NR4A2 and Parkinson disease: Two retinoid X receptor agonists, bexarotine and IRX4204, with specificity for activating RXR-Nurr1 heterodimers, have also shown efficacy for protection from the pathology associated with Parkinson’s and Alzheimer’s disease models (McFarland et al., 2013; Wang et al., 2016; Spathis et al., 2017).