SORT1 and major depressive disorder: Consequently, because sortilin is a crucial partner in the sorting of several factors and enzymes (Lefrancois et al., 2003; Kandror and Pilch, 2011), we analyzed in details the depression-related phenotype of mice in which the gene encoding sortilin (Sort1) has been inactivated, with a focus on the expression of its partner TREK-1 and the subsequent consequences on the TREK-1 function.