Cinnamon Y, Kahane N, Kalcheim C
Department of Anatomy and Cell Biology, Hebrew University-Hadassah Medical School, Jerusalem 91120, P.O. Box 12272, Israel.
Development. 1999 Oct;126(19):4305-15. doi: 10.1242/dev.126.19.4305.
We have previously found that the myotome is formed by a first wave of pioneer cells generated along the medial epithelial somite and a second wave emanating from the dorsomedial lip (DML), rostral and caudal edges of the dermomyotome (Kahane, N., Cinnamon, Y. and Kalcheim, C. (1998a) Mech. Dev. 74, 59-73; Kahane, N., Cinnamon, Y. and Kalcheim, C. (1998b) Development 125, 4259-4271). In this study, we have addressed the development and precise fate of the ventrolateral lip (VLL) in non-limb regions of the axis. To this end, fluorescent vital dyes were iontophoretically injected in the center of the VLL and the translocation of labeled cells was followed by confocal microscopy. VLL-derived cells colonized the ventrolateral portion of the myotome. This occurred following an early longitudinal cell translocation along the medial boundary until reaching the rostral or caudal dermomyotome lips from which fibers emerged into the myotome. Thus, the behavior of VLL cells parallels that of their DML counterparts which colonize the opposite, dorsomedial portion of the myotome. To precisely understand the way the myotome expands, we addressed the early generation of hypaxial intercostal muscles. We found that intercostal muscles were formed by VLL-derived fibers that intermingled with fibers emerging from the ventrolateral aspect of both rostral and caudal edges of the dermomyotome. Notably, hypaxial intercostal muscles also contained pioneer myofibers (first wave) showing for the first time that lateral myotome-derived muscles contain a fundamental component of fibers generated in the medial domain of the somite. In addition, we show that during myotome growth and evolution into muscle, second-wave myofibers progressively intercalate between the pioneer fibers, suggesting a constant mode of myotomal expansion in its dorsomedial to ventrolateral extent. This further suggests that specific hypaxial muscles develop following a consistent ventral expansion of a 'compound myotome' into the somatopleure.
我们之前发现，肌节由沿内侧上皮体节产生的第一波先驱细胞以及从背内侧唇（DML）、皮肌节的头侧和尾侧边缘发出的第二波细胞形成（卡哈内，N.，辛纳蒙，Y.和卡尔海姆，C.（1998a）《机制与发育》74，59 - 73；卡哈内，N.，辛纳蒙，Y.和卡尔海姆，C.（1998b）《发育》125，4259 - 4271）。在本研究中，我们探讨了轴的非肢体区域腹外侧唇（VLL）的发育及精确命运。为此，将荧光活性染料通过离子电渗法注入VLL中心，并通过共聚焦显微镜追踪标记细胞的迁移。VLL来源的细胞定殖于肌节的腹外侧部分。这一过程是在细胞早期沿内侧边界纵向迁移之后发生的，直至到达头侧或尾侧皮肌节唇，纤维从这些部位延伸至肌节。因此，VLL细胞的行为与其在DML的对应细胞相似，后者定殖于肌节相对的背内侧部分。为了精确了解肌节扩展的方式，我们研究了轴下肋间肌的早期生成。我们发现肋间肌由VLL来源的纤维形成，这些纤维与从皮肌节头侧和尾侧边缘腹外侧伸出的纤维相互交织。值得注意的是，轴下肋间肌还包含先驱肌纤维（第一波），首次表明外侧肌节来源的肌肉包含在体节内侧区域产生的纤维的基本成分。此外，我们表明在肌节生长并演变为肌肉的过程中，第二波肌纤维逐渐插入先驱纤维之间，这表明肌节在其背内侧到腹外侧范围内以一种恒定的方式扩展。这进一步表明，特定的轴下肌肉是在“复合肌节”向体壁持续腹侧扩展之后发育形成的。
