Uitto J, Hsu-Wong S, Katchman S D, Bashir M M, Rosenbloom J
Department of Dermatology, Jefferson Medical College, Philadelphia, PA, USA.
Ciba Found Symp. 1995;192:237-53; discussion 253-8. doi: 10.1002/9780470514771.ch13.
Elastic fibres form an extracellular network which provides elasticity and resilience to tissues such as the skin. To study the regulation of human elastin gene expression, we have developed a line of transgenic mice which harbour 5.2 kb of human elastin gene promoter region in their genome. This promoter is linked to the chloramphenicol acetyltransferase (CAT) reporter gene which allows determination of the expression of human elastin promoter in different tissues. The highest CAT activity was found in the lungs and aorta, tissues rich in elastin, while lower levels were detected in a variety of other tissues, including skin. Assay of CAT activity in the lungs of fetal and newborn animals revealed high activity which progressively declined during the postnatal period up to six months. Thus, there was evidence of tissue-specific and developmentally regulated expression of the human elastin promoter activity in these mice. These animals were then used to examine the expression of the elastin gene by a variety of factors which have previously shown to alter elastin gene expression, as determined at the mRNA or protein levels. First, injection of transforming growth factor beta 1 (100 ng) subcutaneously into the transgenic animals resulted in a time-dependent elevation of the promoter activity up to 10-fold after a single injection. Secondly, enhancement of the human elastin promoter activity by interleukin 1 beta injected subcutaneously resulted in an approximately 10-fold elevation of the CAT activity. Finally, subcutaneous injection of these animals with triamcinolone acetonide or dexamethasone, two glucocorticosteroids in clinical use, resulted in marked enhancement of human elastin promoter activity. Similar changes were noted in fibroblast cultures established from the transgenic animals. These data indicate that the 5.2 kb upstream segment of the human elastin gene contains cis-elements which allow tissue-specific and developmentally regulated expression of the human elastin promoter. Furthermore, this segment of the gene contains responsive elements to a variety of cytokines and pharmacological agents. Collectively, these data indicate that elastin gene expression in the skin in vivo can be regulated at the transcriptional level.
弹性纤维形成一个细胞外网络，为诸如皮肤等组织提供弹性和韧性。为了研究人类弹性蛋白基因表达的调控，我们培育了一系列转基因小鼠，其基因组中含有5.2 kb的人类弹性蛋白基因启动子区域。该启动子与氯霉素乙酰转移酶（CAT）报告基因相连，这使得能够确定人类弹性蛋白启动子在不同组织中的表达情况。在富含弹性蛋白的肺和主动脉中发现了最高的CAT活性，而在包括皮肤在内的多种其他组织中检测到较低水平的活性。对胎儿和新生动物肺中CAT活性的检测显示活性很高，在出生后直至六个月的期间逐渐下降。因此，有证据表明在这些小鼠中人类弹性蛋白启动子活性存在组织特异性和发育调控性表达。然后利用这些动物来检测弹性蛋白基因受多种先前已表明能在mRNA或蛋白质水平改变弹性蛋白基因表达的因素的影响情况。首先，将转化生长因子β1（100 ng）皮下注射到转基因动物体内，单次注射后启动子活性会随时间依赖性升高至10倍。其次，皮下注射白细胞介素1β可增强人类弹性蛋白启动子活性，导致CAT活性升高约10倍。最后，给这些动物皮下注射曲安奈德或地塞米松这两种临床使用的糖皮质激素，会导致人类弹性蛋白启动子活性显著增强。从转基因动物建立的成纤维细胞培养物中也观察到了类似变化。这些数据表明，人类弹性蛋白基因5.2 kb的上游片段包含顺式元件，这些元件允许人类弹性蛋白启动子进行组织特异性和发育调控性表达。此外，该基因片段包含对多种细胞因子和药物制剂的反应元件。总体而言，这些数据表明体内皮肤中的弹性蛋白基因表达可在转录水平受到调控。
