Makover A, Soprano D R, Wyatt M L, Goodman D S
Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032.
Differentiation. 1989 Mar;40(1):17-25. doi: 10.1111/j.1432-0436.1989.tb00809.x.
The patterns, and the cellular sites, of expression of the genes for retinol-binding protein (RBP) and transthyretin (TTR) were studied during early- to mid-stages of rat embryogenesis. In situ hybridization of single-stranded RNA probes to rat embryo sections revealed specific sites at which RBP messenger RNA (mRNA) and TTR mRNA were localized in rat conceptuses from 7 to 13 days of gestation. RBP and TTR mRNAs were both observed in the visceral endoderm as early as at 7 days of gestation. The transcripts were not expressed in the parietal endoderm. At 9 days of gestation, TTR mRNA was strongly detected in the visceral extraembryonic endoderm and in the foregut endoderm, whereas RBP mRNA was detected only in the visceral extraembryonic endoderm. From the 10th day to the 13th day of gestation, both transcripts were increasingly expressed in the visceral yolk sac endoderm and in the developing fetal liver, and gradually decreased in the foregut. At 11 days of gestation, TTR mRNA was first detected in the tela choroidea of the fourth ventricle in the brain; and at 13 days, the TTR mRNA was strongly evident in the developing choroid plexus of the fourth and lateral ventricles. These in situ hybridization studies with embryos at different developmental stages show that RBP and TTR mRNAs are transcribed quite early during embryogenesis. The protein products of these transcripts may play important roles in vitamin A and thyroid hormone metabolism, and in the functions that these regulatory compounds play, in the developing rat embryo.
在大鼠胚胎发育的早期至中期，研究了视黄醇结合蛋白（RBP）和转甲状腺素蛋白（TTR）基因的表达模式及细胞定位。将单链RNA探针与大鼠胚胎切片进行原位杂交，结果显示在妊娠7至13天的大鼠胚胎中，RBP信使核糖核酸（mRNA）和TTR mRNA的特定定位位点。早在妊娠7天时，在内脏内胚层中就同时观察到了RBP和TTR mRNA。这些转录本在体壁内胚层中不表达。在妊娠9天时，在内脏胚外内胚层和前肠内胚层中强烈检测到TTR mRNA，而RBP mRNA仅在内脏胚外内胚层中检测到。从妊娠第10天到第13天，两种转录本在内脏卵黄囊内胚层和发育中的胎儿肝脏中表达逐渐增加，而在前肠中逐渐减少。在妊娠11天时，首次在脑第四脑室脉络膜中检测到TTR mRNA；在13天时，在第四脑室和侧脑室发育中的脉络丛中TTR mRNA非常明显。这些对不同发育阶段胚胎的原位杂交研究表明，RBP和TTR mRNA在胚胎发育过程中很早就开始转录。这些转录本的蛋白质产物可能在维生素A和甲状腺激素代谢以及这些调节化合物在发育中的大鼠胚胎中所起的功能中发挥重要作用。
