Fig. 3. Cellular specificity of neocortical human and chimpanzee-specific differential expression.

(A–B) Radar plots depicting neocortical neuron cell-type enrichments of (A) human- or (B) chimpanzee-specific differences of genes associated with (i) neuropsychiatric disorders, (ii) neurotransmitter biosynthesis, degradation, and transport proteins, and (iii) encoding ion channels (table S10). Only genes expressed in the respective cell type are plotted. The distance of each gene from the center represents differential expression between human and the average of chimpanzee and macaque (red) or between chimpanzee and the other two species (blue). The direction of triangles denotes up- or downregulation; filled triangles represent cell-type specific expression (Pearson correlations > 0.5). (C) In situ hybridization shows that PKD2L1 is expressed in pyramid-shaped cell bodies of excitatory projection neurons of human, but not chimpanzee or macaque, neocortex. (D) TH-immunopositive interneurons (filled arrowheads) are present in neocortex of human and macaque, but not chimpanzee, where only TH+ midbrain dopaminergic axons (open arrowheads) are present. Scale bar represents 30 µm.