Mao C A, Wikramanayake A H, Gan L, Chuang C K, Summers R G, Klein W H
Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston 77030, USA.
Development. 1996 May;122(5):1489-98. doi: 10.1242/dev.122.5.1489.
While many general features of cell fate specification in the sea urchin embryo are understood, specific factors associated with these events remain unidentified. SpOtx, an orthodenticle-related protein, has been implicated as a transcriptional activator of the aboral ectoderm-specific Spec2a gene. Here, we present evidence that SpOtx has the potential to alter cell fates. SpOtx was found in the cytoplasm of early cleavage stage embryos and was translocated into nuclei between the 60- and 120-cell stage, coincident with Spec gene activation. Eggs injected with SpOtx mRNA developed into epithelial balls of aboral ectoderm suggesting that SpOtx redirected nonaboral ectoderm cells to an aboral ectoderm fate. At least three distinct domains on SpOtx, the homeobox and regions in the N-terminal and C-terminal halves of the protein, were required for the morphological alterations. These same N-terminal and C-terminal regions were shown to be transactivation domains in a yeast transactivation assay, indicating that the biological effects of overexpressing SpOtx were due to its action as a transcription factor. Our results suggest that SpOtx is involved in aboral ectoderm differentiation by activating aboral ectoderm-specific genes and that modulating its expression can lead to changes in cell fate.
虽然海胆胚胎细胞命运特化的许多一般特征已为人所知，但与这些事件相关的特定因子仍未明确。SpOtx是一种与orthodenticle相关的蛋白，被认为是口外胚层特异性Spec2a基因的转录激活因子。在此，我们提供证据表明SpOtx具有改变细胞命运的潜力。在早期卵裂阶段胚胎的细胞质中发现了SpOtx，并且在60到120细胞阶段之间它会转移到细胞核中，这与Spec基因的激活同时发生。注射了SpOtx mRNA的卵发育成口外胚层的上皮球，这表明SpOtx将非口外胚层细胞重定向为口外胚层命运。SpOtx上至少三个不同的结构域，即同源异型框以及蛋白质N端和C端的区域，是形态改变所必需的。在酵母转录激活试验中，这些相同的N端和C端区域被证明是转录激活结构域，表明过表达SpOtx的生物学效应是由于其作为转录因子的作用。我们的结果表明，SpOtx通过激活口外胚层特异性基因参与口外胚层分化，并且调节其表达可导致细胞命运的改变。
