Two lineage boundaries coordinate vertebrate apical ectodermal ridge formation.
Two lineage boundaries coordinate vertebrate apical ectodermal ridge formation.
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DOI：
10.1101/gad.14.11.1377
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发表时间：
2000-06
影响因子：
10.5
通讯作者：
Robin A. Kimmel;D. Turnbull;V. Blanquet;W. Wurst;C. Loomis;A. Joyner
中科院分区：
文献类型：
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作者：
Robin A. Kimmel;D. Turnbull;V. Blanquet;W. Wurst;C. Loomis;A. Joyner
脊椎动物肢芽的近远端生长受顶端外胚层脊（AER）的调节，该脊形成于沿胚胎背腹（D/V）轴的不变位置。我们研究了调节小鼠 AER 形成的遗传和细胞事件。与之前对小鸡的研究的结果相反，我们使用基于 Cre/loxP 的命运图谱方法和新型逆转录病毒细胞标记技术，在肢芽生长之前确定了小鼠外胚层中两个不同的谱系边界。第一个边界是瞬时的，处于腹侧基因 En1 的表达极限，对应于 AER 的 D/V 中线，第二个边界对应于 AER 背侧边缘。使用诱导型 Cre 标记 AER 前体表明，并非所有最初表达 AER 基因的细胞都会形成 AER，这表明需要信号传导来维持 AER 表型。研究发现，En1 在中等水平的错误表达（特别是在转基因小鼠的背部 AER 中）会产生背侧移位的 AER 片段，而高水平的 En1 会消除 AER 的形成。在这两种情况下，背侧基因 Wnt7a 在与 En1 表达细胞相邻的细胞中受到抑制，这表明 EN1 调节的信号传导发生在 D/V 边界。最后，这些突变体中 AER 结构域的命运图谱表明，En1 在定位和维持两个谱系边界方面发挥着作用。
Proximal-distal outgrowth of the vertebrate limb bud is regulated by the apical ectodermal ridge (AER), which forms at an invariant position along the dorsal-ventral (D/V) axis of the embryo. We have studied the genetic and cellular events that regulate AER formation in the mouse. In contrast to implications from previous studies in chick, we identified two distinct lineage boundaries in mouse ectoderm prior to limb bud outgrowth using a Cre/loxP-based fate-mapping approach and a novel retroviral cell-labeling technique. One border is transient and at the limit of expression of the ventral gene En1, which corresponds to the D/V midline of the AER, and the second border corresponds to the dorsal AER margin. Labeling of AER precursors using an inducible Cre showed that not all cells that initially express AER genes form the AER, indicating that signaling is required to maintain an AER phenotype. Misexpression of En1 at moderate levels specifically in the dorsal AER of transgenic mice was found to produce dorsally shifted AER fragments, whereas high levels of En1 abolished AER formation. In both cases, the dorsal gene Wnt7a was repressed in cells adjacent to the En1-expressing cells, demonstrating that signaling regulated by EN1 occurs across the D/V border. Finally, fate mapping of AER domains in these mutants showed that En1 plays a part in positioning and maintaining the two lineage borders.