SNP Shot: Genomic Insights

Amelogenesis imperfecta (AI) is a genetic condition that disrupts the normal formation of tooth enamel. Individuals with AI often have teeth that are abnormally small, discolored (e.g., yellow or brown), and have surface defects like pits or grooves. These teeth are also susceptible to rapid wear and fracture. The specific dental problems and their severity vary significantly from person to person. Both the primary (baby) teeth and the permanent (adult) teeth can be affected.

Scientists have identified at least 14 different types of AI, each characterized by unique enamel defects and inheritance patterns. AI can occur as an isolated dental condition, or it can be a feature of a broader syndrome affecting other parts of the body.

Inheritance:

The way AI is passed down through families depends on the specific gene that is mutated. A significant number of AI cases are due to mutations in the FAM83H gene and follow an autosomal dominant inheritance pattern. This means that only one copy of the altered gene is needed to cause the condition. Some mutations in the ENAM gene also result in autosomal dominant AI. Autosomal recessive inheritance is another possibility, often linked to mutations in the ENAM or MMP20 genes. In this case, two copies of the mutated gene are required, one from each parent. The parents are carriers, meaning they have one copy of the mutated gene but do not usually exhibit symptoms. Approximately 5% of AI cases are X-linked, caused by mutations in the AMELX gene, which resides on the X chromosome. Males with X-linked AI typically experience more severe enamel defects than females. Finally, some instances of AI arise from spontaneous, new gene mutations and occur in individuals with no family history of the disorder.