α-Synuclein, which is an important marker present in the brains of PD patients, is believed to activate the ERK pathway among others in microglial cells (Su et al. 2008), and this causes the release of tumor-necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β), bringing about an inflammation in the region, which might in turn be responsible for the neurodegeneration observed. The gene discussed is MAPK1; the disease is Parkinson disease.