The ontogeny of alpha-fetoprotein gene expression in the mouse gastrointestinal tract.
The ontogeny of alpha-fetoprotein gene expression in the mouse gastrointestinal tract.
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DOI：
10.1083/jcb.110.4.915
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发表时间：
1990-04
期刊：
影响因子：
--
通讯作者：
Tilghman SM
中科院分区：
文献类型：
--
作者：
Tyner AL;Godbout R;Compton RS;Tilghman SM
甲胎蛋白(AFP)基因在胚胎和成年小鼠胃肠道中的表达的个体发育已被研究。AFP信使核糖核酸约占胎儿肠道总信使RNA的0.1%。转录本通过原位杂交定位于胎儿肠道绒毛内的上皮细胞。在出生时，AFP mRNA迅速下降，达到较低的成人基础水平，这不受RAF的不同等位基因的影响，RAF基因决定了成人肝脏中AFP mRNA的基础水平。成人肠道中的基础水平是少数肠道内分泌细胞持续转录甲胎蛋白的结果，这些细胞很少分布在绒毛上。用嗜铬粒素A和甲胎蛋白双抗体染色鉴定这些细胞。之前的研究导致了一系列转基因小鼠的产生，该转基因小鼠含有内部缺失的AFP基因，该基因在胎儿肠道中大量过度表达。转基因不适当高水平表达的基础被证明是绒毛上皮细胞中非常高水平转录的结果，而不是在不适当的细胞类型中表达的结果。用人结肠腺癌细胞系Caco-2研究了AFP基因在肠道表达所需的顺式作用DNA序列。这些实验表明，除了一个例外，该基因启动子和增强子区域所需的调控元件与肝脏高水平表达所必需的调控元件一致。唯一的例外是位于该基因上游5kbp DNA的增强子II，它在Caco-2细胞中没有表现出活性。
The ontogeny of alpha-fetoprotein (AFP) gene expression has been examined in the fetal and adult mouse gastrointestinal tract. AFP mRNA constitutes approximately 0.1% of total mRNA in the fetal gut. The transcripts were localized by in situ hybridization to the epithelial cells lining the villi of the fetal gut. At birth, AFP mRNA declines rapidly to achieve low adult basal levels, which are not affected by different alleles of raf, a gene that determines the adult basal level of AFP mRNA in the liver. The basal level in the adult gut is the consequence of continued AFP transcription in a small number of enteroendocrine cells that are distributed infrequently on the villi. These cells were identified by double antibody staining with antibodies to chromogranin A, an enteroendocrine cell marker and AFP. Previous studies resulted in the generation of a line of transgenic mice containing an internally deleted AFP gene that was greatly overexpressed in the fetal gut. The basis for the inappropriately high level expression of the transgene was shown to be the consequence of very high levels of transcription in the epithelial cells of the villi rather than to expression in inappropriate cell types. The cis-acting DNA sequences required for expression of the AFP gene in the gut were investigated using Caco-2 cells, a human colon adenocarcinoma cell line. These experiments indicated that, with one exception, the regulatory elements required in both the promoter and enhancer regions of the gene coincided with those that are necessary for high level expression in the liver. The one exception was enhancer II, located 5 kbp of DNA upstream of the gene, which exhibited no activity in Caco-2 cells.