Department of Biology, University of Florida, Gainesville, USA.
Department of Biology, University of Florida, Gainesville, USA; Department of Biology, California State University Fullerton, Fullerton, USA.
Dev Biol. 2024 Dec;516:221-236. doi: 10.1016/j.ydbio.2024.08.009. Epub 2024 Aug 16.
Sharks and their relatives are typically covered in highly specialized epithelial appendages embedded in the skin called dermal denticles; ancient tooth-like units (odontodes) composed of dentine and enamel-like tissues. These 'skin teeth' are remarkably similar to oral teeth of vertebrates and share comparable morphological and genetic signatures. Here we review the histological and morphological data from embryonic sharks to uncover characters that unite all tooth-like elements (odontodes), including teeth and skin denticles in sharks. In addition, we review the differences between the skin and oral odontodes that reflect their varied capacity for renewal. Our observations have begun to decipher the developmental and genetic shifts that separate these seemingly similar dental units, including elements of the regenerative nature in both oral teeth and the emerging skin denticles from the small-spotted catshark (Scyliorhinus canicula) and other chondrichthyan models. Ultimately, we ask what defines a tooth at both the molecular and morphological level. These insights aim to help us understand how nature makes, replaces and evolves a vast array of odontodes.
鲨鱼及其亲属的皮肤中通常覆盖着高度专业化的上皮附属物，称为真皮齿状突；这些由牙本质和釉质样组织组成的古老的牙齿状单位（odontodes）。这些“皮肤牙齿”与脊椎动物的口腔牙齿非常相似，具有相似的形态和遗传特征。在这里，我们回顾了来自胚胎鲨鱼的组织学和形态学数据，以揭示将所有牙齿状元素（odontodes），包括鲨鱼的牙齿和皮肤齿状突联系在一起的特征。此外，我们还研究了皮肤和口腔齿状突之间的差异，这些差异反映了它们在更新能力上的不同。我们的观察结果开始揭示了将这些看似相似的牙齿单位（包括口腔牙齿和新兴的小斑点猫鲨（Scyliorhinus canicula）和其他软骨鱼类模型中的皮肤齿状突的再生性质）分离的发育和遗传变化。最终，我们会问在分子和形态水平上，什么定义了牙齿。这些见解旨在帮助我们了解大自然如何制造、替代和进化出大量的齿状突。
