Abstract：
The vertebrate organizer plays a crucial role in building the main (antero-posterior) axis of the embryo: it neuralizes the surrounding ectoderm, and is the site of emigration for cells making axial and paraxial mesendoderm during elongation. The chick organizer becomes a stem zone at the onset of elongation; it stops recruiting cells from the neighbouring ectoderm and generates all its derivatives from the small number of resident cells it contains at the end of gastrulation stages. Nothing is known about the molecular identity of this stem zone. Here, we specifically labelled long-term resident cells of the organizer and compared their RNA-seq profile to that of the neighbouring cell populations. Screening by reverse transcription-polymerase chain reaction and in situ hybridization identified four genes (WIF1, PTGDS, ThPO and UCKL1) that are upregulated only in the organizer region when it becomes a stem zone and remain expressed there during axial elongation. In experiments specifically labelling the resident cells of the mature organizer, we show that only these cells express these genes. These findings molecularly define the organizer as a stem zone and offer a key to understanding how this zone is set up, the molecular control of its cells\' behaviour and the evolution of axial growth zones.
摘要：
脊椎动物的组织者在建立胚胎的主要（前后）轴方面起着至关重要的作用：它使周围的外胚层神经化，并且是在伸长过程中产生轴向和旁轴中内胚层的细胞的迁移部位。小鸡组织者在伸长开始时成为茎区；它停止从邻近的外胚层募集细胞，并在原肠胚形成阶段结束时从其包含的少量常驻细胞中产生其所有衍生物。对该茎区的分子身份一无所知。这里,我们专门标记了组织者的长期驻留细胞，并将其RNA-seq谱与相邻细胞群的RNA-seq谱进行了比较。通过逆转录聚合酶链反应和原位杂交进行筛选，鉴定出四个基因（WIF1，PTGDS，ThPO和UCKL1）仅在组织者区域成为茎区时上调，并在轴向伸长期间保持表达。在专门标记成熟组织者的常驻细胞的实验中，我们发现只有这些细胞表达这些基因。这些发现在分子上将组织者定义为茎区，并为了解该区域的设置提供了关键，其细胞行为的分子控制和轴向生长区的演化。
