Figure 2.

Pitx2^cre/null; N-lacZ mutants exhibit defects in hypothalamic neuronal location. Littermate embryos of genotype Pitx2^cre/+; N-lacZ or Pitx2^cre/null; N-lacZ were fixed, stained for β-galactosidase activity, and vibratome sectioned at 100 μm in the plane of section indicated in A (for C–H) and 150 μm in the plane of section shown in B (for I–P). Anterior is up for each section. Hatched areas depict the lateral hypothalamus where subthalamic nucleus neurons are located. Serial adjacent sections of caudal to rostral hypothalamus from E14.5 embryos (C–H) reveal absence of β-galactosidase positive cells in the lateral hypothalamus of Pitx2^cre/null; N-lacZ mutants and a medial abundance of β-galactosidase positive cells. Pitx2^cre/null mutants also exhibit increased β-galactosidase expression at the ventral midline (brackets), suggesting a failure of these cells to respect the midline boundary. Serial sections from E13.5 embryos (I, J, M, N) also exhibit medially shifted β-galactosidase positive cells in Pitx2^cre/null; N-lacZ embryos, whereas locations of β-galactosidase expressing cells are similar in E12.5 Pitx2^cre/+; N-lacZ (K, L) and Pitx2^cre/null; N-lacZ (O, P) mutants. Abbreviations: latV, lateral ventricle; STN, subthalamic nucleus; IIIv, third ventricle; Aq, cerebral aqueduct; pit, pituitary.