Novel MMP20 (matrix metalloproteinase 20) mutations causing hypoplastic-hypomaturation amelogenesis imperfecta

Area of Science:

• Genetics
• Biochemistry
• Dentistry

Background:

• Matrix metalloproteinase 20 (MMP20) is vital for dental enamel formation.
• Mutations in MMP20 cause autosomal recessive amelogenesis imperfecta (AI), leading to thin, soft enamel.

Purpose of the Study:

• Investigate the genetic basis of hypoplastic-hypomaturation AI in five families.
• Identify novel MMP20 mutations and characterize their functional impact.

Main Methods:

• Whole-exome sequencing and Sanger sequencing to identify mutations.
• Protein expression in HEK293T cells, immunoblotting, and gelatin zymography to assess variant pathogenicity.

Main Results:

• Six pathogenic MMP20 variants identified, including three novel mutations (c.289A>T, c.547G>A, c.686G>A).
• Novel missense mutations affect conserved residues in the catalytic domain, impairing MMP20 secretion and enzymatic activity.
• Affected individuals presented with thin, hypomineralized enamel, discoloration, and attrition.

Conclusions:

• Expands the genotypic spectrum of MMP20-associated AI.
• Identifies critical residues in the MMP20 catalytic domain essential for secretion and function.