Department of Biological Sciences, University of New Hampshire, 38 College Road, Durham, NH 03824, USA.
Gen Comp Endocrinol. 2012 Nov 1;179(2):296-304. doi: 10.1016/j.ygcen.2012.09.003. Epub 2012 Sep 13.
Follicular maturational competence and ovulatory competence in teleost fish refer to the ability of the ovarian follicle to undergo final oocyte maturation and ovulation, respectively, in response to gonadotropin stimulation and other external cues. Some gene products related to competence acquisition are likely synthesized during vitellogenic growth, as these follicles gain in vivo responsiveness to exogenous gonadotropin stimulation and can be induced to undergo maturation and ovulation. In Atlantic cod (Gadus morhua), gonadotropin responsiveness has been shown to be oocyte size-dependent, and only ovaries containing late-stage vitellogenic follicles can be induced to ovulate. The purpose of the present study was to compare gene expression patterns between mid (unresponsive) and late (responsive) vitellogenic ovaries to identify genes involved in gonadotropin responsiveness and the acquisition of maturational and ovulatory competencies. Representational difference analysis was conducted in two reciprocal comparisons using intact ovarian fragments and follicle wall-enriched tissues, and genes of interest were used in real time quantitative PCR to confirm differential expression. Few differences were detected in intact ovarian fragments, but type IV ice-structuring protein and gephyrin were upregulated later in development and may be involved in lipid and sulfur metabolism, respectively. Candidate gene assays for luteinizing hormone receptor and aromatase also exhibited significant upregulation during vitellogenesis. Many genes were differentially expressed in follicle wall-enriched tissues, including endocrine maturational regulators and smooth muscle genes. Overall, maturational and ovulatory competencies during vitellogenesis in Atlantic cod are associated with up- and downregulation of many genes involved in lipid metabolism, endocrine regulation, and ovulatory preparation.
鱼类卵母细胞的滤泡成熟能力和排卵能力分别指的是卵巢滤泡对促性腺激素刺激和其他外部信号的最终卵母细胞成熟和排卵的能力。一些与获得能力相关的基因产物可能在卵黄发生生长过程中合成，因为这些滤泡对体外促性腺激素刺激的反应性增加，并且可以被诱导成熟和排卵。在大西洋鳕鱼（Gadus morhua）中，已证明促性腺激素的反应性与卵母细胞大小有关，只有含有晚期卵黄发生滤泡的卵巢才能被诱导排卵。本研究的目的是比较中（无反应）期和晚期（反应）卵黄发生卵巢之间的基因表达模式，以鉴定与促性腺激素反应性和获得成熟及排卵能力相关的基因。使用完整的卵巢片段和滤泡壁富集组织进行了两次相互比较的代表性差异分析，并使用实时定量 PCR 对感兴趣的基因进行了验证，以确认差异表达。在完整的卵巢片段中检测到的差异很少，但在发育后期，IV 型冰晶蛋白和 Gephyrin 的表达上调，可能分别参与脂质和硫代谢。黄体生成素受体和芳香化酶的候选基因检测在卵黄发生过程中也表现出明显的上调。在滤泡壁富集组织中，许多基因表达差异，包括内分泌成熟调节剂和平滑肌基因。总的来说，大西洋鳕鱼卵黄发生过程中的成熟和排卵能力与涉及脂质代谢、内分泌调节和排卵准备的许多基因的上调和下调有关。
