In support of a similar function in humans, the expression of BMP2 showed the highest correlation with five mDA-specific marker genes in the human SNc and BMP2 transcript levels were downregulated in late-stage PD (Goulding et al., 2019), whereas the protein levels of the inhibitory SMAD6 appeared to be upregulated in the SNc of PD patients (Vitic et al., 2021). Here, BMP2 is linked to Parkinson disease.