Genexpression während der Zahnentwicklung der Maus (Mus musculus)

Gene expression in the tooth development of mice (Mus musculus) The development of teeth and jaw bones are lead by mechanisms that determine cells to become, teeth, bones or cartilages. The ectomesenchymal cells of the lower jaw receives signals from overlying epithelium to differentiate into odontoblasts, osteoblasts and chondrocytes. Cells from the neural crest are influenced by ectodermal signals. An early signal (Fgf8) comes from the oral epithelium and induces the development of the lower jaw. Molar morphogenesis in the maxillary starts from the mesenchyme, influenced by genes like Barx1, Dlx2 and Dlx2. At the same time the absence of genes like Msx1 and genes from the Alx-family is necessary for a normal development (McCollum and Sharpe, 2001). The expression of Msx1 and Alx-genes causes the development of incisors. Mice with null mutation of Dlx1 and Dlx2 fail to develop maxillary molars. Also additional abnormalities appear in the upper jaw. All other teeth are regularly developed (Qiu et al., 1997; Thomas et al., 1997). Dlx5 and Dlx6 are believed to be involved in the development of the lower molar teeth. Ectopic expression of Barx1 in the distal mandibular mesenchym, accompanied by loss of Msx1, results in a transformation of incisors into molars (Tucker et al., 1998). Msx1 mutant mice have defects in the distal jaw skeletal tissue. In conclusion, genes that determine the expression of molar teeth also control the development of the proximal jaw and genes that regulate incisor morphogenesis also regulate distal jaw development (McCollum and Sharpe, 2001). Generation of canine and premolar teeth is caused by overlapping domains of homeobox genes like Msx1, Dlx1 and Dlx2. In mice, the development of teeth in the maxilla seems to be different compared to the mandibula. Activin ßA null mutant mice shows no incisor and molar teeth in the lower jaw. Growth of teeth stops at bud stage in the mandibula while tooth development in the upper jaw in unaffected (Matzuk et al., 1995b). Most of the basic genetic mechanisms during the development of the teeth in the upper and lower jaw are identical. Only some of them lead into a different developmental pattern. This could be due to the different origin of mesenchymal cells (McCollum and Sharpe, 2001). The lower jaw is formed by ectomesenchymal cells originating from the neural crest from the cranial rostral hindbrain and the caudal middlebrain while neural crest cells from the caudal forebrain and middlebrain contribute to the fronto-nasal region (Osumi-Yamashita et al., 1994).

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Ludwig-Maximilians-Universität

Year

2004

Author dc:creator

• Schroll, Ilse

Repository record source_url

https://edoc.ub.uni-muenchen.de/1842/

OAI identifier oai:identifier

oai:edoc.ub.uni-muenchen.de:1842