Wilson P A, Hemmati-Brivanlou A
Rockefeller University, New York, New York 10021-6322, USA.
Nature. 1995 Jul 27;376(6538):331-3. doi: 10.1038/376331a0.
During gastrulation in vertebrates, ectodermal cells choose between two fates, neural and epidermal. The nervous system forms in response to signals from the Spemann organizer; ectoderm that does not receive these signals becomes epidermis. Unexpectedly, however, in Xenopus, neural tissue also forms when cell-cell communication within the ectoderm is disrupted by cell dissociation or by antagonists of the growth factor activin. These observations suggest that epidermal specification depends on local signalling, by activin or a close relative, and that neural tissue forms when this communication is blocked. Here we report that bone morphogenesis protein 4 (Bmp-4), a relative of activin that is expressed in the embryo at the time of ectodermal fate determination, is a potent epidermal inducer and neural inhibitor, the first reported in any vertebrate. Activin can inhibit neuralization by inducing mesoderm, but does not induce epidermis. Moreover, the dominant-negative activin receptor, which stimulates neuralization when expressed in the embryo, blocks Bmp-4 in our assay. Our findings demonstrate that epidermal fate can be induced, and thus provide further evidence that neural specification is under inhibitory control in vertebrates.
在脊椎动物原肠胚形成过程中，外胚层细胞在两种命运之间做出选择，即分化为神经细胞和表皮细胞。神经系统的形成是对斯佩曼组织者发出的信号作出的反应；未接收到这些信号的外胚层会发育成表皮。然而，出乎意料的是，在非洲爪蟾中，当外胚层内的细胞间通讯因细胞解离或生长因子激活素的拮抗剂而受到破坏时，也会形成神经组织。这些观察结果表明，表皮的特化取决于激活素或其近亲的局部信号传导，并且当这种通讯被阻断时会形成神经组织。在此，我们报告骨形态发生蛋白4（Bmp - 4），它是激活素的亲属，在胚胎外胚层命运确定时表达，是一种有效的表皮诱导剂和神经抑制剂，这是在任何脊椎动物中首次报道的。激活素可以通过诱导中胚层来抑制神经分化，但不会诱导表皮形成。此外，在胚胎中表达时会刺激神经分化的显性负性激活素受体，在我们的实验中会阻断Bmp - 4。我们的研究结果表明表皮命运是可以被诱导的，从而进一步证明在脊椎动物中神经特化处于抑制性控制之下。
