The HDAC inhibitor SAHA improves depressive-like behavior of CRTC1-deficient mice: Possible relevance for treatment-resistant depression.

Major depression is a highly complex disabling psychiatric disorder affecting millions of people worldwide. Despite the availability of several classes of antidepressants, a substantial percentage of patients are unresponsive to these medications. A better understanding of the neurobiology of depression and the mechanisms underlying antidepressant response is thus critically needed. We previously reported that mice lacking CREB-regulated transcription coactivator 1 (CRTC1) exhibit a depressive-like phenotype and a blunted antidepressant response to the selective serotonin reuptake inhibitor fluoxetine. In this study, we similarly show that Crtc1(-/-) mice are resistant to the antidepressant effect of chronic desipramine in a behavioral despair paradigm. Supporting the blunted response to this tricyclic antidepressant, we found that desipramine does not significantly increase the expression of Bdnf and Nr4a1-3 in the hippocampus and prefrontal cortex of Crtc1(-/-) mice. Epigenetic regulation of neuroplasticity gene expression has been associated with depression and antidepressant response, and histone deacetylase (HDAC) inhibitors have been shown to have antidepressant-like properties. Here, we show that unlike conventional antidepressants, chronic systemic administration of the HDAC inhibitor SAHA partially rescues the depressive-like behavior of Crtc1(-/-) mice. This behavioral effect is accompanied by an increased expression of Bdnf, but not Nr4a1-3, in the prefrontal cortex of these mice, suggesting that this epigenetic intervention restores the expression of a subset of genes by acting downstream of CRTC1. These findings suggest that CRTC1 alterations may be associated with treatment-resistant depression, and support the interesting possibility that targeting HDACs may be a useful therapeutic strategy in antidepressant development.

Deletion of CREB-regulated transcription coactivator 1 induces pathological aggression, depression-related behaviors, and neuroplasticity genes dysregulation in mice.

BACKGROUND: Mood disorders are polygenic disorders in which the alteration of several susceptibility genes results in dysfunctional mood regulation. However, the molecular mechanisms underlying their transcriptional dysregulation are still unclear. The transcription factor cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) and the neurotrophin brain-derived neurotrophic factor (BDNF) have been implicated in rodent models of depression. We previously provided evidence that Bdnf expression critically rely on a potent CREB coactivator called CREB-regulated transcription coactivator 1 (CRTC1). METHODS: To further evaluate the role of CRTC1 in the brain, we generated a knockout mouse line and analyzed its behavioral and molecular phenotype. RESULTS: We found that mice lacking CRTC1 associate neurobehavioral endophenotypes related to mood disorders. Crtc1(-/-) mice exhibit impulsive aggressiveness, social withdrawal, and decreased sexual motivation, together with increased behavioral despair, anhedonia, and anxiety-related behavior in the novelty-induced hypophagia test. They also present psychomotor retardation as well as increased emotional response to stressful events. Crtc1(-/-) mice have a blunted response to the antidepressant fluoxetine in behavioral despair paradigms, whereas fluoxetine normalizes their aggressiveness and their behavioral response in the novelty-induced hypophagia test. Crtc1(-/-) mice strikingly show, in addition to a reduced dopamine and serotonin turnover in the prefrontal cortex, a concomitant decreased expression of several susceptibility genes involved in neuroplasticity, including Bdnf, its receptor TrkB, the nuclear receptors Nr4a1-3, and several other CREB-regulated genes. CONCLUSIONS: Collectively, these findings support a role for the CRTC1-CREB pathway in mood disorders etiology and behavioral response to antidepressants and identify CRTC1 as an essential coactivator of genes involved in mood regulation.