Zebrafish sp7 mutants show tooth cycling independent of attachment, eruption and poor differentiation of teeth

• Published in: Developmental biology 2018-03, Vol.435 (2), p.176-184
• Main Authors: Kague, E., Witten, P.E., Soenens, M., Campos, CL, Lubiana, T., Fisher, S., Hammond, C., Brown, K. Robson, Passos-Bueno, MR, Huysseune, A.
• Format: Article
• Language: English
• Subjects: Alveolar Process - pathology; Animals; Animals, Genetically Modified; Dental Pulp - pathology; Dentin - abnormalities; Dentinogenesis - genetics; Dentinogenesis - physiology; Gene Expression Regulation, Developmental; Genes, Reporter; Odontoblasts - pathology; Odontogenesis - genetics; Odontogenesis - physiology; Osteoclasts - metabolism; Regeneration; Sp7 Transcription Factor - deficiency; Sp7 Transcription Factor - genetics; Sp7 Transcription Factor - physiology; Tooth Abnormalities - genetics; Tooth Root - pathology; Zebrafish - genetics; Zebrafish Proteins - deficiency; Zebrafish Proteins - genetics; Zebrafish Proteins - physiology
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2018.01.021

The capacity to fully replace teeth continuously makes zebrafish an attractive model to explore regeneration and tooth development. The requirement of attachment bone for the appearance of replacement teeth has been hypothesized but not yet investigated. The transcription factor sp7 (osterix) is known in mammals to play an important role during odontoblast differentiation and root formation. Here we study tooth replacement in the absence of attachment bone using sp7 zebrafish mutants. We analysed the pattern of tooth replacement at different stages of development and demonstrated that in zebrafish lacking sp7, attachment bone is never present, independent of the stage of tooth development or fish age, yet replacement is not interrupted. Without bone of attachment we observed abnormal orientation of teeth, and abnormal connection of pulp cavities of predecessor and replacement teeth. Mutants lacking sp7 show arrested dentinogenesis, with non-polarization of odontoblasts and only a thin layer of dentin deposited. Osteoclast activity was observed in sp7 mutants; due to the lack of bone of attachment, remodelling was diminished but nevertheless present along the pharyngeal bone. We conclude that tooth replacement is ongoing in the sp7 mutant despite poor differentiation and defective attachment. Without bone of attachment tooth orientation and pulp organization are compromised. •Attachment of bone is never present in zebrafish lacking sp7.•sp7-/- show arrested dentinogenesis, with non-polarization of odontoblasts and with only a thin layer of dentin.•Tooth replacement is not interrupted in the absence of bone of attachment, or eruption of predecessor tooth.•defective differentiation of the tooth does not prevent a successional tooth to be formed.•Abnormal orientation of teeth and pulp connection between predecessor and replacement tooth were often observed in sp7 -/-.