Genetic Control of Nociceptive Sensory Neuron Development and Pain Behavior

描述(由申请者提供)：长期目标是确定控制特定感觉通路形成的遗传程序，并深入了解疼痛感知的分子和细胞基础。在此续订申请中，我们试图解决两个主要的知识差距。首先，大多数临床上相关的疼痛来自深层组织，如肌肉、关节、骨骼和内脏器官。尽管有这种临床意义，但分子 “深层”疼痛的细胞基础仍然知之甚少，这与过去几十年在理解皮肤疼痛方面取得的巨大进步形成了鲜明对比。在目标1的研究中，我们将建立支配不同深层组织的感觉神经元的分子图谱。我们还将确定Meis1是否代表控制深层组织感觉神经元发育的第一个转录因子。其次，机械性超感痛症(由无害的机械刺激引起的疼痛)的细胞基础需要进一步澄清，这是大多数(如果不是全部)慢性疼痛障碍的标志。在神经病理性疼痛的情况下，有人认为中枢去抑制将允许低阈值有髓A�机械感受器直接激活疼痛通路。然而，最近的一项研究表明，以囊泡谷氨酸转运体VGLUT3表达为标志的无髓鞘低阈值c-机械受体可能在机械性痛觉异常的读出中发挥重要作用。我们的初步遗传命运图谱研究表明，VGLUT3系神经元实际上由两部分组成：1)在皮肤表皮形成游离神经末梢和毛囊周围披针状神经末梢的无髓鞘c-机械受体，以及2)形成Merkel-细胞轴突复合体的有髓m-机械受体。在目标2中，我们将确定转录因子Zfp521是否对这些c-机械受体的发育是必需的。Zfp521是一种专门在VGLUT3系c-机械受体中表达的转录因子。我们还将确定，在VGLUT3系c-机械受体或表达VGLUT3的Merkel细胞-轴突复合体存在选择性发育缺陷的小鼠中，机械性痛觉异常是否受到不同程度的影响。总而言之，这些研究将深入了解1)控制深层组织疼痛通路形成的遗传程序，以及2)调节机械性痛觉异常读数的低阈值机械感受器的身份。

DESCRIPTION (provided by applicant): The long-range goal is to identify the genetic programs controlling the formations of specific sensory pathways and to gain insight into the molecular and cellular basis of pain perception. In this renewal application, we try to address two major knowledge gaps. First, most clinically relevant pain is derived from deep tissues, such as muscle, joint, bone, and visceral organs. Despite this clinical significance, the molecular and cellular basis of "deep" pain is still poorly understood, which is in stark contrast to the tremendous progress made in the past decades in understanding cutaneous pain. In Aim 1 studies, we will establish a molecular map for sensory neurons innervating distinct deep tissues. We will also determine if Meis1 represents the first transcription factor that controls the development of deep tissue sensory neurons. Second, the cellular basis of mechanical allodynia (pain evoked by innocuous mechanical stimuli), a hallmark for most, if not all, chronic pain disorders, needs further clarification. In case of neuropathic pain, it was proposed that central disinhibition will allow low threshold myelinated A� mechanoreceptors to directly activate the pain pathways. However, a recent study proposed that unmyelinated low threshold c- mechanoreceptors, marked by the expression of the vesticular glutamate transporter VGLUT3, may play an essential role in the readout of the mechanical allodynia. Our preliminary genetic fate-mapping studies show that VGLUT3 lineage neurons are in fact composed of both 1) unmyelinated c-mechanoreceptors that form free nerve endings in the skin epidermis and lanceolate endings around hair follicles, and 2) myelinated m-mechanoreceptors that form the Merkel-cell neurite complex. In Aim 2, we will determine if Zfp521, a transcription factor expressed exclusively in VGLUT3 lineage c-mechanoreceptor, is necessary for the development of these c-mechnaoreceptors. We will also determine if mechanical allodynia is differentially affected in mice that will have a selective developmental defect in VGLUT3 lineage c- mechanoreceptors or a defect in the VGLUT3-expressing Merkel cell-neurite complex. Together, these studies will gain insight into 1) the genetic programs that control the formation of the deep tissue pain pathways, and 2) the identities of low threshold mechanoreceptors mediating the readout of mechanical allodynia.