Projection-Specific Intersectional Optogenetics for Precise Excitation and Inhibition in the Marmoset Brain
Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
The primate cerebral cortex relies on long-range connections to integrate information between functionally specialized areas. Investigating these processes requires tools that can selectively modulate specific projection pathways. While cell-class-specific optogenetics can modulate local circuits, these approaches often lack pathway specificity. Projection-specific optogenetics offers greater precision, especially in primates, where cortical areas are spatially and functionally well-separated. To address challenges in translating this approach from rodents to primates, we developed a mouse-to-marmoset pipeline. We first validated that optogenetic targeting of inhibitory neurons (AAV9-Dlx-ChR2) effectively silenced local cortical areas in marmosets. We then tested selective excitation and inhibition of defined projection pathways. By intersecting retrogradely delivered Cre-recombinase (AAVretro-Cre) with locally injected Cre-dependent opsins (AAV8-FLEx-ChR2 or Jaws), we achieved efficient, direction-specific labeling of both callosal and longitudinal projections. This intersectional strategy enabled precise excitatory and inhibitory control of cortical activity using distinct light wavelengths, advancing projection-specific optogenetics for investigating primate brain circuit function.
Graphical Abstract
A: Local suppression of cortical activity that is non-selective across cell classes can be accomplished by excitation of inhibitory interneurons expressing mDlx-ChR2 yielding broad inhibition. B: By contrast, targeting a specific cortico-cortical projection pathway for suppression can be accomplished through an intersectional approach. For a successful intersection, a retrograde AAV carrying hSyn-Cre is injected at the projection terminal and a locally expressing AAV carrying CAG-FLEx-opsin is injected at the soma. These viruses meet at the nucleus and yield opsin expression restricted to projection neurons. C: Inhibition or excitation is possible in targeted projection neurons due to co-expression of the blue light triggered excitatory opsin ChR2 or the red shifted inhibitory opsin Jaws.
