Mouse germline cysts, on average, develop into six oocytes supported by 24 nurse cells that transfer cytoplasm and organelles to generate a Balbiani body. We showed that between E14.5 and P5, cysts periodically activate some nurse cells to begin cytoplasmic transfer, which causes them to shrink and turnover within 2 days. Nurse cells die by a programmed cell death (PCD) pathway involving acidification, similar to Drosophila nurse cells, and only infrequently by apoptosis. Prior to initiating transfer, nurse cells co-cluster by scRNA-seq with their pro-oocyte sisters, but during their final 2 days, they cluster separately. The genes promoting oocyte development and nurse cell PCD are upregulated, whereas the genes that repress transfer, such as Tex14, and oocyte factors, such as Nobox and Lhx8, are under-expressed. The transferred nurse cell centrosomes build a cytocentrum that establishes a large microtubule aster in the primordial oocyte that organizes the Balbiani body, defining the earliest oocyte polarity.

小鼠生殖系囊肿平均发育成 6 个卵母细胞，由 24 个护士细胞支持，这些细胞转移细胞质和细胞器以产生 Balbiani 体。我们发现，在 E14.5 和 P5 之间，囊肿会周期性地激活一些护士细胞以开始细胞质转移，这导致它们在 2 天内收缩和周转。护士细胞死于涉及酸化的程序性细胞死亡 (PCD) 途径，类似于果蝇护士细胞，而且很少发生细胞凋亡。在开始转移之前，护士细胞通过 scRNA-seq 与其亲卵母细胞姐妹共同聚集，但在最后 2 天，它们分开聚集。促进卵母细胞发育和护理细胞 PCD 的基因被上调，而抑制转移的基因（如 Tex14）和卵母细胞因子（如 Nobox 和 Lhx8）表达不足。转移的护士细胞中心体构建了一个细胞中心，在组织 Balbiani 体的原始卵母细胞中建立了一个大的微管紫菀，定义了最早的卵母细胞极性。