CBLN2 promoter enables genetic access to wide-field neurons of the tree shrew superior colliculus.

Wide-field (WF) neurons of the tectopulvinar pathway integrate retinal and cortical inputs via large dendritic arbors crucial for rapid visual motion detection. Previous studies identified potential marker genes for mouse WF neurons. Here, we validate CBLN2 as a molecular marker of the tree shrew WF neurons and construct AAVs that exploit CBLN2 promoter to selectively target WF neurons across species. Using intersectional genetics in the tree shrew, we show that WF neuron dendrites receive a distinct pattern of VGluT1+ and VGluT2+ inputs based on their distance from the cell body in the dorsoventral axis of the superior colliculus (SC). This represents the first example of a viral tool derived from the tree shrew genome for cell-type-specific targeting across species. Our results provide a foundation for studying SC circuitry in higher-order mammals and for extending this approach to additional conserved cell types in the SC and other brain regions.