LPS and stress, both related to MDD induce the expression of miR-34aMiR-34a targets synaptotagmin-1 and Bcl-2 associated with neuronal spine damageMiR-34a induce depressive-like behavior and impact in the serotoninergic activity in the raphe nuclei of mice Patients with MDD show a significant decrease in NOTCH signaling components, inversely related to miR-34b/c expression. This evidence concerns the gene SYT1 and major depressive disorder.