Fan et al. found that the exosomes secreted by microglia carrying mir-146a-5p are transported to the dentate gyrus, where they downregulates the expression of Krüppel-like factor 4 (KLF4) and cyclin-dependent kinase-like 5 (CDKL5), inhibits the proliferation and differentiation of neurons, and participates in the onset of depression [226]. The gene discussed is CDKL5; the disease is major depressive disorder.