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The primary enamel knot determines the position of the first buccal cusp in developing mice molars

 Sung-Won Cho  ;  Hyun-A Lee  ;  Han-Sung Jung  ;  Hayato Ohshima  ;  Jae-Young Kim  ;  Min-Jung Lee  ;  Jinglei Cai 
 DIFFERENTIATION, Vol.75(5) : 441-451, 2007 
Journal Title
Issue Date
Animals ; Bone Morphogenetic Protein 4 ; Bone Morphogenetic Proteins/metabolism ; Dental Enamel/cytology ; Dental Enamel/embryology* ; Dental Enamel/metabolism ; Female ; Gene Expression Regulation, Developmental ; In Situ Hybridization ; Mesoderm/cytology ; Mesoderm/metabolism ; Mice ; Mice, Inbred ICR ; Molar/cytology ; Molar/embryology* ; Molar/metabolism ; Morphogenesis ; Odontogenesis/genetics* ; Pregnancy
The enamel knot (EK), which is located in the center of bud and cap stage tooth germs, is a transitory cluster of non-dividing epithelial cells. The EK acts as a signaling center that provides positional information for tooth morphogenesis and regulates the growth of tooth cusps by inducing secondary EKs. The morphological, cellular, and molecular events leading to the relationship between the primary and secondary EKs have not been described clearly. This study investigated the relationship between the primary and secondary EKs in the maxillary and mandibular first molars of mice. The location of the primary EK and secondary EKs was investigated by chasing Fgf4 expression patterns in tooth germ at some intervals of in vitro culture, and the relationship between the primary EK and secondary EK was examined by tracing the primary EK cells in the E13.5 tooth germs which were frontally half sliced to expose the primary EK. After 48 hr, the primary EK cells in the sliced tooth germs were located on the buccal secondary EKs, which correspond to the future paracone in maxilla and protoconid in mandible. The Bmp4 expression in buccal part of the dental mesenchyme might be related with the lower growth in buccal epithelium than in lingual epithelium, and the Msx2 expressing area in epithelium was overlapped with the enamel cord (or septum) and cell dense area. The enamel cord might connect the primary EK with enamel navel to fix the location of the primary EK in the buccal side during the cap to bell stages. Overall, these results suggest that primary EK cells strictly contribute to form the paracone or protoconid, which are the main cusps of the tooth in the maxilla or mandible.
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2. College of Dentistry (치과대학) > Dept. of Oral Biology (구강생물학교실) > 1. Journal Papers
Yonsei Authors
Kim, Jae Young(김재영)
Lee, Min Jung(이민정)
Lee, Hyun A(이현아)
Jung, Han Sung(정한성) ORCID logo https://orcid.org/0000-0003-2795-531X
Cho, Sung Won(조성원) ORCID logo https://orcid.org/0000-0001-7505-9769
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