Our overall strategy is to compare high resolution transcription profiles of a set of well characterized GABAergic neurons defined by their anatomical, physiological and developmental attributes. We developed combinatorial recombinase driver lines to capture 6 GABAergic subpopulations (He et al., 2016) (Figure 1A–B; see Methods): 1) The Nkx2.1-CreER driver allows lineage and birth timing based targeting of chandelier cells (CHC) that target the axon initial segment (AIS) of pyramidal neurons (Taniguchi et al., 2013), 2) the PV-Cre driver labels fast-spiking basket cells (PVBC) that innervate the perisomatic region (Hu et al., 2014), 3) the SST-Flp;NOS1-CreER drivers target a unique type of long-projecting GABAergic cells (LPC) (Kilduff et al., 2011), 4) the SST-Flp;CR-Cre drivers include Martinotti cells (MNC) that target distal dendrites (Silberberg and Markram, 2007) and likely another cell type, 5) the VIP-Flp;CR-Cre drivers include interneuron-selective cells (ISC) (Staiger et al., 2004) and likely other types, 6) the VIP-Flp;CCK-Cre drivers include CCK basket cells (CCKC) (Armstrong and Soltesz, 2012) and likely other types. Accumulated anatomical, physiological, and molecular evidence indicate that these are non-overlapping subpopulations, and CHC, LPC and PVBC are considered cardinal types (He et al., 2016). We define these 6 populations as Phenotype Characterized Populations, or PCPs.
