Representative coronal sections, stained for tyrosine hydroxylase (TH), are shown for wild type (left panel), Arx(GCG)7/Y (middle panel) and Arx−/Y (right panel) mice. The approximate boundaries of the A13 subnucleus of the zona incerta (ZI) are demarcated by dotted white lines. TH expression is apparent in this region for both wild type and Arx(GCG)7/Y, but is absent from Arx−/Y sections. Other areas of expected TH staining, such as the arcuate nucleus (*) and the retrochiasmatic projection fibers from the median forebrain bundle (arrow) maintained TH expression. Scale bar = 500 µm.