Constance Lane Mary, Davidson Lance, Sheets Michael D
Department of Biomolecular Chemistry, University of Wisconsin School of Medicine, Madison, WI 53706, USA.
Dev Biol. 2004 Nov 15;275(2):356-74. doi: 10.1016/j.ydbio.2004.08.012.
Recent revisions to the Xenopus fate map challenge the interpretation of previous maps and current models of amphibian axial patterning (Lane, M.C., Smith, W.C., 1999. The origins of primitive blood in Xenopus: implications for axial patterning. Development 126 (3), 423-434.; Lane, M.C., Sheets, M.D., 2000. Designation of the anterior/posterior axis in pregastrula Xenopus laevis. Dev. Biol. 225, 37-58). We determined the rostralmost contributions to both dorsal and ventral mesoderm concomitantly from marginal zone progenitors in stage 6 embryos. Data reveal an unequivocal rostral-to-caudal progression of both dorsal and ventral mesoderm across the pre-gastrula axis historically called the dorsal-ventral axis, and a dorsal-to-ventral progression from animal-to-vegetal in the marginal zone. These findings support the proposed revisions to the fate and axis orientation maps. Most importantly, these results raise questions about the role of the organizer grafts and organizer-derived BMP antagonists in the "induction" of secondary axes. We re-examine both phenomena, and find that organizer grafts and BMP antagonists evoke caudal-to-rostral mesodermal fate transformations, and not ventral-to-dorsal transformations as currently believed. We demonstrate that BMP antagonism evokes a second axis because it stimulates precocious mediolateral intercalation of caudal, dorsal mesoderm. The implications of these findings for models of organizer function in vertebrate axial patterning are discussed.
非洲爪蟾命运图谱的最新修订对先前图谱的解读以及当前两栖动物轴向模式形成模型提出了挑战（莱恩，M.C.，史密斯，W.C.，1999年。非洲爪蟾原始血液的起源：对轴向模式形成的影响。《发育》126(3)，423 - 434页；莱恩，M.C.，希茨，M.D.，2000年。非洲爪蟾原肠胚前期前后轴的确定。《发育生物学》225，37 - 58页）。我们同时确定了6期胚胎边缘区祖细胞对背侧和腹侧中胚层的最前端贡献。数据揭示了背侧和腹侧中胚层在历史上被称为背腹轴的原肠胚前期轴上从吻端到尾端的明确进展，以及在边缘区从动物极到植物极的背侧到腹侧的进展。这些发现支持了对命运和轴取向图谱的提议修订。最重要的是，这些结果对组织者移植和组织者衍生的骨形态发生蛋白（BMP）拮抗剂在次级轴“诱导”中的作用提出了疑问。我们重新审视了这两种现象，发现组织者移植和BMP拮抗剂引发的是从尾端到吻端的中胚层命运转变，而非目前所认为的从腹侧到背侧的转变。我们证明，BMP拮抗作用引发第二条轴是因为它刺激了尾端背侧中胚层的早熟中外侧插入。本文讨论了这些发现对脊椎动物轴向模式形成中组织者功能模型的意义。
