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Dev Genes Evol (2008) 218:427437 DOI 10.1007/s00427-008-0237-9
ORIGINAL ARTICLE
Unique and shared gene expression patterns in Atlantic salmon (Salmo salar) tooth development
Ann Huysseune & Harald Takle & Mieke Soenens &
Karen Taerwe & Paul Eckhard Witten
Received: 13 January 2008 /Accepted: 16 June 2008 / Published online: 19 July 2008 # Springer-Verlag 2008
Abstract To validate the use of Atlantic salmon (Salmo salar L.) as a model species in research on the mechanism of continuous tooth replacement, we have started to collect data on the molecular control underlying tooth formation in this species. This study reports expression patterns in the lower jaw dentition of a number of key regulatory genes such as bmp2, bmp4, and sox9 and structural genes such as col11 and osteocalcin (= bgp, Bone Gla Protein) by means of in situ hybridization using salmon-specific, digoxygenin-labeled antisense riboprobes. We compare expression of these genes to that in other skeletogenic cells in the lower jaw (osteoblasts, chondroblasts, and chondrocytes). Our studies reveal both expression patterns that are in accordance to studies on mammalian tooth development and patterns that are specific to salmon, or teleosts. The epithelial expression of sox9 and a shift of the expression of bmp2 from epithelium to mesenchyme have also been observed during mammalian tooth development. Different from previous reports are the expressions of col11 and osteocalcin. In contrast to what has been reported for zebrafish, osteocalcin is not expressed in odontoblasts, nor in the osteoblasts involved in the attachment of the teeth. At the lower jaw, osteocalcin is expressed in mature and/or
resting osteoblasts only. As expected, col11 is expressed in odontoblasts. Surprisingly, it is also strongly expressed in the inner dental epithelium, representing the first report of ameloblast involvement in collagen type I transcription. Whether the collagen is translated and secreted into the enameloid remains to be demonstrated.
Keywords Tooth development . Atlantic salmon . Bmp . Collagen type I . Osteocalcin
Introduction
Many decades after the pioneering papers of Parker (1873), De Beer (1937), and Tchernavin (1938), salmonids are increasingly used in fundamental studies of jaw development and remodeling (Witten and Hall 2002, 2003; Gillis et al. 2006) as well as in studies on tooth development and lifelong tooth renewal (Domon et al. 2006; Fraser et al....