Markl J, Franke W W
Division of Membrane Biology and Biochemistry, German Cancer Research Center, Heidelberg.
Differentiation. 1988 Dec;39(2):97-122. doi: 10.1111/j.1432-0436.1988.tb00086.x.
Using a panel of antibodies against different cytokeratins in immunofluorescence microscopy on frozen tissue sections and two-dimensional gel electrophoresis of cytoskeletal proteins from these tissues, we have studied the tissue distribution of cytokeratins in a fish, the rainbow trout Salmo gairdneri. We have distinguished at least 14 different cytokeratin polypeptides in only a limited number of tissues, thus demonstrating the great complexity of the cytokeratin pattern in a fish species. The simplest cytokeratin pattern was that present in hepatocytes, comprising one type-II (L1) and two type-I (L2, L3) polypeptides that appear to be related to mammalian cytokeratins 8 and 18, respectively. Two or all three cytokeratins of this group were also identified in several other epithelial tissues, such as kidney. Epithelia associated with the digestive tract contained, in addition, other major tissue-specific cytokeratins, such as components D1-D3 (stomach, intestine and swim bladder) and B1 and B2 (biliary tract). With the exception of D1, all these polypeptides were also found in a cultured cell line (RTG-2). Epidermal keratinocytes contained D1 and six other major cytokeratins, termed E1-E6. The most complex cytokeratin pattern was that found in the gill epithelium. Surprisingly, antibodies specific for cytokeratins of the L1-L3 group also reacted with certain cell-sheet-forming tissues that are not considered typical epithelia and in higher vertebrates express primarily, if not exclusively, vimentin. Such tissues were (a) endothelia, including the pillar cells of the "gill filaments", (b) scale-associated cells, and (c) the ocular lens epithelium, and also several nonepithelial cell types, such as (d) fibroblasts and other mesenchymal cells, (e) chondrocytes, (f) certain vascular smooth muscle cells, and (g) astroglial cells of the optic nerve. The differences between the patterns of cytokeratin expression in this fish species and those of higher vertebrates are discussed. It is concluded that the diversity of cytokeratins has already been established in lower vertebrates such as fish, but that the tissue-expression pattern of certain cytokeratins has been restricted during vertebrate evolution. We discuss the value of antibodies specific for individual cytokeratin polypeptides as marker molecules indicating cell and tissue differentiation in fish histology, embryology, and pathology.
我们运用一组针对不同细胞角蛋白的抗体，通过对冷冻组织切片进行免疫荧光显微镜观察，以及对这些组织的细胞骨架蛋白进行二维凝胶电泳，研究了虹鳟鱼（Salmo gairdneri）体内细胞角蛋白的组织分布情况。我们仅在有限数量的组织中就鉴别出了至少14种不同的细胞角蛋白多肽，这表明鱼类细胞角蛋白模式具有极大的复杂性。最简单的细胞角蛋白模式存在于肝细胞中，包括一种II型（L1）和两种I型（L2、L3）多肽，它们似乎分别与哺乳动物的细胞角蛋白8和18相关。在其他一些上皮组织，如肾脏中，也鉴定出了该组中的两种或所有三种细胞角蛋白。与消化道相关的上皮组织还含有其他主要的组织特异性细胞角蛋白，如D1 - D3组分（胃、肠和鳔）以及B1和B2（胆道）。除了D1之外，所有这些多肽在一种培养细胞系（RTG - 2）中也能被检测到。表皮角质形成细胞含有D1和其他六种主要的细胞角蛋白，称为E1 - E6。最复杂的细胞角蛋白模式出现在鳃上皮中。令人惊讶的是，针对L1 - L3组细胞角蛋白的特异性抗体也与某些不被视为典型上皮的细胞片状组织发生反应，在高等脊椎动物中这些组织主要（如果不是唯一）表达波形蛋白。这类组织包括：（a）内皮细胞，包括“鳃丝”的柱状细胞；（b）与鳞片相关的细胞；（c）晶状体上皮细胞，以及几种非上皮细胞类型，如（d）成纤维细胞和其他间充质细胞；（e）软骨细胞；（f）某些血管平滑肌细胞；（g）视神经的星形胶质细胞。本文讨论了该鱼类细胞角蛋白表达模式与高等脊椎动物之间的差异。得出的结论是，细胞角蛋白的多样性在鱼类等低等脊椎动物中就已经确立，但某些细胞角蛋白的组织表达模式在脊椎动物进化过程中受到了限制。我们讨论了针对单个细胞角蛋白多肽的特异性抗体作为标记分子在鱼类组织学、胚胎学和病理学中指示细胞和组织分化的价值。
