Lane M C, Smith W C
Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, CA 93106, USA.
Development. 1999 Feb;126(3):423-34. doi: 10.1242/dev.126.3.423.
The marginal zone in Xenopus laevis is proposed to be patterned with dorsal mesoderm situated near the upper blastoporal lip and ventral mesoderm near the lower blastoporal lip. We determined the origins of the ventralmost mesoderm, primitive blood, and show it arises from all vegetal blastomeres at the 32-cell stage, including blastomere C1, a progenitor of Spemann's organizer. This demonstrates that cells located at the upper blastoporal lip become ventral mesoderm, not solely dorsal mesoderm as previously believed. Reassessment of extant fate maps shows dorsal mesoderm and dorsal endoderm descend from the animal region of the marginal zone, whereas ventral mesoderm descends from the vegetal region of the marginal zone, and ventral endoderm descends from cells located vegetal of the bottle cells. Thus, the orientation of the dorsal-ventral axis of the mesoderm and endoderm is rotated 90( degrees) from its current portrayal in fate maps. This reassessment leads us to propose revisions in the nomenclature of the marginal zone and the orientation of the axes in pre-gastrula Xenopus embryos.
背侧中胚层位于上胚孔唇附近，腹侧中胚层位于下胚孔唇附近。我们确定了最腹侧中胚层、原始血液的起源，并表明它们起源于32细胞期的所有植物性卵裂球，包括卵裂球C1，即施佩曼组织者的一个祖细胞。这表明位于上胚孔唇的细胞会变成腹侧中胚层，而不只是如之前所认为的那样只变成背侧中胚层。对现有命运图谱的重新评估表明，背侧中胚层和背侧内胚层起源于边缘区的动物区域，而腹侧中胚层起源于边缘区的植物区域，腹侧内胚层起源于瓶状细胞植物侧的细胞。因此，中胚层和内胚层背腹轴的方向与其在命运图谱中的当前描绘相比旋转了90度。这种重新评估使我们提议对非洲爪蟾原肠胚形成前胚胎边缘区的命名法和轴的方向进行修订。
