Gene defect in hypodontia: exclusion of EGF, EGFR, and FGF-3 as candidate genes.

Hypodontia, congenital absence of one or a few permanent teeth without any systemic disorders, is regarded as an autosomally inherited dominant condition with varying expression and incomplete penetrance. Many studies have reported that the prevalence of hypodontia varies from 5% to 10% among European and Asian populations. The teeth most often missing are second premolars, upper lateral incisors, and lower central incisors. Consequently, we call this trait incisor-premolar hypodontia. Peg-shaped or strongly mesio-distally reduced upper lateral incisors demonstrate variation in the expression of the trait. The gene or genes causing incisorpremolar hypodontia are not known. We have begun the genetic mapping of hypodontia by using linkage analyses in seven Finnish three-generation families with 77 individuals, 31 affected with incisor-premolar hypodontia. As the first step, we studied the possibility of linkage between hypodontia and some candidate genes which have been suggested to have important functions during tooth development. Here we report the exclusion of EGF, EGFR, and FGF-3 loci as possible sites for gene mutation causing incisor-premolar hypodontia in our family material. Because of the close location of the FGF-3 and FGF-4 genes, the results also suggest the exclusion of the FGF-4 locus.