FAM83H and Autosomal Dominant Hypocalcified Amelogenesis Imperfecta

Area of Science:

• Genetics
• Molecular Biology
• Biochemistry

Background:

• Autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI) presents with severe enamel defects and is linked to FAM83H mutations.
• The precise function of FAM83H in enamel formation and its disease mechanism remain unclear.
• Previous studies suggest FAM83H interacts with casein kinase 1 and keratins, potentially acting as a scaffold protein.

Purpose of the Study:

• To characterize the phenotypic and genotypic spectrum of ADHCAI in affected kindreds.
• To identify novel mutations in the FAM83H gene associated with ADHCAI.
• To investigate the molecular function of FAM83H, particularly its role in protein trafficking.

Main Methods:

• Genetic analysis of 9 kindreds with ADHCAI to identify FAM83H mutations.
• Clinical phenotyping, including dental and craniofacial assessments.
• In vitro pull-down assays using overexpressed FAM83H and SEC16A in HEK293 cells.

Main Results:

• Identified three novel FAM83H truncation mutations: p.His437*, p.Gln459*, and p.Glu610*.
• Observed hypoplastic phenotypes and failed tooth eruption in some affected individuals, broadening the ADHCAI phenotype.
• Demonstrated an interaction between FAM83H and SEC16A, a component of the COP II complex, suggesting a role in ER-to-Golgi trafficking.

Conclusions:

• The study expands the known spectrum of FAM83H mutations and associated phenotypes in ADHCAI.
• FAM83H may play a crucial role in endoplasmic reticulum-to-Golgi vesicle trafficking and protein secretion.
• These findings provide new insights into the molecular mechanisms underlying ADHCAI.