Aberrant Somatosensory Processing and Connectivity in Mice Lacking Engrailed-2

Biological subtyping of autism via cross-species fMRI

It is frequently assumed that the phenotypic heterogeneity in autism spectrum disorder reflects underlying pathobiological variation. However, direct evidence in support of this hypothesis is lacking. Here, we leverage cross-species functional neuroimaging to examine whether variability in brain functional connectivity reflects distinct biological mechanisms. We find that fMRI connectivity alterations in 20 distinct mouse models of autism (n=549 individual mice) can be clustered into two prominent hypo- and hyperconnectivity subtypes. We show that these connectivity profiles are linked to distinct signaling pathways, with hypoconnectivity being associated with synaptic dysfunction, and hyperconnectivity reflecting transcriptional and immune-related alterations. Extending these findings to humans, we identify analogous hypo- and hyperconnectivity subtypes in a large, multicenter resting state fMRI dataset of n=940 autistic and n=1036 neurotypical individuals. Remarkably, hypo- and hyperconnectivity autism subtypes are replicable across independent cohorts (accounting for 25.1% of all autism data), exhibit distinct functional network architecture, are behaviorally dissociable, and recapitulate synaptic and immune mechanisms identified in corresponding mouse subtypes. Our cross-species investigation, thus, decodes the heterogeneity of fMRI connectivity in autism into distinct pathway-specific etiologies, offering a new empirical framework for targeted subtyping of autism.

Altered primary somatosensory neuron development in a Pten heterozygous model for autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by deficits in social interactions, repetitive behaviors, and hyper- or hyposensitivity to sensory stimuli. The mechanisms underlying the emergence of sensory features in ASD are not fully understood, but recent studies in rodent models highlight that these may result from differences in primary sensory neurons themselves. We examined sensory behaviors in a Pten haploinsufficient mouse model ( Pten Het ) for syndromic ASD and identified elevated responses to mechanical stimuli and a higher threshold to thermal responses. Transcriptomic and in vivo anatomical analysis identified alterations in subtype-specific markers of primary somatosensory neurons in Pten Het dorsal root ganglia (DRG). These defects emerge early during DRG development and involve dysregulation of multiple signaling pathways downstream of Pten . Finally, we show that mice harboring an ASD-associated mutation ( Pten Y69H ) also show altered expression of somatosensory neuron subtype-specific markers. Together, these results show that precise levels of Pten are required for proper somatosensory development and provide insight into the molecular and cellular basis of sensory abnormalities in a model for syndromic ASD.

Post-traumatic stress disorder-induced behavioral modulation by the medial septum-medial habenula neural pathway

Post-traumatic stress disorder (PTSD) is characterized by anxiety, excessive fear, distress, and weakness as symptoms of a psychiatric disorder. However, the mechanism associated with its symptoms such as anxiety-like behaviors is not well understood. It is aimed to investigate the underlying mechanisms of the medial septum (MS)-medial habenula (MHb) neural circuit modulating the anxiety-like behaviors of PTSD mice through in vivo fiber photometry recording, optogenetics, behavioral testing by open-field and elevated plus maze, fluorescent gold retrograde tracer technology, and viral tracer technology. In the mouse PTSD model induced by compound stress consisting of single-prolonged stress combined with electrical foot shock, the average peak value of the Ca2 + signals in both the MHb and MS glutamatergic neurons significantly increased. The anterograde and retrograde tracer markers were used to indicate the possible connection between MS and MHb via glutamatergic neural pathway. After the optogenetic manipulation of the MS-MHb pathway in mice with PTSD, if the MS-MHb glutamatergic pathway was inhibited, anxiety was relieved based on changes in the various indices of behavioral experiments in mice with PTSD. Moreover, the heart rate of mice decreased. In conclusion, both glutamatergic neurons located in MS and MHb can be engaged in the development of PTSD anxiety-like behavior, and the MS-MHb can be related to the regulation of PTSD anxiety-like behavior and cardiac function through the glutamatergic neural pathway.

Microglial cathepsin B promotes neuronal efferocytosis during brain development

Half of all newborn neurons in the developing brain are removed via efferocytosis - the phagocytic clearance of apoptotic cells. Microglia are brain-resident professional phagocytes that play important roles in neural circuit development including as primary effectors of efferocytosis. While the mechanisms through which microglia recognize potential phagocytic cargo are widely studied, the lysosomal mechanisms that are necessary for efficient digestion are less well defined. Here we show that the lysosomal protease cathepsin B promotes microglial efferocytosis of neurons and restricts the accumulation of apoptotic cells during brain development. We show that cathepsin B is microglia-specific and enriched in brain regions where neuronal turnover is high in both zebrafish and mouse. Myeloid-specific cathepsin B knockdown in zebrafish led to dysmorphic microglia containing undigested dead cells, as well as an accumulation of dead cells in surrounding tissue. These effects where phenocopied in mice globally deficient for Ctsb using markers for apoptosis. We also observed behavioral impairments in both models. Live imaging studies in zebrafish revealed deficits in phagolysosomal fusion and acidification, and live imaging of cultured mouse microglia reveal delayed phagocytosis consistent with impairments in digestion and resolution of phagocytosis rather than initial uptake. These data reveal a novel role for microglial cathepsin B in mediating neuronal efferocytosis during typical brain development.

Early postnatal whisker deprivation cross-modally modulates prefrontal cortex myelination and leads to social novelty deficit

Sensory experience affects not only the corresponding primary sensory cortex, but also synaptic and neural circuit functions in other brain regions in a cross-modal manner. However, it remains unclear whether oligodendrocyte (OL) generation and myelination can also undergo cross-modal modulation. Here, we report that while early life short-term whisker deprivation from birth significantly reduces in the number of mature of OLs and the degree of myelination in the primary somatosensory cortex(S1) at postnatal day 14 (P14), it also simultaneously affects the primary visual cortex (V1), but not the medial prefrontal cortex (mPFC) with a similar reduction. Interestingly, when mice were subjected to long-term early whisker deprivation from birth (P0) to P35, they exhibited dramatically impaired myelination and a deduced number of differentiated OLs in regions including the S1, V1, and mPFC, as detected at P60. Meanwhile, the process complexity of OL precursor cells (OPCs) was also rduced, as detected in the mPFC. However, when whisker deprivation occurred during the mid-late postnatal period (P35 to P50), myelination was unaffected in both V1 and mPFC brain regions at P60. In addition to impaired OL and myelin development in the mPFC, long-term early whisker-deprived mice also showed deficits in social novelty, accompanied by abnormal activation of c-Fos in the mPFC. Thus, our results reveal a novel form of cross-modal modulation of myelination by sensory experience that can lead to abnormalities in social behavioral, suggesting a possible similar mechanism underlying brain pathological conditions that suffer from both sensory and social behavioral deficits, such as autism spectrum disorders.

Specificity in the commonalities of inhibition control: using meta-analysis and regression analysis to identify the key brain regions in psychiatric disorders

BACKGROUND

The differential diagnosis of psychiatric disorders is relatively challenging for several reasons. In this context, we believe that task-based magnetic resonance imaging (MRI) can serve as a tool for differential diagnosis. The aim of this study was to explore the commonalities in brain activities among individuals with psychiatric disorders and to identify the key brain regions that can distinguish between these disorders.

METHODS

The PubMed, MEDLINE, EMBASE, Web of Science, Scopus, PsycINFO, and Google Scholar databases were searched for whole-brain functional MRI studies that compared psychiatric patients and normal controls. The psychiatric disorders included schizophrenia (SCZ), bipolar disorder (BD), major depressive disorder (MDD), obsessive-compulsive disorder, attention-deficit/hyperactivity disorder (ADHD), and autism spectrum disorder (ASD). Studies using go-nogo paradigms were selected, we then conducted activation likelihood estimation (ALE) meta-analysis, factor analysis, and regression analysis on these studies subsequently.

RESULTS

A total of 152 studies (108 with patients) were selected and a consistent pattern was found, that is, decreased activities in the same brain regions across six disorders. Factor analysis clustered six disorders into three pairs: SCZ and ASD, MDD and BD, and ADHD and BD. Furthermore, the heterogeneity of SCZ and ASD was located in the left and right thalamus; and the heterogeneity of MDD and BD was located in the thalamus, insula, and superior frontal gyrus.

CONCLUSION

The results can lead to a new classification method for psychiatric disorders, benefit the differential diagnosis at an early stage, and help to understand the biobasis of psychiatric disorders.

Anterior cingulate cortex-related functional hyperconnectivity underlies sensory hypersensitivity in Grin2b-mutant mice

Sensory abnormalities are observed in ~90% of individuals with autism spectrum disorders (ASD), but the underlying mechanisms are poorly understood. GluN2B, an NMDA receptor subunit that regulates long-term depression and circuit refinement during brain development, has been strongly implicated in ASD, but whether GRIN2B mutations lead to sensory abnormalities remains unclear. Here, we report that Grin2b-mutant mice show behavioral sensory hypersensitivity and brain hyperconnectivity associated with the anterior cingulate cortex (ACC). Grin2b-mutant mice with a patient-derived C456Y mutation (Grin2bC456Y/+) show sensory hypersensitivity to mechanical, thermal, and electrical stimuli through supraspinal mechanisms. c-fos and functional magnetic resonance imaging indicate that the ACC is hyperactive and hyperconnected with other brain regions under baseline and stimulation conditions. ACC pyramidal neurons show increased excitatory synaptic transmission. Chemogenetic inhibition of ACC pyramidal neurons normalizes ACC hyperconnectivity and sensory hypersensitivity. These results suggest that GluN2B critically regulates ASD-related cortical connectivity and sensory brain functions.

Restoring thalamocortical circuit dysfunction by correcting HCN channelopathy in Shank3 mutant mice

Thalamocortical (TC) circuits are essential for sensory information processing. Clinical and preclinical studies of autism spectrum disorders (ASDs) have highlighted abnormal thalamic development and TC circuit dysfunction. However, mechanistic understanding of how TC dysfunction contributes to behavioral abnormalities in ASDs is limited. Here, our study on a Shank3 mouse model of ASD reveals TC neuron hyperexcitability with excessive burst firing and a temporal mismatch relationship with slow cortical rhythms during sleep. These TC electrophysiological alterations and the consequent sensory hypersensitivity and sleep fragmentation in Shank3 mutant mice are causally linked to HCN2 channelopathy. Restoring HCN2 function early in postnatal development via a viral approach or lamotrigine (LTG) ameliorates sensory and sleep problems. A retrospective case series also supports beneficial effects of LTG treatment on sensory behavior in ASD patients. Our study identifies a clinically relevant circuit mechanism and proposes a targeted molecular intervention for ASD-related behavioral impairments.

Alterations of Perineuronal Net Expression and Abnormal Social Behavior and Whisker-dependent Texture Discrimination in Mice Lacking the Autism Candidate Gene Engrailed 2

GABAergic interneurons and perineuronal nets (PNNs) are important regulators of plasticity throughout life and their dysfunction has been implicated in the pathogenesis of several neuropsychiatric conditions, including autism spectrum disorders (ASD). PNNs are condensed portions of the extracellular matrix (ECM) that are crucial for neural development and proper formation of synaptic connections. We previously showed a reduced expression of GABAergic interneuron markers in the hippocampus and somatosensory cortex of adult mice lacking the Engrailed2 gene (En2-/- mice), a mouse model of ASD. Since alterations in PNNs have been proposed as a possible pathogenic mechanism in ASD, we hypothesized that the PNN dysfunction may contribute to the neural and behavioral abnormalities of En2-/- mice. Here, we show an increase in the PNN fluorescence intensity, evaluated by Wisteria floribunda agglutinin, in brain regions involved in social behavior and somatosensory processing. In addition, we found that En2-/- mice exhibit altered texture discrimination through whiskers and display a marked decrease in the preference for social novelty. Our results raise the possibility that altered expression of PNNs, together with defects of GABAergic interneurons, might contribute to the pathogenesis of social and sensory behavioral abnormalities.

Type-I-interferon-responsive microglia shape cortical development and behavior

Microglia are brain-resident macrophages that shape neural circuit development and are implicated in neurodevelopmental diseases. Multiple microglial transcriptional states have been defined, but their functional significance is unclear. Here, we identify a type I interferon (IFN-I)-responsive microglial state in the developing somatosensory cortex (postnatal day 5) that is actively engulfing whole neurons. This population expands during cortical remodeling induced by partial whisker deprivation. Global or microglial-specific loss of the IFN-I receptor resulted in microglia with phagolysosomal dysfunction and an accumulation of neurons with nuclear DNA damage. IFN-I gain of function increased neuronal engulfment by microglia in both mouse and zebrafish and restricted the accumulation of DNA-damaged neurons. Finally, IFN-I deficiency resulted in excess cortical excitatory neurons and tactile hypersensitivity. These data define a role for neuron-engulfing microglia during a critical window of brain development and reveal homeostatic functions of a canonical antiviral signaling pathway in the brain.

Glial cells are affected more than interneurons by the loss of Engrailed 2 gene in the mouse cerebellum

Glial cells play a pivotal role in the inflammatory processes, which are common features of several neurodevelopmental and neurodegenerative disorders. Their major role in modulating neuroinflammation underscores their significance in these conditions. Engrailed-2 knockout mice (En2-/- ) are considered a valuable model for autism spectrum disorder (ASD) due to their distinctive neuroanatomical and behavioral traits. Given the higher prevalence of ASD in males, our objective was to investigate glial and interneuron alterations in the cerebellum of En2-/- mice compared with wild-type (WT) mice in both sexes. We employed immunohistochemical analysis to assess cell density for all cell types studied and analyzed the area (A) and shape factor (SF) of microglia cell bodies. Our findings revealed the following: (a) In WT mice, the density of microglia and astrocytes was higher in females than in males, while interneuron density was lower in females. Notably, in En2-mutant mice, these differences between males and females were not present. (b) In both male and female En2-/- mice, astrocyte density exceeded that in WT mice, with microglia density being greater only in females. (c) In WT females, microglia cell bodies exhibited a larger area and a lower shape factor compared to WT males. Remarkably, the En2 mutation did not appear to influence these sex-related differences. (d) In both male and female En2-/- mice, we observed a consistent pattern: microglia cell bodies displayed a larger area and a smaller shape factor. Given the ongoing debate surrounding the roles of glia and sex-related factors in ASD, our observations provide valuable insights into understanding how an ASD-associated gene En2 affects specific cell types in the cerebellum.

Gene Expression Profiling in Trigeminal Ganglia from Cntnap2-/- and Shank3b-/- Mouse Models of Autism Spectrum Disorder

Sensory difficulties represent a crucial issue in the life of autistic individuals. The diagnostic and statistical manual of mental disorders describes both hyper- and hypo-responsiveness to sensory stimulation as a criterion for the diagnosis autism spectrum disorders (ASD). Among the sensory domain affected in ASD, altered responses to tactile stimulation represent the most commonly reported sensory deficits. Although tactile abnormalities have been reported in monogenic cohorts of patients and genetic mouse models of ASD, the underlying mechanisms are still unknown. Traditionally, autism research has focused on the central nervous system as the target to infer the neurobiological bases of such tactile abnormalities. Nonetheless, the peripheral nervous system represents the initial site of processing of sensory information and a potential site of dysfunction in the sensory cascade. Here we investigated the gene expression deregulation in the trigeminal ganglion (which directly receives tactile information from whiskers) in two genetic models of syndromic autism (Shank3b and Cntnap2 mutant mice) at both adult and juvenile ages. We found several neuronal and non-neuronal markers involved in inhibitory, excitatory, neuroinflammatory and sensory neurotransmission to be differentially regulated within the trigeminal ganglia of both adult and juvenile Shank3b and Cntnap2 mutant mice. These results may help in disentangling the multifaced complexity of sensory abnormalities in autism and open avenues for the development of peripherally targeted treatments for tactile sensory deficits exhibited in ASD.

Cortex-restricted deletion of Foxp1 impairs barrel formation and induces aberrant tactile responses in a mouse model of autism

BACKGROUND

Many children and young people with autism spectrum disorder (ASD) display touch defensiveness or avoidance (hypersensitivity), or engage in sensory seeking by touching people or objects (hyposensitivity). Abnormal sensory responses have also been noticed in mice lacking ASD-associated genes. Tactile sensory information is normally processed by the somatosensory system that travels along the thalamus to the primary somatosensory cortex. The neurobiology behind tactile sensory abnormalities, however, is not fully understood.

METHODS

We employed cortex-specific Foxp1 knockout (Foxp1-cKO) mice as a model of autism in this study. Tactile sensory deficits were measured by the adhesive removal test. The mice's behavior and neural activity were further evaluated by the whisker nuisance test and c-Fos immunofluorescence, respectively. We also studied the dendritic spines and barrel formation in the primary somatosensory cortex by Golgi staining and immunofluorescence.

RESULTS

Foxp1-cKO mice had a deferred response to the tactile environment. However, the mice exhibited avoidance behavior and hyper-reaction following repeated whisker stimulation, similar to a fight-or-flight response. In contrast to the wild-type, c-Fos was activated in the basolateral amygdala but not in layer IV of the primary somatosensory cortex of the cKO mice. Moreover, Foxp1 deficiency in cortical neurons altered the dendrite development, reduced the number of dendritic spines, and disrupted barrel formation in the somatosensory cortex, suggesting impaired somatosensory processing may underlie the aberrant tactile responses.

LIMITATIONS

It is still unclear how the defective thalamocortical connection gives rise to the hyper-reactive response. Future experiments with electrophysiological recording are needed to analyze the role of thalamo-cortical-amygdala circuits in the disinhibiting amygdala and enhanced fearful responses in the mouse model of autism.

CONCLUSIONS

Foxp1-cKO mice have tactile sensory deficits while exhibit hyper-reactivity, which may represent fearful and emotional responses controlled by the amygdala. This study presents anatomical evidence for reduced thalamocortical connectivity in a genetic mouse model of ASD and demonstrates that the cerebral cortex can be the origin of atypical sensory behaviors.

Automated Segmentation of the Mouse Body Language to Study Stimulus-Evoked Emotional Behaviors

Understanding the neural basis of emotions is a critical step to uncover the biological substrates of neuropsychiatric disorders. To study this aspect in freely behaving mice, neuroscientists have relied on the observation of ethologically relevant bodily cues to infer the affective content of the subject, both in neutral conditions or in response to a stimulus. The best example of that is the widespread assessment of freezing in experiments testing both conditioned and unconditioned fear responses. While robust and powerful, these approaches come at a cost: they are usually confined within selected time windows, accounting for only a limited portion of the complexity of emotional fluctuation. Moreover, they often rely on visual inspection and subjective judgment, resulting in inconsistency across experiments and questionable result interpretations. To overcome these limitations, novel tools are arising, fostering a new avenue in the study of the mouse naturalistic behavior. In this work we developed a computational tool [stimulus-evoked behavioral tracking in 3D for rodents (SEB3R)] to automate and standardize an ethologically driven observation of freely moving mice. Using a combination of machine learning-based behavioral tracking and unsupervised cluster analysis, we identified statistically meaningful postures that could be used for empirical inference on a subsecond scale. We validated the efficacy of this tool in a stimulus-driven test, the whisker nuisance (WN) task, where mice are challenged with a prolonged and invasive whisker stimulation, showing that identified postures can be reliably used as a proxy for stimulus-driven fearful and explorative behaviors.

Modeling Brain Dysconnectivity in Rodents

Altered or atypical functional connectivity as measured with functional magnetic resonance imaging (fMRI) is a hallmark feature of brain connectopathy in psychiatric, developmental, and neurological disorders. However, the biological underpinnings and etiopathological significance of this phenomenon remain unclear. The recent development of MRI-based techniques for mapping brain function in rodents provides a powerful platform to uncover the determinants of functional (dys)connectivity, whether they are genetic mutations, environmental risk factors, or specific cellular and circuit dysfunctions. Here, we summarize the recent contribution of rodent fMRI toward a deeper understanding of network dysconnectivity in developmental and psychiatric disorders. We highlight substantial correspondences in the spatiotemporal organization of rodent and human fMRI networks, supporting the translational relevance of this approach. We then show how this research platform might help us comprehend the importance of connectional heterogeneity in complex brain disorders and causally relate multiscale pathogenic contributors to functional dysconnectivity patterns. Finally, we explore how perturbational techniques can be used to dissect the fundamental aspects of fMRI coupling and reveal the causal contribution of neuromodulatory systems to macroscale network activity, as well as its altered dynamics in brain diseases. These examples outline how rodent functional imaging is poised to advance our understanding of the bases and determinants of human functional dysconnectivity.

Reversal of hyperactive higher-order thalamus attenuates defensiveness in a mouse model of PTSD

Posttraumatic stress disorder (PTSD) is a highly prevalent and debilitating psychiatric disease often accompanied by severe defensive behaviors, preventing individuals from integrating into society. However, the neural mechanisms of defensiveness in PTSD remain largely unknown. Here, we identified that the higher-order thalamus, the posteromedial complex of the thalamus (PoM), was overactivated in a mouse model of PTSD, and suppressing PoM activity alleviated excessive defensive behaviors. Moreover, we found that diminished thalamic inhibition derived from the thalamic reticular nucleus was the major cause of thalamic hyperactivity in PTSD mice. Overloaded thalamic innervation to the downstream cortical area, frontal association cortex, drove abnormal defensiveness. Overall, our study revealed that the malfunction of the higher-order thalamus mediates defensive behaviors and highlighted the thalamocortical circuit as a potential target for treating PTSD-related overreactivity symptoms.

Progress in magnetic resonance imaging of autism model mice brain

Autism spectrum disorder (ASD) is a neurodevelopmental disease characterized by social disorder and stereotypical behaviors with an increasing incidence. ASD patients are suffering from varying degrees of mental retardation and language development abnormalities. Magnetic resonance imaging (MRI) is a noninvasive imaging technology to detect brain structural and functional dysfunction in vivo, playing an important role in the early diagnosisbasic research of ASD. High-field, small-animal MRI in basic research of autism model mice has provided a new approach to research the pathogenesis, characteristics, and intervention efficacy in autism. This article reviews MRI studies of mouse models of autism over the past 20 years. Reduced gray matter, abnormal connections of brain networks, and abnormal development of white matter fibers have been demonstrated in these studies, which are present in different proportions in the various mouse models. This provides a more macroscopic view for subsequent research on autism model mice. This article is categorized under: Cognitive Biology > Genes and Environment Neuroscience > Computation Neuroscience > Genes, Molecules, and Cells Neuroscience > Development.

Early life oxytocin treatment improves thermo-sensory reactivity and maternal behavior in neonates lacking the autism-associated gene Magel2

Atypical responses to sensory stimuli are considered as a core aspect and early life marker of autism spectrum disorders (ASD). Although recent findings performed in mouse ASD genetic models report sensory deficits, these were explored exclusively during juvenile or adult period. Whether sensory dysfunctions might be present at the early life stage and rescued by therapeutic strategy are fairly uninvestigated. Here we found that under cool environment neonatal mice lacking the autism-associated gene Magel2 present pup calls hypo-reactivity and are retrieved with delay by their wild-type dam. This neonatal atypical sensory reactivity to cool stimuli was not associated with autonomic thermoregulatory alteration but with a deficit of the oxytocinergic system. Indeed, we show in control neonates that pharmacogenetic inactivation of hypothalamic oxytocin neurons mimicked atypical thermosensory reactivity found in Magel2 mutants. Furthermore, pharmacological intranasal administration of oxytocin to Magel2 neonates was able to rescue both the atypical thermosensory response and the maternal pup retrieval. This preclinical study establishes for the first-time early life impairments in thermosensory integration and suggest a therapeutic potential benefit of intranasal oxytocin treatment on neonatal atypical sensory reactivity for autism.

Auditory processing in rodent models of autism: a systematic review

Autism is a complex condition with many traits, including differences in auditory sensitivity. Studies in human autism are plagued by the difficulty of controlling for aetiology, whereas studies in individual rodent models cannot represent the full spectrum of human autism. This systematic review compares results in auditory studies across a wide range of established rodent models of autism to mimic the wide range of aetiologies in the human population. A search was conducted in the PubMed and Web of Science databases to find primary research articles in mouse or rat models of autism which investigate central auditory processing. A total of 88 studies were included. These used non-invasive measures of auditory function, such as auditory brainstem response recordings, cortical event-related potentials, electroencephalography, and behavioural tests, which are translatable to human studies. They also included invasive measures, such as electrophysiology and histology, which shed insight on the origins of the phenotypes found in the non-invasive studies. The most consistent results across these studies were increased latency of the N1 peak of event-related potentials, decreased power and coherence of gamma activity in the auditory cortex, and increased auditory startle responses to high sound levels. Invasive studies indicated loss of subcortical inhibitory neurons, hyperactivity in the lateral superior olive and auditory thalamus, and reduced specificity of responses in the auditory cortex. This review compares the auditory phenotypes across rodent models and highlights those that mimic findings in human studies, providing a framework and avenues for future studies to inform understanding of the auditory system in autism.

Sex difference in cognitive behavioral alterations and barrel cortex neuronal responses in rats exposed prenatally to valproic acid under continuous environmental enrichment

Autism spectrum disorder is a developmental disorder that can affect social interactions and sensory-motor behaviors. The present study investigates the effect of environmental enrichment (EE) on behavioral alterations and neuron responses associated with the barrel cortex of young adult female and male rats exposed prenatally to valproic acid (VPA). Pregnant female rats were pretreated with either saline or VPA (500 mg/kg, IP) on day 12.5 of gestation. Male and female pups were exposed to either EE or standard-setting (non-enrichment) conditions for 1 month (between postnatal day [PND] 30 and 63-65) and were divided into non-EE (control), EE, VPA, and VPA + EE groups. Three-chamber sociability and social novelty, acoustic startle reflex, and texture discrimination tests were conducted on PND 62. Responses of barrel cortex neurons of male pups were evaluated using the extracellular single-unit recording technique on PND 63-65. Results showed that the performance of rats of both sexes in social interactions, texture discrimination tasks, and acoustic startle reflex significantly decreased in the VPA groups compared with the control rats (P < 0.05). In this regard, EE attenuated the altered deficit performance observed in the VPA animals compared with the VPA-EE animals (P < 0.05). The performance of females was better than males in the discrimination tasks and acoustic startle reflex. In contrast, males were better than females in the three-chamber social interaction test. Additionally, the excitatory receptive field response magnitude of the barrel cortex neurons in the VPA + EE group increased compared with the VPA group (P < 0.05). The results suggest that continuous EE can attenuate cognitive function disturbances in autistic-like rats and, at least at the behavioral level, the effects depend on sex.

Acupuncture Regulates Symptoms of Parkinson’s Disease via Brain Neural Activity and Functional Connectivity in Mice

Parkinson’s disease (PD) is a multilayered progressive brain disease characterized by motor dysfunction and a variety of other symptoms. Although acupuncture has been used to ameliorate various symptoms of neurodegenerative disorders, including PD, the underlying mechanisms are unclear. Here, we investigated the mechanism of acupuncture by revealing the effects of acupuncture treatment on brain neural responses and its functional connectivity in an animal model of PD. We observed that destruction of neuronal network between many brain regions in PD mice were reversed by acupuncture. Using machine learning analysis, we found that the key region associated with the improvement of abnormal behaviors might be related to the neural activity of M1, suggesting that the changes of c-Fos in M1 could predict the improvement of motor function induced by acupuncture treatment. In addition, acupuncture treatment was shown to significantly normalize the brain neural activity not only in M1 but also in other brain regions related to motor behavior (striatum, substantia nigra pars compacta, and globus pallidus) and non-motor symptoms (hippocampus, lateral hypothalamus, and solitary tract) of PD. Taken together, our results demonstrate that acupuncture treatment might improve the PD symptoms by normalizing the brain functional connectivity in PD mice model and provide new insights that enhance our current understanding of acupuncture mechanisms for non-motor symptoms.

Translational Magnetic Resonance Imaging in Autism Spectrum Disorder From the Mouse Model to Human

Autism spectrum disorder (ASD) is a heterogeneous syndrome characterized by behavioral features such as impaired social communication, repetitive behavior patterns, and a lack of interest in novel objects. A multimodal neuroimaging using magnetic resonance imaging (MRI) in patients with ASD shows highly heterogeneous abnormalities in function and structure in the brain associated with specific behavioral features. To elucidate the mechanism of ASD, several ASD mouse models have been generated, by focusing on some of the ASD risk genes. A specific behavioral feature of an ASD mouse model is caused by an altered gene expression or a modification of a gene product. Using these mouse models, a high field preclinical MRI enables us to non-invasively investigate the neuronal mechanism of the altered brain function associated with the behavior and ASD risk genes. Thus, MRI is a promising translational approach to bridge the gap between mice and humans. This review presents the evidence for multimodal MRI, including functional MRI (fMRI), diffusion tensor imaging (DTI), and volumetric analysis, in ASD mouse models and in patients with ASD and discusses the future directions for the translational study of ASD.

Somatosensory cortex hyperconnectivity and impaired whisker-dependent responses in Cntnap2-/- mice

Sensory abnormalities are a common feature in autism spectrum disorders (ASDs). Tactile responsiveness is altered in autistic individuals, with hypo-responsiveness being associated with the severity of ASD core symptoms. Similarly, sensory abnormalities have been described in mice lacking ASD-associated genes. Loss-of-function mutations in CNTNAP2 result in cortical dysplasia-focal epilepsy syndrome (CDFE) and autism. Likewise, Cntnap2^-/- mice show epilepsy and deficits relevant with core symptoms of human ASDs, and are considered a reliable model to study ASDs. Altered synaptic transmission and synchronicity found in the cerebral cortex of Cntnap2^-/- mice would suggest a network dysfunction. Here, we investigated the neural substrates of whisker-dependent responses in Cntnap2^+/+ and Cntnap2^-/- adult mice. When compared to controls, Cntnap2^-/- mice showed focal hyper-connectivity within the primary somatosensory cortex (S1), in the absence of altered connectivity between S1 and other somatosensory areas. This data suggests the presence of impaired somatosensory processing in these mutants. Accordingly, Cntnap2^-/- mice displayed impaired whisker-dependent discrimination in the textured novel object recognition test (tNORT) and increased c-fos mRNA induction within S1 following whisker stimulation. S1 functional hyperconnectivity might underlie the aberrant whisker-dependent responses observed in Cntnap2^-/- mice, indicating that Cntnap2 mice are a reliable model to investigate sensory abnormalities that characterize ASDs.

Multimodal Gradient Mapping of Rodent Hippocampus

The hippocampus plays a central role in supporting our coherent and enduring sense of self and our place in the world. Understanding its functional organisation is central to understanding this complex role. Previous studies suggest function varies along a long hippocampal axis, but there is disagreement about the presence of sharp discontinuities or gradual change along that axis. Other open questions relate to the underlying drivers of this variation and the conservation of organisational principles across species. Here, we delineate the primary organisational principles underlying patterns of hippocampal functional connectivity (FC) in the mouse using gradient analysis on resting state fMRI data. We further applied gradient analysis to mouse gene co-expression data to examine the relationship between variation in genomic anatomy and functional organisation. Two principal FC gradients along a hippocampal axis were revealed. The principal gradient exhibited a sharp discontinuity that divided the hippocampus into dorsal and ventral compartments. The second, more continuous, gradient followed the long axis of the ventral compartment. Dorsal regions were more strongly connected to areas involved in spatial navigation while ventral regions were more strongly connected to areas involved in emotion, recapitulating patterns seen in humans. In contrast, gene co-expression gradients showed a more segregated and discrete organisation. Our findings suggest that hippocampal functional organisation exhibits both sharp and gradual transitions and that hippocampal genomic anatomy exerts only a subtle influence on this organisation.

Unique spatiotemporal fMRI dynamics in the awake mouse brain

Human imaging studies have shown that spontaneous brain activity exhibits stereotypic spatiotemporal reorganization in awake, conscious conditions with respect to minimally conscious states. However, whether and how this phenomenon can be generalized to lower mammalian species remains unclear. Leveraging a robust protocol for resting-state fMRI (rsfMRI) mapping in non-anesthetized, head-fixed mice, we investigated functional network topography and dynamic structure of spontaneous brain activity in wakeful animals. We found that rsfMRI networks in the awake state, while anatomically comparable to those observed under anesthesia, are topologically configured to maximize interregional communication, departing from the underlying community structure of the mouse axonal connectome. We further report that rsfMRI activity in wakeful animals exhibits unique spatiotemporal dynamics characterized by a state-dependent, dominant occurrence of coactivation patterns encompassing a prominent participation of arousal-related forebrain nuclei and functional anti-coordination between visual-auditory and polymodal cortical areas. We finally show that rsfMRI dynamics in awake mice exhibits a stereotypical temporal structure, in which state-dominant coactivation patterns are configured as network attractors. These findings suggest that spontaneous brain activity in awake mice is critically shaped by state-specific involvement of basal forebrain arousal systems and document that its dynamic structure recapitulates distinctive, evolutionarily relevant principles that are predictive of conscious states in higher mammalian species.

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fMRI networks in awake mice depart from underlying anatomical structure

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fMRI dynamics in wakeful mice is critically shaped by arousal-related nuclei

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Occurrence and topography of rsfMRI coactivation patterns define conscious states

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fMRI coactivation dynamics defines a signature of consciousness in the mouse brain

Brain mapping across 16 autism mouse models reveals a spectrum of functional connectivity subtypes

Autism Spectrum Disorder (ASD) is characterized by substantial, yet highly heterogeneous abnormalities in functional brain connectivity. However, the origin and significance of this phenomenon remain unclear. To unravel ASD connectopathy and relate it to underlying etiological heterogeneity, we carried out a bi-center cross-etiological investigation of fMRI-based connectivity in the mouse, in which specific ASD-relevant mutations can be isolated and modeled minimizing environmental contributions. By performing brain-wide connectivity mapping across 16 mouse mutants, we show that different ASD-associated etiologies cause a broad spectrum of connectional abnormalities in which diverse, often diverging, connectivity signatures are recognizable. Despite this heterogeneity, the identified connectivity alterations could be classified into four subtypes characterized by discrete signatures of network dysfunction. Our findings show that etiological variability is a key determinant of connectivity heterogeneity in ASD, hence reconciling conflicting findings in clinical populations. The identification of etiologically-relevant connectivity subtypes could improve diagnostic label accuracy in the non-syndromic ASD population and paves the way for personalized treatment approaches.

Abnormal Whisker-Dependent Behaviors and Altered Cortico-Hippocampal Connectivity in Shank3b-/- Mice

Abnormal tactile response is an integral feature of Autism Spectrum Disorders (ASDs), and hypo-responsiveness to tactile stimuli is often associated with the severity of ASDs core symptoms. Patients with Phelan-McDermid syndrome (PMS), caused by mutations in the SHANK3 gene, show ASD-like symptoms associated with aberrant tactile responses. The neural underpinnings of these abnormalities are still poorly understood. Here we investigated, in Shank3b^−/− adult mice, the neural substrates of whisker-guided behaviors, a key component of rodents’ interaction with the surrounding environment. We assessed whisker-dependent behaviors in Shank3b^−/− adult mice and age-matched controls, using the textured novel object recognition (tNORT) and whisker nuisance (WN) test. Shank3b^−/− mice showed deficits in whisker-dependent texture discrimination in tNORT and behavioral hypo-responsiveness to repetitive whisker stimulation in WN. Sensory hypo-responsiveness was accompanied by a significantly reduced activation of the primary somatosensory cortex (S1) and hippocampus, as measured by c-fos mRNA induction, a proxy of neuronal activity following whisker stimulation. Moreover, resting-state fMRI showed a significantly reduced S1-hippocampal connectivity in Shank3b mutants, in the absence of altered connectivity between S1 and other somatosensory areas. Impaired crosstalk between hippocampus and S1 might underlie Shank3b^−/− hypo-reactivity to whisker-dependent cues, highlighting a potentially generalizable somatosensory dysfunction in ASD.

Emerging imaging methods to study whole-brain function in rodent models

In the past decade, the idea that single populations of neurons support cognition and behavior has gradually given way to the realization that connectivity matters and that complex behavior results from interactions between remote yet anatomically connected areas that form specialized networks. In parallel, innovation in brain imaging techniques has led to the availability of a broad set of imaging tools to characterize the functional organization of complex networks. However, each of these tools poses significant technical challenges and faces limitations, which require careful consideration of their underlying anatomical, physiological, and physical specificity. In this review, we focus on emerging methods for measuring spontaneous or evoked activity in the brain. We discuss methods that can measure large-scale brain activity (directly or indirectly) with a relatively high temporal resolution, from milliseconds to seconds. We further focus on methods designed for studying the mammalian brain in preclinical models, specifically in mice and rats. This field has seen a great deal of innovation in recent years, facilitated by concomitant innovation in gene-editing techniques and the possibility of more invasive recordings. This review aims to give an overview of currently available preclinical imaging methods and an outlook on future developments. This information is suitable for educational purposes and for assisting scientists in choosing the appropriate method for their own research question.

Epigenome-Wide DNA Methylation and Pesticide Use in the Agricultural Lung Health Study

BACKGROUND

Pesticide exposure is associated with many long-term health outcomes; the potential underlying mechanisms are not well established for most associations. Epigenetic modifications, such as DNA methylation, may contribute. Individual pesticides may be associated with specific DNA methylation patterns but no epigenome-wide association study (EWAS) has evaluated methylation in relation to individual pesticides.

OBJECTIVES

We conducted an EWAS of DNA methylation in relation to several pesticide active ingredients.

METHODS

The Agricultural Lung Health Study is a case-control study of asthma, nested within the Agricultural Health Study. We analyzed blood DNA methylation measured using Illumina's EPIC array in 1,170 male farmers of European ancestry. For pesticides still on the market at blood collection (2009-2013), we evaluated nine active ingredients for which at least 30 participants reported past and current (within the last 12 months) use, as well as seven banned organochlorines with at least 30 participants reporting past use. We used robust linear regression to compare methylation at individual C-phosphate-G sites (CpGs) among users of a specific pesticide to never users.

RESULTS

Using family-wise error rate (p<9×10-8) or false-discovery rate (FDR<0.05), we identified 162 differentially methylated CpGs across 8 of 9 currently marketed active ingredients (acetochlor, atrazine, dicamba, glyphosate, malathion, metolachlor, mesotrione, and picloram) and one banned organochlorine (heptachlor). Differentially methylated CpGs were unique to each active ingredient, and a dose-response relationship with lifetime days of use was observed for most. Significant CpGs were enriched for transcription motifs and 28% of CpGs were associated with whole blood cis-gene expression, supporting functional effects of findings. We corroborated a previously reported association between dichlorodiphenyltrichloroethane (banned in the United States in 1972) and epigenetic age acceleration.

DISCUSSION

We identified differential methylation for several active ingredients in male farmers of European ancestry. These may serve as biomarkers of chronic exposure and could inform mechanisms of long-term health outcomes from pesticide exposure. https://doi.org/10.1289/EHP8928.

Engrailed 2 deficiency and chronic stress alter avoidance and motivation behaviors

Autism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder characterized by impairments in social interaction, cognition, and communication, as well as the presence of repetitive or stereotyped behaviors and interests. ASD is most often studied as a neurodevelopmental disease, but it is a lifelong disorder. Adults with ASD experience more stressful life events and greater perceived stress, and frequently have comorbid mood disorders such as anxiety and depression. It remains unclear whether adult exposure to chronic stress can exacerbate the behavioral and neurodevelopmental phenotypes associated with ASD. To address this issue, we first investigated whether adult male and female Engrailed-2 deficient (En2-KO, En2-/-) mice, which display behavioral disturbances in avoidance tasks and dysregulated monoaminergic neurotransmitter levels, also display impairments in instrumental behaviors associated with motivation, such as the progressive ratio task. We then exposed adult En2-KO mice to chronic environmental stress (CSDS, chronic social defeat stress), to determine if stress exacerbated the behavioral and neuroanatomical effects of En2 deletion. En2-/- mice showed impaired instrumental acquisition and significantly lower breakpoints in a progressive ratio test, demonstrating En2 deficiency decreases motivation to exert effort for reward. Furthermore, adult CSDS exposure increased avoidance behaviors in En2-KO mice. Interestingly, adult CSDS exposure also exacerbated the deleterious effects of En2 deficiency on forebrain-projecting monoaminergic fibers. Our findings thus suggest that adult exposure to stress may exacerbate behavioral and neuroanatomical phenotypes associated with developmental effects of genetic En2 deficiency.

Transcription factors in neurodevelopmental and associated psychiatric disorders: A potential convergence for genetic and environmental risk factors

Neurodevelopmental disorders (NDDs) are a heterogeneous and highly prevalent group of psychiatric conditions marked by impairments in the nervous system. Their onset occurs during gestation, and the alterations are observed throughout the postnatal life. Although many genetic and environmental risk factors have been described in this context, the interactions between them challenge the understanding of the pathways associated with NDDs. Transcription factors (TFs)-a group of over 1,600 proteins that can interact with DNA, regulating gene expression through modulation of RNA synthesis-represent a point of convergence for different risk factors. In addition, TFs organize critical processes like angiogenesis, blood-brain barrier formation, myelination, neuronal migration, immune activation, and many others in a time and location-dependent way. In this review, we summarize important TF alterations in NDD and associated disorders, along with specific impairments observed in animal models, and, finally, establish hypotheses to explain how these proteins may be critical mediators in the context of genome-environment interactions.

Engrailed-2 is a cell autonomous regulator of neurogenesis in cultured hippocampal neural stem cells

Abnormalities in genes that regulate early brain development are known risk factors for neurodevelopmental disorders. Engrailed-2 (En2) is a homeodomain transcription factor with established roles in cerebellar patterning. En2 is highly expressed in the developing mid-hindbrain region, and En2 knockout (KO) mice exhibit major deficits in mid-hindbrain structures. However, En2 is also expressed in forebrain regions including the hippocampus, but its function is unknown. Previous studies have shown that the hippocampus of En2-KO mice exhibits reductions in its volume and cell numbers due to aberrant neurogenesis. Aberrant neurogenesis is due, in part, to noncell autonomous effects, specifically, reductions of innervating norepinephrine fibers from the locus coeruleus. In this study, we investigate possible cell autonomous roles of En2 in hippocampal neurogenesis. We examine proliferation, survival, and differentiation using cultures of hippocampal neurospheres of P7 wild-type (WT) and En2-KO hippocampal neural progenitor cells (NPCs). At 7 days, En2-KO neurospheres were larger on average than WT spheres and exhibited 2.5-fold greater proliferation and 2-fold increase in apoptotic cells, similar to in vivo KO phenotype. Further, En2-KO cultures exhibited 40% less cells with neurite projections, suggesting decreased differentiation. Lastly, reestablishing En2 expression in En2-KO NPCs rescued excess proliferation. These results indicate that En2 functions in hippocampal NPCs by inhibiting proliferation and promoting survival and differentiation in a cell autonomous manner. More broadly, this study suggests that En2 impacts brain structure and function in diverse regions outside of the mid-hindbrain.

Perineuronal net abnormalities in Slc13a4+/- mice are rescued by postnatal administration of N-acetylcysteine

Disruptions to either sulfate supply or sulfation enzymes can affect brain development and have long-lasting effects on brain function, yet our understanding of the molecular mechanisms governing this are incomplete. Perineuronal nets (PNNs) are highly sulfated, specialized extracellular matrix structures that regulate the maturation of synaptic connections and neuronal plasticity. We have previously shown that mice heterozygous for the brain sulfate transporter Slc13a4 have abnormal social interactions, memory, exploratory behaviors, stress and anxiety of postnatal origin, pointing to potential deficits in PNN biology, and implicate SLC13A4 as a critical factor required for regulating normal synaptic connectivity and function. Here, we sought to investigate aberrant PNN formation as a potential mechanism contributing to the functional deficits displayed by Slc13a4^+/- mice. Following social interactions, we reveal reduced neuronal activation in the somatosensory cortex of Slc13a4^+/- mice, and altered inhibitory and excitatory postsynaptic currents. In line with this, we found a reduction in parvalbumin-expressing neurons decorated with PNNs, as well as reduced expression of markers for PNN maturation. Finally, we reveal that postnatal administration of N-acetylcysteine prevented PNN abnormalities from manifesting in Slc13a4^+/- adult animals. Collectively, these data highlight a central role for postnatal SLC13A4 in normal PNN formation, circuit function and subsequent animal behavior.

Behavioural and neural markers of tactile sensory processing in infants at elevated likelihood of autism spectrum disorder and/or attention deficit hyperactivity disorder

Backgrounds

Atypicalities in tactile processing are reported in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) but it remains unknown if they precede and associate with the traits of these disorders emerging in childhood. We investigated behavioural and neural markers of tactile sensory processing in infants at elevated likelihood of ASD and/or ADHD compared to infants at typical likelihood of the disorders. Further, we assessed the specificity of associations between infant markers and later ASD or ADHD traits.

Methods

Ninety-one 10-month-old infants participated in the study (n = 44 infants at elevated likelihood of ASD; n = 20 infants at elevated likelihood of ADHD; n = 9 infants at elevated likelihood of ASD and ADHD; n = 18 infants at typical likelihood of the disorders). Behavioural and EEG responses to pairs of tactile stimuli were experimentally recorded and concurrent parental reports of tactile responsiveness were collected. ASD and ADHD traits were measured at 24 months through standardized assessment (ADOS-2) and parental report (ECBQ), respectively.

Results

There was no effect of infants’ likelihood status on behavioural markers of tactile sensory processing. Conversely, increased ASD likelihood associated with reduced neural repetition suppression to tactile input. Reduced neural repetition suppression at 10 months significantly predicted ASD (but not ADHD) traits at 24 months across the entire sample. Elevated tactile sensory seeking at 10 months moderated the relationship between early reduced neural repetition suppression and later ASD traits.

Conclusions

Reduced tactile neural repetition suppression is an early marker of later ASD traits in infants at elevated likelihood of ASD or ADHD, suggesting that a common pathway to later ASD traits exists despite different familial backgrounds. Elevated tactile sensory seeking may act as a protective factor, mitigating the relationship between early tactile neural repetition suppression and later ASD traits.

Chd8 mutation in oligodendrocytes alters microstructure and functional connectivity in the mouse brain

CHD8 encodes a chromatin-remodeling factor and is one of the most recurrently mutated genes in individuals with autism spectrum disorder (ASD). Although we have recently shown that mice heterozygous for Chd8 mutation manifest myelination defects and ASD-like behaviors, the detailed mechanisms underlying ASD pathogenesis have remained unclear. Here we performed diffusion tensor imaging (DTI) and resting-state functional magnetic resonance imaging (rsfMRI) in oligodendrocyte lineage-specific Chd8 heterozygous mutant mice. DTI revealed that ablation of Chd8 specifically in oligodendrocytes of mice was associated with microstructural changes of specific brain regions including the cortex and striatum. The extent of these changes in white matter including the corpus callosum and fornix was correlated with total contact time in the reciprocal social interaction test. Analysis with rsfMRI revealed changes in functional brain connectivity in the mutant mice, and the extent of such changes in the cortex, hippocampus, and amygdala was also correlated with the change in social interaction. Our results thus suggest that changes in brain microstructure and functional connectivity induced by oligodendrocyte dysfunction might underlie altered social interaction in mice with oligodendrocyte-specific CHD8 haploinsufficiency.

Abnormal morphology and subcortical projections to the medial geniculate in an animal model of autism

Auditory dysfunction, including hypersensitivity and tinnitus, is a common symptom of autism spectrum disorder (ASD). Prenatal exposure to the antiseizure medication valproic acid (VPA) significantly increases the risk of ASD in humans and similar exposure is utilized as an animal model of ASD in rodents. Animals exposed to VPA in utero have abnormal activity in their auditory cortex in response to sounds, fewer neurons, abnormal neuronal morphology, reduced expression of calcium-binding proteins, and reduced ascending projections to the central nucleus of the inferior colliculus. Unfortunately, these previous studies of central auditory circuits neglect the medial geniculate (MG), which serves as an important auditory relay from the midbrain to the auditory cortex. Here, we examine the structure and connectivity of the medial geniculate (MG) in rats prenatally exposed to VPA. Our results indicate that VPA exposure results in significantly smaller and fewer neurons in the ventral and medial nuclei of the MG. Furthermore, injections of the retrograde tract tracer fluorogold (FG) in the MG result in significantly fewer FG+ neurons in the inferior colliculus, superior olivary complex, and ventral cochlear nucleus. Together, we interpret these findings to indicate that VPA exposure results in hypoplasia throughout the auditory circuits and that VPA has a differential impact on some long-range axonal projections from brainstem centers to the thalamus. Together, our findings support the widespread impact of VPA on neurons and sensory circuits in the developing brain.

Brain Structural and Functional Alterations in Mice Prenatally Exposed to LPS Are Only Partially Rescued by Anti-Inflammatory Treatment

Aberrant immune activity during neurodevelopment could participate in the generation of neurological dysfunctions characteristic of several neurodevelopmental disorders (NDDs). Numerous epidemiological studies have shown a link between maternal infections and NDDs risk; animal models of maternal immune activation (MIA) have confirmed this association. Activation of maternal immune system during pregnancy induces behavioral and functional alterations in offspring but the biological mechanisms at the basis of these effects are still poorly understood. In this study, we investigated the effects of prenatal lipopolysaccharide (LPS) exposure in peripheral and central inflammation, cortical cytoarchitecture and behavior of offspring (LPS-mice). LPS-mice reported a significant increase in interleukin-1β (IL-1β) serum level, glial fibrillary acidic protein (GFAP)- and ionized calcium-binding adapter molecule 1 (Iba1)-positive cells in the cortex. Furthermore, cytoarchitecture analysis in specific brain areas, showed aberrant alterations in minicolumns’ organization in LPS-mice adult brain. In addition, we demonstrated that LPS-mice presented behavioral alterations throughout life. In order to better understand biological mechanisms whereby LPS induced these alterations, dams were treated with meloxicam. We demonstrated for the first time that exposure to LPS throughout pregnancy induces structural permanent alterations in offspring brain. LPS-mice also present severe behavioral impairments. Preventive treatment with meloxicam reduced inflammation in offspring but did not rescue them from structural and behavioral alterations.

Altered Expression of GABAergic Markers in the Forebrain of Young and Adult Engrailed-2 Knockout Mice

Impaired function of GABAergic interneurons, and the subsequent alteration of excitation/inhibition balance, is thought to contribute to autism spectrum disorders (ASD). Altered numbers of GABAergic interneurons and reduced expression of GABA receptors has been detected in the brain of ASD subjects and mouse models of ASD. We previously showed a reduced expression of GABAergic interneuron markers parvalbumin (PV) and somatostatin (SST) in the forebrain of adult mice lacking the Engrailed2 gene (En2^-/- mice). Here, we extended this analysis to postnatal day (P) 30 by using in situ hybridization, immunohistochemistry, and quantitative RT-PCR to study the expression of GABAergic interneuron markers in the hippocampus and somatosensory cortex of En2^-/- and wild type (WT) mice. In addition, GABA receptor subunit mRNA expression was investigated by quantitative RT-PCR in the same brain regions of P30 and adult En2^-/- and WT mice. As observed in adult animals, PV and SST expression was decreased in En2^-/- forebrain of P30 mice. The expression of GABA receptor subunits (including the ASD-relevant Gabrb3) was also altered in young and adult En2^-/- forebrain. Our results suggest that GABAergic neurotransmission deficits are already evident at P30, confirming that neurodevelopmental defects of GABAergic interneurons occur in the En2 mouse model of ASD.

Sensory Abnormalities in Autism Spectrum Disorders: A Focus on the Tactile Domain, From Genetic Mouse Models to the Clinic

Sensory abnormalities are commonly recognized as diagnostic criteria in autism spectrum disorder (ASD), as reported in the last edition of the Diagnostic and Statistical Manual of Mental Disorder (DSM-V). About 90% of ASD individuals have atypical sensory experiences, described as both hyper- and hypo-reactivity, with abnormal responses to tactile stimulation representing a very frequent finding. In this review, we will address the neurobiological bases of sensory processing in ASD, with a specific focus of tactile sensitivity. In the first part, we will review the most relevant sensory abnormalities detected in ASD, and then focus on tactile processing deficits through the discussion of recent clinical and experimental studies. In the search for the neurobiological bases of ASD, several mouse models have been generated with knockout and humanized knockin mutations in many ASD-associated genes. Here, we will therefore give a brief overview of the anatomical structure of the mouse somatosensory system, and describe the somatosensory abnormalities so far reported in different mouse models of ASD. Understanding the neurobiological bases of sensory processing in ASD mouse models may represent an opportunity for a better comprehension of the mechanisms underlying sensory abnormalities, and for the development of novel effective therapeutic strategies.

Morphological alterations of the reticular thalamic nucleus in Engrailed-2 knockout mice

The reticular thalamic nucleus (Rt) is a sheet of neurons that surrounds the dorsal thalamus laterally, along its dorso-ventral and rostro-caudal axes. It consists of inhibitory neurons releasing gamma-aminobutyric acid (GABA). This nucleus participates in the circuitry between the thalamus and the cerebral cortex, and its impairment is associated with neuro-psychiatric disorders. In this study, we investigated the Rt anatomy of Engrailed-2 knockout mice (En2^-/- ), a mouse model of autism spectrum disorder (ASD), using parvalbumin as an immunohistochemical marker. We compared 4- and 6-week-old wild type (WT) and En2^-/- mice using various morphometric parameters: cell area, shape factor, circularity and cell density. Significant differences were present in 6-week-old male mice with different genetic background (WT vs. En2^-/- ): the Rt neurons of En2^-/- mice showed a bigger cell area, shape factor and circularity when compared with WT. Age (4 weeks vs. 6 weeks) influenced the shape factor of WT females, the circularity and cell density of En2^-/- males, and the shape factor and circularity of En2^-/- females. Gender affected cell density in 4-week-old WT mice, shape factor and cellularity of 6-week-old WT mice, and cell area, shape factor and cell density of En2^-/- at 6 weeks. Intrasubject (left-right) asymmetry of Rt was never observed. These results show for the first time that sex- and age-related changes occur in the Rt GABAergic neurons of the En2^-/- ASD mouse model.

Can we and should we use animal models to study neurobehavioral comorbidities of epilepsy?

Animal systems have been widely used to examine mechanisms of neurobehavioral comorbidities of epilepsy and to help in developing their effective therapies. Despite the progress made in the field, animal studies have their limitations stemming both from issues with modeling neuropsychiatric disorders in the laboratory and from drawbacks of animal models of epilepsy themselves. This review discusses advantages and weaknesses of experimental paradigms and approaches used to model and to analyze neurobehavioral comorbidities of epilepsy, from the perspectives of their needs, interpretation, ways of improvement, and clinical relevance. Developmental studies are required to adequately address age-specific aspects of the comorbidities. The deployment of preclinical Common Data Elements (pCDEs) for epilepsy research should facilitate the standardization and the harmonization of studies in question, while the application of Research Domain Criteria (RDoC) to characterize neurobehavioral disorders in animals with epilepsy should help in closing the bench-to-bedside gap. Special Issue: Epilepsy & Behavior's 20th Anniversary.

Structural Bases of Atypical Whisker Responses in a Mouse Model of CDKL5 Deficiency Disorder

Mutations in the CDKL5 (cyclin-dependent kinase-like 5) gene cause CDKL5 Deficiency Disorder (CDD), a severe neurodevelopmental syndrome where patients exhibit early-onset seizures, intellectual disability, stereotypies, limited or absent speech, autism-like symptoms and sensory impairments. Mounting evidences indicate that disrupted sensory perception and processing represent core signs also in mouse models of CDD; however we have very limited knowledge on their underlying causes. In this study, we investigated how CDKL5 deficiency affects synaptic organization and experience-dependent plasticity in the thalamo-cortical (TC) pathway carrying whisker-related tactile information to the barrel cortex (BC). By using synapse-specific antibodies and confocal microscopy, we found that Cdkl5-KO mice display a lower density of TC synapses in the BC that was paralleled by a reduction of cortico-cortical (CC) connections compared to wild-type mice. These synaptic defects were accompanied by reduced BC activation, as shown by a robust decrease of c-fos immunostaining, and atypical behavioral responses to whisker-mediated tactile stimulation. Notably, a 2-day paradigm of enriched whisker stimulation rescued both number and configuration of excitatory synapses in Cdkl5-KO mice, restored cortical activity and normalized behavioral responses to wild-type mice levels. Our findings disclose a novel and unsuspected role of CDKL5 in controlling the organization and experience-induced modifications of excitatory connections in the BC and indicate how mutations of CDKL5 produce failures in higher-order processing of somatosensory stimuli. This article is part of a Special Issue entitled: Animal Models of Neurodevelopmental Disorders.

Whisker Nuisance Test: A Valuable Tool to Assess Tactile Hypersensitivity in Mice

Abnormal response to tactile stimulation, described as both hyper- and hypo-reactivity, is a common sensory impairment in multiple neuropsychiatric disorders. The neural bases of tactile sensitivity remain so far unknown. In the last years, animal studies have proven to be useful for shedding light on the cellular and molecular mechanism underlying sensory impairments. However, few behavioral tests have been developed in mice for assessing tactile perception abnormalities (e.g., the whisker nuisance [WN] test and the tactile prepulse inhibition assay). Here we provide a modified version of the WN test, which is based on the previously developed method by McNamara et al. (2010). The WN test permits to specifically detect tactile hypo/hyper-sensitivity relative to whisker stimulation in mice. The test starts with a habituation phase in which the mouse familiarizes itself with the experimental cage and the researcher/experimenter. After a sham session, the experimental session begins, consisting of bilateral whisker stimulation with a wooden stick. The advantages of using this protocol are many: it is relatively simple to set with no particular or expensive equipment needed, it is easily reproducible, it allows researchers to assess a variety of behavioral responses to a whisker-specific tactile perception in mice (i.e., fearful behavior, stance, hyperventilation, aggressive behavior and evasiveness) and provides important translational opportunities.

Deletion of Autism Risk Gene Shank3 Disrupts Prefrontal Connectivity

Mutations in the synaptic scaffolding protein SHANK3 are a major cause of autism and are associated with prominent intellectual and language deficits. However, the neural mechanisms whereby SHANK3 deficiency affects higher-order socio-communicative functions remain unclear. Using high-resolution functional and structural MRI in adult male mice, here we show that loss of Shank3 (Shank3B ^-/-) results in disrupted local and long-range prefrontal and frontostriatal functional connectivity. We document that prefrontal hypoconnectivity is associated with reduced short-range cortical projections density, and reduced gray matter volume. Finally, we show that prefrontal disconnectivity is predictive of social communication deficits, as assessed with ultrasound vocalization recordings. Collectively, our results reveal a critical role of SHANK3 in the development of prefrontal anatomy and function, and suggest that SHANK3 deficiency may predispose to intellectual disability and socio-communicative impairments via dysregulation of higher-order cortical connectivity.SIGNIFICANCE STATEMENT Mutations in the synaptic scaffolding protein SHANK3 are commonly associated with autism, intellectual, and language deficits. Previous research has linked SHANK3 deficiency to basal ganglia dysfunction, motor stereotypies, and social deficits. However, the neural mechanism whereby Shank3 gene mutations affects cortical functional connectivity and higher-order socio-communicative functions remain unclear. Here we show that loss of SHANK3 in mice results in largely disrupted functional connectivity and abnormal gray matter anatomy in prefrontal areas. We also show that prefrontal connectivity disruption is tightly linked to socio-communicative deficits. Our findings suggest that SHANK3 is a critical orchestrator of frontocortical function, and that disrupted connectivity of prefrontal areas may underpin socio-communicative impairments observed in SHANK3 mutation carriers.