Temporal regulation of C. elegans metabolic gene expression by the heterochronic protein LIN-29 at the larval to adult transition

项目摘要 在动物和人类发育过程中，单细胞胚胎分裂产生所有已发现的细胞类型 在成人身上。为了正确地进行这一过程，储存在每个细胞基因组中的遗传信息 必须在正确的单元格中、在正确的时间以及当这些事件未正确发生时表达 可能会发生发育异常和出生缺陷。虽然对空间控制的了解很多，但 在后生动物中的基因表达，对基因表达的时间控制以及如何控制基因表达知之甚少 在动物发育过程中，事件是及时协调的。在线虫线虫中，一条途径是 基因和微RNA被称为“异时通路”，其特征是控制着 幼虫生命中的发育事件。这条通路的末端组件是锌指 转录因子Lin-29，它调控从幼虫晚期到幼虫的重要发育转变 成虫(L/A转换)在表皮和其他虫体组织中。林-29的直接目标鲜为人知： 最具代表性的是在L/A转换期表达的一个基因，它编码一种角质层胶原，这种角质层是主要的 蠕虫外壳的一种成分，由表皮细胞分泌。要理解时代性 通过时间错配鉴定LIN-29调控基因对发育转换的调控 在发育早期表达LIN-29，并进行基因表达分析。这个RNA序列 分析发现，LIN-29上调了232个基因，其中许多基因编码角质层胶原(33/232)。 和/或在L4/A转变之前显示正常的表达高峰(63/232)。这一分析还确定了 352个基因因LIN-29早期表达不当而下调。最重要的是 下调清单上被过度表达的基因类别是一大群与脂肪酸有关的基因 在蠕虫肠道中表达的代谢，其基因产物是蛋白质-蛋白质的一部分 互动网络在人类中是保守的。此外，LIN-29在成年期的时间性错误表达 导致寿命显著缩短。这些结果和其他结果表明，LIN-29调节A 从表皮移动到肠道的信号，接收到的信号会导致转录 下调一组脂肪酸代谢基因，从而改变蠕虫的新陈代谢 满足幼虫的需要(快速生长)到满足成虫的需要(长寿、卵黄生成)。 将进行实验来验证这一假设，并具体识别信号的性质(S) 以及调节这种组织间通讯的转录因子(S)。这项工作的完成 这里提出的将对我们理解基因表达的时间调控产生重大影响 在后生动物模型中，并揭示了在发育转变过程中新陈代谢的控制。 由于LIN-29及其假定靶点的同源基因在人类中是保守的，因此获得的知识将 与我们对人类正常发育、健康和衰老的理解有关。

Project Summary During animal and human development, the single-cell embryo divides to generate all of the cell types found in the adult. For this process to occur correctly, the genetic information stored in the genome of every cell must be expressed in the right cells and at the right time, and when these events do not occur correctly developmental anomalies and birth defects can occur. While much is known about the spatial control of gene expression in metazoans, less is known about the temporal control of gene expression and how events are coordinated in time during animal development. In the nematode worm C. elegans, a pathway of genes and microRNAs called the ‘heterochronic pathway’ has been characterized that controls the timing of developmental events during larval life. The terminal component of this pathway is the zinc finger transcription factor LIN-29, which regulates the important developmental transition from late larval life to adulthood (L/A transition) in the epidermis and other worm tissues. Few direct targets of LIN-29 are known: the best characterized is a gene expressed at the L/A transition which encodes a cuticle collagen, the major component of the outer covering of the worm secreted by the epidermal cells. To understand the temporal regulation of developmental transitions LIN-29 regulated genes were identified by temporally mis- expressing LIN-29 at an earlier developmental time and analyzing gene expression. This RNA-Seq analysis identified 232 genes upregulated by LIN-29, many of which encode cuticle collagens (33/232), and/or show a normal peak of expression before the L4/A transition (63/232). This analysis also identified 352 genes down-regulated upon inappropriate early expression of LIN-29. The most significantly overrepresented category of genes on the down-regulated list are a large group involved in fatty acid metabolism that are expressed in the worm intestine, and whose gene products are part of a protein-protein interaction network conserved in humans. In addition, temporal mis-expression of LIN-29 during adulthood leads to a significant shortening of lifespan. These results and others suggest that LIN-29 regulates a signal that moves from the epidermis to the intestine, the reception of which results in the transcriptional down-regulation of a set of fatty acid metabolic genes which shifts the metabolism of the worm from that meeting the needs of the larva (rapid growth) to that meeting the needs of the adult (long life, vitellogenesis). Experiments to test this hypothesis will be performed, and to specifically identify the nature of the signal(s) and the transcription factor(s) mediating this inter-tissue communication. The accomplishment of the work proposed here will have a significant impact on our understanding of temporal regulation of gene expression in a model metazoan, and shed new light on the control of metabolism during developmental transitions. Because homologs of LIN-29 and its putative targets are conserved in humans, the knowledge gained will have relevance to our understanding of normal human development, health and aging.