Richardson M K, Hornbruch A, Wolpert L
Department of Anatomy and Developmental Biology, University College, Middlesex School of Medicine, London, United Kingdom.
Dev Biol. 1991 Feb;143(2):309-19. doi: 10.1016/0012-1606(91)90082-e.
The pattern of pigmentation in bird embryos is determined by the spatial organization of melanocyte differentiation. Some of the results from recent, neural crest transplantation experiments support a model based on a prepattern in the feathers; others could be interpreted in terms of a nonspecific pattern resulting from a failure of the crest cells to read the positional values in another species. To distinguish between these possibilities, the crucial test is to construct chimeras from two species with different pigment patterns. We have examined the wing plumage of quail and guinea fowl embryos. The quail has a characteristic pattern of pigmented and unpigmented feather papillae, whereas the guinea fowl shows uniform pigmentation. Chimeras were constructed by grafting wing buds isotopically between embryos. The wing buds were transplanted before they had become invaded by neural crest cells. Quail wing buds grafted to the guinea fowl developed, in most cases, a pigment pattern resembling that of the quail and not that of the guinea fowl. A few cases became uniformly pigmented and appeared to represent nonspecific patterns. The reciprocal grafts (guinea fowl wing buds grafted to the quail) became pigmented all over. We found evidence that the timing of melanocyte differentiation is controlled by cues in the feather papillae. Some cases developed a severe inflammatory response. The model which best accounts for these findings--and which can account for inconsistencies in previous reports--is the following. A prepattern is present in the feathers and this can control the differentiation of melanoblasts, even if they come from a different species. The local cues which constitute the prepattern are not positional values. In some chimeras melanoblasts fail to respond to the prepattern and so a nonspecific pattern of uniform pigmentation is produced.
鸟类胚胎中的色素沉着模式是由黑素细胞分化的空间组织决定的。近期神经嵴移植实验的一些结果支持了一种基于羽毛预模式的模型；其他结果则可解释为由于嵴细胞未能读取另一物种中的位置值而产生的非特异性模式。为了区分这些可能性，关键测试是构建来自两种具有不同色素模式物种的嵌合体。我们研究了鹌鹑和珍珠鸡胚胎的翅羽。鹌鹑具有色素沉着和无色素羽毛乳头的特征模式，而珍珠鸡则表现出均匀的色素沉着。通过在胚胎之间同位素移植翅芽构建嵌合体。翅芽在被神经嵴细胞侵入之前进行移植。移植到珍珠鸡的鹌鹑翅芽在大多数情况下发育出类似于鹌鹑而非珍珠鸡的色素模式。少数情况变得均匀色素沉着，似乎代表非特异性模式。反向移植（将珍珠鸡翅芽移植到鹌鹑）全身都有色素沉着。我们发现有证据表明黑素细胞分化的时间受羽毛乳头中的线索控制。一些情况出现了严重的炎症反应。最能解释这些发现——也能解释先前报告中不一致之处——的模型如下。羽毛中存在一种预模式，即使黑素母细胞来自不同物种，这种预模式也能控制其分化。构成预模式的局部线索不是位置值。在一些嵌合体中，黑素母细胞无法对预模式做出反应，因此产生了均匀色素沉着的非特异性模式。
