Cloning of the factors determining specific production of GH in somatotrophs and their pathophysiological significance

Pit-1是一种垂体特异性转录因子，可刺激生长激素（GH）、催乳素（PRL）和促甲状腺激素-β（TSH-β）基因的表达。然而，难以解释GH、PRL和TSH-β的细胞特异性表达，因为它们在不同的细胞中产生。尽管GH基因的基因座控制区（LCR）对于决定GH的生长激素特异性表达很重要，但尚不清楚是什么机制调节GH的细胞特异性表达。为了阐明该机制，我们试图通过从基因组DNA和RNA干扰文库中对含有LCR-GH-GFP报告基因的垂体细胞进行细胞分选来寻找与LCR结合的因子。不幸的是，我们直到现在还不能得到这些因素。然而，LCR在细胞分化中的意义在我们的研究中已经阐明。我们建立了在其基因组中含有LCR-GH-GFP基因的ES细胞。GFP表达与ES细胞向生长激素细胞分化过程中的GH产生平行。转染LCR-GH-GFP基因的细胞中GFP的表达高于转染GH-GFP基因的细胞。接下来，我们测试了激素、生长因子和细胞因子刺激向生长激素细胞分化的功能，出乎意料地发现LIF是一种有效的因子。

Pit-1 is a pituitary specific transcription factor that stimulates growth hormone (GH), prolactin (PRL) and TSH-β gene expression. However it is difficult to explain cell-specific expression of GH, PRL and TSH-β since they are produced in different cells. Although locus control region (LCR) of GH gene is important to determine somatotroph-specific expression of GH, it is unknown what mechanism regulates cell-specific expression of GH. To clarify the mechanism, we tried to find factors that bind to the LCR using cell sorting of pituitary cells containing LCR-GH-GFP reporter in genome DNA and RNA interference library. Unfortunately we cannot obtain the factors until now. However the significance of LCR in cell differentiation has been clarified in our study. We established ES cells that contain LCR-GH-GFP gene in their genomes. GFP expression was parallel to GH production in the ES cells during differentiation to somatotrophs. GFP expression was higher in the cells containing LCR-GH-GFP gene than the cells with GH-GFP gene. Next, we tested the functions of hormones, growth factors and cytokines to stimulate differentiation to somatotrophs and unexpectedly found LIF was a potent factor.