Nurr1 (NR4A2) belongs to the nuclear receptor (NR)4 family of orphan nuclear receptors and is known to function as a constitutively active transcription factor by binding to target genes as a monomer, homodimer or heterodimer with retinoid X receptors (RXRs) (Aarnisalo et al., 2002; Maira et al., 1999; Wang et al., 2003). Deletion of the Nurr1 gene in mice results in a severe reduction in dopaminergic neurons and perinatal lethality (Zetterstrom et al., 1997), consistent with an essential role for Nurr1 in the development and/or maintenance of dopaminergic neurons. Human mutations resulting in reduced expression of Nurr1 are associated with late-onset familial PD (Le et al., 2003), indicating that Nurr1 may play a protective role.
