Fig. 2.

Cell loss by apoptosis and no change in neurotransmitter phenotype. (A, B, and C) Coronal section at level of SN of P20 En^HT mouse stained against TH (green), activated caspase-3 (red), and DAPI (blue). The nigral DA neuron shows signs of apoptosis, a small rounded cell body, activated caspase-3, and a pyknotic nucleus (arrows). (D–H) Immunostaining against aromatic amino acid decarboxylase (Aadc) (D), Pbx1 (E), the En1-reporter β-Gal (G), and glutamate decarboxylase (Gad; H), and in situ hybridization against Ret (F), all on adult coronal brain sections of En2−/− (D–F, H), En1+/tLZ;En2−/− (En^HT) (D′–H′) and En1+/tLZ mice (G). Aadc, Pbx1, Ret, and β-Gal expression reveal all loss of nigral DA neurons in En^HT mice, whereas the Gad staining is the same in both genotypes (H). [Scale bars (A–C): 20 μm; (D–H): 500 μm.]