Pagán-Westphal S M, Tabin C J
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Cell. 1998 Apr 3;93(1):25-35. doi: 10.1016/s0092-8674(00)81143-5.
The earliest known left-right asymmetric genes are expressed at Hensen's node during chick gastrulation. Gene expression following reorientation of the node shows asymmetry is instructed by adjacent tissue, hence left-right information originates outside the node. Subsequently, the node signals back to the lateral tissue, initiating a cascade leading to left-sided expression of nodal in the lateral plate mesoderm. Loss of nodal expression in the presence of blocking antibodies confirms that Sonic hedgehog is the key signal conveying left-right information from the node; however, manipulation of explant cultures suggests that the induction of nodal requires secondary signals produced in the paraxial mesoderm. These experiments establish the time of action of these signals to and from Hensen's node in establishing left-right asymmetry.
已知最早的左右不对称基因在鸡胚原肠胚形成期间于亨氏结处表达。结重新定向后的基因表达显示，不对称是由相邻组织引导的，因此左右信息源自结之外。随后，结向外侧组织发出信号，启动一系列反应，导致侧板中胚层中左侧的结节状基因表达。在存在阻断抗体的情况下结节状基因表达缺失，证实了音猬因子是从结传递左右信息的关键信号；然而，外植体培养实验表明，结节状基因的诱导需要在近轴中胚层产生的二级信号。这些实验确定了这些往返于亨氏结的信号在建立左右不对称过程中的作用时间。
