Additionally, during the last decade, an increase in pERK in leucocytes from patients carrying the G2019S mutation [132], the presence of cytoplasmic granules of pERK in Lewy body aggregates in the substantia nigra of LRRK2 G2019S PD patients [130], and a G2019S-LRRK2-associated neurite retraction triggered by ERK-dependent mechanisms in a PD in vitro model have been described [155]. This evidence concerns the gene MAPK1 and Parkinson disease.