Targeting barrel field spiny stellate cells using a vesicular monoaminergic transporter 2-Cre mouse line

Abstract

AbstractRodent primary somatosensory cortex (S1) is organized in defined layers, where layer IV serves as the main target for thalamocortical projections. Serotoninergic signaling is important for the organization of thalamocortical projections and consequently proper barrel field development in rodents, and the vesicular monoamine transporter 2 (VMAT2) can be detected locally in layer IV S1 cortical neurons in mice as old as P10, but the identity of the Vmat2-expressing neurons is unknown. We here show thatVmat2mRNA and also Vmat2-Cre recombinase are still expressed in adult mice in a sub-population of the S1 cortical neurons in the barrel field. The Vmat2-Cre cells showed a homogenous intrinsically bursting firing pattern determined by whole-cell patch-clamp, localized radial densely spinous basal dendritic trees and almost exclusively lack of apical dendrite, indicative of layer IV spiny stellate cells. Single cell mRNA sequencing analysis showed that S1 cortical Vmat2-Cre;tdTomatocells express the layer IV markerRorband mainly cluster with layer IV neurons, and RNAscope analysis revealed that adult Vmat2-Cre neurons expressVmat2and vesicular glutamate transporter 1 (Vglut1) andVglut2mRNA to a high extent. In conclusion, our analysis shows that corticalVmat2expression is mainly confined to layer IV neurons with morphological, electrophysiological and transcriptional characteristics indicative of spiny stellate cells.