Fig. 3. Mash1 and Ngn1 do not contribute significantly to the loss of Th⁺ DA neurons in Ngn2 mutant mice. Mice double mutant for Ngn2 and Ngn1 do not show any further loss of Th⁺ cells at E14.5, compared with Ngn2 single mutants (A-C), indicating that only Ngn2 is required for the development of midbrain DA neurons. A severe reduction in the number of Th⁺ cells is detected at E11.5 in Mash1;Ngn2 double mutant mice (D-F), but the defect is not more severe than in Ngn2 single mutant mice (see Fig. 2). Consistently, no alteration in the number or distribution of Th⁺ cells is detected in Mash1 single mutant mice at E11.5 (G-I) or E14.5 (J-L). ^*P<0.01, as assessed by Student's t-test with Welch's correction (D) or one-way ANOVA, with Bonferroni's correction for multiple comparisons (G,J). n=3-6. Scale bar: 100 µm.