Center for Species Survival, Smithsonian Conservation Biology Institute, Washington, DC 20008, USA.
Hum Reprod. 2011 Aug;26(8):2165-77. doi: 10.1093/humrep/der176. Epub 2011 Jun 10.
Chromatin configuration of the germinal vesicle (GV) and quality of the cytoplasm are critical factors in achieving oocyte meiotic and developmental capacity during folliculogenesis. Besides gaining new insights into the timing and cellular mechanisms associated with the acquisition and regulation of GV oocyte competence, the domestic cat model was used to examine (i) the relation between GV chromatin configuration and oocyte functionality during folliculogenesis and (ii) the role of the cytoplasmic environment on the GV competence and stability.
Structural and functional properties of GV oocytes were characterized after isolation from different follicle stages of non-stimulated cat ovaries. GV transfers, artificial chromatin compaction and oocyte vitrification were used to demonstrate the respective roles of GV and cytoplasm on the oocyte functionality.
GVs acquired the intrinsic capability to resume meiosis during the pre-antral follicle stage, whereas the capacity to support embryo development occurred while the antrum started to form. Chromatin configuration of the GV did not undergo extensive modification during the acquisition of competence or during the arrest of transcriptional activity at the large antral follicle stage. However, the quality and quantity of the cytoplasm regulated and enhanced GV functionality. This finding also held for GVs transferred from incompetent or subpar oocytes into the cytoplasm of good quality oocytes or when chromatin was artificially modified or vitrified.
The cat model provides a new insight into GV oocyte structure and function during folliculogenesis while challenging current concepts about oocyte quality criteria based on the GV morphology. This suggests alternative evaluative approaches for oocytes from other species too, including humans. Cat GVs also appear competent at an early follicle stage and are resilient to perturbations which designate this organelle as an attractive target for developing novel fertility preservation tactics.
卵母细胞生发泡（GV）的染色质构型和细胞质质量是卵母细胞在卵泡发生过程中获得减数分裂和发育能力的关键因素。除了深入了解与 GV 卵母细胞获得和调控能力相关的时间和细胞机制外，还使用家猫模型研究了：（i）在卵泡发生过程中，GV 染色质构型与卵母细胞功能之间的关系；（ii）细胞质环境对 GV 能力和稳定性的作用。
从非刺激猫卵巢的不同卵泡阶段分离出 GV 卵母细胞后，对其结构和功能特性进行了表征。GV 转移、人工染色质浓缩和卵母细胞玻璃化用于证明 GV 和细胞质各自对卵母细胞功能的作用。
GV 在窦前卵泡阶段获得了恢复减数分裂的内在能力，而支持胚胎发育的能力则是在窦开始形成时发生的。在获得能力或在大窦卵泡阶段转录活性停止时，GV 的染色质构型没有发生广泛修饰。然而，细胞质的质量和数量调节并增强了 GV 的功能。即使将无能力或次等的 GV 转移到高质量卵母细胞的细胞质中，或者人工修饰或玻璃化染色质时，也会出现这种情况。
猫模型为卵泡发生过程中 GV 卵母细胞的结构和功能提供了新的见解，同时对基于 GV 形态的卵母细胞质量标准提出了挑战。这表明，对于包括人类在内的其他物种的卵母细胞，也可以采用替代评估方法。猫 GV 在早期卵泡阶段就具有能力，并且对干扰具有弹性，这使该细胞器成为开发新的生育力保存策略的有吸引力的目标。
