Sinclair G D, Brasch K
Rev Can Biol. 1975 Dec;34(4):287-303.
The process of erythropoiesis is characterized by several distinctive features which render it a very useful model of cell differentiation. Mature erythrocytes arise from stem cells in a series of intermediate stages which are fairly well defined both on morphological and on biochemical grounds. During this development, the erythrocytes genome is gradually inactivated and the cell becomes geared to the production of primarily one gene product, hemoglobin. Recently, erythropoiesis has been closely studied in avian species since it has become technically possible to fractionate the blood of anemic birds into high-yield populations of young, developing and mature red cells. Attention has focused on patterns of RNA synthesis including globin m-RNA, in relation to cytoplasmic constitutents becoming modified for reduced activity. From the point of view of gene regulation, erythrocyte development is especially interesting in non-mammals, where in contrast to mammals, even fully mature red cells retain their nuclei. These erythrocytes rank among the most extreme examples of cell specialization and gene repression known. The nuclei of avian erythrocytes and others, contain a tissue-specific histone protein in addition to the more usual complement of vertebrate histone. This histone (H5, V, F2c) has been extensively investigated with a view to linking its presence to structural and molecular changes involved in the condensation and repression of red cell nuclei. The evidence to dat suggests that H5, in conjunction with tissue-specific changes in non-histone proteins, may be responsible for keeping the genomes of nucleated erythrocytes permanently inactive.
红细胞生成过程具有几个显著特征，这些特征使其成为细胞分化的一个非常有用的模型。成熟红细胞起源于干细胞，经过一系列中间阶段，这些阶段在形态学和生物化学方面都有相当明确的定义。在这个发育过程中，红细胞基因组逐渐失活，细胞逐渐倾向于主要产生一种基因产物——血红蛋白。最近，由于技术上已经能够将贫血鸟类的血液分离成高产的年轻、发育中和成熟红细胞群体，因此对鸟类的红细胞生成进行了深入研究。研究重点集中在RNA合成模式，包括珠蛋白信使核糖核酸，以及与细胞质成分因活性降低而发生修饰的关系。从基因调控的角度来看，非哺乳动物的红细胞发育特别有趣，因为与哺乳动物不同，即使是完全成熟的红细胞也保留着细胞核。这些红细胞是已知的细胞特化和基因抑制的最极端例子之一。鸟类红细胞和其他一些红细胞的细胞核，除了含有更常见的脊椎动物组蛋白外，还含有一种组织特异性组蛋白。这种组蛋白（H5、V、F2c）已经得到了广泛研究，目的是将其存在与红细胞核浓缩和抑制所涉及的结构和分子变化联系起来。目前的证据表明，H5与非组蛋白的组织特异性变化一起，可能负责使有核红细胞的基因组永久失活。
