Notch pathway maintenance of the immortal germ line

描述（由申请人提供）：当动物的索马老化并最终死亡时，生殖系通过将可遗传信息传递给下一代而保持有效的永生。生物体的健康完全取决于这种信息的高保真传输;因此，生殖细胞受到独特的保护，免受与衰老有关的损害。生殖细胞的保护是在其最初的分离，往往通过一个专门的细胞质的不对称遗传，并保持长期与性腺生态位。对生态位-生殖细胞关系的全面理解将阐明抑制衰老过程的机制。我们研究的长期目标是了解生殖细胞生态位维持中的转录网络。这项建议的目的是调查一个假定的Notch-Delta途径的成员，SpMibL，丰富的假定生殖细胞称为小微粒（SMMs）的海胆的功能。这些细胞在早期发育的早期被分配，并在变态期间用于构建成体组织，包括生殖细胞。令人惊讶的是，如果SMM被消融，胚胎可以通过重新编程先前提交的谱系来补偿。我们假设SpMibL是SMM分配的上游调节器，并且对于消融后重新分配新的SMM也至关重要。SpMibL通过直接抑制SMM中的δ配体来实现这一点，建立分子不对称性; SMM成为表达notch的接收细胞，而它们的邻居成为表达δ的小生境细胞。为了验证这一假设，我们将在体内敲低并过表达SpMibL，分析所得表型，并鉴定下游转录靶点。我们还将测试在SMM消融后是否在其他谱系中诱导SpMibL以及其他已知因子。我们的研究结果将提供关于生殖系生态位如何维持的新的分子细节，以及生殖细胞可以从先前的定向细胞编程。

DESCRIPTION (provided by applicant): While the soma of an animal ages and ultimately dies, the germ line remains effectively immortal by passing heritable information to the next generation. The fitness of the organism absolutely depends on the high-fidelity transmission of this information; therefore, germ cells are uniquely protected against aging-related damage. The protection of the germ cells is conferred at their initial segregation, often through the asymmetric inheritance of a specialized cytoplasm, and maintained long-term by association with a gonadal niche. A comprehensive understanding of the niche-germ cell relationship will illuminate mechanisms that suppress the aging process. The long-term goal of our research is to understand the transcriptional networks involved in germ cell-niche maintenance. The objective of this proposal is to investigate the function of a putative Notch-Delta pathway member, SpMibL, enriched in the presumptive germ cells called small micromeres (SMMs) of the sea urchin Strongylocentrotus purpuratus. These cells are allocated early in early development and are used to construct adult tissues during metamorphosis, including the germ line. Surprisingly, if the SMMs are ablated, the embryo can compensate by reprogramming previously committed lineages. We hypothesize that SpMibL is an upstream regulator of SMM allocation, and also critical for reallocating new SMMs following ablation. SpMibL achieves this by directly repressing delta ligand in the SMMs, establishing a molecular asymmetry; SMMs becoming the notch expressing, receiving cells, and their neighbors become the delta expressing, niche cells. To test this hypothesis, we will knock down and overexpress SpMibL in vivo, analyze the resulting phenotype, and identify downstream transcriptional targets. We will also test whether SpMibL, as well as other known factors are induced in other lineages following SMM ablation. Our results will provide fresh molecular detail on how the germ line niche is maintained, and germ cells can be programmed from previously committed cells.