Adult stem cells have a unique ability to self-renew and to generate differentiated daughter cells that are required in the body tissues. The identity of adult stem cells is maintained by extrinsic signals from other cell types, known as niche cells. Thus, the niche is required for appropriate tissue homeostasis. Niche is formed and recruits stem cells during tissue development; therefore, it is essential to establish niche cells and stem cells in proper numbers during development. A small niche may recruit too few stem cells and cause tissue degeneration, while a large niche may maintain too many stem cells and lead to tumorigenesis. Given that vertebrate tissues are not suitable for large-scale forward genetics studies, the Drosophila ovary stands out as an excellent model for studying how multiple niche cell types and germ cells (GCs) are coordinately regulated in vivo. Recent studies are beginning to reveal how various signaling molecules regulate niche formation and how niche cells non-autonomously influence GC number. In this review, we summarize the ovarian niche structure, the key signaling pathways for niche formation, and how niche cells generate extrinsic factors to control GC proliferation during ovarian development.

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发育组织中的生态位形成和功能：来自果蝇卵巢的研究

成体干细胞具有独特的自我更新和产生身体组织所需的分化子细胞的能力。成体干细胞的特性由来自其他细胞类型（称为生态位细胞）的外在信号维持。因此，适当的组织稳态需要生态位。生态位在组织发育过程中形成并募集干细胞；因此，在发育过程中必须建立适当数量的生态位细胞和干细胞。小生态位可能会募集太少的干细胞并导致组织退化，而大生态位可能会维持过多的干细胞并导致肿瘤发生。鉴于脊椎动物组织不适合大规模正向遗传学研究，果蝇卵巢作为研究多种生态位细胞类型和生殖细胞 (GC) 如何在体内协调调节的优秀模型而脱颖而出。最近的研究开始揭示各种信号分子如何调节生态位形成以及生态位细胞如何非自主地影响 GC 数量。在这篇综述中，我们总结了卵巢生态位结构、生态位形成的关键信号通路，以及生态位细胞如何产生外在因子来控制卵巢发育过程中的 GC 增殖。