Aberrant outputs of glutamatergic neurons in deep cerebellar nuclei mediate dystonic movements

While the deep cerebellar nuclei (DCN) are known to be involved in movement disorders, the specific contributions of distinct neuronal populations within the DCN—glutamatergic, glycinergic, and GABAergic—to the generation of dystonic movements have remained unclear. This study aimed to identify which of these populations drives dystonia in a mouse model of paroxysmal kinesigenic dyskinesia (Prrt2-mutant mice) and a kainic acid-induced dystonia model.

Using a combination of fiber photometry, optogenetic manipulation, and cell-type-specific ablation, the researchers monitored and manipulated DCN neurons in awake, behaving mice. They specifically targeted glutamatergic, glycinergic, and GABAergic inferior olive-projecting neurons to determine their causal role in dystonic episodes. By using Cre-dependent viral strategies, they were able to selectively ablate these populations to observe the impact on dystonia severity and frequency.

The researchers found that all three DCN neuronal populations exhibit sustained calcium activity elevation during dystonic episodes in Prrt2-mutant mice. However, optogenetic activation experiments revealed that only the glutamatergic DCN neurons are sufficient to trigger dystonia-like behaviors in wild-type mice. Crucially, selective ablation of these glutamatergic neurons significantly reduced the severity and duration of dystonia in both the Prrt2-mutant and kainic acid-induced models. The study further suggests that this aberrant glutamatergic activity is likely caused by the disinhibition of DCN neurons following the suppression of Purkinje cell inhibitory output during cerebellar spreading depolarization.

These findings identify DCN glutamatergic neurons as a central, common node in the pathophysiology of cerebellar-originated dystonia. By pinpointing this specific population, the research provides a clear target for future therapeutic interventions, such as localized neuromodulation or targeted pharmacological strategies, to treat dystonia across different etiologies.