The increased anxiety in FTO–/– mice could be caused by the restricted neuronal differentiation in the hippocampus induced by reduced level of MMP-9 (Spychala and Ruther, 2019), and the mBDNF level is reduced by loss of FTO in the hippocampus, but the mechanism by which FTO regulates the amount of MMP-9 cannot be clearly determined. The gene discussed is MMP9; the disease is Anxiety.