Mitsiadis Thimios A, Caton Javier, Cobourne Martyn
Department of Craniofacial Development, King's College London, Dental Institute, London Bridge, London SE1 9RT, UK.
J Exp Zool B Mol Dev Evol. 2006 May 15;306(3):227-33. doi: 10.1002/jez.b.21094.
Recent advances in molecular and developmental genetics have provided tools for understanding evolutionary changes in the nature of the epithelial-mesenchymal interactions regulating the patterned outgrowth of the tooth primordia. Tissue recombination experiments in mice have identified the oral epithelium as providing the instructive information for the initiation of tooth development. Teeth were lost in birds for more than 80 million years ago, but despite their disappearance, a number of gene products and the requisite tissue interactions needed for tooth formation are found in the avian oral region. It is believed that the avian ectomesenchyme has lost the odontogenic capacity, whilst the oral epithelium retains the molecular signaling required to induce odontogenesis. In order to investigate the odontogenic capacity of the neural crest-derived mesenchyme and its potential activation of the avian oral epithelium, we have realized mouse neural tube transplantations to chick embryos to replace the neural crest cells of chick with those of mouse. Teeth are formed in the mouse/chick chimeras, indicating that timing is critical for the acquisition of the odontogenic potential by the epithelium and, furthermore, suggesting that odontogenesis is initially directed by species-specific mesenchymal signals interplaying with common epithelial signals.
分子遗传学和发育遗传学的最新进展为理解调节牙原基模式生长的上皮-间充质相互作用本质的进化变化提供了工具。小鼠组织重组实验已确定口腔上皮为牙齿发育起始提供指导信息。鸟类在八千多万年前就失去了牙齿，尽管牙齿消失了，但在鸟类口腔区域仍发现了一些牙齿形成所需的基因产物和必要的组织相互作用。据信鸟类外胚间充质已丧失牙发生能力，而口腔上皮保留了诱导牙发生所需的分子信号。为了研究神经嵴来源间充质的牙发生能力及其对鸟类口腔上皮的潜在激活作用，我们将小鼠神经管移植到鸡胚中，用小鼠的神经嵴细胞取代鸡的神经嵴细胞。在小鼠/鸡嵌合体中形成了牙齿，这表明时间对于上皮获得牙发生潜能至关重要，此外，还表明牙发生最初由物种特异性间充质信号与共同上皮信号相互作用所引导。
