Putting habenula pathways on the map

描述（由申请人提供）：这是一项新的 R01 提案，涉及缰核-中脑回路中的神经通路和基因表达。缰核是丘脑背核，由参与不同神经通路的内侧 (MH) 和外侧 (LH) 亚核组成。 MH和LH都通过突出的反屈束（FR）将其输出纤维发送到腹侧中脑，但只有LH直接支配中脑多巴胺（DA）和血清素（5HT）系统，而MH首先投射到脚间核（IP），脚间核又投射到腹侧中脑。最近的行为实验表明，缰核-中脑通路和单胺系统之间存在强大的功能相互作用，对情绪障碍、认知障碍和成瘾具有重大影响。 使用微阵列和生物信息学方法，我们最近表明分子标记可以识别 MH 和 LH 中的神经元亚群，这表明这些细胞核内的功能异质性。了解缰核功能的进一步进展将需要更好地了解缰核神经元的这些不同分子类别，包括它们的解剖和功能连接，这是传统的束追踪方法无法实现的。 在这里，我们提出了三个具体目标，将探索缰核回路并快速描绘 MH、LH 和 IP 中特定神经元群的连接。这些实验计划在很短的时间内（3 年）进行，并以具有成本效益的方式使用现有工具，包括来自 Gensat 和艾伦大脑研究所脑图项目的基因组和生物信息资产。 目标 1. 检验 MH 和 LH 神经元的特定亚群参与不同神经通路的假设。使用带有 LacZ、GFP 和 Cre 报告基因的转基因小鼠追踪遗传定义的 MH、LH 和 IP 神经元类别到中脑的投射。可用的细胞系针对 Brn3a、Gpr151、Tac2/SK、Slc18a3、Chrnb4、Prokr2、Chrna5、Tac1/SP 和 Chat 基因。 目标 2. 检验以下假设：小鼠 LH 通过中桥脑内侧被盖核 (RMTg) 的 GABA 能神经元向中脑边缘 DA 系统提供输入，就像在大鼠中一样。使用 cFos 诱导、LH 的顺行道追踪和 GABA 标记表达来定位小鼠 RMTg。使用转基因追踪识别投射到 RMTg 的 LH 亚群。 目标 3. 与艾伦研究所合作，利用生物信息学分析来检验以下假设：缰核通路的关键节​​点，特别是前脑间隔核、LH、IP 和 RMTg，具有独特的基因表达谱，正如之前针对 MH 所证明的那样。这些基因表达谱将构成未来研究中缰核通路遗传操作的基础。

DESCRIPTION (provided by applicant): This is a new R01 proposal addressing neural pathways and gene expression in habenula- midbrain circuits. The habenula is a dorsal thalamic nucleus consisting of medial (MH) and lateral (LH) subnuclei that participate in distinct neural pathways. The MH and LH both send their output fibers to the ventral midbrain via the prominent fasciculus retroflexus (FR), but only the LH directly innervates midbrain dopamine (DA) and serotonin (5HT) systems, while the MH projects first to the interpeduncular nucleus (IP), which in turn projects to ventral midbrain. Recent behavioral experiments suggest strong functional interactions between the habenula-midbrain pathway and the monoamine systems, with major implications for mood disorders, cognitive disorders, and addiction. Using microarrays and bioinformatic approaches, we have recently shown that molecular markers identify subpopulations of neurons in the MH and LH which suggest functional heterogeneity within these nuclei. Further progress in understanding habenula function will require a much better understanding of these distinct molecular classes of habenula neurons, including their anatomic and functional connectivity, which are not accessible to conventional tract-tracing methods. Here we propose three Specific Aims that will explore habenula circuits and rapidly delineate the connections of defined populations of neurons in the MH, LH and IP. These experiments are planned in a short time-frame (3 years) and with cost-effective use of existing tools, including genomic and bioinformatic assets from the Gensat and Allen Brain Institute brain mapping projects. Aim 1. Test the hypothesis that specific subpopulations of MH and LH neurons participate in distinct neural pathways. Use transgenic mice with LacZ, GFP, and Cre reporters to trace the projections of genetically defined classes of MH, LH, and IP neurons to the midbrain. Available lines target the Brn3a, Gpr151, Tac2/SK, Slc18a3, Chrnb4, Prokr2, Chrna5, Tac1/SP, and Chat genes. Aim 2. Test the hypothesis that the LH provides input to the mesolimbic DA system via GABAergic neurons of the mesopontine rostromedial tegmental nucleus (RMTg) in mice as it does in rats. Localize the mouse RMTg using cFos induction, anterograde tract tracing from the LH, and GABA marker expression. Identify the LH subpopulations projecting to the RMTg using transgenic tracing. Aim 3. In collaboration with the Allen Institute, use bioinformatic analysis to test the hypothesis that key nodes of the habenula pathway, specifically the forebrain septal nuclei, LH, IP and RMTg, have distinctive gene expression profiles, as previously demonstrated for the MH. These gene expression profiles will form the basis for the genetic manipulation of habenula pathways in future studies.