Expression of mutant DISC1 in Purkinje cells increases their spontaneous activity and impairs cognitive and social behaviors in mice

- Expression of mutant DISC1 in Purkinje cells (PCs) of the cerebellum impaired novel place and social recognition memory.
- Expression of mutant DISC1 decreased the number of PCs with large body size but did not affect the total number or dendrite arborization of PCs at P21.
- Expression of mutant DISC1 increased spontaneous activity, the amplitude and frequency of mEPSCs in PCs at P21.
- DISC1 may be involved in physiology of PCs to contribute to cognitive and social behaviors.

In addition to motor function, the cerebellum has been implicated in cognitive and social behaviors. Various structural and functional abnormalities of Purkinje cells (PCs) have been observed in schizophrenia and autism. As PCs express the gene Disrupted-In-Schizophrenia-1 (DISC1), and DISC1 variants have been associated with neurodevelopmental disorders, we evaluated the role of DISC1 in cerebellar physiology and associated behaviors using a mouse model of inducible and selective expression of a dominant-negative, C-terminus truncated human DISC1 (mutant DISC1) in PCs. Mutant DISC1 male mice demonstrated impaired social and novel placement recognition. No group differences were found in novelty-induced hyperactivity, elevated plus maze test, spontaneous alternation, spatial recognition in Y maze, sociability or accelerated rotarod. Expression of mutant DISC1 was associated with a decreased number of large somata PCs (volume: 3000-5000 μm3) and an increased number of smaller somata PCs (volume: 750-1000 μm3) without affecting the total number of PCs or the volume of the cerebellum. Compared to control mice, attached loose patch recordings of PCs in mutant DISC1 mice revealed increased spontaneous firing of PCs; and whole cell recordings showed increased amplitude and frequency of mEPSCs without significant changes in either Rinput or parallel fiber EPSC paired-pulse ratio. Our findings indicate that mutant DISC1 alters the physiology of PCs, possibly leading to abnormal recognition memory in mice.