Altered social behavior in mice carrying a cortical Foxp2 deletion.

Genetic disruptions of the forkhead box transcription factor FOXP2 in humans cause an autosomal-dominant speech and language disorder. While FOXP2 expression pattern are highly conserved, its role in specific brain areas for mammalian social behaviors remains largely unknown. Here we studied mice carrying a homozygous cortical Foxp2 deletion. The postnatal development and gross morphological architecture of mutant mice was indistinguishable from wildtype (WT) littermates. Unbiased behavioral profiling of adult mice revealed abnormalities in approach behavior towards conspecifics as well as in the reciprocal responses of WT interaction partners. Furthermore mutant mice showed alterations in acoustical parameters of ultrasonic vocalizations, which also differed in function of the social context. Cell type-specific gene expression profiling of cortical pyramidal neurons revealed aberrant regulation of genes involved in social behavior. In particular Foxp2 mutants showed the downregulation of Mint2 (Apba2), a gene involved in approach behavior in mice and autism spectrum disorder in humans. Taken together these data demonstrate that cortical Foxp2 is required for normal social behaviors in mice.

Neuroinflammation and depression: A review.

Some recent clinical and preclinical evidence suggests that neuroinflammation is a key factor that interacts with the three neurobiological correlates of major depressive disorder: depletion of brain serotonin, dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis and alteration of the continuous production of adult-generated neurons in the dentate gyrus of the hippocampus. This review discusses the main players in brain immunity as well as how inflammation interacts with the above three mechanisms. It is reported that kynurenine (KYN) pathway alteration in favour of its excitotoxic component and HPA axis dysregulation have the common effect of increasing extracellular glutamate levels and glutamate neurotransmission, which can impact hippocampal neurogenesis. This pathophysiological cascade appears to be triggered or sustained and reinforced by any chronic inflammatory condition involving increased circulating markers of inflammation that are able to cross the blood-brain barrier and activate microglia; it can also be the consequence of primary brain neuroinflammation, such as in neurodegenerative disorders with early manifestations that are frequently depressive symptoms. Further recent data indicate that primary microglial activation may also result from a direct impact of chronic stress on vascular function. The intricated dynamic crosstalk between neuroinflammation and other relevant neurobiological correlates of depression add to evidence that neuroinflammation may be a key therapeutic target for future therapeutic strategies in major depressive disorder.

Computerized video analysis of social interactions in mice.

The study of social interactions in mice is used as a model for normal and pathological cognitive and emotional processes. But extracting comprehensive behavioral information from videos of interacting mice is still a challenge. We describe a computerized method and software, MiceProfiler, that uses geometrical primitives to model and track two mice without requiring any specific tagging. The program monitors a comprehensive repertoire of behavioral states and their temporal evolution, allowing the identification of key elements that trigger social contact. Using MiceProfiler we studied the role of neuronal nicotinic receptors in the establishment of social interactions and risk-prone postures. We found that the duration and type of social interactions with a conspecific evolves differently over time in mice lacking neuronal nicotinic receptors (Chrnb2-/-, here called ß2(-/-)), compared to C57BL/6J mice, and identified a new type of coordinated posture, called back-to-back posture, that we rarely observed in ß2(-/-) mice.

Nonaggressive and adapted social cognition is controlled by the interplay between noradrenergic and nicotinic receptor mechanisms in the prefrontal cortex.

Social animals establish flexible behaviors and integrated decision-making processes to adapt to social environments. Such behaviors are impaired in all major neuropsychiatric disorders and depend on the prefrontal cortex (PFC). We previously showed that nicotinic acetylcholine receptors (nAChRs) and norepinephrine (NE) in the PFC are necessary for mice to show adapted social cognition. Here, we investigated how the cholinergic and NE systems converge within the PFC to modulate social behavior. We used a social interaction task (SIT) in C57BL/6 mice and mice lacking ß2*nAChRs (ß2(-/-) mice), making use of dedicated software to analyze >20 social sequences and pinpoint social decisions. We performed specific PFC NE depletions before SIT and measured monoamines and acetylcholine (ACh) levels in limbic corticostriatal circuitry. After PFC-NE depletion, C57BL/6 mice exhibited impoverished and more rigid social behavior and were 6-fold more aggressive than sham-lesioned animals, whereas ß2(-/-) mice showed unimpaired social behavior. Our biochemical measures suggest a critical involvement of DA in SIT. In addition, we show that the balance between basal levels of monoamines and of ACh modulates aggressiveness and this modulation requires functional ß2*nAChRs. These findings demonstrate the critical interplay between prefrontal NE and nAChRs for the development of adapted and nonaggressive social cognition.

Cognition- and circuit-based dysfunction in a mouse model of 22q11.2 microdeletion syndrome: effects of stress.

Genetic microdeletion at the 22q11 locus is associated with very high risk for schizophrenia. The 22q11.2 microdeletion (Df(h22q11)/+) mouse model shows cognitive deficits observed in this disorder, some of which can be linked to dysfunction of the prefrontal cortex (PFC). We used behavioral (n = 10 per genotype), electrophysiological (n = 7 per genotype per group), and neuroanatomical (n = 5 per genotype) techniques to investigate schizophrenia-related pathology of Df(h22q11)/+ mice, which showed a significant decrease in the total number of parvalbumin positive interneurons in the medial PFC. The Df(h22q11)/+ mice when tested on PFC-dependent behavioral tasks, including gambling tasks, perform significantly worse than control animals while exhibiting normal behavior on hippocampus-dependent tasks. They also show a significant decrease in hippocampus-medial Prefrontal cortex (H-PFC) synaptic plasticity (long-term potentiation, LTP). Acute platform stress almost abolished H-PFC LTP in both wild-type and Df(h22q11)/+ mice. H-PFC LTP was restored to prestress levels by clozapine (3 mg/kg i.p.) in stressed Df(h22q11)/+ mice, but the restoration of stress-induced LTP, while significant, was similar between wild-type and Df(h22q11)/+ mice. A medial PFC dysfunction may underlie the negative and cognitive symptoms in human 22q11 deletion carriers, and these results are relevant to the current debate on the utility of clozapine in such subjects.

Spatial learning in Long-Evans Hooded rats and C57BL/6J mice: different strategies for different performance.

Spatial learning abilities of rodents have been extensively used to explore the management of a wide range of cognitive and emotional processes such as learning, memory, attention and anxiety. Knowledge about the organization and processing of spatial learning has mainly been obtained in rats. Due to increasing generation of genetically modified mice, cognitive abilities of mice are now extensively tested. The present paper aimed at comparing spatial representation, learning and strategies in C57BL/6J mice and Long-Evans Hooded rats when subjected to the same spatial learning paradigm, i.e. learning a food location in a crossmaze. We also analyzed the influence of environmental richness on learning modalities in both species. Our results showed that rats and mice could exhibit similar spatial learning abilities in some circumstances. However, Long-Evans rats and C57BL/6J mice may set up different strategies depending on the availability of visual information within the environment. Rats' learning strategies mainly relied on distant visual cues and seemed more efficient than those used by mice as they needed less time than mice to solve the task. We emphasize that the strategies of mice are less robust and flexible than the ones set up by rats. Finally, the richness of the environment was shown to affect speed and quality of spatial learning in both species.

Social behaviors and acoustic vocalizations in different strains of mice.

Proposing a framework for the study of core functions is valuable for understanding how they are altered in multiple mental disorders involving prefrontal dysfunction, for understanding genetic influences and for testing therapeutic compounds. Social and communication disabilities are reported in several major psychiatric disorders, and social communication disorders also can occur independently. Being able to study social communication involving interactions and associated acoustic vocalizations in animal models is thus important. All rodents display extensive social behaviors, including interactions and acoustic vocalizations. It is therefore important to pinpoint potential genetic-related strain differences -and similarities- in social behavior and vocalization. One approach is to compare different mouse strains, and this may be useful in choosing which strains may be best suitable in modeling psychiatric disorders where social and communication deficits are core symptoms. We compared social behavior and ultrasonic acoustic vocalization profiles in males of four mouse strains (129S2/Sv, C57BL/6J, DBA/2, and CD-1) using a social interaction task that we previously showed to rely on prefrontal network activity. Our social interaction task promotes a high level of ultrasonic vocalization with both social and acoustic parameters, and further allows other measures of social behaviors. The duration of social contact, dominance and aggressiveness varied with the mouse strains. Only C57BL/6J mice showed no attacks, with social contact being highly affiliative, whereas others strains emitted aggressive attacks. C57BL/6J mice also exhibited a significantly higher rate of ultrasonic vocalizations (USV), especially during social interaction.

Loss-of-function of PTPR γ and ζ, observed in sporadic schizophrenia, causes brain region-specific deregulation of monoamine levels and altered behavior in mice.

RATIONALE: The receptor protein tyrosine phosphatase PTPRG has been genetically associated with psychiatric disorders and is a ligand for members of the contactin family, which are themselves linked to autism spectrum disorders. OBJECTIVE: Based on our finding of a phosphatase-null de novo mutation in PTPRG associated with a case of sporadic schizophrenia, we used PTPRG knockout (KO) mice to model the effect of a loss-of-function mutation. We compared the results with loss-of-function in its close paralogue PTPRZ, previously associated with schizophrenia. We tested PTPRG -/- , PTPRZ -/- , and wild-type male mice for effects on social behavior, forced swim test, and anxiety, as well as on regional brain neurochemistry. RESULTS: The most notable behavioral consequences of PTPRG gene inactivation were reduced immobilization in the forced swim test, suggestive of some negative symptoms of schizophrenia. By contrast, PTPRZ -/- mice demonstrated marked social alteration with increased aggressivity, reminiscent of some positive symptoms of schizophrenia. Both knockouts showed elevated dopamine levels in prefrontal cortex, hippocampus, and most particularly amygdala, but not striatum, accompanied by reduced dopamine beta hydroxylase activity only in amygdala. In addition, PTPRG KO elicited a distinct increase in hippocampal serotonin level not observed in PTPRZ KO. CONCLUSION: PTPRG and PTPRZ gene loss therefore induces distinct patterns of behavioral change and region-specific alterations in neurotransmitters, highlighting their usefulness as models for neuropsychiatric disorder mechanisms and making these receptors attractive targets for therapy.

Neuronal Nicotinic Receptors Are Crucial for Tuning of E/I Balance in Prelimbic Cortex and for Decision-Making Processes.

RATIONALE: Decision-making is an essential component of our everyday life commonly disabled in a myriad of psychiatric conditions, such as bipolar and impulsive control disorders, addiction and pathological gambling, or schizophrenia. A large cerebral network encompassing the prefrontal cortex, the amygdala, and the nucleus accumbens is activated for efficient decision-making. METHODS: We developed a mouse gambling task well suited to investigate the influence of uncertainty and risk in decision-making and the role of neurobiological circuits and their monoaminergic inputs. Neuronal nicotinic acetylcholine receptors (nAChRs) of the PFC are important for decision-making processes but their presumed roles in risk-taking and uncertainty management, as well as in cellular balance of excitation and inhibition (E/I) need to be investigated. RESULTS: Using mice lacking nAChRs - ß2-/- mice, we evidence for the first time the crucial role of nAChRs in the fine tuning of prefrontal E/I balance together with the PFC, insular, and hippocampal alterations in gambling behavior likely due to sensitivity to penalties and flexibility alterations. Risky behaviors and perseveration in extinction task were largely increased in ß2-/- mice as compared to control mice, suggesting the important role of nAChRs in the ability to make appropriate choices adapted to the outcome.

Improved behavior and neuropathology in the mouse model of Sanfilippo type IIIB disease after adeno-associated virus-mediated gene transfer in the striatum.

Sanfilippo syndrome is a mucopolysaccharidosis (MPS) caused by a lysosomal enzyme defect interrupting the degradation pathway of heparan sulfates. Affected children develop hyperactivity, aggressiveness, delayed development, and severe neuropathology. We observed relevant behaviors in the mouse model of Sanfilippo syndrome type B (MPSIIIB), in which the gene coding for alpha-N-acetylglucosaminidase (NaGlu) is invalidated. We addressed the feasibility of gene therapy in these animals. Vectors derived from adeno-associated virus serotype 2 (AAV2) or 5 (AAV5) coding for NaGlu were injected at a single site in the putamen of 45 6-week-old MPSIIIB mice. Normal behavior was observed in treated mice. High NaGlu activity, far above physiological levels, was measured in the brain and persisted at 38 weeks of age. NaGlu immunoreactivity was detected in neuron intracellular organelles, including lysosomes. Enzyme activity spread beyond vector diffusion areas. Delivery to the entire brain was reproducibly obtained with both vector types. NaGlu activity was higher and distribution was broader with AAV5-NaGlu than with AAV2-NaGlu vectors. The compensatory increase in the activity of various lysosomal enzymes was improved. The accumulation of gangliosides GM2 and GM3 present before treatment and possibly participating in neuropathology was reversed. Characteristic vacuolations in microglia, perivascular cells, and neurons, which were prominent before the age of treatment, disappeared in areas in which NaGlu was present. However, improvement was only partial in some animals, in contrast to high NaGlu activity. These results indicate that NaGlu delivery from intracerebral sources has the capacity to alleviate most disease manifestations in the MPSIIIB mouse model.

Histopathological and cognitive defects induced by Nef in the brain.

Complex mechanisms of human immunodeficiency virus type-1 (HIV-1) brain pathogenesis suggest the contribution of individual HIV-1 gene products. Among them, the Nef protein has been reported to harbor a major determinant of pathogenicity in AIDS-like disease. The goal of the present study was to determine whether Nef protein expressed in vivo by primary macrophages could induce a brain toxicity also affecting the behavior of the rat. To achieve this goal we grafted Nef-transduced macrophages into the rat hippocampus. Two months post-transplantation, we observed that Nef induces monocyte/macrophage recruitment, expression of TNF-alpha, and astrogliosis. No apoptotic event was detected. We further demonstrated that Nef neurotoxicity is associated with cognitive deficits.

Definition of a new maze paradigm for the study of spatial behavior in rats.

The present work defines a simple behavioral paradigm to evaluate spatial representation in rats. In two experimental conditions differing in the richness of distal visual cues, rats learned to locate a food goal in a cross maze from various starting points. We conducted different challenges consisting of (i) reaching the same goal from a modified arrangement of the maze arms (geometric challenge), (ii) reaching the goal within a 90 degrees rotated maze, herein checking the use of a place strategy, and (iii) investigating the effect of central cholinergic blockade over the retention of the task. Results showed that rats needed 12-30 trials to learn a place response, depending upon the richness of the visual environment. The maze rotation did not produce any impairment whereas the geometric challenge affected the performance specifically under the visually richer environment. Scopolamine injection (i.p.) produced a significant impairment in place recognition. Our present work shows that this maze procedure constitutes a useful paradigm to assess learning and processing of a place representation by rats. Similarly to what has been shown in other popular maze paradigms, our results show that rats mostly rely on distal extra-maze cues to solve the task, but also compute intra-maze information.

Acute stress in adulthood impoverishes social choices and triggers aggressiveness in preclinical models.

Adult C57BL/6J mice are known to exhibit high level of social flexibility while mice lacking the ß2 subunit of nicotinic receptors (ß2(-/-) mice) present social rigidity. We asked ourselves what would be the consequences of a restraint acute stress (45 min) on social interactions in adult mice of both genotypes, hence the contribution of neuronal nicotinic receptors in this process. We therefore dissected social interaction complexity of stressed and not stressed dyads of mice in a social interaction task. We also measured plasma corticosterone levels in our experimental conditions. We showed that a single stress exposure occurring in adulthood reduced and disorganized social interaction complexity in both C57BL/6J and ß2(-/-) mice. These stress-induced maladaptive social interactions involved alteration of distinct social categories and strategies in both genotypes, suggesting a dissociable impact of stress depending on the functioning of the cholinergic nicotinic system. In both genotypes, social behaviors under stress were coupled to aggressive reactions with no plasma corticosterone changes. Thus, aggressiveness appeared a general response independent of nicotinic function. We demonstrate here that a single stress exposure occurring in adulthood is sufficient to impoverish social interactions: stress impaired social flexibility in C57BL/6J mice whereas it reinforced ß2(-/-) mice behavioral rigidity.

Making choice between competing rewards in uncertain vs. safe social environment: role of neuronal nicotinic receptors of acetylcholine.

In social environments, choosing between multiple rewards is modulated by the uncertainty of the situation. Here, we compared how mice interact with a conspecific and how they use acoustic communication during this interaction in a three chambers task (no social threat was possible) and a Social Interaction Task, SIT (uncertain situation as two mice interact freely). We further manipulated the motivational state of the mice to see how they rank natural rewards such as social contact, food, and novelty seeking. We previously showed that beta2-subunit containing nicotinic receptors-ß2(*)nAChRs- are required for establishing reward ranking between social interaction, novelty exploration, and food consumption in social situations with high uncertainty. Knockout mice for ß2(*)nAChRs-ß2(-/-)mice- exhibit profound impairment in making social flexible choices, as compared to control -WT- mice. Our current data shows that being confronted with a conspecific in a socially safe environment as compared to a more uncertain environment, drastically reduced communication between the two mice, and changed their way to deal with a social conspecific. Furthermore, we demonstrated for the first time, that ß2(-/-) mice had the same motivational ranking than WT mice when placed in a socially safe environment. Therefore, ß2(*)nAChRs are not necessary for integrating social information or social rewards per se, but are important for making choices, only in a socially uncertain environment. This seems particularly important in the context of Social Neuroscience, as numerous animal models are used to provide novel insights and to test promising novel treatments of human pathologies affecting social and communication processes, among which Autistic spectrum disorders and schizophrenia.

Human alpha-iduronidase gene transfer mediated by adeno-associated virus types 1, 2, and 5 in the brain of nonhuman primates: vector diffusion and biodistribution.

We have previously demonstrated that delivery of a recombinant adeno-associated virus (rAAV) encoding human alpha-iduronidase (hIDUA) in the putamen and centrum semiovale was feasible and beneficial in a dog model of Hurler's syndrome. In the present study, we investigated the safety and vector diffusion profile of three rAAV serotypes (rAAV2/1, rAAV2/2, and rAAV2/5), encoding hIDUA in the central and peripheral nervous systems of nonhuman primates. Six macaques received the same vector dose injected into the right putamen and the homolateral internal capsule. Neurological examinations were done regularly and showed no detectable clinical consequence of the intracerebral injections. Because transgene IDUA was indistinguishable from endogenous enzymatic activity, we looked for vector diffusion by performing quantitative polymerase chain reaction on serial sections from the brain and spinal cord. We found that global diffusion throughout the brain was not significantly different between the three serotypes. However, rAAV2/1 and rAAV2/5 resulted in higher vector copy numbers per cell than did rAAV2/2, respectively, in the brain and the distal neuronal structures (spinal cord and peripheral nerves).

Reinnervation of hind limb extremity after lumbar dorsal root ganglion injury.

Loss of dorsal root ganglion neuron, or injury to dorsal roots, induces permanent somatosensory defect without therapeutic option. We explored an approach to restoring hind limb somatosensory innervation after elimination of L4, L5 and L6 dorsal root ganglion neurons in rats. Somatosensory pathways were reconstructed by connecting L4, L5 and L6 lumbar dorsal roots to T10, T11 and T12 intercostal nerves, respectively, thus allowing elongation of thoracic ganglion neuron peripheral axons into the sciatic nerve. Connection of thoracic dorsal root ganglion neurons to peripheral tissues was documented 4 and 7 months after injury. Myelinated and unmyelinated fibers regrew in the sciatic nerve. Nerve terminations expressing calcitonin-gene-related-peptide colonized the footpad skin. Retrograde tracing showed that T10, T11 and T12 dorsal root ganglion neurons expressing calcitonin-gene-related-peptide or the neurofilament RT97 projected axons to the sciatic nerve and the footpad skin. Recording of somatosensory evoked potentials in the upper spinal cord indicated connection between the sciatic nerve and the central nervous system. Hind limb retraction in response to nociceptive stimulation of the reinnervated footpads and reversion of skin lesions suggested partial recovery of sensory function. Proprioceptive defects persisted. Delayed somatosensory reinnervation of the hind limb after destruction of lumbar dorsal root neurons in rats indicates potential approaches to reduce chronic disability after severe injury to somatosensory pathways.

Remapping of place cell firing patterns after maze rotations.

When place cells are recorded from rats running on an elevated T-maze inside a curtained enclosure that contains distinct, experimenter selected stimuli, rotations of the maze plus stimuli cause equal rotations of firing fields. Here, we examined the effects of conflicting rotations of a T-maze relative to a laboratory frame that contained a large number of fixed stimuli in the environment and asked whether positional firing patterns stayed in register with the maze or the room cues or were modified in some more complex way. After maze rotations of 90 degrees, 180 degrees or 270 degrees, firing fields were stable in the laboratory frame and thus shifted to a different maze arm. In contrast, rotations of 45 degrees or -45 degrees resulted in dramatic changes of positional firing patterns regardless of their initial position on the maze. Crucially, even cells whose fields were initially on the central platform underwent major firing pattern alterations although the view of the environment from the platform was unchanged by such rotations. Finally, we found that altering the visual appearance by removing without rotation one or two maze arms did not alter firing fields on the remaining part of the maze. Thus, the "remappings" caused by 45 degrees rotations could result from the disturbed relationship between all arms and the room cues or from the changes in the possible paths the animal can take in the environment. Taken together, our results provide an example of combinatorial coding by the hippocampus, in which the place cell representation of the environment was seen to be modified as a unit and not piecewise according to locally available stimuli.

Homotopic septal grafts combined with a hydrogel bridge promote functional recovery in rats with fimbria-fornix lesions: A unit recording study.

Fimbria-fornix lesions abolish the hippocampal electrophysiological activity time-locked to the theta rhythm and alter some functional characteristics of place cells. The present experiment investigated whether homotopic grafts of fetal septal cells can alleviate some of these alter-ations when combined with a polymeric hydrogel bridging a fimbria-fornix lesion-cavity. Eleven months after grafting surgery, unit recordings were obtained from hippocampal neurons of seven rats [two sham-operated (S), two lesion-only (L) and three grafted (G)] while they explored a radial maze. The lesions induced dramatic loss of hippocampal acetylcholinesterase(AChE)-positive reaction products. Surviving grafts were found in the three grafted rats and several AChE-positive processes could be observed in the polymeric hydrogel, as well as in the most dorsal portion of the hippocampal parenchyma. Of 168 recorded units, 132 were hippocampal interneurons (i.e., fired rapidly everywhere in the maze), and 36 were pyramidal place cells (i.e., fired only when the rat was in a specific location in the maze, the place field). The overall firing characteristics of either cell type were similar in S, L and G rats. However, while none of the interneurons recorded from L rats was found to fire rhythmically, a significant proportion of interneurons recorded from S and G rats had an activity pattern time-locked to the theta rhythm [S: 16/19 (84 %); G : 22/70 (31 %)]. In addition, the increase in firing activity observed in interneurons recorded from S rats when they were moving was disrupted in cells from L rats, but partially restored in cells from G rats. Concerning place cells, most (93 %) place fields in S rats were stable relative to extra-maze cues when the radial maze was rotated, while they followed the maze rotation in both L and G rats. Because of the low number of rats used, the present results should be considered with caution. Nevertheless, they indicate graft-induced recovery of some properties of hippocampal function following fimbria-fornix damage, and suggest that homotopic transplants of projection neurons may foster some func-tional recovery when provided with a biomaterial allowing the host or grafted neurons to cross the lesion cavity.