Fujiwara Shigeki, Kawamura Kazuo
Department of Biology, Faculty of Science, Kochi University, Kochi 780, Japan.
Dev Growth Differ. 1992 Aug;34(4):463-472. doi: 10.1111/j.1440-169X.1992.00463.x.
During bud development of the ascidian Polyandrocarpa misakiensis, most of the new tissues are formed from foldings of atrial epithelium. Although the atrial epithelium has been believed to be undifferentiated, we found that this epithelium of P. misakiensis strongly expressed a tissue-restricted antigen, named Pae 1. Cross-reactivity of the antibody was found only in a few differentiated tissues such as branchial epithelium and phagocyte-like cells. In developing buds, the antigen disappeared selectively from the regions where the atrial epithelium forms organ rudiments. These regions corresponded with that of mitotic activity, thickening of the epithelium, swelling of nuclei, the appearance of nucleoli and accumulation of a large amount of RNA. From these observations, we assume that the change in antigen expression indicates a change in the state of differentiation of the atrial epithelium. Although Pae 1 antigen was never detected in functional gut, it was detected in the invaginating gut epithelium. This result indicates that gut cells were derived from the cells which had expressed the antigen. We therefore conclude that the conversion of the atrial epithelium into gut can be regarded as a transdifferentiation-like process.
在海鞘三崎聚雄海鞘芽体发育过程中，大部分新组织由围鳃腔上皮折叠形成。尽管围鳃腔上皮一直被认为是未分化的，但我们发现三崎聚雄海鞘的这种上皮强烈表达一种组织限制性抗原，命名为Pae 1。仅在少数分化组织如鳃上皮和吞噬细胞样细胞中发现该抗体的交叉反应性。在发育中的芽体中，抗原从围鳃腔上皮形成器官原基的区域选择性消失。这些区域与有丝分裂活性区域、上皮增厚、细胞核肿胀、核仁出现以及大量RNA积累区域相对应。从这些观察结果来看，我们推测抗原表达的变化表明围鳃腔上皮分化状态的改变。尽管在功能性肠道中从未检测到Pae 1抗原，但在内陷的肠道上皮中检测到了。这一结果表明肠道细胞来源于表达该抗原的细胞。因此，我们得出结论，围鳃腔上皮向肠道的转变可被视为一种类似转分化的过程。
