Molecular Mechanism of Transdifferentiation in the Pigmented Epithelial Cell

基于蝾螈Wolffian透镜再生的研究，其中透镜可以从虹膜色素上皮再生，我们已经调查了调节色素上皮细胞（佩奇）转分化为透镜细胞的过程的分子机制。以下是1987年至1989年三年的调查结果。(1)本实验室开发的细胞培养方法已证明，从完全生长的人眼分离的佩奇容易转分化为透镜表型，其方式与在鸡胚佩奇中观察到的方式相同。此外，我们成功地从去分化的人佩奇中分离出永久性细胞系，并建立了独特的体外细胞培养系统的基础，该系统对于研究人细胞转分化的细胞和分子机制非常有用。(2)我们已经完整地描述了鸡胚佩奇中透镜转分化整个序列中色素细胞和透镜细胞特异性基因的表达模式。它还表明，这些细胞类型特异性基因的表达在多能去分化佩奇的reddiferentiation过程中受到转录调控。(3)从鸡胚佩奇中分离到两个不同的基因。从结构分析的结果推测，这两个基因编码负责调节佩奇的去分化和转分化的蛋白质。(4)我们已经发现了一种细胞表面糖蛋白，它稳定了蝾螈原位佩奇的分化状态。虽然这种糖蛋白不是特异性的佩奇，但广泛存在于中胚层起源的组织和一些外胚层起源的上皮细胞中，这种细胞表面分子在蝾螈透镜再生过程中虹膜佩奇的去分化中起着重要作用。

Based on studies of Wolffian lens regeneration in the newt, in which the lens can be regenerated from the iris pigmented epithelium, we have investigated molecular mechanisms regulating the processes of transdifferentiation of pigmented epithelial cells (PECs) to lens cells. The following findings have been established for three years from 1987 to 1989.(1) It has been proved by application of cell culture procedures developed in our laboratory that PECs dissociated from fully-grown human eyes readily transdifferentiate into lens phenotype in the manner observed in chick embryo PECs. In addition, we succeeded in isolation of permanent cell lines from dedifferentiated human PECs, and also in establishing the basis of a unique in vitro cell culture system which must be highly useful for studying cellular and molecular mechanisms of transdifferentiation in human cells.(2) We have completely described the pattern of expression of both pigment cell- and lens cell-specific genes in the whole sequence of lens transdifferentiation in chick embryo PECs. It has also shown that expression of these cell type-specific genes are transcriptionally regulated in the processes of reddiferentiation of multipotent dedifferentiated PECs.(3) Two different genes were isolated from chick embryo PECs. It has been assumed from the result of structural analyses that both genes code for a protein responsible for regulation of dedifferentiation and transdifferentiation of PECs.(4) We have found a cell surface glycoprotein which stabilize the differentiated state of PECs of the newt in situ. Although this glycoprotein is not specific to the PECs but widely detected in mesoderm-originated tissues and some of ectoderm-originated epithelia, this cell surface molecule plays an essential role in dedifferentiation of iris PECs in the process of lens regeneration in the newt.