Regulatory mechanisms of cerebellar lineage development

项目摘要 颗粒细胞（GC）占小脑体积的95%以上。他们接收并整合感觉，运动， 和非感觉运动信号来微调运动行为和认知任务。GC生成自 颗粒细胞前体细胞（GCPs）从胚胎早期开始长时间短暂增殖 直到人类出生后的第一年。因此，小脑发育不全是最常见的脑 早产儿并发症与不良的发展结果。我们的基本知识非常有限 GC血统是如何建立的我们的长期目标是阐明GC谱系的调控机制 发展，并了解不同的风险因素如何导致小脑发育不全。的主要调节剂 GCP的形成是bHLH转录因子Atoh 1，它通过激活 自己的表达。这种自动调节反馈回路还得到细胞周期调节因子Ccnd 1的支持， 稳定Atoh 1蛋白质免于降解。然而，Atoh 1和Ccnd 1的表达如何影响细胞的功能仍不清楚。 终止，以便及时从GCP进展到GC。我们的初步数据表明，Sin 3A， 组蛋白去乙酰化酶（HSP 70）的转录辅抑制因子复合物的组成部分，是GCP所必需的 通过表观遗传学沉默Atoh 1表达来分化。我们还鉴定了一种锌指蛋白Insm 1， 转录因子，作为抑制Atoh 1和Ccnd 1表达的Sin 3A-Hind复合物的潜在伴侣。 基于这些和其他初步观察，我们提出了新的假设，Atoh 1表达是 由Atoh 1增强子处的H3 K27表观遗传特征动态控制，Insm 1是关键 转录抑制因子破坏Atoh 1自动调节环和细胞周期进程， 谱系分化这一假设将通过确定（1）Atoh 1的表观遗传机制来检验 （2）Insm 1在胃癌细胞分化过程中的功能和调控格局 （3）Insm 1在Atoh 1蛋白稳定性和GC谱系进展中的作用。

PROJECT SUMMARY Granule cells (GCs) constitute over 95% of the cerebellar volume. They receive and integrate sensory, motor, and non-sensorimotor signals to fine-tune motor behaviors and cognitive tasks. GCs are generated from transiently proliferating granule cell precursors (GCPs) over a long time extending from early embryonic period until first postnatal year in human. Accordingly, cerebellar hypoplasia is one of the most common brain complications in premature infants with poor developmental outcomes. We have very limited basic knowledge of how GC lineage is established. Our long term goals are to elucidate the regulatory mechanisms of GC lineage development, and to understand how different risk factors cause cerebellar hypoplasia. A master regulator of GCP development is the bHLH transcription factor Atoh1 that maintains the GCP fate through activation of its own expression. This autoregulatory feedback loop is further supported by a cell cycle regulator Ccnd1 that stabilizes Atoh1 protein from degradation. However, it remains unclear as to how Atoh1 and Ccnd1 expressions are terminated to enable timely progression from GCPs to GCs. Our preliminary data suggest that Sin3A, a component of histone deacetylase (Hdac)–containing transcriptional corepressor complex, is essential for GCP differentiation by epigenetically silencing Atoh1 expression. We have also identified Insm1, a zinc-finger transcription factor, as a potential partner of the Sin3A-Hdac complex that inhibits Atoh1 and Ccnd1 expression. Based on these and other preliminary observations, we propose the novel hypothesis that Atoh1 expression is dynamically controlled by H3K27 epigenetic signatures at the Atoh1 enhancer, with Insm1 as a key transcriptional repressor disrupting the Atoh1 autoregulatory loop and cell cycle progression, and enabling GC lineage differentiation. This hypothesis will be tested by determining (1) the epigenetic mechanism of Atoh1 expression and GC lineage differentiation, (2) Insm1 function and regulatory landscape during GC lineage development, and (3) the contribution of Insm1 in Atoh1 protein stability and GC lineage progression.