Evolutionary Developmental Biology Research Group, Department of Biology, Ghent University, Ghent, Belgium.
Dev Dyn. 2021 Jul;250(7):1021-1035. doi: 10.1002/dvdy.300. Epub 2021 Jan 25.
Organs that develop early in life, and are replaced by a larger version as the animal grows, often represent a miniature version of the adult organ. Teeth constituting the first functional dentition in small-sized teleost fish, such as medaka (Oryzias latipes), are examples of such miniature organs. With a dentin cone as small as the size of one human cell, or even smaller, these teeth raise the question how many dentin-producing cells (odontoblasts) are required to build such a tooth, and whether this number can be as little as one.
Based on detailed observations with transmission electron microscopy (TEM) and TEM-based 3D-reconstructions, we show that only one mesenchymal cell qualifies as a true odontoblast. A second mesenchymal cell potentially participates in dentin formation, but only at a late stage of tooth development. Moreover, the fate of these cells appears to be specified very early during tooth development.
Our observations indicate that in this system, one single odontoblast fulfills roles normally exerted by a large and communicating cell population. First-generation teeth in medaka thus provide an exciting model to study integration of multiple functions into a single cell.
在生命早期发育并随着动物生长而被更大版本替代的器官，通常代表成人器官的缩小版。牙齿是小型硬骨鱼（如斑马鱼）中首次形成的功能性牙齿，是此类微型器官的一个例子。这些牙齿的牙本质锥体小到只有一个人类细胞那么大，甚至更小，这就提出了一个问题，即需要多少个产生牙本质的细胞（成牙本质细胞）来构建这样一颗牙齿，而这个数量是否可以少到只有一个。
基于透射电子显微镜（TEM）和基于 TEM 的 3D 重建的详细观察，我们表明只有一个间充质细胞符合真正成牙本质细胞的标准。第二个间充质细胞可能参与牙本质的形成，但仅在牙齿发育的后期。此外，这些细胞的命运似乎在牙齿发育的早期就已经确定。
我们的观察表明，在这个系统中，一个单一的成牙本质细胞完成了通常由一个大的、相互交流的细胞群体发挥的作用。因此，斑马鱼的第一代牙齿为研究将多种功能整合到单个细胞中提供了一个令人兴奋的模型。
