Department of Physiology & Neurobiology, University of Connecticut, Storrs, CT 06269, USA.
Department of Physiology & Neurobiology, University of Connecticut, Storrs, CT 06269, USA
Development. 2019 Sep 19;146(18):dev179002. doi: 10.1242/dev.179002.
Proper development and maturation of a follicle is essential for successful ovulation and reproduction; however, the molecular mechanisms for follicle maturation, particularly for somatic follicle cell differentiation, are poorly understood. During oogenesis, the somatic follicle cells encasing oocytes undergo two distinct well-established transitions: the mitotic to endocycle switch at stage 6/7 and the endocycle to gene amplification switch at stage10A/10B. Here, we identify a novel third follicle cell transition that occurs in the final stages of oogenesis (stage 13/14). This late follicle cell transition is characterized by upregulation of the transcription factor Hindsight (Hnt), and downregulation of the homeodomain transcription factor Cut and the zinc-finger transcription factor Tramtrack-69 (Ttk69). We demonstrate that inducing expression of Cut in stage 14 follicle cells is sufficient to inhibit follicle rupture and ovulation through its negative regulation of Hnt and promotion of Ttk69 expression. Our work illustrates the importance of the stage13/14 transition for follicle maturation and demonstrates the complex regulation required for somatic follicle cells to differentiate into a state primed for follicle rupture and ovulation.
卵泡的正常发育和成熟对于排卵和生殖至关重要；然而，卵泡成熟的分子机制，特别是体细胞卵泡细胞分化的分子机制，还知之甚少。在卵子发生过程中，包围卵母细胞的体细胞卵泡细胞经历两个截然不同的明确转变：在第 6/7 阶段发生有丝分裂向内周期的转变，以及在第 10A/10B 阶段发生内周期向基因扩增的转变。在这里，我们发现了一个新的第三个卵泡细胞转变，它发生在卵子发生的最后阶段（第 13/14 阶段）。这个晚期卵泡细胞的转变特征是转录因子 Hindsight（Hnt）的上调，以及同源域转录因子 Cut 和锌指转录因子 Tramtrack-69（Ttk69）的下调。我们证明，在第 14 阶段的卵泡细胞中诱导表达 Cut，足以通过其对 Hnt 的负调控和促进 Ttk69 的表达来抑制卵泡破裂和排卵。我们的工作说明了第 13/14 阶段转变对于卵泡成熟的重要性，并表明了体细胞卵泡细胞分化为为卵泡破裂和排卵做好准备的状态所需要的复杂调控。
