Fadaili Yara, Lu Hui-Chun, Lee Hyung Chul, Ryazapova Amra, Stern Claudio D
Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
Development. 2025 Jan 15;152(2). doi: 10.1242/dev.204350. Epub 2025 Jan 23.
In chick embryos before primitive streak formation, the outermost extra-embryonic region, known as the area opaca (AO), was generally thought to act only by providing nutrients and mechanical support to the embryo. Immediately internal to the AO is a ring of epiblast called the marginal zone (MZ), separating the former from the inner area pellucida (AP) epiblast. The MZ does not contribute cells to any part of the embryo but is involved in determining the position of primitive streak formation from the adjacent AP epiblast. Recently, it was discovered that the AO can induce an MZ from AP epiblast. Here, we explore the nature of this inductive signal. We find that WNT8C is highly expressed in the AO, whereas canonical Wnt pathway targets are enriched in the MZ, along with strong nuclear β-catenin localization. Using isolation and recombination experiments combined with gain- and loss-of-function by exogenous chemical modulators of the pathway, we reveal that Wnt signalling is essential for induction and maintenance of the MZ, as well as sufficient to induce MZ properties in AP epiblast. We propose that canonical Wnt signalling is responsible for induction of the MZ by the area opaca.
在原条形成之前的鸡胚中，最外层的胚外区域，即明区（AO），通常被认为仅通过为胚胎提供营养和机械支持来发挥作用。AO的内侧紧邻着一圈称为边缘区（MZ）的上胚层，将前者与内部的透明区（AP）上胚层分隔开来。MZ不会为胚胎的任何部分提供细胞，但参与确定来自相邻AP上胚层的原条形成位置。最近，人们发现AO可以从AP上胚层诱导形成MZ。在此，我们探究这种诱导信号的本质。我们发现WNT8C在AO中高表达，而经典Wnt信号通路的靶标在MZ中富集，同时伴有强烈的核β-连环蛋白定位。通过分离和重组实验，结合该信号通路的外源性化学调节剂进行功能获得和功能缺失研究，我们揭示Wnt信号对于MZ的诱导和维持至关重要，并且足以在AP上胚层中诱导出MZ特性。我们提出经典Wnt信号传导负责明区对边缘区的诱导。
