Royzman Irena, Hayashi-Hagihara Aki, Dej Kimberley J, Bosco Giovanni, Lee Janice Y, Orr-Weaver Terry L
Whitehead Institute, Nine Cambridge Center, Cambridge, MA 02142, USA.
Mech Dev. 2002 Dec;119(2):225-37. doi: 10.1016/s0925-4773(02)00388-x.
During Drosophila oogenesis nurse cells become polyploid, enabling them to provide the developing oocyte with vast amounts of maternal messages and products. The nurse cells then die by apoptosis. In nurse cells, as in many other polyploid or polytene tissues, replication is differentially controlled and the heterochromatin is underreplicated. The nurse cell chromosomes also undergo developmentally induced morphological changes from being polytene, with tightly associated sister chromatids, to polyploid, with dispersed sister chromatids. We used female-sterile dE2F1 and dDP mutants to assess the role of the E2F cell cycle regulator in oogenesis and the relative contributions of transcriptional activation versus repression during nurse cell development. We report here that E2F1 transcriptional activity in nurse cells is essential for the robust synthesis of S-phase transcripts that are deposited into the oocyte. dE2F1 and dDP are needed to limit the replication of heterochromatin in nurse cells. In dE2F1 mutants the nurse cell chromosomes do not properly undergo the transition from polyteny to polyploidy. We also find that dDP and dE2F1 are needed for nurse cell apoptosis, implicating transcriptional activation of E2F target genes in this process.
在果蝇卵子发生过程中，营养细胞会变成多倍体，使其能够为发育中的卵母细胞提供大量母源信息和产物。然后，营养细胞通过凋亡死亡。在营养细胞中，与许多其他多倍体或多线组织一样，复制受到差异控制，异染色质复制不足。营养细胞染色体也会经历发育诱导的形态变化，从具有紧密相连姐妹染色单体的多线染色体，转变为具有分散姐妹染色单体的多倍体染色体。我们使用雌性不育的dE2F1和dDP突变体来评估E2F细胞周期调节因子在卵子发生中的作用，以及在营养细胞发育过程中转录激活与抑制的相对贡献。我们在此报告，营养细胞中的E2F1转录活性对于沉积到卵母细胞中的S期转录本的强劲合成至关重要。dE2F1和dDP是限制营养细胞中异染色质复制所必需的。在dE2F1突变体中，营养细胞染色体不能正确地从多线染色体转变为多倍体染色体。我们还发现，dDP和dE2F1是营养细胞凋亡所必需的，这意味着在此过程中E2F靶基因的转录激活。
