Assessing the mechanisms directing cell fate in the dorsal spinal cord

项目摘要 体感系统允许我们通过以下方式感知环境并对其做出反应 包括触摸、伤害感、体温感觉和本体感觉。接收体感信息 脊髓背侧中间神经元(d1-dI6)由不同群体的背侧中间神经元(dis；dI1-dI6)在周围传递，然后由不同群体的背侧中间神经元(d1-dI6)中枢传递 电源线。我们的研究目标是了解在发展和发展过程中建立分布交互作用的机制。 然后将这些原则应用于设计分化方案，以指导特定的 从多能干细胞中分离出的群体。这些细胞具有修复受损感觉的潜力。 作为药物筛选平台的衬底。我们一直专注于解剖骨骼的作用 Di命运规范中的形态发生蛋白(BMP)家族。BMP被广泛认为是形态发生物， 以浓度依赖的机制形成背侧脊髓的图案，类似于Sonic 刺猬(Shh)形成腹侧脊髓的图案。然而，我们最近使用老鼠、鸡和 小鼠胚胎干细胞(MESC)模型发现，没有证据表明BMP具有形态起源作用。 相反，BMP具有信号特异性的活性，具有不同的能力来指导背侧祖细胞(DP)的构图 和/或通过特定的I型BMP受体分化。我们最近的体内和体外研究也 认为命运建立在一系列嵌套的选择点中。在我们的模型中，脊髓祖细胞是 用维甲酸(RA)背侧，通过BMP信号将其细分为多个潜在的DP亚组，然后 分解成特定的命运。由于对这种图案化过程知之甚少，我们将在目标1中评估如何 多潜能DP命运首先由RA和BMP信号建立，并确定引导机制 多势DPS转化为特定的Di身份。在目标2中，我们将确定细胞内反应的性质 这允许特定的BMP驱动DPS走向不同的Di身份，解决了两个悬而未决的问题：[1] 典型的受体调节(R)-Smads是否以BMP特异的方式被激活以导致不同的图案 活动?以及[2]R-SMADs又调节哪些因素来促进Di命运？总而言之，这些研究 将研究发育生物学中的一个长期存在的问题，即了解特定的结果如何 来自一个共同的信号，并阐明了允许瘫痪所需的细胞类型的规范 患者需要再次解释他们的感觉环境。我们的具体目标如下： 目的1：找出建立多潜能DPS的机制(S)，并将其分配给个体的Di命运。 假设：Ra±BMP4指导多潜能DP亚群的形成，这些亚群分解成特定的Di命运 通过不对称地激活额外的内源信号通路，如Wnt途径。 目的2：评估Smad和ID家族在BMP诱导的Di命运规范中的作用。 假设：BMP通过不同途径激活Smad1和/或Smad5，调节ID家族成员的活动。

Project Summary The somatosensory system permits us to perceive and react to the environment through modalities that include touch, nociception, thermosensation and proprioception. Somatosensory information is received peripherally and then relayed centrally by different populations of dorsal interneurons (dIs; dI1-dI6) in the spinal cord. Our research objectives are to understand the mechanisms that establish dIs during development and then apply these principles towards designing differentiation protocols to direct the formation of specific populations of dIs from pluripotent stem cells. These cells have the potential to repair damaged sensory circuits and act as substrates for drug screening platforms. We have focused on dissecting the role of the bone morphogenetic protein (BMP) family in dI fate specification. BMPs were widely assumed to act as morphogens, patterning the dorsal spinal cord in a concentration-dependent mechanism similar to the manner in which sonic hedgehog (Shh) patterns the ventral spinal cord. However, our recent studies using mouse, chicken, and mouse embryonic stem cell (mESC) models have found that no evidence that BMPs act as morphogens. Rather, BMPs have signal-specific activities, with differential abilities to direct dorsal progenitor (dP) patterning and/or differentiation through specific type I BMP receptors. Our recent in vivo and in vitro studies have also suggested that dI fates are established in a series of nested choice points. In our model, spinal progenitors are dorsalized by retinoic acid (RA), subdivided into multipotential dP subgroups by BMP signaling, and then resolve into specific dI fates. Since little is known about this patterning process, we will assess in Aim 1 how multipotential dP fates are first established by RA and BMP signaling and identify the mechanisms directing multipotential dPs into specific dI identities. In Aim 2, we will determine the nature of the intracellular response that permits specific BMPs to drive dPs towards different dI identities, addressing two unresolved questions: [1] are canonical receptor regulated (R)-Smads activated in a BMP-specific manner to result in distinct patterning activities? And [2] what factors do the R-Smads in turn regulate to promote dI fates? Together, these studies will investigate a long-standing problem in developmental biology, i.e., understanding how specific outcomes arise from a common signal, and shed light on the specification of dIs, cell types needed to permit paralyzed patients to again interpret their sensory environment. Our specific aims are as follows: Aim 1: Identify the mechanism(s) that establish multipotential dPs and assign them into individual dI fates. Hypothesis: RA±BMP4 direct the formation of multipotential dP subgroups, which resolve into specific dI fates by the asymmetric activation of additional endogenous signaling pathways, such as the Wnt pathway. Aim 2: Assess the role of the Smad and Id families in BMP-induced dI fate specification. Hypothesis: BMPs differentially activate Smad1 and/or Smad5, to regulate the activity of Id family members.