Department of Molecular and Human Genetics.
Medical Scientist Training Program.
J Neurosci. 2018 Feb 7;38(6):1443-1461. doi: 10.1523/JNEUROSCI.1641-17.2017. Epub 2018 Jan 5.
The mouse olfactory bulb (OB) features continued, activity-dependent integration of adult-born neurons, providing a robust model with which to examine mechanisms of plasticity in the adult brain. We previously reported that local OB interneurons secrete the neuropeptide corticotropin-releasing hormone (CRH) in an activity-dependent manner onto adult-born granule neurons and that local CRH signaling promotes expression of synaptic machinery in the bulb. This effect is mediated via activation of the CRH receptor 1 (), which is developmentally regulated during adult-born neuron maturation. CRHR1 is a G-protein-coupled receptor that activates CREB-dependent transcription in the presence of CRH. Therefore, we hypothesized that locally secreted CRH activates CRHR1 to initiate circuit plasticity programs. To identify such programs, we profiled gene expression changes associated with CRHR1 activity in adult-born neurons of the OB. Here, we show that CRHR1 activity influences expression of the brain-specific Homeobox-containing transcription factor POU Class 6 Homeobox 1 (). To elucidate the contributions of toward activity-dependent circuit remodeling, we targeted CRHR1 neurons in male and female mice for cell-type-specific manipulation of expression. Whereas loss of in CRHR1 neurons resulted in reduced dendritic complexity and decreased synaptic connectivity, overexpression of in CRHR1 neurons promoted dendritic outgrowth and branching and influenced synaptic function. Together, these findings suggest that the transcriptional program directed by downstream of local CRH signaling in adult-born neurons influences circuit dynamics in response to activity-dependent peptide signaling in the adult brain. Elucidating mechanisms of plasticity in the adult brain is helpful for devising strategies to understand and treat neurodegeneration. Circuit plasticity in the adult mouse olfactory bulb is exemplified by both continued cell integration and synaptogenesis. We previously reported that these processes are influenced by local neuropeptide signaling in an activity-dependent manner. Here, we show that local corticotropin-releasing hormone (CRH) signaling induces dynamic gene expression changes in CRH receptor expressing adult-born neurons, including altered expression of the transcription factor We further show that is necessary for proper dendrite specification and patterning, as well as synapse development and function in adult-born neurons. Together, these findings reveal a novel mechanism by which peptide signaling modulates adult brain circuit plasticity.
小鼠嗅球(OB)具有持续的、活性依赖性的成年神经元整合,为研究成年大脑中的可塑性机制提供了一个强大的模型。我们之前报道过,局部 OB 中间神经元以活性依赖的方式将神经肽促肾上腺皮质释放激素(CRH)分泌到成年神经元上,局部 CRH 信号促进了 OB 中突触机制的表达。这种效应是通过激活 CRH 受体 1()介导的,该受体在成年神经元成熟过程中受到发育调控。CRHR1 是一种 G 蛋白偶联受体,在存在 CRH 的情况下激活 CREB 依赖性转录。因此,我们假设局部分泌的 CRH 通过激活 CRHR1 来启动电路可塑性程序。为了确定这些程序,我们对 OB 中成年神经元的 CRHR1 活性相关的基因表达变化进行了分析。在这里,我们显示 CRHR1 活性影响大脑特异性 Homeobox 包含转录因子 POA 类 6 Homeobox 1()的表达。为了阐明 对活性依赖性电路重塑的贡献,我们针对雄性和雌性小鼠的 CRHR1 神经元进行了细胞类型特异性的 表达操作。虽然 CRHR1 神经元中 的缺失导致树突复杂性降低和突触连接减少,但 过表达在 CRHR1 神经元中促进了树突的生长和分支,并影响了突触功能。总之,这些发现表明,在成年大脑中,局部 CRH 信号下游的 转录程序影响活性依赖性肽信号对成年大脑中电路动力学的影响。阐明成年大脑中的可塑性机制有助于设计理解和治疗神经退行性变的策略。成年小鼠嗅球中的电路可塑性既包括持续的细胞整合又包括突触发生。我们之前报道过,这些过程受到局部神经肽信号的活性依赖性影响。在这里,我们显示局部促肾上腺皮质释放激素(CRH)信号诱导 CRH 受体表达的成年神经元中的动态基因表达变化,包括转录因子的改变 我们进一步表明,在成年神经元中, 对于正确的树突特化和模式形成以及突触发育和功能是必要的。总之,这些发现揭示了一种新的机制,即肽信号调节成年大脑电路可塑性。