Neural circuit-specific gene manipulation in mouse brain in vivo using split-intein-mediated split-Cre system.

Neural network studies require efficient genetic tools to analyze individual neural circuit functions in vivo. Thus, we developed an advanced circuit-selective gene manipulating tool utilizing anterograde and retrograde adeno-associated viruses (AAVs) encoding split-intein-mediated split-Cre. This strategy can be applied to visualize a specific neural circuit as well as manipulate multiple genes in the circuit neurons. Here, we describe the production and purification of the AAVs, viral injection to the mouse brain, and imaging analysis for a specific neural circuit. For complete details on the use and execution of this protocol, please refer to Kim et al. (2022).

Simultaneous analysis of social behaviors and neural responses in mice using round social arena system.

Stable and accurate capturing of detailed social behaviors is essential for studying rodent sociability. Here, we introduce a round social arena (RSA) system that enables close-up monitoring of detailed social behaviors in mice. We describe the steps to build RSA apparatus and set up the wiring for video synchronization. We then detail how to conduct RSA experiment with simultaneous Ca2+ imaging or optogenetics. This protocol also includes a custom MATLAB script for aligning the behavioral dataset to Ca2+ trace data. For complete details on the use and execution of this protocol, please refer to Kim et al. (2022).

Neural circuit pathology driven by Shank3 mutation disrupts social behaviors.

Dysfunctional sociability is a core symptom in autism spectrum disorder (ASD) that may arise from neural-network dysconnectivity between multiple brain regions. However, pathogenic neural-network mechanisms underlying social dysfunction are largely unknown. Here, we demonstrate that circuit-selective mutation (ctMUT) of ASD-risk Shank3 gene within a unidirectional projection from the prefrontal cortex to the basolateral amygdala alters spine morphology and excitatory-inhibitory balance of the circuit. Shank3 ctMUT mice show reduced sociability as well as elevated neural activity and its amplitude variability, which is consistent with the neuroimaging results from human ASD patients. Moreover, the circuit hyper-activity disrupts the temporal correlation of socially tuned neurons to the events of social interactions. Finally, optogenetic circuit activation in wild-type mice partially recapitulates the reduced sociability of Shank3 ctMUT mice, while circuit inhibition in Shank3 ctMUT mice partially rescues social behavior. Collectively, these results highlight a circuit-level pathogenic mechanism of Shank3 mutation that drives social dysfunction.

Dysregulation of the Synaptic Cytoskeleton in the PFC Drives Neural Circuit Pathology, Leading to Social Dysfunction.

Psychiatric disorders are highly heritable pathologies of altered neural circuit functioning. How genetic mutations lead to specific neural circuit abnormalities underlying behavioral disruptions, however, remains unclear. Using circuit-selective transgenic tools and a mouse model of maladaptive social behavior (ArpC3 mutant), we identify a neural circuit mechanism driving dysfunctional social behavior. We demonstrate that circuit-selective knockout (ctKO) of the ArpC3 gene within prefrontal cortical neurons that project to the basolateral amygdala elevates the excitability of the circuit neurons, leading to disruption of socially evoked neural activity and resulting in abnormal social behavior. Optogenetic activation of this circuit in wild-type mice recapitulates the social dysfunction observed in ArpC3 mutant mice. Finally, the maladaptive sociability of ctKO mice is rescued by optogenetically silencing neurons within this circuit. These results highlight a mechanism of how a gene-to-neural circuit interaction drives altered social behavior, a common phenotype of several psychiatric disorders.