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-中脑回路中的神经通路和基因表达。缰核是丘脑背核，由内侧（MH）和外侧（LH）亚核组成，参与不同的神经通路。MH和LH都通过突出的后屈束（FR）将其输出纤维发送到中脑腹侧，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），后者再投射到中脑腹侧。最近的行为实验表明缰-中脑通路和单胺系统之间有很强的功能相互作用，对情绪障碍、认知障碍和成瘾有重要影响。利用微阵列和生物信息学方法，我们最近发现分子标记可以识别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。进一步了解缰状核功能需要更好地了解缰状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，这是传统的束迹追踪方法无法获得的。在这里，我们提出了三个特定的目标，将探索缰核回路，并快速描述MH， LH和IP中定义的神经元群体的连接。这些实验计划在较短的时间框架内（3年），并具有成本效益地使用现有工具，包括Gensat和艾伦大脑研究所大脑测绘项目的基因组和生物信息学资产。目的1。验证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，追踪基因定义的MH、LH和IP神经元向中脑的投射。现有的基因系靶向Brn3a、Gpr151、Tac2/SK、Slc18a3、Chrnb4、Prokr2、Chrna5、Tac1/SP和Chat基因。目标2。验证LH像在大鼠中一样，在小鼠中通过中脑边前内侧被盖核（RMTg）的gaba能神经元向中边缘DA系统提供输入的假设。利用cFos诱导、顺行性LH追踪和GABA标记表达来定位小鼠RMTg。利用转基因示踪技术鉴定投射到RMTg的LH亚群。目标3。与Allen研究所合作，使用生物信息学分析来验证habenula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的假设，如先前对MH的证明。这些基因表达谱将形成未来研究中habenula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.