Optogenetic activation of VIP-INs restores cortical activity and ameliorates motor deficits in Huntington's disease mice

Huntington's disease (HD) is a devastating, monogenic neurodegenerative movement disorder with no cure. While the genetic basis is clear, the complex downstream effects leading to behavioral symptoms, particularly cortical dysfunction, are poorly understood. Current treatments primarily manage symptoms, failing to address the progressive neuronal loss and synaptic dysfunction. This study investigates the roles of specific cortical inhibitory neuron (IN) subtypes, like vasoactive intestinal peptide (VIP)-INs, and excitatory corticostriatal (CStr) projection neurons in HD symptoms, aiming to identify novel therapeutic targets beyond symptomatic relief.

Researchers used longitudinal in vivo two-photon calcium imaging to monitor the activity of three cortical inhibitory neuron subtypes and excitatory CStr projection neurons in the motor cortex of transgenic R6/2 HD mouse model and knock-in zQ175DN HD mouse model throughout disease progression. To test therapeutic potential, they employed optogenetic activation of VIP-INs in R6/2 mice. The primary endpoints included assessing neuron subtype-specific activity abnormalities, restoration of healthy neuronal activity post-stimulation, and amelioration of motor deficits, with behavioral improvements tracked for duration.

Motor deficits in R6/2 mice were accompanied by neuron subtype-specific abnormalities in movement-related activity. A marked hypoactivity of vasoactive intestinal peptide (VIP)-INs and CStr neurons was observed, a finding consistent across both the R6/2 and zQ175DN HD mouse models. This suggests a conserved cortical dysfunction mechanism. Optogenetic activation of VIP-INs in R6/2 mice successfully restored healthy levels of activity in these specific interneurons and their downstream CStr neurons. This intervention directly addressed the identified hypoactivity, indicating a functional rescue. Importantly, this neuronal restoration translated into significant behavioral improvements.

Optogenetic activation of VIP-INs ameliorated motor deficits in R6/2 mice, with behavioral improvements persisting for days after stimulation.