Teeth are anchored in the jaw in a highly variable manner across vertebrates. In mammals and crocodiles, the teeth are cushioned inside bony sockets by periodontal ligaments, whereas most squamate reptiles have teeth firmly attached to the jawbone. Here, we analyzed the development of the attachment tissue in the veiled chameleon, a species with firm acrodont tooth attachment, to reveal the cellular processes establishing ankylosis and to determine the cell types contributing to the attachment. The tooth-bearing bones formed pedicles with edges fusing to the dentine via an attachment tissue produced by morphologically distinct cells exhibiting both osteoblastic and odontoblastic features. These cells were RUNX2-positive, suggesting their potential to differentiate into hard-tissue-producing cells. However, in contrast to the osteoblasts of the bony pedicles, tooth-bone interface (TBI) cells expressed elevated levels of Na+-/K+-ATPase and thus resembled odontoblasts. TBI cells were visible only temporarily, and after tooth-bone fusion they were removed by apoptosis and phagocytosis. Dynamic deposition of the hard matrix continued on both sides of the TBI and during the posthatching stages through the participation of osteoblasts. Overall, our findings demonstrate both odontoblast- and osteoblast-like characteristics of cells producing the attachment tissue at the TBI during development in chameleons, highlighting the existence of a transient intermediate cell population, which we call ankyloblasts.

Central European Institute of Technology Brno University of Technology Brno Czech Republic

Centre for Craniofacial and Regenerative Biology Floor 27 Guy's Tower Guy's Hospital King's College London London UK

Department of Experimental Biology Faculty of Science Masaryk University Brno Czech Republic

Department of Histology and Embryology Faculty of Medicine Masaryk University Brno Czech Republic

Department of Neuroimmunology Center for Brain Research Medical University of Vienna Vienna Austria

Department of Physiology and Pharmacology Karolinska Institutet Stockholm Sweden

Department of Radiation Dosimetry Nuclear Physics Institute Czech Academy of Sciences Prague Czech Republic

Laboratory of Molecular Morphogenesis Institute of Animal Physiology and Genetics v v i Czech Academy of Sciences Brno Czech Republic

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