Detection and analysis of a factor concerned with cell differentiation and growth during mouse molar tooth development by means of the grafting to a chick wing bud.

牙齿发育涉及上皮-间质相互作用和复杂的形态发生事件。由于这些过程与肢体发育中发生的过程相似，我们询问肢体中发现的信号机制是否也发生在牙齿中。我们将小鼠胚胎牙胚移植到宿主鸡胚翅芽前缘，并检测牙组织是否具有极化活性。事实上，移植的牙胚诱导形成的异位手指米勒图像以及表面结构。磨牙牙胚的这些活性从蕾状期到帽状期逐渐增加，钟状晚期达到最大值。随着进一步发育，极化活性开始下降，然而，一旦它成为新生儿的最高水平。原位杂交结果表明，牙胚移植物诱导鸡HoxD簇基因表达先于异位趾的形成。我们的结论是牙胚产生的因子类似于肢体发育中极化活动区的因子，可能调节磨牙发育中的形态发生和分化。

Tooth development involves reciprocal epithelio-mesenchymal interactions and complex morphogenetic events. Because these processes bear similarities to those occurring in the developing limb, we asked whether signaling mechanisms found in the limb also occur in the tooth. We grafted mouse embryonic tooth germs to the anterior margin of the host chick embryonic wing buds and determined whether the tooth tissues had polarizing activity. Indeed the grafted tooth germs induced the formation of the ectopic digits as a miller image as well as the surface structures. These activity of the molar tooth germ increased from bud to cap stage and reached at the maximum at late bell stage. With further development, the polarizing activity began to decrease, however, once it became the highest level at neonates. And then the activity decreased to undetectable level at 3-week old.In situ hybridization demonstrated that the tooth germ grafts induced expression of chick HoxD cluster genes prior to induction of ectopic digits. We concluded that the factors produced by the tooth germs were similar to those in the zone of polarizing activity in the limb development and might regulate morphogenesis and differentiation in the molar tooth development.