RECOVERY EFFECTS OF CLEMASTINE, A MYELINATION-PROMOTING AGENT, ON THE DEPRESSION-LIKE BEHAVIORS-INDUCED BY TENEURIN-4 KNOCK-DOWN OF THE HIPPOCAMPUS IN MICE
Authors: Suzuki *Seiryu , Asano Takashi , Sugimori Yuichiro , Izuo Naotaka , Muramatsu Shin-Ichi , Nitta Atsumi 
Published: February 2025

Abstract

Depression is a frequent and serious illness, and 30% of depressed patients are resistant to antidepressants1. Teneurin-4 (Tenm4) is a protein encoded by ODZ4, and Tenm4 has been shown to contribute to myelin formation by being involved in cell adhesion2,3. Our previous study has been reported that mice with hippocampal Tenm4 knockdown show depressive-like behaviors4. However, detailed mechanisms of induction of the depressive-like behavior are not clarified in the hippocampal Tenm4 knockdown mice. We aim to elucidate the mechanisms of induction of the depressive-like behavior in the hippocampal Tenm4 knockdown mice, and identify novel therapeutic targets for depression.We hypothesized that reduction of myelination in the hippocampus is resulted in the induction of depressive-behaviors in the Tenm4-knockdown mice. To examine whether the reduction of myelination is occurred in the hippocampus-specific Tenm4 knockdown mice we investigated the recovery effects of clemasitne, a myelination-promoting agents, against the deperessive-behaviors. 8-week-old male C57BL/6J mice were injected AAVgRNA vectors using the CRISPR-Cas9 system bilaterally into the mice hippocampus, were knockdown Tenm4 (Tenm4KD group). Mock vectors were injected (mock group) into the mice hippocampus as control group. Clemastine was identified by a functional screen of compounds that promote myelin sheath remodeling in mice with damaged myelin sheath5. Tenm4KD group and mock group were intraperitoneally injected clemastine in 10% DMSO as a solvent at a dosage of 10 mg/kg (clemastine group) or 10% DMSO (vehicle group) for 2 weeks. Four groups (Tenm4KD-clemasitine, Tenm4KD-vehicle, mock-clemastine, mock-vehicle) performed behavioral tests including sucrose preference test, tail suspension test and forced swim test. After their behavioral tests, brain sections were prepared, and immunofluorescence staining for myelin basic protein (MBP) expressed in the myelin sheath was performed. In the sucrose preference test, sucrose preference in the Tenm4KD-vehicle group was significantly reduced comparing with the mock-vehicle group, while the Tenm4KD-clemastine group significantly suppressed the reduction of the preference. In the tail suspension test, the immobility time of the Tenm4KD-vehicle group was significantly prolonged comparing with the mock-vehicle group, while the Tenm4KD-clemastine group significantly suppressed the prolonged time. In the forced swimming test, the immobility time of the Tenm4KD-vehicle group was significantly prolonged comparing with the mock-vehicle group, while the Tenm4KD-clemastine group was tended to suppress the prolonged time.
Immunohistochemical staining of hippocampal sections showed that MBP in the Tenm4KD-vehicle group was significantly reduced comparing with that of the mock-vehicle group, while the decrease was significantly suppressed in the Tenm4KD-clemastine group. In conclusion, the depressive-like behavior in mice with hippocampus-specific Tenm4 knockdown was suppressed by clemastine, a myelination- promoting agent. Myelination was decreased by hippocampus specific Tenm4 knockdown and increased by clemastine administration. These findings suggest that hippocampus Tenm4 is involved in depressive-like behavior via its function to promote myelination. These results of this study may provide insight into the development of new treatments for depression.

References
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