Another possible etiology of PD could be due to the loss of serum response factor (SRF), which leads to a decrease in the levels of antiapoptotic proteins, brain-derived neurotrophic factor (BDNF), and Bcl-2, all of which are considered to be a key cause of increased sensitivity to oxidative stress and dysfunction of the SRF-activating mitogen-associated kinase pathway [42]. This evidence concerns the gene BDNF and Parkinson disease.