Representative coronal sections are shown from wild type (left panels), Arx(GCG)7/Y (middle panels), and Arx−/Y (right panels), that were probed with Six3 (top panels) or stained for Isl-1 (bottom panels). The approximate boundaries of the thalamic reticular nucleus (TRN), majority of the zona incerta (ZI) and the ZI’s A13 subnucleus (A13) are illustrated with dotted lines in all images. Staining is present for both markers within these regions in the wild type and Arx(GCG)7/Y sections, but is absent in the Arx−/Y sections. Scale bar = 500 µm.