Signaling pathways that regulate scaling and regeneration of the cerebellum

 描述(申请人提供)：小脑(CB)由人脑80%的神经元组成，不仅在平衡和运动协调方面发挥重要作用，而且通过连接整个前脑的神经回路调节语言、推理和社交过程。在哺乳动物物种中，CB中神经元的数量与大脑皮层的比例非常稳定，这表明相互连接的电路在进化过程中一起扩大。由于脐带血的生长大部分发生在妊娠晚期，并在出生后持续一年，因此脐带血特别容易受到临床和环境因素的影响。颗粒细胞的产生受浦肯野细胞分泌的Sonic Hedgehog(Shh)刺激，在此期间占小脑生长的大部分。早产儿患小脑发育不全和神经功能障碍的风险明显更高，部分原因可能是他们接受了糖皮质激素。在啮齿动物模型中，糖皮质激素通过改变SHH-GLI信号，增加颗粒细胞外层(EGL)中颗粒细胞前体(GCP)的死亡。然而，我们的初步结果和其他实验模型表明，发育中的啮齿动物CB具有很大的再生耗尽的EGL的能力。为了加强对发育中的CB的短暂损伤的恢复，关键是要确定刺激细胞代偿扩张的信号通路，并确保所有类型的细胞一起伸缩，以便拥有正常功能的电路。我们将利用复杂的小鼠遗传学方法来识别这样的途径。我们的研究是基于我们的独特发现，当出生时脐带前部EGL耗尽时，白质中标记有Nestin-FlpoER的细胞扩张并填充EGL，然后分化，产生重大恢复。我们的初步研究和新的遗传学方法为研究正常和突变的表达巢蛋白的白质干细胞在EGL耗尽时的细胞行为提供了强有力的方法，并发现了刺激白质干细胞及其EGL群体扩张的信号。我们的研究应该提供一些见解，可以用来开发新的方法，在早产、糖皮质激素治疗或其他损伤(包括出血)的情况下，促进婴儿CB的恢复。我们的具体目标是：目的1.确定小脑白质Nestin+干细胞的再生潜能。目的2.鉴定Nestin+干细胞在EGL再生过程中发生改变的信号通路。目的3.测试SHH信号或某些已识别的通路是否能促进Nestin+干细胞向耗尽的EGL募集。

 DESCRIPTION (provided by applicant): The cerebellum (CB), consisting of 80% of the neurons in the human brain, not only has a major role in balance and motor coordination, but also modulates language, reasoning and social processes via neural circuits that connect throughout the forebrain. The ratio of the number of neurons in the CB to the cerebral cortex is remarkably constant across mammalian species, indicating that interconnected circuits have scaled together during evolution. Since much of CB growth occurs in the third trimester and continues for a year after birth, the CB is particularly vulnerable to clinical and environmental factors. Granule cell production, stimulated Sonic Hedgehog (Shh) secreted by Purkinje cells, accounts for a majority of cerebellar growth during this period. Pre-term babies are at a significantly higher risk of developing cerebellar hypoplasia and neurological dysfunction, likely in part because they receive glucocorticoids. In rodent models, glucocorticoids increase death of granule cell precursors (GCPs) in the external granule cell layer (EGL), through a mechanism that involves altered SHH-GLI signaling. However, our preliminary results and other experimental models have demonstrated that the developing rodent CB has a large capacity to regenerate a depleted EGL. In order to enhance recovery from a transient insult to the developing CB, it is critical to identify the signaling pathways that stimulate compensatory expansion of cells, and ensure that all cell types scale together in order to have normally functioning circuits. We will utilize sophisticated mouse genetics approaches to identify such pathways. Our studies are based on the unique discovery we made that when the anterior EGL of the CB is depleted at birth, cells marked with Nestin-FlpoER in the white matter expand and populate the EGL and then differentiate, producing a major recovery. Our preliminary studies and novel genetic approaches provide a powerful approach for studying the cellular behaviors of normal and mutant Nestin-expressing white matter stem cells in response to depletion of the EGL and discovering the signals that stimulate expansion of white matter stem cells and their population of the EGL. Our studies should provide insights that can be used to develop new approaches for augmenting recovery of the infant CB in the face of premature birth, glucocorticoid treatment or other injuries including hemorrhage. Our specific aims are: Aim 1. To determine the regenerative potential of cerebellar white matter Nestin+ stem cells. Aim 2. To identify signaling pathways which are altered in Nestin+ stem cells during regeneration of the EGL. Aim 3. To test whether SHH signaling or some of the identified pathways enhance recruitment of Nestin+ stem cells to a depleted EGL.