Shelton C A, Bowerman B
Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403-1229, USA.
Development. 1996 Jul;122(7):2043-50. doi: 10.1242/dev.122.7.2043.
In an embryo of the nematode Caenorhabditis elegans, two blastomeres at the 4-cell stage, ABa and ABp, are born with equivalent developmental potential. Subsequently, interactions with the P2 blastomere at the 4-cell stage and the MS blastomere at the 12-cell stage generate differences in developmental fate among descendants of ABa and ABp. We have reproduced these inductions in vitro using embryonic blastomeres isolated in cell-culture medium. We show that during these inductions only the responding AB descendants require the activity of the glp-1 gene, which is similar in sequence to Drosophila Notch, supporting models in which GLP-1 protein acts as a receptor for both the P2 and MS signals. We also show that P2 signaling requires the activity of the apx-1 gene, similar in sequence to Drosophila Delta, and that MS signaling requires the putative transcription factor SKN-1. We present evidence that the primary factor determining the different responses to these two signals is the age of the AB descendants, not the identity of the signaling cell or ligand. Therefore, we suggest that time-dependent changes in factors within AB descendants are responsible for their different responses to inductive signals that use a common receptor.
在秀丽隐杆线虫的胚胎中，4细胞期的两个卵裂球ABa和ABp，具有同等的发育潜能。随后，4细胞期与P2卵裂球以及12细胞期与MS卵裂球的相互作用，使得ABa和ABp的后代在发育命运上产生差异。我们利用在细胞培养基中分离出的胚胎卵裂球在体外重现了这些诱导过程。我们发现，在这些诱导过程中，只有做出反应的AB后代需要glp-1基因的活性，该基因在序列上与果蝇的Notch相似，这支持了GLP-1蛋白作为P2和MS信号两者受体的模型。我们还发现，P2信号传导需要apx-1基因的活性，该基因在序列上与果蝇的Delta相似，并且MS信号传导需要假定的转录因子SKN-1。我们提供的证据表明，决定对这两种信号产生不同反应的主要因素是AB后代的年龄，而不是信号传导细胞或配体的身份。因此，我们认为AB后代内因子的时间依赖性变化导致了它们对使用共同受体的诱导信号产生不同反应。
