Schmidt C, Christ B, Patel K, Brand-Saberi B
Institut of Anatomy, University of Freiburg, Freiburg, D-79001, Germany.
Dev Biol. 1998 Oct 15;202(2):253-63. doi: 10.1006/dbio.1998.9011.
In the avian embryo, epithelialization of the segmental plate and formation of an epithelial dermomyotome depend on signals from the neural tube and the ectoderm overlying the paraxial mesoderm. In this study, we report that ectoderm removal in combination with barrier insertion between the axial organs and the segmental plate leads to an induction of BMP-4 expression in the paraxial mesoderm. In the lateral plate, ectoderm removal alone leads to an increase of BMP-4 expression. Application of BMP-4 protein results in a lack of epithelialization of the paraxial mesoderm. In order to investigate whether the loss of epithelial structures after these manipulations can be attributed to a change in cell fate, a change in cell proliferation, or the induction of apoptosis, the paraxial mesoderm was tested for expression of Msx-2, BMP-2, BMP-4, and BMP-7. Moreover, BrdU and TUNEL staining were carried out. The inhibition of epithelialization after ectoderm removal alone and after segregation of the axial organs is accompanied neither by an increase in apoptosis nor by a reduction of the proliferation rate in the paraxial mesoderm. On the other hand, an ectopic BMP-4 expression in the paraxial mesoderm after ectoderm removal in combination with barrier insertion coincides with the occurrence of apoptotic cells and reduction of proliferation rate in this tissue. Increase of apoptosis and decrease in cell proliferation are observed in the paraxial and lateral plate mesoderm also after application of BMP-4 protein.
在禽类胚胎中，体节板的上皮化以及上皮性生皮节的形成依赖于来自神经管和覆盖在轴旁中胚层上方的外胚层的信号。在本研究中，我们报告称，去除外胚层并在轴器官和体节板之间插入屏障会导致轴旁中胚层中BMP - 4表达的诱导。在侧板中，单独去除外胚层会导致BMP - 4表达增加。应用BMP - 4蛋白会导致轴旁中胚层上皮化缺失。为了研究这些操作后上皮结构的丧失是否可归因于细胞命运的改变、细胞增殖的改变或细胞凋亡的诱导，检测了轴旁中胚层中Msx - 2、BMP - 2、BMP - 4和BMP - 7的表达。此外，还进行了BrdU和TUNEL染色。单独去除外胚层以及轴器官分离后上皮化的抑制，既不伴随着轴旁中胚层细胞凋亡的增加，也不伴随着增殖率的降低。另一方面，去除外胚层并插入屏障后轴旁中胚层中异位BMP - 4的表达与该组织中凋亡细胞的出现和增殖率的降低相一致。应用BMP - 4蛋白后，在轴旁和侧板中胚层也观察到细胞凋亡增加和细胞增殖减少。
