Hermesz E, Mackem S, Mahon K A
Laboratory of Mammalian Genes and Development, NICHD, National Institutes of Health, Bethesda, MD 20892, USA.
Development. 1996 Jan;122(1):41-52. doi: 10.1242/dev.122.1.41.
We have isolated a new murine homeobox gene, Rpx (for Rathke's pouch homeobox), that is dynamically expressed in the prospective cephalic region of the embryo during gastrulation. Early expression is seen in the anterior midline endoderm and prechordal plate precursor. Expression is subsequently activated in the overlying ectoderm of the cephalic neural plate, suggesting that inductive contact with Rpx-expressing mesendoderm is required for this expression. Subsequently, Rpx expression is extinguished in the mesendoderm while remaining in the prospective prosencephalic region of the neural plate ectoderm. Ultimately, transcripts become restricted to Rathke's pouch, the primordium of the pituitary, which is known to be derived from the most anterior ectoderm of the early embryo. Down regulation of Rpx in the pouch coincides with the differentiation of pituitary-specific cell types. Rpx is the earliest known marker for the pituitary primordium, suggestive of a role in the early determination or differentiation of the pituitary. Since Rpx is expressed so dynamically and so early in the anterior region of the embryo, and since its early expression domain is much more extensive than the region fated to form the pituitary, it is likely that Rpx is involved in the initial determination of the anterior (prechordal) region of the embryo.
我们分离出了一个新的小鼠同源框基因Rpx（Rathke囊同源框基因），该基因在原肠胚形成期在胚胎的预期头部区域动态表达。早期表达见于前中线内胚层和前索板前体。随后，在头部神经板的上覆外胚层中表达被激活，这表明与表达Rpx的中内胚层的诱导性接触是这种表达所必需的。随后，Rpx在中内胚层中表达消失，而在神经板外胚层的预期前脑区域中仍保留表达。最终，转录本局限于Rathke囊，即垂体原基，已知其起源于早期胚胎最前端的外胚层。Rpx在囊中表达下调与垂体特异性细胞类型的分化同时发生。Rpx是已知最早的垂体原基标志物，提示其在垂体早期决定或分化中起作用。由于Rpx在胚胎前部如此动态且如此早期地表达，并且由于其早期表达区域比注定形成垂体的区域广泛得多，因此Rpx可能参与胚胎前部（前索）区域的初始决定。
