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Irma Thesleff, Professor, Research Director, Developmental Biology Programme

Phone: +358-9-708 59401
Fax: 708 59560

The molecular mechanisms regulating embryonic development have been conserved to a great extent during evolution. Of central importance is intercellular communication mediated by complex signaling networks. We use the mammalian tooth as a model to analyse the signaling pathways in the inductive cell and tissue interactions that govern morphogenesis and cell differentiation. In addition, we have started to analyse signaling systems regulating intramembranous bone formation.
We use a variety of methods for morphological and functional analysis. In addition to mouse, also rat, vole and opossum are used as experimental animals. The methods include in situ hybridization analysis of gene expression, monitoring of cell division and apoptosis by computerized 3D- reconstructions. In organ cultures of dissected embryonic tissues, the effects of signals are analysed, and cell fate is followed by DiI labelling. In addition, different transfection strategies and transgenic approaches are used in functional analysis. We have also constructed a graphical WWW database presenting gene expression patterns in developing teeth. This is now widely used internationally as a tool to detect coexpression of genes and potential molecular interactions.

The specific aims of the project are: 1) to analyse the roles of individual components of the signaling pathways, including signals, receptors and transcription factors, especially in the families of hedgehog, BMP, wnt, and FGF signals, 2) to analyse the function of the enamel knot, 3) to examine the role of apoptosis, cell division and cell migration in tooth and bone morphogenesis, 4) to search for new developmental regulatory genes, 5) to clarify the functions of the recently cloned Tabby- and Cbfa-1 genes in tooth development, and  6) to identify genes controlling the developmental basis of tooth shape evolution


Post-docs: Jukka Jernvall, Risto Jaatinen, Marja Mikkola, Janna Waltimo, David Rice, Ph.D. students: Soile Keränen, Tuija Mustonen,  Pekka Nieminen, Leila Pakarinen, Johanna Pispa,  Johanna Laurikkala, Mark Tummers, Thomas Åberg. Technicians: Kaija Kettunen, Merja Mäkinen, Riikka Santalahti

Selected publications

Vainio, S., Karavanova, I., Jowett, A., Thesleff, I. Identification of BMP-4 as a signal mediating
 secondaryinduction between epithelial and mesenchymal tissues during early tooth development.
 Cell 75: 45-58, 1993.

Vaahtokari, A., Åberg, T., Jernvall, J., Keränen, S., Thesleff, I. The enamel knot as a signaling
 center in the developing mouse tooth. Mech Dev 54: 39-43, 1996.

Vaahtokari, A., Åberg, T., Thesleff, I. Apoptosis in the developing tooth: Association with an
 embryonic signalling center and suppression by EGF and FGF-4. Development 122: 121-129,

Åberg, T., Wozney, J., Thesleff, I. Expression patterns of BMPs in the developing mouse tooth suggests roles in morphogenesis and cell differentiation. Dev. Dyn. 210: 407-416, 1997.

Jernvall, J., Åberg, T., Kettunen,P., Keränen,S., Thesleff, I. The life history of an embryonic signaling center: BMP-4 induces p21 and is associated with apoptosis in the mouse tooth enamel knot. Development 125: 161-169, 1998.

Kim, HJ, Rice, DPC, Kettunen, PJ, Thesleff, I. FGF, BMP, and Shh mediated signalling pathways  in the regulation of cranial suture morphogenesis and calvarial bone development. Development 125: 1241-1251, 1998.

Harada, H, Kettunen, P, Jung, HS, Mustonen, T, Wang, YA, Thesleff, I. Localization of putative stem cells in dental epithelium and their association with Notch and FGF signaling. J Cell Biol: 147(1): 105-120, 1999.

Gene expression in tooth (WWW database): Developmental Biology Programme of the University of Helsinki, 1996.


Academy of Finland, University of Helsinki (center of excellence grant), Human Frontier Science Program, Sigrid Jusélius Foundation, European Orthodontic Society, Ministry of Education of Japan, Institute of Biotechnology, Biocentrum Helsinki.


Jukka Jernvall homepage

Last update 24.1.01 Updated by Pekka Nieminen (