Genetics of Isolated Tooth Agenesis
Tooth agenesis occurs more frequently among a few specific teeth (the lateral incisors, second premolars, and third molars). Familial tooth agenesis is transmitted as an autosomal dominant, autosomal recessive or X-linked condition, but can also show no clear segregation pattern. Genetic defects responsible for tooth agenesis are only now beginning to be uncovered. Mutations in AXIN2, MSX1 and PAX9 have been associated with tooth agenesis in humans, but these mutations account for very few cases. To date, the number of genes identified as having a role in tooth development exceeds 100 and all of these genes are potential candidates for tooth agenesis in humans. Our assumption is that most of the cases of human tooth agenesis are caused by several independent defective genes, acting alone or in combination with other genes, and leading to a specific phenotype pattern. Data from animal models are still very complex, and the human embryology is still poorly understood. We believe oral clefts (cleft individuals have a much higher chance to present with tooth agenesis outside the cleft area than the general population), and syndromic forms of tooth agenesis are the best models for the genetics of isolated tooth agenesis. Our efforts are targeting the following genes: