Grenier Julien, Teillet Marie-Aimée, Grifone Raphaëlle, Kelly Robert G, Duprez Delphine
CNRS, UMR 7622 Biologie Moléculaire et Cellulaire du Développement, Université Pierre et Marie Curie, Paris, France.
PLoS One. 2009;4(2):e4381. doi: 10.1371/journal.pone.0004381. Epub 2009 Feb 9.
In vertebrates, the skeletal elements of the jaw, together with the connective tissues and tendons, originate from neural crest cells, while the associated muscles derive mainly from cranial mesoderm. Previous studies have shown that neural crest cells migrate in close association with cranial mesoderm and then circumscribe but do not penetrate the core of muscle precursor cells of the branchial arches at early stages of development, thus defining a sharp boundary between neural crest cells and mesodermal muscle progenitor cells. Tendons constitute one of the neural crest derivatives likely to interact with muscle formation. However, head tendon formation has not been studied, nor have tendon and muscle interactions in the head.
METHODOLOGY/PRINCIPAL FINDINGS: Reinvestigation of the relationship between cranial neural crest cells and muscle precursor cells during development of the first branchial arch, using quail/chick chimeras and molecular markers revealed several novel features concerning the interface between neural crest cells and mesoderm. We observed that neural crest cells migrate into the cephalic mesoderm containing myogenic precursor cells, leading to the presence of neural crest cells inside the mesodermal core of the first branchial arch. We have also established that all the forming tendons associated with branchiomeric and eye muscles are of neural crest origin and express the Scleraxis marker in chick and mouse embryos. Moreover, analysis of Scleraxis expression in the absence of branchiomeric muscles in Tbx1(-/-) mutant mice, showed that muscles are not necessary for the initiation of tendon formation but are required for further tendon development.
CONCLUSIONS/SIGNIFICANCE: This results show that neural crest cells and muscle progenitor cells are more extensively mixed than previously believed during arch development. In addition, our results show that interactions between muscles and tendons during craniofacial development are similar to those observed in the limb, despite the distinct embryological origin of these cell types in the head.
在脊椎动物中，颌骨的骨骼成分以及结缔组织和肌腱起源于神经嵴细胞，而相关肌肉主要源自颅中胚层。先前的研究表明，神经嵴细胞与颅中胚层紧密相伴迁移，然后在发育早期围绕但不穿透鳃弓肌肉前体细胞的核心，从而在神经嵴细胞和中胚层肌肉祖细胞之间形成了一个清晰的边界。肌腱是可能与肌肉形成相互作用的神经嵴衍生物之一。然而，头部肌腱的形成尚未得到研究，头部的肌腱与肌肉之间的相互作用也未被研究过。
方法/主要发现：利用鹌鹑/鸡嵌合体和分子标记物，对第一鳃弓发育过程中颅神经嵴细胞与肌肉前体细胞之间的关系进行重新研究，揭示了一些关于神经嵴细胞与中胚层之间界面的新特征。我们观察到神经嵴细胞迁移到含有成肌前体细胞的头部中胚层，导致第一鳃弓中胚层核心内存在神经嵴细胞。我们还确定，与鳃节肌和眼肌相关的所有正在形成的肌腱均起源于神经嵴，并在鸡和小鼠胚胎中表达硬骨蛋白标记物。此外，对Tbx1(-/-)突变小鼠中缺乏鳃节肌时硬骨蛋白表达的分析表明，肌肉对于肌腱形成的起始并非必需，但对于肌腱的进一步发育是必需的。
结论/意义：这些结果表明，在鳃弓发育过程中，神经嵴细胞和肌肉祖细胞的混合比先前认为的更为广泛。此外，我们的结果表明，尽管这些细胞类型在头部的胚胎起源不同，但颅面发育过程中肌肉与肌腱之间的相互作用与在肢体中观察到的相似。
