Wolpert L, Lewis J, Summerbell D
Ciba Found Symp. 1975;0(29):95-130. doi: 10.1002/9780470720110.ch6.
Pattern formation in both the developing and the regenerating vertebrate limb can be understood in terms of the assignment of positional values to cells. The positional value may then control the selection of a course of cytodifferentiation as, say, muscle or cartilage. It is proposed that the proximodistal coordinate of positional value is extablished by a mechanism based on autonomous change with time in a 'progress zone' at the tip of the limb bud. The anteroposterior coordinate seems to be specified by a positional signal from an orgainzing region. Only cells in the progress zone respond to this signal. The change of character in the progress zone may be linked to cell division. It seems that each skeletal rudiment may initially be the same length, corresponding to the amount of tissue that leaves the progress zone during one cell cycle. The lengths on the skeletal elements are already specified shortly after exit from the progress zone, and are capable of very little regulation. The positional value may determine the pregramme of later growth. The relevance of the progress zone model to epimorphic regulation, and amphibian limb regeneration in particular, is discussed.
无论是在发育中的还是再生的脊椎动物肢体中，模式形成都可以通过给细胞赋予位置值来理解。然后，位置值可以控制细胞分化过程的选择，比如分化为肌肉或软骨。有人提出，位置值的近远轴坐标是由一种基于肢体芽尖“进展区”随时间自主变化的机制建立的。前后轴坐标似乎是由一个组织区域发出的位置信号所指定的。只有进展区的细胞对这个信号作出反应。进展区特征的变化可能与细胞分裂有关。似乎每个骨骼原基最初长度相同，这与在一个细胞周期内离开进展区的组织量相对应。骨骼元素的长度在离开进展区后不久就已确定，并且调节能力很小。位置值可能决定后期生长的程序。文中讨论了进展区模型与形态调节，特别是与两栖动物肢体再生的相关性。
