Sarapura Virginia D, Wood William M, Woodmansee Whitney W, Haakinson Danielle J, Dowding Janet M, Gordon David F, Ridgway E Chester
Department of Medicine, Division of Endocrinology, University of Colorado Health Sciences Center, Denver, CO 80045, USA.
Pituitary. 2006;9(1):11-8. doi: 10.1007/s11102-006-7865-8.
Glycoprotein-hormone alpha-subunit deficient (alphaSUnull) mice are hypothyroid and hypogonadal due to the absence of functional TSH, LH and FSH, despite normal production of the corresponding beta subunits. Pituitary tumors spontaneously developing in alphaSUnull mice were propagated in hypothyroid mice. The purpose of the current studies was to compare the gene expression profile of these alphaSUnull tumors with previously characterized TtT-97 thyrotropic tumors. A group of animals bearing each tumor type was treated with thyroid hormone (T4) prior to tumor removal. Both tumor types equally expressed TSHbeta mRNA, which significantly decreased when exposed to T4, whereas alpha-subunit mRNA was absent in alphaSUnull tumors. Northern blot analysis was performed using cDNA probes for the following transcription factors: Pit1, GATA2, pLIM, Msx1, Ptx1 and Ptx2. Both tumors were found to contain identical transcripts with similar responses to T4, with the exception of Pit1. In contrast to the signal pattern seen in TtT-97, only two bands were seen in alphaSUnull tumors, which were similar in size to those in alphaTSH cells, a thyrotropic cell line that lacks TSHbeta-subunit expression and Pit1 protein. However, western blot analysis revealed a protein band in the alphaSUnull tumors consistent with Pit1, while this signal was absent in alphaTSH cells. Northern blot analysis was also performed with specific cDNA probes for the following receptors: TRbeta1, TRbeta2, TRalpha1, non-T3 binding alpha2, RXRgamma and Sst5. Similarly-sized transcripts were found in both types of tumor, although the signal for Sst5 was seen in T4-treated alphaSUnull tumors only with a more sensitive RT-PCR analysis. The overall similarity between the two tumor types renders the alphaSUnull tumor as a suitable thyrotropic tumor model.
糖蛋白激素α亚基缺陷（αSU缺失）小鼠由于缺乏功能性促甲状腺激素（TSH）、促黄体生成素（LH）和促卵泡激素（FSH）而表现为甲状腺功能减退和性腺功能减退，尽管相应的β亚基产生正常。αSU缺失小鼠自发形成的垂体肿瘤在甲状腺功能减退的小鼠中得以传代。本研究的目的是比较这些αSU缺失肿瘤与先前已表征的TtT-97促甲状腺肿瘤的基因表达谱。一组携带每种肿瘤类型的动物在切除肿瘤前接受甲状腺激素（T4）治疗。两种肿瘤类型均等量表达TSHβ mRNA，暴露于T4时该mRNA显著减少，而αSU缺失肿瘤中不存在α亚基mRNA。使用针对以下转录因子的cDNA探针进行Northern印迹分析：Pit1、GATA2、pLIM、Msx1、Ptx1和Ptx2。发现两种肿瘤含有相同的转录本，对T4的反应相似，但Pit1除外。与TtT-97中观察到的信号模式不同，αSU缺失肿瘤中仅可见两条带，其大小与αTSH细胞中的带相似，αTSH细胞是一种缺乏TSHβ亚基表达和Pit1蛋白的促甲状腺细胞系。然而，蛋白质印迹分析显示αSU缺失肿瘤中有一条与Pit1一致的蛋白带，而αTSH细胞中不存在该信号。还使用针对以下受体的特异性cDNA探针进行Northern印迹分析：TRβ1、TRβ2、TRα1、非T3结合α2、RXRγ和Sst5。两种肿瘤类型中发现了大小相似的转录本，尽管仅在经T4处理的αSU缺失肿瘤中通过更灵敏的逆转录-聚合酶链反应（RT-PCR）分析才能看到Sst5的信号。两种肿瘤类型之间的总体相似性使αSU缺失肿瘤成为一种合适的促甲状腺肿瘤模型。
