Irving C, Mason I
MRC Brain Development Programme, Department of Developmental Neurobiology, Guy's, King's and St. Thomas' Hospital Medical School, Hodgkin Building, Guy's Campus, London SE1 9RT, UK.
Development. 1999 Sep;126(18):3981-9. doi: 10.1242/dev.126.18.3981.
The midbrain-hindbrain boundary, or isthmus, is the source of signals that are responsible for regional specification of both the midbrain and anterior hindbrain. Fibroblast growth factor 8 (Fgf8) is expressed specifically at the isthmus and there is now good evidence that it forms at least part of the patterning signal. In this study, we use Fgf8 as a marker for isthmic cells to examine how interactions between midbrain and hindbrain can regenerate isthmic tissue and, thereby, gain insight into the normal formation and/or maintenance of the isthmus. We show that Fgf8-expressing tissue with properties of the isthmic organiser is generated when midbrain and rhombomere 1 tissue are juxtaposed but not when midbrain contacts any other rhombomere. The use of chick/quail chimeras shows that the isthmic tissue is largely derived from rhombomere 1. In a few cases a small proportion of the Fgf8-positive cells were of midbrain origin but this appears to be the result of a local respecification to a hindbrain phenotype, a process mimicked by ectopic FGF8. Studies in vitro show that the induction of Fgf8 is the result of a direct planar interaction between the two tissues and involves a diffusible signal.
中脑-后脑边界，即峡部，是负责中脑和前脑区域特化的信号源。成纤维细胞生长因子8（Fgf8）特异性地在峡部表达，现在有充分的证据表明它至少构成了部分模式信号。在本研究中，我们使用Fgf8作为峡部细胞的标志物，以研究中脑和后脑之间的相互作用如何再生峡部组织，从而深入了解峡部的正常形成和/或维持。我们发现，当中脑和菱脑节1组织并列时，会产生具有峡部组织者特性的Fgf8表达组织，但当中脑与任何其他菱脑节接触时则不会。鸡/鹌鹑嵌合体的实验表明，峡部组织主要来源于菱脑节1。在少数情况下，一小部分Fgf8阳性细胞来源于中脑，但这似乎是局部重新特化为后脑表型的结果，异位FGF8可模拟这一过程。体外研究表明，Fgf8的诱导是两种组织之间直接平面相互作用的结果，涉及一种可扩散信号。
