Conclusions
We verified the FAM83H p.Lys639* protein as a gain-of-function variant causing ADHCAI. Abnormal enamel rod head structure was observed in teeth with mutant FAM83H proteins. We also investigated the molecular pathogenesis and presented data on the abnormal degradation of mutant FAM83H proteins. Clinical relevance: This study helped the family members to understand the disease progression and provided new insights into the pathogenesis of ADHCAI. Due to the large heterogeneity of ADHCAI, this study also provided a genetic basis for individuals who exhibit similar clinical phenotypes.
Methods
The ultrastructure of enamel was analyzed by micro-CT and scanning electron microscopy. Whole-exome sequencing (WES) was performed to identify the pathogenic gene. The function of the mutant FAM83H was studied by real-time PCR, western blotting, subcellular localization, and protein degradation pathway analyses.
Results
WES identified a known nonsense mutation (c.1915A > T) in exon 5 of the FAM83H gene, causing a truncated protein (p.Lys639*). However, the cases reported herein exhibited significant differences in the clinical phenotype compared with that the previously reported case. An abnormal enamel rod head structure was observed in affected teeth. In vitro functional studies showed altered protein localization and a decreased protein degradation rate for mutant FAM83H. Conclusions: We verified the FAM83H p.Lys639* protein as a gain-of-function variant causing ADHCAI. Abnormal enamel rod head structure was observed in teeth with mutant FAM83H proteins. We also investigated the molecular pathogenesis and presented data on the abnormal degradation of mutant FAM83H proteins. Clinical relevance: This study helped the family members to understand the disease progression and provided new insights into the pathogenesis of ADHCAI. Due to the large heterogeneity of ADHCAI, this study also provided a genetic basis for individuals who exhibit similar clinical phenotypes.