Hitoshi Miyachi

Summary: Reduced BDNF and GABAergic inhibition co-occur in neuropsychiatric diseases, including major depression. Genetic rodent studies show a causal link, suggesting the presence of biological pathways that mediate this co-occurrence. Here we show that mice with reduced Bdnf ( Bdnf ^+/- ) have upregulated expression of sequestosome-1/p62, an autophagy-associated stress response protein, and reduced surface presentation of α5 subunit-containing GABA _A receptor (α5-GABA _A R) in prefrontal cortex (PFC) pyramidal neurons. Reducing p62 gene dosage restored α5-GABA _A R surface expression and rescued the PFC-relevant behavioral deficits of Bdnf ^+/- mice, including cognitive inflexibility and sensorimotor gating deficits. Increasing p62 levels was sufficient to recreate the molecular and behavioral profiles of Bdnf ^+/- mice. Finally, human postmortem corticolimbic transcriptome analysis suggested reduced autophagic activity in depression. Collectively, the data reveal that autophagy regulation through control of p62 dosage may serve as a mechanism linking reduced BDNF signaling, GABAergic deficits, and psychopathology associated with PFC functional deficits across psychiatric disorders. HIGHLIGHTS: BDNF constitutively promotes autophagy in cortical pyramidal neurons Reduced BDNF causes elevated autophagy-regulator p62 expression, leading to lower surface α5-GABA _A R presentation Increasing p62 levels mimics cognition-related behavioral deficits in Bdnf ^+/- mice Altered postmortem corticolimbic gene expression suggests reduced autophagic activity in depression

Understanding the mechanisms of cellular differentiation is challenging because differentiation is initiated by signaling pathways that drive temporally dynamic processes, which are difficult to analyse in vivo. We establish a new Tool, Timer-of-cell-kinetics-and-activity (Tocky [toki], time in Japanese). Tocky uses the Fluorescent Timer protein, which spontaneously shifts its emission spectrum from blue-to-red, in combination with computer algorithms to reveal the dynamics of differentiation in vivo. Using a transcriptional target of T cell receptor (TCR)-signaling, we establish Nr4a3-Tocky to follow downstream effects of TCR signaling. Nr4a3-Tocky reveals the temporal sequence of events during regulatory T cell (Treg) differentiation and shows that persistent TCR signals occur during Treg generation. Remarkably, antigen-specific T cells at the site of autoimmune inflammation also show persistent TCR signaling. In addition, by generating Foxp3-Tocky, we reveal the in vivo dynamics of demethylation of the Foxp3 gene. Thus, Tocky is a Tool for cell biologists to address previously inaccessible questions by directly revealing dynamic processes in vivo. Summary: The authors establish a new Tool, Timer-of-cell-kinetics-and-activity (Tocky) revealing the temporal dynamics of cellular activation and differentiation in vivo. The tool analyses the temporal sequence of molecular processes during cellular differentiation and identifies cells that receive persistent signals in vivo.