Weng Wei, Stemple Derek L
Vertebrate Development and Genetics (Team31), Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom.
Birth Defects Res C Embryo Today. 2003 Nov;69(4):325-32. doi: 10.1002/bdrc.10027.
The understanding of germ layer formation in vertebrates began with classical experimental embryology. Early in the 20th century, Spemann and Mangold (1924) identified a region of the early embryo capable of inducing an entire embryonic axis. Termed the dorsal organizer, the tissue and the activity have been shown to exist in all vertebrates examined. In mice, for example, the activity resides in a region of the gastrula embryo known as the node. Experiments by the Dutch embryologist Nieuwkoop (1967a, 1967b, 1973, 1977) showed that a signal derived from the vegetal half of the amphibian embryo is responsible for the formation of mesoderm. Nieuwkoop's results allowed the development of in vitro assays that led, in the late 1980s and early 1990s, to the identification of growth factors essential for germ layer formation. Through more recent genetic investigations in mice and zebrafish, we now know that one class of secreted growth factor, called Nodal because of its localized expression in the mouse node, is essential for formation of mesoderm and endoderm and for the morphological rearrangements that occur during gastrulation.
对脊椎动物中胚层形成的理解始于经典实验胚胎学。20世纪初，施佩曼和曼戈尔德（1924年）确定了早期胚胎中一个能够诱导整个胚胎轴形成的区域。这个组织和活性被称为背侧组织者，已被证明存在于所有被研究的脊椎动物中。例如，在小鼠中，这种活性存在于原肠胚胚胎的一个称为节点的区域。荷兰胚胎学家尼乌科普（1967年a、1967年b、1973年、1977年）的实验表明，来自两栖类胚胎植物极一半的信号负责中胚层的形成。尼乌科普的结果推动了体外测定法的发展，在20世纪80年代末和90年代初，这些测定法导致了对胚层形成所必需的生长因子的鉴定。通过最近对小鼠和斑马鱼的基因研究，我们现在知道，一类分泌型生长因子，因其在小鼠节点中的局部表达而被称为Nodal，对于中胚层和内胚层的形成以及原肠胚形成期间发生的形态重排至关重要。
