NR2B subunit—the PDZ binding domain and the clathrin adaptor protein (AP-2) binding motif—in the synaptic localization of NMDA receptors. NR2B subunits lacking functional PDZ binding are excluded from the synapse. Mutations in the AP-2 binding motif, YEKL, significantly increase the number of synaptic receptors and allow the synaptic localization of NR2B subunits lacking PDZ binding. Peptides corresponding to YEKL increase the synaptic response within minutes. In contrast, the NR2A subunit localizes to the synapse in the absence of PDZ binding and is not altered by mutations in its motif corresponding to YEKL of NR2B. This study identifies a dynamic regulation of synaptic NR2B-containing NMDARs through PDZ protein-mediated stabilization and AP-2-mediated internalization that is modulated by phosphorylation by Fyn kinase. [Copyright &y& Elsevier]

The central command for breathing arises mainly from two interconnected rhythmogenic hindbrain networks, the parafacial respiratory group (pFRG or epF at embryonic stages) and the preBötzinger complex (preBötC), which are comprised of a limited number of neurons located in confined regions of the ventral medulla. In rodents, both networks become active toward the end of gestation but little is known about the signaling pathways involved in their anatomical and functional establishment during embryogenesis. During embryonic development, epF and preBötC neurons migrate from their territories of origin to their final positions in ventral brainstem areas. Planar Cell Polarity (PCP) signaling, including the molecule Scrib , is known to control the developmental migration of several hindbrain neuronal groups. Accordingly, a homozygous mutation of Scrib leads to severe disruption of hindbrain anatomy and function. Here, we aimed to determine whether Scrib is also involved in the prenatal development of the hindbrain nuclei controlling breathing. We combined immunostaining, calcium imaging and electrophysiological recordings of neuronal activity in isolated in vitro preparations. In the Scrib mutant, despite severe neural tube defects, epF and preBötC neurons settled at their expected hindbrain positions. Furthermore, both networks remained capable of generating rhythmically organized, respiratory-related activities and exhibited normal sensitivity to pharmacological agents known to modify respiratory circuit function. Thus Scrib is not required for the proper migration of epF and preBötC neurons during mouse embryogenesis. Our findings thus further illustrate the robustness and specificity of the developmental processes involved in the establishment of hindbrain respiratory circuits. [ABSTRACT FROM AUTHOR]

• AlphaLISA SureFire Ultra technology is well-adapted for studying cell signaling. • Alpha technology allows detection of phosphoproteins from brain tissue homogenates. • Alpha technology is compatible with cell fractionation and synaptosomal protocols. • Alpha technology is rapid, sensitive, reproducible and cost-effective. • Alpha lysis buffer is fully compatible with the Western blot technique. Phosphorylation by protein kinases is a fundamental molecular process involved in the regulation of signaling activities in living organisms. Understanding this complex network of phosphorylation, especially phosphoproteins, is a necessary step for grasping the basis of cellular pathophysiology. Studying brain intracellular signaling is a particularly complex task due to the heterogeneous complex nature of the brain tissue, which consists of many embedded structures. Overcoming this degree of complexity requires a technology with a high throughput and economical in the amount of biological material used, so that a large number of signaling pathways may be analyzed in a large number of samples. We have turned to Alpha (Amplified Luminescent Proximity Homogeneous Assay) technology. Western blot is certainly the most commonly used method to measure the phosphorylation state of proteins. Even though Western blot is an accurate and reliable method for analyzing modifications of proteins, it is a time-consuming and large amounts of samples are required. Those two parameters are critical when the goal of the research is to comprehend multi-signaling proteic events so as to analyze several targets from small brain areas. Here we demonstrate that Alpha technology is particularly suitable for studying brain signaling pathways by allowing rapid, sensitive, reproducible and semi-quantitative detection of phosphoproteins from individual mouse brain tissue homogenates and from cell fractionation and synaptosomal preparations of mouse hippocampus. Alpha technology represents a major experimental step forward in unraveling the brain phosphoprotein-related molecular mechanisms involved in brain-related disorders. [ABSTRACT FROM AUTHOR]

Core planar cell polarity (PCP) genes, which are involved in various neurodevelopmental disorders such as neural tube closure, epilepsy, and autism spectrum disorder, have poorly defined molecular signatures in neurons, mostly synapse-centric. Here, we show that the core PCP protein Prickle-like protein 2 (Prickle2) controls neuronal polarity and is a previously unidentified member of the axonal initial segment (AIS) proteome. We found that Prickle2 is present and colocalizes with AnkG480, the AIS master organizer, in the earliest stages of axonal specification and AIS formation. Furthermore, by binding to and regulating AnkG480, Prickle2 modulates its ability to bundle microtubules, a crucial mechanism for establishing neuronal polarity and AIS formation. Prickle2 depletion alters cytoskeleton organization, and Prickle2 levels determine both axon number and AIS maturation. Last, early Prickle2 depletion produces impaired action potential firing.

GluN2B subunits of NMDA receptors have been proposed as a target for treating age-related memory decline. They are indeed considered as crucial for hippocampal synaptic plasticity and hippocampus-dependent memory formation, which are both altered in aging. Because a synaptic enrichment in GluN2B is associated with hippocampal LTP in vitro, a similar mechanism is expected to occur during memory formation. We show instead that a reduction of GluN2B synaptic localization induced by a single-session learning in dorsal CA1 apical dendrites is predictive of efficient memorization of a temporal association. Furthermore, synaptic accumulation of GluN2B, rather than insufficient synaptic localization of these subunits, is causally involved in the age-related impairment of memory. These challenging data identify extra-synaptic redistribution of GluN2B-containing NMDAR induced by learning as a molecular signature of memory formation and indicate that modulating GluN2B synaptic localization might represent a useful therapeutic strategy in cognitive aging., (© 2020 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.)

The organization of spatial information, including pattern completion and pattern separation processes, relies on the hippocampal circuits, yet the molecular and cellular mechanisms underlying these two processes are elusive. Here, we find that loss of Vangl2, a core PCP gene, results in opposite effects on pattern completion and pattern separation processes. Mechanistically, we show that Vangl2 loss maintains young postmitotic granule cells in an immature state, providing increased cellular input for pattern separation. The genetic ablation of Vangl2 disrupts granule cell morpho-functional maturation and further prevents CaMKII and GluA1 phosphorylation, disrupting the stabilization of AMPA receptors. As a functional consequence, LTP at lateral perforant path-GC synapses is impaired, leading to defects in pattern completion behavior. In conclusion, we show that Vangl2 exerts a bimodal regulation on young and mature GCs, and its disruption leads to an imbalance in hippocampus-dependent pattern completion and separation processes., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Dynamic mechanical interactions between adhesion complexes and the cytoskeleton are essential for axon outgrowth and guidance. Whether planar cell polarity (PCP) proteins, which regulate cytoskeleton dynamics and appear necessary for some axon guidance, also mediate interactions with membrane adhesion is still unclear. Here we show that Vangl2 controls growth cone velocity by regulating the internal retrograde actin flow in an N-cadherin-dependent fashion. Single molecule tracking experiments show that the loss of Vangl2 decreased fast-diffusing N-cadherin membrane molecules and increased confined N-cadherin trajectories. Using optically manipulated N-cadherin-coated microspheres, we correlated this behavior to a stronger mechanical coupling of N-cadherin with the actin cytoskeleton. Lastly, we show that the spatial distribution of Vangl2 within the growth cone is selectively affected by an N-cadherin-coated substrate. Altogether, our data show that Vangl2 acts as a negative regulator of axonal outgrowth by regulating the strength of the molecular clutch between N-cadherin and the actin cytoskeleton., Competing Interests: SD, MM, YH, MG, NA, DH, VS, NS, OT, MM No competing interests declared, (© 2020, Dos-Santos Carvalho et al.)

This corrects the article DOI: 10.1038/ncomms14907.

Mutations in GPSM2 cause Chudley-McCullough syndrome (CMCS), an autosomal recessive neurological disorder characterized by early-onset sensorineural deafness and brain anomalies. Here, we show that mutation of the mouse orthologue of GPSM2 affects actin-rich stereocilia elongation in auditory and vestibular hair cells, causing deafness and balance defects. The G-protein subunit Gα i3 , a well-documented partner of Gpsm2, participates in the elongation process, and its absence also causes hearing deficits. We show that Gpsm2 defines an ∼200 nm nanodomain at the tips of stereocilia and this localization requires the presence of Gα i3 , myosin 15 and whirlin. Using single-molecule tracking, we report that loss of Gpsm2 leads to decreased outgrowth and a disruption of actin dynamics in neuronal growth cones. Our results elucidate the aetiology of CMCS and highlight a new molecular role for Gpsm2/Gα i3 in the regulation of actin dynamics in epithelial and neuronal tissues.