Eppig J J, Wigglesworth K, Chesnel F
Jackson Laboratory, Bar Harbor, Maine 04609.
Dev Biol. 1993 Aug;158(2):400-9. doi: 10.1006/dbio.1993.1198.
Fully grown mouse oocytes secrete a factor that enables the surrounding cumulus cells to undergo cumulus expansion upon stimulation of the cumulus cells with follicle-stimulating hormone in vitro. The secretion of the enabling factor by the oocytes is developmentally regulated; it is normally secreted in significant amounts only by oocytes that are competent of undergoing spontaneous germinal vesicle breakdown (GVB) and resuming the first meiotic division. The objective of this study was to determine the relationship, if any, among secretion of this factor, oocyte growth, and the competence to undergo GVB. Three experimental systems were used to assess these relationships. First, 20 to 25% of the oocytes isolated from the small antral follicles of mutant hypogonadal mice were GVB-incompetent even though they had achieved a size typical of GVB-competent oocytes. These large GVB-incompetent oocytes secreted almost as much cumulus expansion enabling factor as the GVB-competent oocytes. Second, GVB-incompetent oocytes cultured under conditions that promote the acquisition of GVB competence but not oocyte growth acquired the ability to secrete the cumulus expansion enabling factor. Third, the precocious activation of maturation promoting factor (MPF) in GVB-incompetent oocytes by okadaic acid did not stimulate the secretion of cumulus expansion enabling factor. It is concluded that the secretion of cumulus expansion enabling factor by oocytes is (1) independent of oocyte growth, (2) independent of competence to undergo GVB, and (3) not induced by the precocious activation of MPF. Thus, although the secretion of the enabling factor normally coincides with the time of acquisition of competence to undergo GVB, the ability to secrete the enabling factor is independent of oocyte maturation. Nevertheless, factors that promote the oocyte's program that leads to competence to undergo GVB probably also promote the ability to secrete the enabling factor.
完全成熟的小鼠卵母细胞分泌一种因子，在体外卵泡刺激素刺激卵丘细胞时，该因子能使周围的卵丘细胞发生卵丘扩展。卵母细胞分泌这种促成因子受发育调控；通常只有能够自发发生生发泡破裂（GVB）并恢复第一次减数分裂的卵母细胞才会大量分泌该因子。本研究的目的是确定这种因子的分泌、卵母细胞生长以及发生GVB的能力之间是否存在关系。使用了三个实验系统来评估这些关系。首先，从突变性腺功能减退小鼠的小窦卵泡中分离出的20%至25%的卵母细胞，尽管它们已经达到了具有GVB能力的卵母细胞的典型大小，但却不具备GVB能力。这些大的无GVB能力的卵母细胞分泌的卵丘扩展促成因子几乎与有GVB能力的卵母细胞一样多。其次，在促进获得GVB能力但不促进卵母细胞生长的条件下培养的无GVB能力的卵母细胞获得了分泌卵丘扩展促成因子的能力。第三，冈田酸对无GVB能力的卵母细胞中成熟促进因子（MPF）的早熟激活并未刺激卵丘扩展促成因子的分泌。得出的结论是，卵母细胞分泌卵丘扩展促成因子（1）与卵母细胞生长无关，（2）与发生GVB的能力无关，（3）不受MPF早熟激活的诱导。因此，尽管促成因子的分泌通常与获得GVB能力的时间一致，但分泌促成因子的能力与卵母细胞成熟无关。然而，促进卵母细胞获得GVB能力的程序的因素可能也会促进分泌促成因子的能力。
