Rebagliati M R, Toyama R, Fricke C, Haffter P, Dawid I B
Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Dev Biol. 1998 Jul 15;199(2):261-72. doi: 10.1006/dbio.1998.8935.
Nodal-related 1 (ndr1) and nodal-related 2 (ndr2) genes in zebrafish encode members of the nodal subgroup of the transforming growth factor-beta superfamily. We report the expression patterns and functional characteristics of these factors, implicating them in the establishment of dorsal-ventral polarity and left-right asymmetry. Ndr1 is expressed maternally, and ndr1 and ndr2 are expressed during blastula stage in the blastoderm margin. During gastrulation, ndr expression subdivides the shield into two domains: a small group of noninvoluting cells, the dorsal forerunner cells, express ndr1, while ndr2 RNA is found in the hypoblast layer of the shield and later in notochord, prechordal plate, and overlying anterior neurectoderm. During somitogenesis, ndr2 is expressed asymmetrically in the lateral plate as are nodal-related genes of other organisms, and in a small domain in the left diencephalon, providing the first observation of asymmetric gene expression in the embryonic forebrain. RNA injections into Xenopus animal caps showed that Ndr1 acts as a mesoderm inducer, whereas Ndr2 is an efficient neural but very inefficient mesoderm inducer. We suggest that Ndr1 has a role in mesoderm induction, while Ndr2 is involved in subsequent specification and patterning of the nervous system and establishment of laterality.
斑马鱼中的节点相关基因1（ndr1）和节点相关基因2（ndr2）编码转化生长因子-β超家族节点亚组的成员。我们报道了这些因子的表达模式和功能特性，表明它们参与了背腹极性和左右不对称性的建立。Ndr1在母源期表达，ndr1和ndr2在囊胚期于胚盘边缘表达。在原肠胚形成过程中，ndr的表达将胚盾分为两个区域：一小群不内卷的细胞，即背侧前体细胞，表达ndr1，而ndr2 RNA则在胚盾的下胚层中发现，随后在脊索、前索板和覆盖其上的前神经外胚层中发现。在体节形成过程中，ndr2像其他生物的节点相关基因一样在侧板中不对称表达，并在左间脑中的一个小区域表达，这是在胚胎前脑中首次观察到不对称基因表达。向非洲爪蟾动物帽中注射RNA表明，Ndr1作为中胚层诱导因子起作用，而Ndr2是一种有效的神经诱导因子，但中胚层诱导效率很低。我们认为Ndr1在中胚层诱导中起作用，而Ndr2参与随后的神经系统特化和模式形成以及左右不对称性的建立。
