Figure 1.

Molecular Heterogeneity of Neurons in the Adult GPe

Immunofluorescence identification of arkypallidal neurons (A)–(C) and prototypic neurons (D)–(F).

(A) The pan-neuronal marker HuCD was used to label all GPe neurons. Preproenkephalin (PPE)-expressing GPe neurons (arrow) also express FoxP2, but not parvalbumin (PV).

(B) Mean expression profiles for PPE, FoxP2, and PV. Filled circles in this and subsequent profiles represent counts from individual animals.

(C) Proportions of GPe neurons (i.e., all HuCD+ neurons) expressing different molecular markers. In this and subsequent pie charts, outer segments represent expression overlap of inner populations with another marker (e.g., all PPE+ neurons also expressed FoxP2, and vice versa), and only populations comprising ≥ 1% of GPe neurons are included. One-fifth of GPe neurons co-express PPE and FoxP2, while another quarter of GPe neurons (“HuCD only”) do not express PPE, FoxP2, or PV.

(D) Nkx2-1+ GPe neurons are numerous; some lack PV (arrows). FoxP2+ neurons (arrowheads) do not express Nkx2-1.

(E) Expression profiles for Nkx2-1, FoxP2, and PV.

(F) Most Nkx2-1+ neurons co-express PV. A minority of HuCD+ neurons express PV, but not any other tested marker (“PV only”).

(G) Representative example (single animal) of locations of neurons expressing different molecular markers at three rostro-caudal levels of GPe. Color code as in (F). For clarity, prototypic neurons (Nkx2-1+/PV+ and Nkx2-1+/PV−, left) are separated from arkypallidal (FoxP2+) and other GPe neurons (right). D, dorsal; L, lateral.

Scale bars in (A) and (D), 20 μm; (G), 200 μm.