Aglyamova Galina V, Agarwala Seema
Section of Neurobiology, University of Texas at Austin, Austin, Texas 78712, USA.
Dev Dyn. 2007 May;236(5):1363-73. doi: 10.1002/dvdy.21146.
The signaling molecule Sonic Hedgehog (SHH) plays a critical role in patterning the ventral midbrain of vertebrates. Our recent studies have established that the requirement for Hedgehog (HH) signaling in the chick midbrain is modulated spatially and temporally in a complex manner across the midbrain anlage. Unfortunately, the patterns of expression of downstream regulators that might modulate the HH signal in the midbrain are not currently known. To fill this gap, we have examined across time, the expression pattern of 14 genes that function in the HH signaling cascade in the midbrain and spinal cord. Our results suggest that SHH expression in the axial mesendoderm begins before the expression of known HH receptors/HH-binding proteins (e.g., PTC1, PTC2, HHIP, BOC, MEGALIN). In the midbrain, PTC and GLI genes are expressed and then eliminated very early from the ventral midline. However, they exhibit high and persistent expression in the midbrain region circumscribing the SHH source. Intriguingly, multiple HH-binding proteins (BOC, MEGALIN) and HH effectors (GLI1-3, SMO, SUFU, DZIP) are expressed in the dorsal midbrain and the midbrain-hindbrain boundary. Finally, we report for the first time that IHH is expressed in intermediate regions of the spinal cord, where its expression does not overlap with that of SHH.
信号分子音猬因子（SHH）在脊椎动物腹侧中脑的模式形成中起着关键作用。我们最近的研究表明，鸡中脑中对刺猬因子（HH）信号的需求在中脑原基上以复杂的方式在空间和时间上受到调节。不幸的是，目前尚不清楚可能调节中脑HH信号的下游调节因子的表达模式。为了填补这一空白，我们一直以来都在研究中脑和脊髓中14个在HH信号级联中起作用的基因的表达模式。我们的结果表明，轴旁中胚层中SHH的表达在已知的HH受体/HH结合蛋白（如PTC1、PTC2、HHIP、BOC、巨膜蛋白）表达之前就开始了。在中脑中，PTC和GLI基因表达，然后很早就从腹侧中线消失。然而，它们在围绕SHH来源的中脑区域表现出高表达且持续存在。有趣的是，多种HH结合蛋白（BOC、巨膜蛋白）和HH效应器（GLI1 - 3、SMO、SUFU、DZIP）在背侧中脑和中脑 - 后脑边界表达。最后，我们首次报道印度刺猬因子（IHH）在脊髓的中间区域表达，其表达与SHH的表达不重叠。
