Shiga T, Lustig M, Grumet M, Shirai T
Department of Anatomy, Yamagata University School of Medicine, Yamagata, 990-23, Japan.
Dev Biol. 1997 Dec 1;192(1):136-48. doi: 10.1006/dbio.1997.8742.
In order to elucidate the mechanisms regulating the projections of dorsal root ganglion (DRG) axons in the dorsal funiculus and invasion into target regions in the mantle layer (prospective gray matter) of the spinal cord, we examined the interactions between DRG axons and spinal cord. DRG neurons were dissociated from chick embryos and cultured for 1-2 days on cryostat sections of the spinal cord at embryonic day 5 (E5) or at E9. E5 and E9 DRG neurons extended neurites onto both marginal zone (prospective white matter) and mantle layer (prospective gray matter) of the spinal cord, suggesting that both of these regions are permissive for neurite growth. When E5 DRG neurites approached cryosections of E5 spinal cord from outside, most of them ran in the marginal zone without invading the mantle layer. In contrast, about half of E9 DRG neurites entered the mantle layer after crossing the marginal zone of E9 spinal cord. These growth patterns of DRG neurites on spinal marginal zone and mantle layer are similar to the pathway formation of DRG axons at comparable stages in vivo; DRG axons run exclusively in the prospective dorsal funiculus before E6, and enter the mantle layer (prospective dorsal horn) to reach the target regions by E9. Perturbation of functions of Ng-CAM, Nr-CAM, and axonin-1/SC2 by adding the specific antibodies in the culture medium increased the ratio of DRG neurites entering the mantle layer of E5 spinal cord, suggesting that these cell adhesion molecules are involved in keeping DRG neurites in the marginal zone. Taken together with the expression of Ng-CAM, Nr-CAM, and axonin-1/SC2, these CAMs on DRG axons may regulate the guidance of these axons in the marginal zone before E6, and the subsequent decrease in the relative levels of these CAMs might allow DRG axons to invade the target mantle layer.
为了阐明调节背根神经节（DRG）轴突在脊髓背索中的投射以及侵入脊髓套层（未来灰质）靶区域的机制，我们研究了DRG轴突与脊髓之间的相互作用。将DRG神经元从鸡胚中分离出来，并在胚胎第5天（E5）或E9的脊髓冰冻切片上培养1 - 2天。E5和E9的DRG神经元将神经突延伸到脊髓的边缘区（未来白质）和套层（未来灰质）上，这表明这两个区域都允许神经突生长。当E5的DRG神经突从外部接近E5脊髓的冰冻切片时，它们中的大多数在边缘区延伸而不侵入套层。相比之下，约一半的E9 DRG神经突在穿过E9脊髓的边缘区后进入套层。DRG神经突在脊髓边缘区和套层上的这些生长模式类似于体内可比阶段DRG轴突的通路形成；在E6之前，DRG轴突仅在前背索中运行，并在E9时进入套层（未来背角）以到达靶区域。通过在培养基中添加特异性抗体来干扰Ng - CAM、Nr - CAM和轴突素 - 1/SC2的功能，增加了进入E5脊髓套层的DRG神经突的比例，这表明这些细胞粘附分子参与将DRG神经突维持在边缘区。结合Ng - CAM、Nr - CAM和轴突素 - 1/SC2的表达来看，DRG轴突上这些细胞粘附分子可能在E6之前调节这些轴突在边缘区的导向，而这些细胞粘附分子相对水平随后的降低可能使DRG轴突能够侵入靶套层。
