Kawamura K, Fujiwara S
Department of Biology, Faculty of Science, Kochi University, Japan.
Int J Dev Biol. 1994 Jun;38(2):369-77.
In the budding tunicate, Polyandrocarpa misakiensis, the atrial epithelium is the major formative tissue giving rise to the pharynx, digestive tract, brain and endostyle of a bud. We show here that this multipotent epithelium carries several differentiation markers that are lost in the process of bud development. In both adult animals and growing buds, the atrial epithelium contained orange-pigmented granules in the cytoplasm. In developing buds, on the other hand, the cells committed to organ primordia have lost the granules, taken a cuboidal shape and have a large nucleus with a prominent nucleolus, like undifferentiated cells. The atrial epithelium was also characterized by ALP expressed on the apical surface of the cell. During budding the enzyme activity disappeared from the atrial epithelium and reappeared in the primordial digestive tract. Immunohistochemical studies suggested strongly that during gut formation, ALP antigens has been switched from the epithelial isoform to the intestinal isoform. These results have shown that in P. misakiensis budding involves transdifferentiation of multipotent, but differentiated epithelium, confirming our previous results (Fujiwara and Kawamura, Dev. Growth Differ. 34:463-472, 1992).
在出芽的被囊动物三崎聚雄海鞘（Polyandrocarpa misakiensis）中，围鳃腔上皮是形成芽体的咽、消化道、脑和内柱的主要组织。我们在此表明，这种多能上皮细胞携带几种在芽体发育过程中会消失的分化标志物。在成年动物和正在生长的芽体中，围鳃腔上皮细胞的细胞质中都含有橙色色素颗粒。另一方面，在发育中的芽体中，形成器官原基的细胞失去了这些颗粒，呈立方形，并且具有一个带有明显核仁的大细胞核，类似于未分化细胞。围鳃腔上皮细胞的另一个特征是在细胞顶端表面表达碱性磷酸酶（ALP）。在出芽过程中，该酶活性从围鳃腔上皮细胞中消失，并在原始消化道中重新出现。免疫组织化学研究强烈表明，在肠道形成过程中，碱性磷酸酶抗原已从上皮同工型转变为肠道同工型。这些结果表明，在三崎聚雄海鞘中，出芽涉及多能但已分化的上皮细胞的转分化，这证实了我们之前的结果（藤原和川村，《发育、生长与分化》34:463 - 472，1992年）。
