Pivotal Role of Slitrk1 in Adult Striatal Cholinergic Neurons in Mice: Implication in Tourette Syndrome

OBJECTIVE: The SLIT and NTRK-like 1 (SLITRK1) gene mutation and striatal cholinergic interneurons (ChIs) loss are associated with Tourette syndrome (TS). ChIs comprise only 1 to 2% of striatal neurons but project widely throughout the stratum to impact various striatal neurotransmission, including TS-related dopaminergic transmission. Here, we link striatal Slitrk1, ChI function, and dopaminergic transmission and their associations with TS-like tic behaviors.

METHODS: Slitrk1-KD mice were induced by bilaterally injecting Slitrk1 siRNA into their dorsal striatum. Control mice received scrambled siRNA injection. Their TS-like tic behaviors, prepulse inhibition, sensory-motor function and dopamine-related behaviors were compared. We also compared dopamine and ACh levels in microdialysates, Slitrk protein and dopamine transporter levels, and numbers of Slitrk-positive ChIs and activated ChIs in the striatum between two mouse groups, and electrophysiological properties between Slitrk-positive and Slitrk-negative striatal ChIs.

RESULTS: Slitrk1-KD mice exhibit TS-like haloperidol-sensitive stereotypic tic behaviors, impaired prepulse inhibition, and delayed sensorimotor response compared with the control group. These TS-like characteristics correlate with lower striatal Slitrk1 protein levels, fewer Slitrk1-containing ChIs, and fewer activated ChIs in Slitrk1-KD mice. Based on their electrophysiological properties, Slitrk1-negative ChIs are less excitable than Slitrk1-positive ChIs. Slitrk1-KD mice have lower evoked acetylcholine and dopamine levels, higher tonic dopamine levels, and downregulated dopamine transporters in the striatum, increased apomorphine-induced climbing behaviors, and impaired methamphetamine-induced hyperlocomotion compared with controls.

INTERPRETATION: Slitrk1 is pivotal in maintaining striatal ChIs activity and subsequent dopaminergic transmission for normal motor functioning. Furthermore, conditional striatal Slitrk1-KD mice may serve as a translational modality with aspects of TS phenomenology. ANN NEUROL 2023.