Replicable in vivo physiological and behavioral phenotypes of the Shank3B null mutant mouse model of autism

Abstract

BackgroundAutism spectrum disorder (ASD) is a clinically and biologically heterogeneous condition characterized by social, repetitive, and sensory behavioral abnormalities. No treatments are approved for the core diagnostic symptoms of ASD. To enable the earliest stages of therapeutic discovery and development for ASD, robust and reproducible behavioral phenotypes and biological markers are essential to establish in preclinical animal models. The goal of this study was to identify electroencephalographic (EEG) and behavioral phenotypes that are replicable between independent cohorts in a mouse model of ASD. The larger goal of our strategy is to empower the preclinical biomedical ASD research field by generating robust and reproducible behavioral and physiological phenotypes in animal models of ASD, for the characterization of mechanistic underpinnings of ASD-relevant phenotypes, and to ensure reliability for the discovery of novel therapeutics. Genetic disruption of the SHANK3 gene, a scaffolding protein involved in the stability of the postsynaptic density in excitatory synapses, is thought to be responsible for a relatively large number of cases of ASD. Therefore, we have thoroughly characterized the robustness of ASD-relevant behavioral phenotypes in two cohorts, and for the first time quantified translational EEG activity in Shank3B null mutant mice.MethodsIn vivo physiology and behavioral assays were conducted in two independently bred and tested full cohorts of Shank3B null mutant (Shank3B KO) and wildtype littermate control (WT) mice. EEG was recorded via wireless implanted telemeters for 7 days of baseline followed by 20 min of recording following pentylenetetrazol (PTZ) challenge. Behaviors relevant to the diagnostic and associated symptoms of ASD were tested on a battery of established behavioral tests. Assays were designed to reproduce and expand on the original behavioral characterization of Shank3B KO mice. Two or more corroborative tests were conducted within each behavioral domain, including social, repetitive, cognitive, anxiety-related, sensory, and motor categories of assays.ResultsRelative to WT mice, Shank3B KO mice displayed a dramatic resistance to PTZ seizure induction and an enhancement of gamma band oscillatory EEG activity indicative of enhanced inhibitory tone. These findings replicated in two separate cohorts. Behaviorally, Shank3B KO mice exhibited repetitive grooming, deficits in aspects of reciprocal social interactions and vocalizations, and reduced open field activity, as well as variable deficits in sensory responses, anxiety-related behaviors, learning and memory.ConclusionsRobust animal models and quantitative, replicable biomarkers of neural dysfunction are needed to decrease risk and enable successful drug discovery and development for ASD and other neurodevelopmental disorders. Complementary to the replicated behavioral phenotypes of the Shank3B mutant mouse is the new identification of a robust, translational in vivo neurophysiological phenotype. Our findings provide strong...

Hypothesis‐driven investigations of diverse pharmacological targets in two mouse models of autism

“…In the TrkB Shank3B cohort, water maze was conducted last. Our previous studies with B6, BTBR, and Shank3 B had revealed similar scores in males and females on the behavioral assays used in the present studies [Yang et al, ; McFarlane et al, ; Silverman et al, , ; Kazdoba et al, ; Dhamne et al, ], therefore both males and females were approximately equally represented in the Ns for each cohort, with the exception of male–female reciprocal social interactions in which only the males were tested. Breeding were designed to yield N = 12–15 per treatment group, to provide sufficient power to detect drug effects, as confirmed in previous studies [Silverman et al, , ; Silverman, Oliver, Karras, Gastrell, & Crawley, ; Kazdoba et al, ; Stoppel et al, ].…”

“…Open field exploratory locomotor activity was conducted as previously described [Silverman et al, , ; Kazdoba et al, ; Dhamne et al, ]. The automated apparatus consisted of four photocell‐equipped open field chambers and VersaMax Animal Activity Monitoring System (AccuScan Instruments, Columbus, OH).…”

“…Dependent on the specific mutation, and the brain region containing the mutation in cases of conditional knockouts, Shank3 mutant mice displayed reduced frequency and amplitude of miniature excitatory postsynaptic currents [Bozdagi et al, ; Peca et al, ], reduced glutamatergic transmission and impaired long‐term potentiation in the hippocampus [Wang et al, ; Yang et al, ; Jaramillo et al, ], reductions in the NMDA/AMPA ratio in hippocampal CA1, prefrontal cortex, and striatal medium spiny neurons [Kouser et al, ; Duffney et al, ; Jaramillo et al, ;. Lee et al, ; Wang et al, ], and resistance to pentyletetrazole‐induced seizures [Dhamne et al, ], indicative of reduced excitatory physiology. Shank3B null mutant mice phenocopy the two diagnostic symptom categories of autism, displaying low scores on social assays and high levels of repetitive self‐grooming [Peca et al, ; Chang et al, ; Wang et al, ; Dhamne et al, ].…”

Succinic semialdehyde dehydrogenase deficiency, a disorder of GABA metabolism: an update on pharmacological and enzyme‐replacement therapeutic strategies

“…EEG was scored offline using semi-automated detection (Neuroscore, Data Sciences International, St. Paul, MN) for seizure frequency (total number of seizures), and total ictal time (cumulative time spent in seizures); where a seizure event was defined as a run of continuous spikes ≥ 3 s in duration on the EEG. Automatically detected events were verified by visual inspection (Dhamne et al 2017) Our prediction was that Torin 2 administration would lead to improvement in both parameters. We found that Torin 2 was ineffective at reducing seizure frequency in aldh5a1 −/− mice (Table 2), and unexpectedly found that it significantly extended the total ictal time (Table 2).…”

Genetic mutations in Ca2+ signaling alter dendrite morphology and social approach in juvenile mice

“…The three‐chambered social approach was conducted as described previously . Animals were moved to the room 1 hour prior to testing.…”