Fig. 2.

p57^Kip2 expression is down-regulated in the Nurr1 mutant midbrain. Coronal sections of wild-type (A, C, E, and G) and Nurr1-null mutant (B, D, F, and H) ventral midbrain at E13.5 showing in situ hybridization detecting p57^Kip2 (A and B), Nurr1 (C and D), TH (E and F), and En1 (G and H) mRNAs. In the Nurr1 mutant midbrain, expression of p57^Kip2 is exclusively down-regulated in the mantle zone (mz) but not in the Nurr1-negative ventricular zone (vz) (B). In the wild type, Nurr1, TH, and En1 are expressed in the mantle zone (C, E, and G). Nurr1 and TH were not detected in the Nurr1 mutant ventral midbrain (D and F), whereas expression of En1 remains expressed in Nurr1-deficient cells (H). (Scale bar, 100 μm.)