Splicing mutations in AMELX and ENAM cause amelogenesis imperfecta

Area of Science:

• Genetics
• Molecular Biology
• Dentistry

Background:

• Amelogenesis imperfecta (AI) is a developmental enamel defect impacting tooth structure, aesthetics, and function.
• While gene mutations are linked to AI, the precise mechanisms of different mutations remain unclear.
• This study investigates the molecular pathogenesis of AI in families with novel pre-mRNA splicing mutations.

Purpose of the Study:

• To identify and characterize novel splicing mutations in genes associated with Amelogenesis Imperfecta (AI).
• To elucidate the molecular mechanisms underlying AI caused by these specific mutations.
• To expand the understanding of genetic factors contributing to enamel formation defects.

Main Methods:

• Recruitment of two Chinese families with AI.
• Whole-exome and Sanger sequencing for mutation identification.
• Minigene splicing assays to assess mRNA splicing alterations.
• AlphaFold2 for predicting three-dimensional structures of mutant proteins.

Main Results:

• A novel splicing mutation (c.570+1G>A) in the AMELX gene was identified in family 1, causing partial intron 6 retention and hypoplastic-hypomature AI.
• A novel splicing mutation (c.123+4A>G) in the ENAM gene was identified in family 2, leading to exon 4 skipping and hypoplastic AI.
• Predicted protein structures revealed significant differences between mutant and wild-type proteins, indicating impaired function.

Conclusions:

• Two novel splicing mutations in AMELX and ENAM genes are identified as causes of hypoplastic-hypomature and hypoplastic AI, respectively.
• These findings broaden the spectrum of known AI-associated genes.
• The study enhances the comprehension of the molecular genetic pathology of enamel formation.