TPPP and major depressive disorder: Three genes emerged as predictors of depression in combination with ELA: DNA-Binding Protein Inhibitor ID–3 (ID3); and Tubulin Polymerization Promoting Protein (TPPP) (Weder et al., 2014); and the neurotransmitter gene glutamate receptor, ionotropic N-methyl-D-aspartate 1 (GRIN1) (Weder et al., 2014).