HTRA2 and Parkinson disease: For PD, the six top-ranked genes, ATP13A2 (position 1), LRRK2 (position 2), PINK1 (position 3), PARK2 also known as PRKN (position 4), PARK7also known as DJ1 (position 5), and SNCA (position 6) are all recognized disease genes, whereas additional genes linked to PD, UCHL1 and HTRA2, were ranked in positions 10 and 138, respectively [21].