Shearman Rebecca Marie, Burke Ann Campbell
Department of Biology, Wesleyan University, Middletown, Connecticut, USA.
J Exp Zool B Mol Dev Evol. 2009 Sep 15;312(6):603-12. doi: 10.1002/jez.b.21246.
The vertebrate musculoskeletal system comprises the axial and appendicular systems. The postcranial axial system consists of the vertebrae, ribs and associated muscles, and the appendicular system comprises the muscles and skeleton of the paired appendages and their respective girdles. The morphology, proportions, and arrangements of these parts have undergone tremendous variation during vertebrate history. Despite this vertebrate diversity, the cells that form all of the key parts of the musculoskeletal system during development arise from two populations of embryonic mesoderm, the somites and somatic lateral plate. Nowicki et al. (2003. Mech Dev 120:227-240) identified two dynamic domains in the developing chick embryo. The primaxial domain is populated exclusively by cells from the somites. The abaxial domain includes muscle and bone that develop within lateral plate-derived connective tissue. The boundary between the two domains is the lateral somitic frontier. We hypothesize that the primaxial and abaxial domains are patterned independently and that morphological evolution of the musculoskeletal system is facilitated by partially independent developmental changes in the abaxial and primaxial domain. Here we present our hypothesis in detail and review recent experimental and comparative studies that use the concept of the lateral somitic frontier in the analysis of the evolution of the highly derived chelonian and limbless squamate body plans.
脊椎动物的肌肉骨骼系统由轴骨骼系统和附肢骨骼系统组成。颅后轴骨骼系统由椎骨、肋骨及相关肌肉构成，而附肢骨骼系统则包括成对附肢及其各自带骨的肌肉和骨骼。在脊椎动物的演化历程中，这些部分的形态、比例和排列发生了巨大变化。尽管脊椎动物具有多样性，但在发育过程中形成肌肉骨骼系统所有关键部分的细胞均源自胚胎中胚层的两个群体，即体节和体壁侧板。诺维基等人（2003年。《机制与发育》120:227 - 240）在发育中的鸡胚中确定了两个动态区域。原轴区仅由来自体节的细胞组成。轴下区包括在侧板衍生的结缔组织内发育的肌肉和骨骼。这两个区域之间的边界是体节外侧边界。我们推测原轴区和轴下区是独立模式化的，并且肌肉骨骼系统的形态演化是由轴下区和原轴区部分独立的发育变化促成的。在此，我们详细阐述我们的假说，并回顾近期的实验和比较研究，这些研究在分析高度特化的龟鳖类和无肢有鳞类身体结构的演化时运用了体节外侧边界这一概念。
