Yingchun Zheng1, Ting Lu2,3, Jianfan Chen1, Meiyi Li1, Jun Xiong4, Fei He1, Zhongzhi Gan1, Yingying Guo1, Leitao Zhang5, Fu Xiong6,7. 1. Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong, China. 2. Department of Stomatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China. 3. College of Stomatology, Southern Medical University, Guangzhou, Guangdong, China. 4. Department of Laboratory Medicine, ZhuJiang Hospital, Southern Medical University, Guangzhou, Guangdong, China. 5. Department of Stomatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China. leitaozhang@126.com. 6. Department of Medical Genetics, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong, China. xiongfu@smu.edu.cn. 7. Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong, China. xiongfu@smu.edu.cn.
Abstract
OBJECTIVES: Autosomal-dominant hypocalcification amelogenesis imperfecta (ADHCAI) is a hereditary disease characterized by enamel defects. ADHCAI is mainly caused by nonsense mutations in a gene called family with sequence similarity 83 member H (FAM83H). To study the pathogenesis of ADHCAI, a Chinese ADHCAI family was investigated. MATERIALS AND 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.
OBJECTIVES: Autosomal-dominant hypocalcification amelogenesis imperfecta (ADHCAI) is a hereditary disease characterized by enamel defects. ADHCAI is mainly caused by nonsense mutations in a gene called family with sequence similarity 83 member H (FAM83H). To study the pathogenesis of ADHCAI, a Chinese ADHCAI family was investigated. MATERIALS AND 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.
Entities:
Keywords:
ADHCAI; FAM83H; Protein degradation; Whole-exome sequencing
Authors: Claire E L Smith; James A Poulter; Agne Antanaviciute; Jennifer Kirkham; Steven J Brookes; Chris F Inglehearn; Alan J Mighell Journal: Front Physiol Date: 2017-06-26 Impact factor: 4.566