Insulin-Like Growth Factor 3 Is Involved in Oocyte Maturation in Zebrafish
Insulin-Like Growth Factor 3 Is Involved in Oocyte Maturation in Zebrafish
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胰岛素样生长因子 3 参与斑马鱼卵母细胞的成熟
DOI：
10.1095/biolreprod.110.086363
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发表时间：
2011-03-01
影响因子：
3.6
通讯作者：
Cheng, Christopher H. K.
中科院分区：
文献类型：
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作者：
Li, Jianzhen;Liu, Zhihao;Cheng, Christopher H. K.
最近发现的IGF亚型(IGF3)在硬骨鱼中的性腺特异性表达表明了这种新的IGF在鱼类生殖功能中的重要作用。在本研究中，我们以斑马鱼为模式生物，进一步研究了Igf3在卵巢中的基因表达模式及其生理作用。斑马鱼的igf3基因被发现交替剪接成两个转录本，其中转录变异体1仅在性腺中表达，转录变异体2仅在发育早期表达。利用针对斑马鱼Igf3开发的特异性抗体，发现Igf3的前肽和成熟肽形式在斑马鱼的卵巢中都有优势表达。实时荧光定量聚合酶链式反应和原位杂交显示，igf3在早期卵泡中相对较低，在卵黄发生中期(中期III)后显著升高，在发育完全的卵泡中表达较高。在发育成熟的卵泡中，igf3mRNA主要在体细胞中表达，在卵母细胞中的表达水平较低。Igf3免疫反应仅局限于滤泡细胞。人绒毛膜促性腺激素处理后，IGF3在卵巢碎片和分离卵泡中的表达均显著上调，且呈剂量和时间依赖关系。用8-溴腺苷3‘，5’-环一磷酸或3-异丁基-1-甲基黄嘌呤处理也可上调成熟卵泡中igf3的表达。重组斑马鱼Igf3与卵泡孵育显著促进卵母细胞成熟，并呈时间、剂量和阶段依赖关系。放线菌素D不能阻断Igf3的作用，但环己亚胺能阻断其作用。综上所述，这些结果支持了Igf3在斑马鱼卵巢功能中的重要作用，尤其是在卵母细胞成熟过程中。
The gonad-specific expression of a recently discovered Igf subtype (Igf3) in teleost has indicated the important role of this novel Igf in the reproductive functions of fish. In the present study using zebrafish as the model organism, we have further examined the gene expression patterns and the physiological role of Igf3 in the ovary. The igf3 gene in zebrafish was found to be alternatively spliced into two transcripts, with transcript variant 1 exclusively expressed in the gonads, and transcript variant 2 only expressed during early development. Using specific antibodies developed for zebrafish Igf3, both the Igf3 prepropeptide and the mature peptide forms of Igf3 were found to be predominantly expressed in the zebrafish ovary. Real-time PCR and in situ hybridization revealed that igf3 mRNA is relatively low in the early follicles, but is significantly increased after the mid-vitellogenic stage (midstage III), and is high in the full-grown follicles. In the full-grown follicles, igf3 mRNA was detected mainly in the somatic follicular cells with a low level of expression in the oocytes. Igf3 immunoreactivity was confined to the follicular cells only. The expression of igf3 was significantly up-regulated in both ovarian fragments and isolated follicles upon treatment with human chorionic gonadotropin in dose-and time-dependent manners. Treatment with 8-bromoadenosine 3',5'-cyclic monophosphate or 3-isobutyl-1-methylxanthine also up-regulated the expression of igf3 in full-grown follicles. Incubation of follicles with recombinant zebrafish Igf3 significantly enhanced oocyte maturation in time-, dose-, and stage-dependent manners. The actions of Igf3 could be blocked by cycloheximide, but not by actinomycin D. Taken together, these results support an important role of Igf3 in the ovarian functions of zebrafish, especially in oocyte maturation.