Pattern and morphogenesis of presumptive superficial mesoderm in two closely related species, Xenopus laevis and Xenopus tropicalis.
Pattern and morphogenesis of presumptive superficial mesoderm in two closely related species, Xenopus laevis and Xenopus tropicalis.
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DOI：
10.1016/j.ydbio.2004.02.021
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发表时间：
2004-06
影响因子：
2.7
通讯作者：
D. Shook;C. Majer;R. Keller
中科院分区：
文献类型：
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作者：
D. Shook;C. Majer;R. Keller
中胚层由完全位于深层的组织组成，起源于早期两栖动物胚胎的浅表上皮和深层间充质层。在这里，我们描述了热带爪蟾中中胚层的表面成分进入下层深层间质层的机制，并扩展了我们之前对非洲爪蟾的研究结果。对前胚期胚胎表面上皮的命运图谱显示，表面细胞向近轴和轴向中胚层（包括下胚层）浸润，在这两个物种中浸润的模式和数量相似。浅推定脊索位于中间，两侧为推定下脊索，均位于推定脊索的深部。这些组织的侧面是浅表的推测体裂中胚层，其前端似乎也覆盖了推测的深脊索。延时记录显示，推定的体索细胞和脊索细胞在神经发育期间从胃索顶部移动到深部区域，而下脊索细胞在神经发育后进入。扫描电子显微镜显示，在入侵发生的阶段和位置，热带扁虱的表面体细胞以瓶状细胞的形式进入深部区域，而热带扁虱的细胞则通过“再分层”进入深部区域（例如，[Dev. Biol. 174(1996) 92]）。在这两个物种中，在神经发育期间，表面衍生的推定体分裂细胞位于推定体分裂的内侧区域。在早期的尾芽阶段，这些细胞位于体的水平肌隔膜上。这些细胞的形态发生途径与斑马鱼的初级慢肌先锋细胞非常相似。我们提出了修订后的爪蟾命运图，并讨论了两栖动物和脊索动物中浅层中胚层的保护及其对该组织在中胚层形成中的作用的影响。
The mesoderm, comprising the tissues that come to lie entirely in the deep layer, originates in both the superficial epithelial and the deep mesenchymal layers of the early amphibian embryo. Here, we characterize the mechanisms by which the superficial component of the presumptive mesoderm ingresses into the underlying deep mesenchymal layer in Xenopus tropicalis and extend our previous findings for Xenopus laevis. Fate mapping the superficial epithelium of pregastrula stage embryos demonstrates ingression of surface cells into both paraxial and axial mesoderm (including hypochord), in similar patterns and amounts in both species. Superficial presumptive notochord lies medially, flanked by presumptive hypochord and both overlie the deep region of the presumptive notochord. These tissues are flanked laterally by superficial presumptive somitic mesoderm, the anterior tip of which also appears to overlay the presumptive deep notochord. Time-lapse recordings show that presumptive somitic and notochordal cells move out of the roof of the gastrocoel and into the deep region during neurulation, whereas hypochordal cells ingress after neurulation. Scanning electron microscopy at the stage and position where ingression occurs suggests that superficial presumptive somitic cells in X. laevis ingress into the deep region as bottle cells whereas those in X. tropicalis ingress by “relamination” (e.g., [Dev. Biol. 174 (1996) 92]). In both species, the superficially derived presumptive somitic cells come to lie in the medial region of the presumptive somites during neurulation. By the early tailbud stages, these cells lie at the horizontal myoseptum of the somites. The morphogenic pathway of these cells strongly resembles that of the primary slow muscle pioneer cells of the zebrafish. We present a revised fate map of Xenopus, and we discuss the conservation of superficial mesoderm within amphibians and across the chordates and its implications for the role of this tissue in patterning the mesoderm.