Whangbo J, Kenyon C
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448, USA.
Mol Cell. 1999 Nov;4(5):851-8. doi: 10.1016/s1097-2765(00)80394-9.
In C. elegans, a bilateral pair of neuroblasts, QL and QR, give rise to cells that migrate in opposite directions along the anteroposterior (A/P) body axis. QL and its descendants migrate posteriorly whereas QR and its descendants migrate anteriorly. We find that a Wnt family member, EGL-20, acts in a dose-dependent manner to specify these opposite migratory behaviors. High levels of EGL-20 promote posterior migration by activating a canonical Wnt signal transduction pathway, whereas low levels promote anterior migration by activating a separate, undefined pathway. We find that the two Q cells respond differently to EGL-20 because they have different response thresholds. Thus, in this system two distinct dose-dependent responses are specified not by graded levels of the Wnt signal, but instead by left-right asymmetrical differences in the cellular responsiveness to Wnt signaling.
在秀丽隐杆线虫中，一对双侧神经母细胞QL和QR产生的细胞沿前后（A/P）身体轴朝相反方向迁移。QL及其后代向后迁移，而QR及其后代向前迁移。我们发现，一种Wnt家族成员EGL-20以剂量依赖的方式作用于指定这些相反的迁移行为。高水平的EGL-20通过激活经典的Wnt信号转导途径促进向后迁移，而低水平则通过激活一条单独的、未明确的途径促进向前迁移。我们发现这两个Q细胞对EGL-20的反应不同，因为它们具有不同的反应阈值。因此，在这个系统中，两种不同的剂量依赖性反应不是由Wnt信号的梯度水平指定的，而是由细胞对Wnt信号反应性的左右不对称差异指定的。
