Heimbucher Thomas, Murko Christina, Bajoghli Baubak, Aghaallaei Narges, Huber Anja, Stebegg Ronald, Eberhard Dirk, Fink Maria, Simeone Antonio, Czerny Thomas
Institute of Animal Breeding and Genetics, University of Veterinary Medicine, Veterinärplatz 1, A-1210 Vienna, Austria.
Mol Cell Biol. 2007 Jan;27(1):340-51. doi: 10.1128/MCB.00811-06. Epub 2006 Oct 23.
One of the earliest organizational decisions in the development of the vertebrate brain is the division of the neural plate into Otx2-positive anterior and Gbx2-positive posterior territories. At the junction of these two expression domains, a local signaling center is formed, known as the midbrain-hindbrain boundary (MHB). This tissue coordinates or "organizes" the development of neighboring brain structures, such as the midbrain and cerebellum. Correct positioning of the MHB is thought to depend on mutual repression involving these two homeobox genes. Using a cell culture colocalization assay and coimmunoprecipitation experiments, we show that engrailed homology region 1 (eh1)-like motifs of both transcription factors physically interact with the WD40 domain of Groucho/Tle corepressor proteins. In addition, heat shock-induced expression of wild-type and mutant Otx2 and Gbx2 in medaka embryos demonstrates that Groucho is required for the repression of Otx2 by Gbx2. On the other hand, the repressive functions of Otx2 on Gbx2 do not appear to be dependent on corepressor interaction. Interestingly, the association of Groucho with Otx2 is also required for the repression of Fgf8 in the MHB. Therefore Groucho/Tle family members appear to regulate key aspects in the MHB development of the vertebrate brain.
脊椎动物大脑发育过程中最早的组织决定之一是神经板分为Otx2阳性的前部区域和Gbx2阳性的后部区域。在这两个表达域的交界处，形成了一个局部信号中心，称为中脑-后脑边界（MHB）。该组织协调或“组织”相邻脑结构（如中脑和小脑）的发育。MHB的正确定位被认为取决于这两个同源异型盒基因之间的相互抑制作用。通过细胞培养共定位分析和免疫共沉淀实验，我们发现这两种转录因子的engrailed同源区域1（eh1）样基序与Groucho/Tle共抑制蛋白的WD40结构域发生物理相互作用。此外，热休克诱导的野生型和突变型Otx2及Gbx2在青鳉胚胎中的表达表明，Groucho是Gbx2抑制Otx2所必需的。另一方面，Otx2对Gbx2的抑制功能似乎不依赖于共抑制因子的相互作用。有趣的是，Groucho与Otx2的结合也是MHB中Fgf8抑制所必需的。因此，Groucho/Tle家族成员似乎在脊椎动物大脑MHB的发育中调节关键方面。
