Wilms' tumor protein WT1 as an ovarian transcription factor: decreases in expression during follicle development and repression of inhibin-alpha gene promoter.
Wilms' tumor protein WT1 as an ovarian transcription factor: decreases in expression during follicle development and repression of inhibin-alpha gene promoter.
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DOI：
10.1210/mend.9.10.8544844
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发表时间：
1995-10
影响因子：
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通讯作者：
S. Hsu;Makoto Kubo;S. Chun;F. Haluska;David E. Housman;Aaron J. W. Hsueh
中科院分区：
文献类型：
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作者：
S. Hsu;Makoto Kubo;S. Chun;F. Haluska;David E. Housman;Aaron J. W. Hsueh
WT1是一些Wilms‘s肿瘤中缺失的一个基因，它编码一个带有锌指的转录因子，并与早期生长反应基因家族的蛋白质有同源性。虽然WT1基因的缺陷与肾母细胞瘤和泌尿生殖系统畸形有关，但WT1在性腺中的具体功能仍不清楚。采用Northern杂交、核糖核酸酶保护实验和原位杂交等方法研究WT1基因在卵泡发育过程中的表达。在卵巢、睾丸、子宫和肾脏中发现了丰富的WT1转录本，心脏和胰腺中的转录本水平较低。雌激素或促性腺激素处理不影响卵巢WT1mRNA的浓度。原位杂交分析表明，卵巢WT1mRNA仅在原始卵泡、初级卵泡和次级卵泡的表面上皮细胞和颗粒细胞中表达，随着卵泡的发育，其表达水平逐渐降低。尽管核糖核酸酶保护实验表明存在四种选择性剪接形式的WT1mRNA，但这些转录本的比例在卵巢生长过程中保持不变。两种颗粒细胞分化标志基因抑制素α和FSH受体表达的发育性变化与WT1水平呈负相关。由于在抑制素α基因的启动子中发现了潜在的WT1结合位点，我们进一步检验了WT1是否可能调节该基因的表达。将WT1表达载体与抑制素-α启动子报告质粒共转染后，CHO细胞中的启动子活性受到抑制，并呈剂量依赖性。这些结果表明WT1在原始卵泡、初级卵泡和次级卵泡的颗粒细胞中高表达，但随着卵泡的发育呈下降趋势。该转录因子可能是颗粒细胞中卵巢分化基因的抑制因子，在抑制未成熟卵泡的分化中发挥作用。
WT1, a gene deleted in some Wilms' tumors, encodes a transcription factor with zinc fingers and shares homology with proteins in the early growth response gene family. Although defects in the WT1 gene are associated with nephroblastoma and genitourinary malformation, the specific function of WT1 in the gonads remains unclear. We investigated the expression of WT1 transcripts in rat ovary during follicle development by Northern blotting, RNase protection assay, and in situ hybridization. Abundant WT1 transcripts were found in the ovary, testis, uterus, and kidney, with lower levels in the heart and pancreas. Treatment with estrogen or gonadotropins did not affect the concentration of ovarian WT1 mRNA. In situ hybridization analysis indicated that ovarian WT1 mRNA is expressed exclusively in the surface epithelium and granulosa cells of primordial, primary, and secondary follicles, and its levels decrease during follicle growth. Although RNase protection assay suggested the presence of four alternatively spliced forms of WT1 mRNA, the ratio of these transcripts remains constant during ovarian growth. Developmental changes in the expression of two granulosa cell differentiation marker genes, inhibin-alpha and FSH receptor, were found to be inversely correlated with WT1 levels. Because potential WT1-binding sites were found in the promoter of inhibin-alpha gene, we further tested whether WT1 might regulate the expression of this gene. Cotransfection of a WT1 expression vector with a promoter reporter plasmid of inhibin-alpha resulted in the repression of promoter activities in CHO cells in a dose-dependent manner. These results suggest that WT1 is expressed in high levels in granulosa cells of primordial, primary, and secondary follicles but decreases with follicle development. This transcription factor might be a repressor of ovarian differentiation genes in the granulosa cells and play a role in arresting the differentiation of immature follicles.