McClay D R, Logan C Y
Developmental, Cellular and Molecular Biology Group, LSRC, Duke University, Durham, NC 27708, USA.
Development. 1996 Feb;122(2):607-16. doi: 10.1242/dev.122.2.607.
Gastrulation in the sea urchin involves an extensive rearrangement of cells of the archenteron giving rise to secondary mesenchyme at the archenteron tip followed by the foregut, midgut and hindgut. To examine the regulative capacity of this structure, pieces of the archenteron were removed or transplanted at different stages of gastrulation. After removal of any or all parts of the archenteron, the remaining veg 1 and /or veg 2 tissue regulated to replace the missing parts. Endoderm transplanted to ectopic positions also regulated to that new position in the archenteron. This ability to replace or regulate endoderm did not decline until after full elongation of the archenteron was completed. When replacement occurred, the new gut was smaller relative to the remaining embryo but the recognizable morphology of the archenteron was re-established. Long after the archenteron reveals territorial specification through expression of specific markers, the endodermal cells remain capable of being respecified to other gut regions. Thus, for much of gastrulation, the gut is conditionally specified. We propose that this regulative ability requires extensive and continuous short-range communication between cells of the archenteron in order to reorganize the tissues and position the boundaries of this structure even after experimental alterations.
海胆的原肠胚形成涉及原肠细胞的广泛重排，在原肠尖端产生次生间充质，随后形成前肠、中肠和后肠。为了研究这种结构的调节能力，在原肠胚形成的不同阶段移除或移植原肠的部分组织。移除原肠的任何部分或全部后，剩余的veg 1和/或veg 2组织会进行调节以替代缺失的部分。移植到异位位置的内胚层也会调节到原肠中的新位置。这种替代或调节内胚层的能力直到原肠完全伸长完成后才会下降。当发生替代时，新的肠道相对于剩余的胚胎较小，但原肠可识别的形态得以重新建立。在原肠通过特定标记物的表达显示区域特化很久之后，内胚层细胞仍能够重新特化为其他肠道区域。因此，在原肠胚形成的大部分时间里，肠道是条件性特化的。我们提出，这种调节能力需要原肠细胞之间进行广泛且持续的短程通讯，以便在实验改变后重组组织并定位该结构的边界。
