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The Department of Biomedicine

BBB Seminar: Paivi Kettunen

Molecular regulation of development of tooth innervation 

Päivi Kettunen
Department of Biomedicine, University of Bergen

The mouse mandibular molar tooth germ is an advantageous model system in which to investigate molecular regulation of morphogenesis and peripheral organ innervation. Innervation of the tooth is supplied by the trigeminal and superior cervical ganglia, which start to develop before the tooth germs are visible. Growth, pathfinding, patterning, and target recognition of the dental nerve fibers are linked with different consecutive developmental stages of the tooth during embryogenesis and after birth. There is increasing evidence that nerve fibers are guided to their targets by classical secreted and membrane-bound axon guidance molecules such as netrins, slits, ephrins, and semaphorins, as well as classical morphogens (Shh, Wnt, and Tgf-beta/Bmp). In addition, cell-adhesion molecules (CAMs) and members of the immunoglobulin (Ig) and cadherin superfamiles are involved in axon guidance. Furthermore, neurotrophins act as survival signals to the developing neurons. We have investigated Semaphorin3a (Sema3a) in dental axon guidance, and have shown that it regulates growth, fasciculation, and patterning of dental axons. Expression of Sema3a itself is regulated by signals provided by the dental epithelium. Our results suggest that epithelial-mesenchymal interactions control Sema3a expression and may coordinate axon navigation and patterning with tooth morphogenesis.

Chair: Jaakko Saraste, Department of Biomedicine