Subclasses of subthalamic nucleus neurons require Pitx2 for normal migration. Sections of E14.5 Pitx2cre/+; N-lacZ (A–D, I–L, Q–T) and Pitx2cre/null; N-lacZ (E–H, M–P, U–X) embryos in the coronal (A–H) or transverse plane (I–X) at the level of the subthalamic nucleus were double labeled with anti-β-galactosidase and anti-LMX1B, anti-FOXP1, or anti-FOXP2. Merged images are in C, G, K, O, S, and W, with enlarged subthalamic nucleus regions shown in D, H, L, P, T, and X. Hatched ovals show the lateral hypothalamic region where the subthalamic nucleus normally resides. Loss of β-galactosidase (E, M, and U), and LMX1B (F) in the lateral hypothalamus of Pitx2cre/null; N-lacZ mutants is consistent with absence of these subthalamic nucleus neurons. In contrast, some FOXP1+/β-gal-negative and FOXP2+/β-gal-negative cells remain in the lateral Pitx2cre/null; N-lacZ hypothalamus (P and X), suggesting that these cells escape the migration defect. Some medially located neurons co-expressβ-galactosidase and LMX1B, FOXP1, or FOXP2, indicating that Pitx2 is not globally required for expression of these genes. Scale bars = 100μm (A–C, E–G, I–K, M–O, Q–R, and U–W) or 50 μm (D, H, L, P, T, and X).