Ndufs4 inactivation does not cause dopamine neuron death. (A) Representative photomicrographs of TH immunostaining of SNpc from 5-wk-old Ndufs4^+/+ and Ndufs4^−/− mice. Bar, 500 µm. (B) Deletion of the Ndufs4 gene does not decrease the total number of TH⁺ neurons in the SNpc of 5-wk-old mice (n = 5 per group). (C) Inactivation of the Ndufs4 gene in culture does not induce dopamine neuron death. E14 mesencephalic neurons were cultured from C57BL/6 or Ndufs4^lox/lox mouse embryos. AAV1 viruses expressing Cre-GFP were added to the culture on DIV 4 to delete the Ndufs4 gene in Ndufs4^lox/lox cells. The number of TH⁺ neurons was quantified 5 d after viral infection. Data are means ± SEM. n = 3.