Dual origins of mesoderm in a basal spiralian: Cell lineage analyses in the polyclad turbellarian Hoploplana inquilina
Dual origins of mesoderm in a basal spiralian: Cell lineage analyses in the polyclad turbellarian Hoploplana inquilina
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DOI：
10.1006/dbio.1996.0264
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发表时间：
1996-11-01
影响因子：
2.7
通讯作者：
Martindale, MQ
中科院分区：
文献类型：
--
作者：
Boyer, BC;Henry, JQ;Martindale, MQ
中胚层的起源和组织的进化修改代表了后生动物身体计划多样化的重要事件。在螺旋藻内，中胚层包括外中胚层和内中胚层，外中胚层通常由第二和第三四分体的微节的衍生物产生，内中胚层由D象限的第四分体微节（4d）形成。据认为，内中胚层产生的大部分成人中胚层衍生物，而幼虫中胚层主要是由外中胚层。这些中胚层来源的进化历史可以通过研究Spiralia的基底成员来澄清，例如polyclad turbellarians，其胚胎表现出典型的四重螺旋卵裂。使用荧光谱系示踪剂DiI，我们表明，幼虫中胚层是来自只有两个细胞，一个来自腹侧胚胎象限（2b，“mesectoblasts”细胞），和其他来自背侧象限（4d，mesectoblasts细胞）。我们比较这些结果与中胚层的起源在其他螺旋门，并得出结论，双重起源的中胚层是螺旋发育的原始特征。我们还认为，外中胚层和内中胚层应分别被认为是幼虫和成虫中胚层的唯一前体。(C)出版社：Academic Press，Inc.
Evolutionary modifications in the origins and organization of the mesoderm represent significant events in the diversification of metazoan body plans. Within the Spiralia, mesoderm comprises ectomesoderm, which typically is generated by derivatives of the second and third quartets of micromeres, and endomesoderm, which is formed from the fourth quartet micromere of the D quadrant (4d). It has been held that endomesoderm generates the majority of adult mesodermal derivatives, while larval mesoderm is formed primarily from ectomesoderm . The evolutionary history of these mesodermal sources could be clarified by examining basal members of the Spiralia such as the polyclad turbellarians, whose embryos exhibit canonical quartet spiral cleavage. Using the fluorescent lineage tracer DiI, we show that larval mesoderm is derived from only two cells, one from the ventral embryonic quadrant (2b, the ''mesectoblast'' cell), and the other from the dorsal quadrant (4d, the mesentoblast cell). We compare these results with mesodermal origins in other spiralian phyla and conclude that a dual origin of mesoderm is a primitive feature of spiralian development. We also argue that ectomesoderm and endomesoderm should trot be considered as the exclusive precursors of larval and adult mesoderm, respectively. (C) 1996 Academic Press, Inc.