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). The gene discussed is TNF; the disease is Parkinson disease.