Brain serotonin neuron gene regulatory networks and chromatin architecture

基因表达的精确时空控制对于有丝分裂后细胞的成熟至关重要。 神经功能和大脑健康的保护。虽然连续表达的神经元转录 被称为末端选择因子的因子，如Pet 1和Lxm 1b，是胎儿基因表达的关键调节因子， 和出生后阶段的生命的潜在分子机制，通过它们控制阶段特异性 神经元的基因表达知之甚少。在这里，我们旨在通过全面调查来填补这一空白， 有丝分裂后5-羟色胺（5-HT）神经元的末端选择功能。Pet 1和Lmx 1b对肾上腺素能的控制 由于5-HT对中枢神经回路具有广泛的调节作用， 并且改变的多巴胺能基因表达与几种发育性神经精神疾病有关。 包括抑郁症、与压力相关的焦虑症、自闭症、强迫症和精神分裂症的疾病。建议的研究 我们发现连续表达的5-HT依赖性不断变化， 随着5-HT神经元的成熟，神经元终末效应基因Pet 1的表达也发生了变化。我们意外地发现Pet 1的终端 5-HT合成基因的选择控制在出生后早期基本上被关闭，而Pet 1 控制神经递质GPCR基因Htr 1a，Adra 1b的上调， 5-HT神经元兴奋性的传入突触调制。这些最近的观察使我们提出了一个 我们称之为“终端选择器目标切换”的新原理。我们认为有丝分裂后的神经元 在生命的进程中，持续的末端选择子调控的转录不是静态的，因为普遍存在的是 假设相反，我们假设末端选择子调控的转录是高度动态的， 随着有丝分裂后神经元的成熟，调节因子与靶基因的相互作用被重塑。我们假设 调节相互作用的重塑植根于有丝分裂后神经元染色质的时间重塑 架构在目的1中，我们将研究Lmx 1b对出生后早期5-HT基因表达的控制， 确定是否有丝分裂后的目标转换是5-HT末端选择器的一般属性。在目标2中， 将使用我们新开发的5 HT-ATAC-seq协议来揭示5-HT开放的时间动态 染色质作为5-HT神经元从胎儿到出生后早期阶段发育和成熟。具体来说，我们将 解决这些问题：开放的染色质状态是否与成熟的变化平行， 5-HT神经元转录组的成熟？靶依赖性的转换是否由基因特异性 开放染色质的变化？目标3将研究一种合理的潜在机制，通过这种机制， 5-HT基因表达模式受到控制：末端选择因子Pet 1和Lmx 1b直接作用于控制5-HT基因的表达。 5-HT神经元开放染色质状态的成熟。了解末端选择因子如何控制有丝分裂后 神经元基因表达可能阐明导致神经发育疾病的潜在机制， 异常神经元基因表达和神经元成熟缺陷。

Precise spatiotemporal control of gene expression is crucial throughout life for maturation of postmitotic neuronal function and preservation of brain health. Although continuously expressed neuronal transcription factors termed terminal selectors, such as Pet1 and Lxm1b, are key regulators of gene expression across fetal and postnatal stages of life the underlying molecular mechanisms through which they control stage specific neuronal gene expression are poorly understood. Here, we aim to fill this gap by comprehensively investigating terminal selector function in postmitotic serotonin (5-HT) neurons. Pet1 and Lmx1b’s control of serotonergic gene expression is of broad interest as 5-HT has wide-ranging modulatory effects on central neural circuitry and altered serotonergic gene expression has been implicated in several developmental neuropsychiatric disorders including depression, stress-related anxiety, autism, OCD, and schizophrenia. The studies proposed here are motivated, in part, by our discovery of changing dependencies of continuously expressed 5-HT neuron terminal effector genes on Pet1 as 5-HT neurons mature. We unexpectedly found that Pet1’s terminal selector control of 5-HT synthesis genes is largely switched off in the early postnatal period and instead Pet1 switches to controlling the upregulation of neurotransmitter GPCR genes, Htr1a, Adra1b, that are needed for afferent synaptic modulation of 5-HT neuron excitability. These recent observations have led us to suggest a new principle that we have termed “terminal selector target switching”. We suggest that as postmitotic neurons progress through life, continuous terminal selector regulated transcription is not static, as is the prevailing assumption. Instead, we hypothesize that terminal selector regulated transcription is highly dynamic in which regulatory factor interactions with target genes are remodeled as postmitotic neurons mature. We hypothesize the remodeling of regulatory interactions is rooted in the temporal remodeling of postmitotic neuronal chromatin architecture. In Aim 1, we will investigate Lmx1b’s control of early postnatal 5-HT gene expression to determine whether postmitotic target switching is a general property of 5-HT terminal selectors. In Aim 2, we will use our newly developed 5HT-ATAC-seq protocol to uncover the temporal dynamics of 5-HT open chromatin as 5-HT neurons develop and mature from fetal to early postnatal stages of life. Specifically, we will address these questions: Do open chromatin states undergo maturational changes in parallel with the maturation of 5-HT neuron transcriptomes? Do switches in target dependence result from gene specific changes in open chromatin? Aim 3 will investigate a plausible potential mechanism through which developing 5-HT gene expression patterns are controlled: Terminal selectors, Pet1 and Lmx1b, directly act to control the maturation of 5-HT neuronal open chromatin states. Understanding how terminal selectors control postmitotic neuronal gene expression may illuminate potential neurodevelopmental disease mechanisms that cause aberrant neuronal gene expression and defects in neuronal maturation.