Genetic dissection of sleep regulation by ventrolateral preoptic area

描述（申请人提供）：先前的研究表明腹外侧视前核（VLPO）是促进睡眠的关键结构。VLPO与下丘脑尾侧和脑干的主要唤醒中枢相互连接，VLPO神经元的丢失（化学损伤）会产生严重的失眠和睡眠破碎。神经化学研究发现丙氨酸是睡眠活跃的VLPO神经元的特殊标记物。然而，过去的VLPO病变研究也敲除了VLPO区域内和周围的许多其他细胞类型（除了半乳糖能神经元），因此选择性损伤半乳糖能VLPO神经元对睡眠-觉醒的影响尚不清楚。在这个项目中，我们将通过立体定向注射腺相关病毒载体（AAV），其中含有转录阻断的促凋亡转基因基因，截断bh3相互作用结构域死亡受体（tBID），进入转基因小鼠的视前下丘脑，在半乳糖能神经元（Gal-Cre敲入小鼠）中特异性表达Cre重组酶（Cre）。视前下丘脑注射AAV-tBID选择性作用于含Cre的半乳糖能VLPO神经元，引发细胞凋亡。我们将研究缺乏半乳糖能VLPO神经元的小鼠的睡眠-觉醒量、结构和状态转换的变化（Specific Aim 1）。我们预计这些神经元的缺失会导致严重的失眠和睡眠断裂。有趣的是，VLPO中所有的丙氨酸能神经元都含有GABA。VLPO-GABA被假设在睡眠中介导促进觉醒的细胞群的抑制，尽管它从未被明确确定。因此，我们将局部和选择性地消除VLPO神经元的GABA释放，并评估继发于VLPO GABA神经传递丧失的睡眠-觉醒变化（Specific Aim 2）。GABA释放的特异性消除将会实现-1)通过将AAV-Cre传递到含有VGAT基因2外显子两侧loxP位点的条件囊泡GABA转运蛋白敲除（VGAT）小鼠的VLPO中，以及2)通过将条件VGAT小鼠与Gal-cre小鼠杂交来实现。Cre的加入切除了VGAT外显子2，使整个基因失去功能，导致VLPO神经元中缺乏功能性VGAT蛋白。由于VGAT对GABA转运到突触囊泡至关重要，VGAT的缺失将导致VLPO神经元GABA神经传递的选择性缺失。研究这些动物的睡眠-觉醒状态将为VLPO-GABA在睡眠调节和睡眠-觉醒转换中的具体作用提供关键的见解。总的来说，这一建议的结果将有助于我们更好地理解控制睡眠产生、维持和状态转换的下丘脑控制机制。这些信息最终将对设计失眠和觉醒障碍的药物治疗具有重要意义。

DESCRIPTION (provided by applicant): Previous studies have shown that the ventrolateral preoptic nucleus (VLPO) is a critical structure for promoting sleep. The VLPO is reciprocally connected with major wake-promoting centers in the caudal hypothalamus and the brainstem, and the loss of VLPO neurons (chemical lesions) produces profound insomnia and sleep fragmentation. Neurochemical studies identified galanin as a specific marker for the sleep-active VLPO neurons. However, past VLPO lesion studies also knocked out many other cell types (other than galaninergic neurons) in and around the VLPO region, and thus the effect of selectively lesioning the galaninergic VLPO neurons on sleep-wakefulness is not known. In this project, we will selectively destroy the galaninergic VLPO neurons by stereotaxically injecting adeno-associated viral vectors (AAV) containing transcriptionally blocked pro-apoptotic transgene, truncated BH3-interacting domain death agonist (tBID), into the preoptic hypothalamus of transgenic mice that express Cre-recombinase (Cre) specifically in the galaninergic neurons (Gal-Cre knockin mice). Injection of AAV-tBID into the preoptic hypothalamus acts selectively on the Cre- containing galaninergic VLPO neurons and triggers apoptotic cell death. We will study the changes in sleep- wake amounts, architecture and state transitions in these mice that lack galaninergic VLPO neurons (Specific Aim 1). We anticipate that the loss of these neurons will result in severe insomnia and sleep fragmentation. Interestingly, all the galaninergic neurons in the VLPO contain GABA. The VLPO-GABA has been hypothesized to mediate the inhibition of wake-promoting cell groups during sleep, although it has never been definitively determined. Hence, we will focally and selectively eliminate GABA release from the VLPO neurons and evaluate sleep-wakefulness changes that are secondary to the loss of VLPO GABA neurotransmission (Specific Aim 2). Specific elimination of GABA release will be achieved -1) by delivering AAV-Cre into the VLPO of conditional vesicular GABA transporter knockout (VGAT) mice that contain loxP sites flanking exon 2 of the VGAT gene and 2) by crossing the conditional VGAT mice with Gal-cre mice. Addition of Cre excises VGAT exon 2 and makes the entire gene non-functional, which results in the absence of functional VGAT protein in the VLPO neurons. As VGAT is critical for transporting GABA into the synaptic vesicles, the loss of VGAT will result in selective loss of GABA neurotransmission from the VLPO neurons. Studying sleep- wakefulness in these animals will provide critical insight into the specific contribution of VLPO-GABA in sleep regulation and in sleep-wake transitions. Collectively, the outcomes of this proposal will help us better understand the hypothalamic control mechanisms controlling sleep generation, maintenance and state transitions. This information will ultimately be important in designing pharmacological treatment for insomnia and arousal disorders.