Translational animal models of autism and neurodevelopmental disorders.

Autism is a neurodevelopmental disorder whose diagnosis is based on three behavioral criteria: unusual reciprocal social interactions, deficits in communication, and stereotyped repetitive behaviors with restricted interests. A large number of de novo single gene mutations and chromosomal deletions are associated with autism spectrum disorders. Based on the strong genetic evidence, mice with targeted mutations in homologous genes have been generated as translational research tools. Mouse models of autism have revealed behavioral and biological outcomes of mutations in risk genes. The field is now poised to employ the most robust phenotypes in the most replicable mouse models for preclinical screening of novel therapeutics

Male mice emit distinct ultrasonic vocalizations when the female leaves the social interaction arena.

Adult male mice emit large number of complex ultrasonic vocalizations (USVs) when interacting with adult females. Call numbers and call categories differ greatly among inbred mouse strains. Little is known about USV emissions when the social partner departs. To investigate whether call repertoires and call rates are different when the male is interacting with a female and after the removal of the female, we designed a novel male-female social interaction test in which vocalizations were recorded across three phases. During phase 1, the male subject freely interacts with an unfamiliar estrus female mouse in a clean cage for 5 min. During phase 2, the female is removed while the male remains in the cage for 3 min. During phase 3, the same female is returned to the cage to rejoin the male subject mouse for 3 min. C57BL/6J (B6), FVB.129P2-Pde6b(+) Tyr(c-ch)/Ant (FVB), and BTBR T+ tf/J (BTBR) male subject mice were tested in this paradigm. All three strains emitted USVs during their initial interaction with the female partner. When the female was reintroduced in phase 3, numbers of USVs were similar to the initial introductory phase 1. Strain comparisons indicated fewer calls in pairs of BTBR males and stimulus females than in pairs of B6 males and stimulus females and pairs of FVB males and stimulus females. In the absence of the female, all FVB males vocalized, while only one third of B6 males and one third of BTBR males vocalized. In all three strains, changes in call category repertoires were detected after the female was removed. Call categories reverted to the phase 1 pattern when the female was returned in phase 3. Present findings indicate that males of commonly used inbred strains emit USVs when a partner female leaves the testing arena, suggesting that removing a salient social stimulus may be a unique approach to elicit USVs from mice. Our three-phase paradigm may also be useful for studying attention to social cues, and qualitative differences in vocalizations when a social partner is present vs. suddenly absent

Light Phase Testing of Social Behaviors: Not a Problem

The rich repertoire of mouse social behaviors makes it possible to use mouse models to study neurodevelopmental disorders characterized by social deficits. The fact that mice are naturally nocturnal animals raises a critical question of whether behavioral experiments should be strictly conducted in the dark phase and whether light phase testing is a major methodologically mistake. Although mouse social tasks have been performed in both phases in different laboratories, there seems to be no general consensus on whether testing phase is a critical factor or not. A recent study from our group showed remarkably similar social scores obtained from inbred mice tested in the light and the dark phase, providing evidence that light phase testing could yield reliable results as robust as dark phase testing for the sociability test. Here we offer a comprehensive review on mouse social behaviors measured in light and dark phases and explain why it is reasonable to test laboratory mice in experimental social tasks in the light phase

Unusual Repertoire of Vocalizations in the BTBR T+tf/J Mouse Model of Autism

BTBR T+ tf/J (BTBR) is an inbred mouse strain that displays social abnormalities and repetitive behaviors analogous to the first and third diagnostic symptoms of autism. Here we investigate ultrasonic vocalizations in BTBR, to address the second diagnostic symptom of autism, communication deficits. As compared to the commonly used C57BL/6J (B6) strain, BTBR pups called more loudly and more frequently when separated from their mothers and siblings. Detailed analysis of ten categories of calls revealed an unusual pattern in BTBR as compared to B6. BTBR emitted high levels of harmonics, two-syllable, and composite calls, but minimal numbers of chevron-shaped syllables, upward, downward, and short calls. Because body weights were higher in BTBR than B6 pups, one possible explanation was that larger thoracic size was responsible for the louder calls and different distribution of syllable categories. To test this possibility, we recorded separation calls from FVB/NJ, a strain with body weights similar to BTBR, and 129X1/SvJ, a strain with body weights similar to B6. BTBR remained the outlier on number of calls, displaying low numbers of complex, upward, chevron, short, and frequency steps calls, along with high harmonics and composites. Further, developmental milestones and growth rates were accelerated in BTBR, indicating an unusual neurodevelopmental trajectory. Overall, our findings demonstrate strain-specific patterns of ultrasonic calls that may represent different lexicons, or innate variations in complex vocal repertoires, in genetically distinct strains of mice. Particularly intriguing is the unusual pattern of vocalizations and the more frequent, loud harmonics evident in the BTBR mouse model of autism that may resemble the atypical vocalizations seen in some autistic infants

Olfactory cues are sufficient to elicit social approach behaviors but not social transmission of food preference in C57BL/6J mice

Mouse models for the study of autistic-like behaviors are increasingly needed to test hypotheses about the causes of autism, and to evaluate potential treatments. Both the automated 3-chambered social approach test and social transmission of food preference have been proposed as mouse behavioral assays with face validity to diagnostic symptoms of autism, including aberrant reciprocal social interactions and impaired communication. Both assays measure aspects of normal social behavior in the mouse. However, little is known regarding the salient cues present in each assay that elicit normal social approach and communication. To deconstruct the critical components, we focused on delivering discrete social and non-social olfactory and visual cues within the context of each assay. Results indicate that social olfactory cues were sufficient to elicit normal sociability in the 3-chambered social approach test On social transmission of food preference, isolated social olfactory cues were sufficient to induce social investigation, but not sufficient to induce food preference. These findings indicate that olfactory cues are important in mouse social interaction, but that additional sensory cues are necessary in certain situations. The present evidence that both the 3-chambered social approach assay and the social transmission of food preference assay require socially relevant cues to elicit normal behavior supports the use of these two assays to investigate autism-related behavioral phenotypes in mice

Social approach and repetitive behavior in eleven inbred mouse strains

Core symptoms of autism include deficits in social interaction, impaired communication, and restricted, repetitive behaviors. The repetitive behavior domain encompasses abnormal motoric stereotypy, an inflexible insistence on sameness, and resistance to change. In recent years, many genetic mouse models of autism and related disorders have been developed, based on candidate genes for disease susceptibility. The present studies are part of an ongoing initiative to develop appropriate behavioral tasks for the evaluation of mouse models relevant to autism. We have previously reported profiles for sociability, preference for social novelty, and resistance to changes in a learned pattern of behavior, as well as other functional domains, for 10 inbred mouse strains of divergent genetic backgrounds. The present studies extend this multi-component behavioral characterization to several additional strains: C58/J, NOD/LtJ, NZB/B1NJ, PL/J, SJL/J, SWR/J, and the wild-derived PERA/EiJ. C58/J, NOD/LtJ, NZB/B1NJ, SJL/J, and PERA/EiJ demonstrated low sociability, measured by time spent in proximity to an unfamiliar conspecific, with 30% to 60% of mice from these strains showing social avoidance. In the Morris water maze, NZB/B1NJ had a persistent bias for the quadrant where the hidden platform was located during acquisition, even after nine days of reversal training. A particularly interesting profile was found for C58/J, which had low social preference, poor performance in the T-maze, and overt motoric stereotypy. Overall, this set of tasks and observational methods provides a strategy for evaluating novel mouse models in behavioral domains relevant to the autism phenotype

Large-Scale Gene Expression Differences Across Brain Regions and Inbred Strains Correlate With a Behavioral Phenotype

Behaviors are often highly heritable, polygenic traits. To investigate molecular mediators of behavior, we analyzed gene expression patterns across seven brain regions (amygdala, basal ganglia, cerebellum, frontal cortex, hippocampus, cingulate cortex, and olfactory bulb) of 10 different inbred mouse strains (129S1/SvImJ, A/J, AKR/J, BALB/cByJ, BTBR T+ tf/J, C3H/HeJ, C57BL/6J, C57L/J, DBA/2J, and FVB/NJ). Extensive variation was observed across both strain and brain region. These data provide potential transcriptional intermediates linking polygenic variation to differences in behavior. For example, mice from different strains had variable performance on the rotarod task, which correlated with the expression of >2000 transcripts in the cerebellum. Correlation with this task was also found in the amygdala and hippocampus, but not in other regions examined, indicating the potential complexity of motor coordination. Thus we can begin to identify expression profiles contributing to behavioral phenotypes through variation in gene expression

Haploinsufficiency of the autism-associated Shank3 gene leads to deficits in synaptic function, social interaction, and social communication

<p>Abstract</p> <p>Background</p> <p>SHANK3 is a protein in the core of the postsynaptic density (PSD) and has a critical role in recruiting many key functional elements to the PSD and to the synapse, including components of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA), metabotropic glutamate (mGlu) and <it>N</it>-methyl-D-aspartic acid (NMDA) glutamate receptors, as well as cytoskeletal elements. Loss of a functional copy of the <it>SHANK3 </it>gene leads to the neurobehavioral manifestations of 22q13 deletion syndrome and/or to autism spectrum disorders. The goal of this study was to examine the effects of haploinsufficiency of full-length <it>Shank3 </it>in mice, focusing on synaptic development, transmission and plasticity, as well as on social behaviors, as a model for understanding <it>SHANK3 </it>haploinsufficiency in humans.</p> <p>Methods</p> <p>We used mice with a targeted disruption of <it>Shank3 </it>in which exons coding for the ankyrin repeat domain were deleted and expression of full-length Shank3 was disrupted. We studied synaptic transmission and plasticity by multiple methods, including patch-clamp whole cell recording, two-photon time-lapse imaging and extracellular recordings of field excitatory postsynaptic potentials. We also studied the density of GluR1-immunoreactive puncta in the CA1 stratum radiatum and carried out assessments of social behaviors.</p> <p>Results</p> <p>In <it>Shank3 </it>heterozygous mice, there was reduced amplitude of miniature excitatory postsynaptic currents from hippocampal CA1 pyramidal neurons and the input-output (I/O) relationship at Schaffer collateral-CA1 synapses in acute hippocampal slices was significantly depressed; both of these findings indicate a reduction in basal neurotransmission. Studies with specific inhibitors demonstrated that the decrease in basal transmission reflected reduced AMPA receptor-mediated transmission. This was further supported by the observation of reduced numbers of GluR1-immunoreactive puncta in the stratum radiatum. Long-term potentiation (LTP), induced either with θ-burst pairing (TBP) or high-frequency stimulation, was impaired in <it>Shank3 </it>heterozygous mice, with no significant change in long-term depression (LTD). In concordance with the LTP results, persistent expansion of spines was observed in control mice after TBP-induced LTP; however, only transient spine expansion was observed in <it>Shank3 </it>heterozygous mice. Male <it>Shank3 </it>heterozygotes displayed less social sniffing and emitted fewer ultrasonic vocalizations during interactions with estrus female mice, as compared to wild-type littermate controls.</p> <p>Conclusions</p> <p>We documented specific deficits in synaptic function and plasticity, along with reduced reciprocal social interactions in <it>Shank3 </it>heterozygous mice. Our results are consistent with altered synaptic development and function in <it>Shank3 </it>haploinsufficiency, highlighting the importance of Shank3 in synaptic function and supporting a link between deficits in synapse function and neurodevelopmental disorders. The reduced glutamatergic transmission that we observed in the <it>Shank3 </it>heterozygous mice represents an interesting therapeutic target in <it>Shank3</it>-haploinsufficiency syndromes.</p