Kinder S J, Tsang T E, Wakamiya M, Sasaki H, Behringer R R, Nagy A, Tam P P
Embryology Unit, Children's Medical Research Institute, Locked Bag 23, Wentworthville, NSW 2145, Australia.
Development. 2001 Sep;128(18):3623-34. doi: 10.1242/dev.128.18.3623.
An organizer population has been identified in the anterior end of the primitive streak of the mid-streak stage embryo, by the expression of Hnf3beta, Gsc(lacZ) and Chrd, and the ability of these cells to induce a second neural axis in the host embryo. This cell population can therefore be regarded as the mid-gastrula organizer and, together with the early-gastrula organizer and the node, constitute the organizer of the mouse embryo at successive stages of development. The profile of genetic activity and the tissue contribution by cells in the organizer change during gastrulation, suggesting that the organizer may be populated by a succession of cell populations with different fates. Fine mapping of the epiblast in the posterior region of the early-streak stage embryo reveals that although the early-gastrula organizer contains cells that give rise to the axial mesoderm, the bulk of the progenitors of the head process and the notochord are localized outside the early gastrula organizer. In the mid-gastrula organizer, early gastrula organizer derived cells that are fated for the prechordal mesoderm are joined by the progenitors of the head process that are recruited from the epiblast previously anterior to the early gastrula organizer. Cells that are fated for the head process move anteriorly from the mid-gastrula organizer in a tight column along the midline of the embryo. Other mid-gastrula organizer cells join the expanding mesodermal layer and colonize the cranial and heart mesoderm. Progenitors of the trunk notochord that are localized in the anterior primitive streak of the mid-streak stage embryo are later incorporated into the node. The gastrula organizer is therefore composed of a constantly changing population of cells that are allocated to different parts of the axial mesoderm.
通过Hnf3β、Gsc(lacZ)和Chrd的表达，以及这些细胞在宿主胚胎中诱导第二条神经轴的能力，已在中胚层期胚胎原条前端鉴定出一个组织者群体。因此，这个细胞群体可被视为中胚层组织者，它与早期原肠胚组织者和节点一起，在发育的连续阶段构成小鼠胚胎的组织者。在原肠胚形成过程中，组织者中细胞的遗传活性谱和组织贡献会发生变化，这表明组织者可能由一系列具有不同命运的细胞群体组成。对早期原条期胚胎后部区域上胚层的精细定位显示，尽管早期原肠胚组织者包含产生轴向中胚层的细胞，但头部突起和脊索的大部分祖细胞位于早期原肠胚组织者之外。在中胚层组织者中，注定形成前脊索中胚层的早期原肠胚组织者衍生细胞，与从早期原肠胚组织者前方的上胚层招募的头部突起祖细胞结合。注定形成头部突起的细胞从中胚层组织者沿胚胎中线紧密排列的柱状结构向前移动。其他中胚层组织者细胞加入不断扩展的中胚层层，并定殖于颅部和心脏中胚层。位于中胚层期胚胎前原条中的躯干脊索祖细胞，随后会并入节点。因此，原肠胚组织者由不断变化的细胞群体组成，这些细胞被分配到轴向中胚层的不同部位。
