Kato N, Aoyama H
Department of Biology, Graduate School of Science, Osaka University and JT Biohistory Research Hall, Takatsuki, Osaka 569-1125, Japan.
Development. 1998 Sep;125(17):3437-43. doi: 10.1242/dev.125.17.3437.
To elucidate role of the dermomyotome in the formation of the axial skeleton, we performed extirpation and transplantation experiments on the dermomyotomes in chick and quail embryos. When the thoracic dermomyotomes of chick embryos were removed, the intercostal muscles and the distal ribs were deficient, while the proximal ribs were more or less normal. Quail tissues including the dermomyotome, the ectoderm and the medial edge of lateral plate, were transplanted to replace chick dermomyotomes. In these chimeras, the ribs, which would be deficient without the back-transplantation, were recovered. The cells of the recovered part of the ribs as well as the intercostal muscles were derived from the quail transplants. These findings suggest that the distal rib originated from the dermomyotomes and not the sclerotome as previously believed. To localize the origin of the distal rib further, we removed restricted regions of the dermomyotomes along the mediolateral and the rostrocaudal axis. The more lateral the part of the dermomyotomes that we removed, the more distal the part of the ribs affected. On the contrary, when the rostral and caudal edges of the dermomyotomes were removed, only the vertebral ribs showed extensive deficiencies while removal of the middle part between the edges caused less deficiency. The sternal ribs were not deficient in either case, but were extensively affected when the entire lateral edge of dermomyotomes was included in the region removed. We conclude that the lateral edges of the dermomyotomes are the primordia of the sternal ribs, and the rostral and/or caudal edges of the medial part of dermomyotomes are the primordia of the distal part and not of the proximal part of the vertebral ribs.
为阐明生皮节在轴骨骼形成中的作用，我们对鸡和鹌鹑胚胎的生皮节进行了切除和移植实验。当切除鸡胚胎的胸生皮节时，肋间肌和远端肋骨缺失，而近端肋骨或多或少正常。将包括生皮节、外胚层和侧板内侧边缘的鹌鹑组织移植来替代鸡的生皮节。在这些嵌合体中，若不进行回植就会缺失的肋骨得以恢复。肋骨恢复部分的细胞以及肋间肌均来源于鹌鹑移植组织。这些发现表明，远端肋骨起源于生皮节，而非如先前认为的那样起源于硬骨节。为进一步确定远端肋骨的起源部位，我们沿内外侧和头尾轴切除了生皮节的特定区域。我们切除的生皮节部分越靠外侧，受影响的肋骨部分就越靠远端。相反，当切除生皮节的头端和尾端边缘时，只有椎肋出现广泛缺失，而切除边缘之间的中间部分则导致较少的缺失。在这两种情况下，胸骨肋均未缺失，但当切除区域包括生皮节的整个外侧边缘时，胸骨肋会受到广泛影响。我们得出结论，生皮节的外侧边缘是胸骨肋的原基，而生皮节内侧部分的头端和/或尾端边缘是椎肋远端而非近端的原基。
