Sncg, Mybpc1, and Parm1 Classify subpopulations of VIP-expressing interneurons in layers 2/3 of the somatosensory cortex

Neocortical vasoactive intestinal polypeptide-expressing (VIP+) interneurons display highly diverse morpho-electrophysiological and molecular properties. To begin to understand the function of VIP+ interneurons in cortical circuits, they must be clearly and comprehensively classified into distinct subpopulations based on specific molecular markers. Here, we utilized patch-clamp RT-PCR (Patch-PCR) to simultaneously obtain the morpho-electric properties and mRNA profiles of 155 VIP+ interneurons in layers 2 and 3 (L2/3) of the mouse somatosensory cortex. Using an unsupervised clustering method, we identified 3 electrophysiological types (E-types) and 2 morphological types (M-types) of VIP+ interneurons. Joint clustering based on the combined electrophysiological and morphological features resulted in 3 morpho-electric types (ME-types). More importantly, we found these 3 ME-types expressed distinct marker genes: similar to 94% of Sncg(+) cells were ME-type 1, 100% of Mybpc1(+) cells were ME-type 2, and similar to 78% of Parm1(+) were ME-type 3. By clarifying the properties of subpopulations of cortical L2/3 VIP+ interneurons, this study establishes a basis for future investigations aiming to elucidate their physiological roles.

Automated summary

In this study, the morpho-electric properties and mRNA profiles of VIP+ interneurons in the mouse somatosensory cortex were comprehensively classified, and 3 electrophysiological types and 2 morphological types were identified. Through joint clustering, 3 morpho-electric types were determined, and distinct marker genes were found to be expressed in each type. This study establishes a basis for future investigations aiming to elucidate the physiological roles of VIP+ interneurons.