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Increased Apoptosis during Morphogenesis of the Lower Cheek Teeth in Tabby/EDA Mice

¹ Department of Teratology, Institute of Experimental Medicine, Academy of Sciences of the CR, Prague, Czech Republic; and
² INSERM U595, Faculté de Médecine, Université Louis Pasteur, Strasbourg, France;

View larger version (41K): [in this window] [in a new window]   Figure 1. Schematic representation of the pattern of the lower cheek tooth primordia in wild-type (WT) and tabby (Ta) mouse fetuses (according to Peterkova et al., 2002). M1, M2, and M3—the first, second, and third lower molar primordia in WT mice. T1, T2, and T3—the prospective first, second, and third functional teeth in the different subtypes of Ta morphotypes I (Ia, Ib, Ic) and II (IIa, IIb). Note the decreasing volume of the most mesial tooth primordium from subtypes Ia to IIb, which is associated with increasing volume of the subsequent tooth primordia and a mesial shift in tooth boundaries compared with WT mice. The abortive tooth primordium (dashed line) represents an abortive cap (**) in subtype IIa and an abortive bud (*) in subtype IIb. These abortive tooth primordia do not give rise to a functional tooth. The first functional tooth (T1) in morphotype II is, in reality, the second tooth primordium, which originates in the mesio-distal sequence during odontogenesis. Accordingly, the morphology of T1 in morphotype II is similar to that of T2 in morphotype I (Peterkova et al., 2002).

View larger version (70K): [in this window] [in a new window]   Figure 2. Apoptosis in 3D reconstructions of the dental epithelium in the cheek region of the mandible at ED 15.5, 16.5, and 17.5. Apoptosis presented by apoptotic cells and bodies (black dots) is increased in Ta mice. It is distributed mesio-distally to a similar extent in all Ta morphotypes, but it affects different structures according to the specific tooth pattern (compare with Fig. 1). The mesenchymal face of the dental and adjacent oral epithelium is shown from an aerial view in wild-type (WT) controls and in subtypes Ia and Ib of Ta dentition. The pictures have been unified to show the right-side dentition. WT and Ta specimens of similar weight (Peterka et al., 2002) were selected for comparison on each of the embryonic days. Consequently, inter- and intra-litter variability in the length of the dental epithelium was minimalized (also see Figs. 3, 4). Various stages of tooth development are represented: The WT mice show the cap stage of M1 at ED 15.5, the cap-bell transition of M1 and the late bud/early cap of M2 at ED 16.5, the bell of M1, and the late cap of M2 at ED 17.5. In Ta subtypes Ia and Ib, the cap stage of T1 and the late bud/early cap of T2 occurred at ED 15.5, the early bell of T1 and the cap of T2 at ED 16.5, and the bell of T1 and T2 and the bud of T3 at ED 17.5. "mer" = mesial epithelial ridge (the epithelial ridge extending mesially from the primordium of the most mesial cheek tooth). Arrow = apoptosis in the pEK.

View larger version (66K): [in this window] [in a new window]   Figure 3. Apoptosis in 3D reconstructions of the dental epithelium in the cheek region of the mandible at ED 15.5, 16.5, and 17.5. Apoptosis presented by apoptotic cells and bodies (black dots) is increased in Ta mice. It is distributed mesio-distally to a similar extent in all Ta morphotypes, but it affects different structures according to the specific tooth pattern (compare with Fig. 1). The mesenchymal face of the dental and adjacent oral epithelium is shown from an aerial view in subtypes Ic, IIa, and IIb of Ta dentition. The pictures have been unified to present the right-side dentition. Various stages of tooth development are shown in subtype Ic: the cap of T1 and the early cap of T2 at ED 15.5, the cap-bell transition stage of T1 and the cap of T2 at ED 16.5, and the bell of both T1 and T2 at ED 17.5. In morphotypes IIa and IIb, the T1 showed from early cap to well-formed cap stage at ED 15.5–16.5 and the bell stage at ED 17.5. The bud of T3 in morphotype Ic and T2 in morphotypes IIa and IIb were distinct at ED 17.5. The abortive cap (double arrowhead) and abortive bud (single arrowhead) represent the most mesial primodium in morphotype II. "mer" = mesial epithelial ridge (the epithelial ridge extending mesially from the primordium of the most mesial cheek tooth). Arrow = apoptosis in the pEK.

View larger version (75K): [in this window] [in a new window]   Figure 4. 3D reconstructions of the dental epithelium in the cheek region of the mandible at ED 15.5, 16.5, and 17.5. The mesenchymal face of the dental and adjacent oral epithelium is shown from a lingual (medial) view. The pictures have been unified to present the right-side dentition. Apoptotic cells and bodies are represented by black dots. The dashed circle indicates apoptosis between the B1 and B2 (G) or B2 and B3 (M) cusps. Such apoptosis was not found in Ta specimens, which can be explained by their different tooth and cusp patterns (Kristenova et al., 2002). Arrow = apoptosis in the pEK. Double arrowhead = the abortive cap. Single arrowhead = abortive bud. For further explanation, see Figs. 1–3.

Journal of Dental Research, Vol. 84, No. 3, 228-233 (2005)
DOI: 10.1177/154405910508400304


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