In vitro, the exposure of the dopaminergic neurons to the TNFα (tumor necrosis factor alpha) or parkinsonian neurotoxin 1-methyl-4-phenylpyridinium (MPP+), important contributors to the pathogenesis of PD, increased the expression of both PROK2 mRNA and secreted protein in the early stage of neuronal death (Gordon et al., 2016). This evidence concerns the gene PROK2 and Parkinson disease.