Comprehensive analysis of a novel mouse model of the 22q11.2 deletion syndrome: a model with the most common 3.0-Mb deletion at the human 22q11.2 locus

Abstract

The 22q11.2 deletion syndrome (22q11.2DS) is associated with an increased risk for psychiatric disorders. Although most of the 22q11.2DS patients have a 3.0-Mb deletion, existing mouse models only mimic a minor mutation of 22q11.2DS, a 1.5-Mb deletion. The role of the genes existing outside the 1.5-Mb deletion in psychiatric symptoms of 22q11.2DS is unclear. In this study, we generated a mouse model that reproduced the 3.0-Mb deletion of the 22q11.2DS (Del(3.0Mb)/+) using the CRISPR/Cas9 system. Ethological and physiological phenotypes of adult male mutants were comprehensively evaluated by visual-evoked potentials, circadian behavioral rhythm, and a series of behavioral tests, such as measurement of locomotor activity, prepulse inhibition, fear-conditioning memory, and visual discrimination learning. As a result, Del(3.0Mb)/+mice showed reduction of auditory prepulse inhibition and attenuated cue-dependent fear memory, which is consistent with the phenotypes of existing 22q11.2DS models. In addition, Del(3.0Mb)/+mice displayed an impaired early visual processing that is commonly seen in patients with schizophrenia. Meanwhile, unlike the existing models, Del(3.0Mb)/+mice exhibited hypoactivity over several behavioral tests, possibly reflecting the fatigability of 22q11.2DS patients. Lastly, Del(3.0Mb)/+mice displayed a faster adaptation to experimental jet lag as compared with wild-type mice. Our results support the validity of Del(3.0Mb)/+mice as a schizophrenia animal model and suggest that our mouse model is a useful resource to understand pathogenic mechanisms of schizophrenia and other psychiatric disorders associated with 22q11.2DS.