Bode Hans R
Department of Developmental and Cell Biology, University of California, Irvine, CA 92697, USA.
Int J Dev Biol. 2012;56(6-8):473-8. doi: 10.1387/ijdb.113448hb.
Organizers and organizing centers play critical roles in axis formation and patterning during the early stages of embryogenesis in many bilaterians. The presence and activity of an organizer was first described in adult Hydra about 100 years ago, and in the following decades organizer regions were identified in a number of bilaterian embryos. In an adult Hydra, the cells of the body column are constantly in the mitotic cycle resulting in continuous displacement of the tissue to the extremities where it is sloughed. In this context, the head organizer located in the hypostome is continuously active sending out signals to maintain the structure and morphology of the head, body column and foot of the animal. The molecular basis of the head organizer involves the canonical Wnt pathway, which acts in a self-renewing manner to maintain itself in the context of the tissue dynamics of Hydra. During bud formation, Hydra's mode of asexual reproduction, a head organizer based on the canonical Wnt pathway is set up to initiate and control the development of a new Hydra. As this pathway plays a central role in vertebrate embryonic organizers, its presence and activity in Hydra indicate that the molecular basis of the organizer arose early in metazoan evolution.
在许多两侧对称动物胚胎发育的早期阶段，组织者和组织中心在轴的形成和模式形成中发挥着关键作用。大约100年前，组织者的存在和活性首次在成年水螅中被描述，在随后的几十年里，在许多两侧对称动物胚胎中鉴定出了组织者区域。在成年水螅中，体柱细胞不断处于有丝分裂周期，导致组织不断向末端移位，在末端组织脱落。在这种情况下，位于口盘的头部组织者持续活跃，发出信号以维持动物头部、体柱和足部的结构和形态。头部组织者的分子基础涉及经典Wnt信号通路，该通路以自我更新的方式发挥作用，在水螅的组织动态环境中维持自身。在出芽形成过程中，即水螅的无性繁殖方式，基于经典Wnt信号通路建立一个头部组织者，以启动和控制新水螅的发育。由于该通路在脊椎动物胚胎组织者中起着核心作用，其在水螅中的存在和活性表明组织者的分子基础在后生动物进化早期就已出现。
