Localization of am3 using EL Congenic Mouse Strains

Tooth number abnormality: from bench to bedside

Tooth number abnormality is one of the most common dental developmental diseases, which includes both tooth agenesis and supernumerary teeth. Tooth development is regulated by numerous developmental signals, such as the well-known Wnt, BMP, FGF, Shh and Eda pathways, which mediate the ongoing complex interactions between epithelium and mesenchyme. Abnormal expression of these crutial signalling during this process may eventually lead to the development of anomalies in tooth number; however, the underlying mechanisms remain elusive. In this review, we summarized the major process of tooth development, the latest progress of mechanism studies and newly reported clinical investigations of tooth number abnormality. In addition, potential treatment approaches for tooth number abnormality based on developmental biology are also discussed. This review not only provides a reference for the diagnosis and treatment of tooth number abnormality in clinical practice but also facilitates the translation of basic research to the clinical application.

Genetic mapping of agenesis of the third molars in mice

EL/Sea mice are characterized by 100% incidence of agenesis of the third molars (M3). In a previous study, chromosomal mapping of the ninth generation EL/Sea congenic strains revealed a major locus for agenesis of M3, designated am3, in the 125-137 Mbp region of chromosome 3. In the present study, to determine the precise location of the am3 locus, we produced further generations of the EL/Sea congenic strains for am3 in which the restricted interval on chromosome 3 of EL/Sea was replaced by a MSM/Msf-derived homolog. The eleventh generation congenic mice that were either heterozygous or homozygous for the MSM/Msf-derived interval exhibited a significant decrease in the incidence of M3 agenesis (p < 0.00001). Results confined the am3 locus to an interval of 1 Mbp on chromosome 3, demonstrating that Lef1, one of the essential transcription factors for early tooth development, is the strongest candidate for am3.