THE EFFECT OF α6 SUBUNIT-CONTAINING GABAA RECEPTOR POSITIVE ALLOSTERIC MODULATORS ON STRIATAL SLITRK1-KNOCKDOWN MICE, A NOVEL ANIMAL MODEL FOR TOURETTE SYNDROME

Abstract Background The SLIT and NTRK-like 1 (SLITRK1) gene 1 is one risk gene of Tourette syndrome (TS), a neurodevelopmental tic disorder. Slitrk1 protein is involved in neurite outgrowth and synapse formation in striatum 2. Developmentally regulated expression of striatal Slitrk1 In mammals 3 and striatal cholinergic interneurons (ChIs) loss in adult TS patients 4 have been reported. Hence, a novel mice model has been developed based on the correlation of Slitrk1 knockdown (Slitrk1-KD )and dysfunction of striatal ChIs 5. The alpha-6GABAA receptors (alpha-6GABAARs) are densely expressed in granule cells of cerebellum, which is also a novel therapeutic target for TS. Aims & Objectives We aimed to investigate the role of Slitrk1 in the pathogenesis of TS and the therapeutic potential of pyrazoloquinolinones (PQs) Compound 6, as alpha-6GABAAR positive allosteric modulators (PAM) 6,on the Slitrk1-KD TS mice model. Methods Slitrk1 or scrambled siRNA was bilaterally injected into the dorsal striatum of adult C57Bl/ 6J male mice, creating Slitrk1-KD and control mice, respectively. Their stereotypic tic behaviors, prepulse inhibition (PPI), and sensorymotor function were compared. We also investigated dopamine(DA) and acetylcholine (AC) levels in microdialysates, Slitrk1 protein and dopamine transporter (DAT) levels, numbers of Slitrk1-positive ChIs in the striatum, as well as electrophysiological properties between Slitrk1-positive and Slitrk1-negative striatal ChIs. We further applied PQs Compound 6 on this model to observe its therapeutic effect. Results As compared with the control group, Slitrk1-KD mice show significantly more stereotypic tic behaviors and sensori-motor dysfunction. These TS-associated behaviors are correlated with fewer Slitrk1-containing ChIs in Slitrk1-KD mice. Slitrk1-KD mice have lower evoked DA and AC levels, higher tonic DA levels, and down-regulated DAT in the striatum. Injection (i.p) of PQs Compound 6 could suppress the stereotypy behaviors in Slitrk1-KD mice as well. Discussion & Conclusion Our study revealed that reducing striatal Sltirk1 expression induces stereotypic tic behaviors and alters endophenotypes in mice, indicating that Slitrk1-KD mice may serve as a novel animal model of TS, and whose tic behaviors can be rescued by PQs Compound 6 as well. References 1.Abelson, J.F., et al., Sequence variants in SLITRK1 are associated with Tourette's syndrome. Science, 2005. 310(5746): p. 317-20. 2.Kajiwara, Y., J.D. Buxbaum, and D.E. Grice, SLITRK1 binds 14-3-3 and regulates neurite outgrowth in a phosphorylation-dependent manner. Biol Psychiatry, 2009. 66(10): p. 918-25. 3.Stillman, A.A., et al., Developmentally regulated and evolutionarily conserved expression of SLITRK1 in brain circuits implicated in Tourette syndrome. J Comp Neurol, 2009. 513(1): p. 21-37. 4.Kataoka, Y., et al., Decreased number of parvalbumin and cholinergic interneurons in the striatum of individuals with Tourette syndrome. J Comp Neurol, 2010. 518(3): p. 277-91. 5.Du, J.C., et al., Pivotal Role of Slitrk1 in Adult Striatal Cholinergic Neurons in Mice: Implication in Tourette Syndrome. Ann Neurol, 2023. 6.Knutson, D.E., et al., Design and Synthesis of Novel Deuterated Ligands Functionally Selective for the gamma-Aminobutyric Acid Type A Receptor (GABA(A)R) alpha6 Subtype with Improved Metabolic Stability and Enhanced Bioavailability. J Med Chem, 2018. 61(6): p. 2422-2446.