Lodde Valentina, Modina Silvia, Galbusera Cristina, Franciosi Federica, Luciano Alberto M
Institute of Anatomy of Domestic Animals, Histology and Embryology, Faculty of Veterinary Medicine, University of Milan, Italy.
Mol Reprod Dev. 2007 Jun;74(6):740-9. doi: 10.1002/mrd.20639.
In mammals, oocyte acquires a series of competencies sequentially during folliculogenesis that play critical roles at fertilization and early stages of embryonic development. In mouse, chromatin in germinal vesicle (GV) undergoes dynamic changes during oocyte growth and its progressive condensation has been related to the achievement of developmental potential. Cumulus cells are essential for the acquisition of meiotic competence and play a role in chromatin remodeling during oocyte growth. This study is aimed to characterize the chromatin configuration of growing and fully grown bovine oocytes, the status of communications between oocyte and cumulus cells and oocyte developmental potential. Following nuclear staining, we identified four discrete stages of GV, characterized by an increase of chromatin condensation. GV0 stage represented 82% of growing oocytes and it was absent in fully grown oocytes. GV1, GV2, and GV3 represented, respectively, 24, 31, and 45% of fully grown oocytes. Our data indicated a moderate but significant increase in oocyte diameter between GV0 and GV3 stage. By dye coupling assay the 98% of GV0 oocytes showed fully open communications while the number of oocytes with functionally closed communications with cumulus cells was significantly higher in GV3 group than GV1 and GV2. However, GV0 oocytes were unable to progress through metaphase II while GV2 and GV3 showed the highest developmental capability. We conclude that in bovine, the progressive chromatin condensation is related to the sequential achievement of meiotic and embryonic developmental competencies during oocyte growth and differentiation. Moreover, gap-junction-mediated communications between oocyte and cumulus cells could be implicated in modulating the chromatin remodeling process.
在哺乳动物中，卵母细胞在卵泡发生过程中依次获得一系列能力，这些能力在受精和胚胎发育早期起着关键作用。在小鼠中，生发泡（GV）中的染色质在卵母细胞生长过程中会发生动态变化，其逐渐凝聚与发育潜能的获得有关。卵丘细胞对于减数分裂能力的获得至关重要，并在卵母细胞生长过程中的染色质重塑中发挥作用。本研究旨在表征生长中和完全成熟的牛卵母细胞的染色质构型、卵母细胞与卵丘细胞之间的通讯状态以及卵母细胞的发育潜能。经过核染色后，我们确定了GV的四个不同阶段，其特征是染色质凝聚增加。GV0阶段占生长中卵母细胞的82%，在完全成熟的卵母细胞中不存在。GV1、GV2和GV3分别占完全成熟卵母细胞的24%、31%和45%。我们的数据表明，GV0和GV3阶段之间卵母细胞直径有适度但显著的增加。通过染料偶联试验，98%的GV0卵母细胞显示出完全开放的通讯，而与卵丘细胞功能上通讯封闭的卵母细胞数量在GV3组中显著高于GV1和GV2组。然而，GV0卵母细胞无法进入减数分裂中期II，而GV2和GV3显示出最高的发育能力。我们得出结论，在牛中，染色质的逐渐凝聚与卵母细胞生长和分化过程中减数分裂和胚胎发育能力的依次获得有关。此外，卵母细胞与卵丘细胞之间间隙连接介导的通讯可能参与调节染色质重塑过程。
