The phylogenetic relationship between humans and nonhuman primates (NHPs) makes NHPs a crucial neuroscientific model. Here, single nucleus RNA-sequencing (snRNA-Seq) revealed at least nine distinct Medium Spiny Neuron (MSN) and MSN-like subtypes in the NHP striatum (Figure 2). The borders between subtype pairs were characterized by discontinuities in gene expression, though we also found continuous axes of variation (Figure 3). We identified five distinct MSN subtypes in the dorsal striatum (DS), including D1- and D2-MSN subtypes specific to the striosome and matrix compartments, as well as a hybrid cell type that contained mRNA for both D1 and D2 receptors (Figure 4). The ventral striatum (VS) contained at least four distinct subtypes, including D1- and D2-MSN subtypes located specifically in the Nucleus Accumbens (NAc) shell and Olfactory Tubercule (OT) regions (Figure 5), and two subtypes associated with the “interface islands” – dense cellular islands located within and near the ventral border of the striatum. Marker genes for one of these VS cluster subtype were highly enriched in the Islands of Calleja (ICjs). Cells from the other VS cluster subtype were restricted
