NURR1 regulates TOP IIβ expression in vivo. Both of the proteins located in the nucleus. In newborn WT mice, immunofluorescent analysis showed the co-expression of these two genes in VM area as arrows show (a-c). The expression of TOP IIβ in the VM is reduced and limited to medial area in coronal brain sections of Nurr1 deficient mice (d-f). Arrowheads showed the ventral terminal of the third ventricle (3V). Scale bar = 100 μm.