A novel ENAM mutation causes hypoplastic amelogenesis imperfecta.

OBJECTIVES: To identify the genetic cause of one Chinese family with hypoplastic amelogenesis imperfecta (AI) and explore the relationship between genotype and its phenotype. MATERIAL AND METHODS: One Chinese family with generalized hypoplastic AI was recruited. One deciduous tooth from the proband was subjected to scanning electron microscopy. Whole-exome sequencing was performed and identified mutation was confirmed by Sanger sequencing. Bioinformatics studies were further conducted to analyze potential deleterious effects of the mutation. RESULTS: The proband presented a typical hypoplastic AI phenotype whose teeth in deciduous and permanent dentitions showed thin, yellow, and hard enamel surface. The affected enamel in deciduous tooth showed irregular, broken, and collapsing enamel rods with borders of the enamel prisms undulated and structural shapes of prisms irregular. A novel homozygous nonsense mutation in the last exon of the enamelin (ENAM) gene (NM_031889.3; c.2078C>G) was identified in the proband, which was predicted to produce a highly truncated protein (NP_114095.2; p.(Ser693*)). This mutation was also identified in the proband's parents in heterozygous form. Surprisingly, the clinical phenotype of the heterozygous parents varied from a lack of penetrance to mild enamel defects. Additional bioinformatics studies demonstrated that the detected mutation could change the 3D structure of the ENAM protein and severely damaged the function of ENAM. CONCLUSION: The novel homozygous ENAM mutation resulted in hypoplastic AI in the present study. Our results provide new genetic evidence that mutations involved in ENAM contribute to hypoplastic AI.

Peptidomic changes of saliva after non-surgical treatment of stage I/II generalized periodontitis.

OBJECTIVE: To explore the changes of peptidome profiles of saliva, serum, and gingival crevicular fluid (GCF) before and after non-surgical periodontal treatment in patients with generalized periodontitis (stage I/II). SUBJECTS AND METHODS: Saliva, serum, and GCF samples were collected from 17 patients at baseline (T0 ), one week after ultrasonic supragingival scaling (T1 ) and eight weeks after subgingival scaling and root planning (T2 ). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was carried out to detect changes in peptidomic profiles. Then, nano-liquid chromatography-electrospray ionization-tandem mass spectrometry (nano-LC/ESI-MS/MS) was performed to identify potential peptide biomarkers. RESULTS: Most of the peptides from the patients exhibited a decreasing trend from the time point of pretreatment to that of post-treatment. Cluster analysis and scatter plots using these peptides indicated that salivary peptidome has an acceptable capability of reflecting the status of stage I/II generalized periodontitis. Seven of these peptides were successfully identified as α-1-antitrypsin, immunoglobulin κ variable 4-1, haptoglobin, and immunoglobulin heavy constant γ2. CONCLUSIONS: Certain peptides in saliva, serum, and GCF were down-regulated after non-surgical periodontal treatment, demonstrating the application prospects of saliva in monitoring and surveillance of periodontal diseases in both clinical settings and communities.

Comparative analysis of the effects of collection methods on salivary steroids.

BACKGROUND: Steroid hormone test for saliva was a promising area of research, however the impact of different collection methods on salivary steroids was underexplored so far. This study was designed to compare the effects of different collection methods (unstimulated or stimulated by chewing paraffin, forepart or midstream) on salivary flow rate, concentrations and secretion rates of steroids in saliva. METHODS: Whole-saliva samples were collected from 10 systemically and orally healthy participants, whose forepart and midstream segments of saliva were collected under unstimulated and stimulated conditions, with the salivary flow rate of each sample recorded. The concentrations and secretion rates of salivary steroids including testosterone, dehydroepiandrosterone (DHEA) and progesterone were measured by ELISA, with the multiple of change calculated. RESULTS: The results indicated mechanical stimulation used in collection of saliva samples could affect concentrations and secretion rates of steroids, whereas forepart and midstream segments had little differences in levels of salivary steroids, which effects could be partly influenced by individual specificity. The asynchronism in change of secretion rate of steroids with that of salivary flow rate might play an important role during this course. CONCLUSION: Based on these findings, we suggested to use the same collection method throughout one analytical study on salivary steroids or in longitudinal observations to ensure the comparability of the saliva samples collected.

A novel FAM83H mutation in one Chinese family with autosomal-dominant hypocalcification amelogenesis imperfecta.

Autosomal-dominant hypocalcification amelogenesis imperfecta (ADHCAI) is characterized by soft enamel that easily disintegrates and exposed dark dentin. ADHCAI is caused by mutations in a gene called family with sequence similarity 83 member H (FAM83H). To investigate the molecular genetics of ADHCAI, a Chinese family in which three generations exhibited ADHCAI was recruited. The enamel ultrastructure was analysed by environmental scanning electron microscopy (ESEM), which showed altered enamel rod (prism) structures in ADHCAI patients compared to the structures in healthy controls. Mutational analysis of the FAM83H gene identified a novel nonsense mutation (c.1222A>T) in the affected family members that encodes a stop codon at amino acid position 408, causing premature protein truncation (p. K408X). Green fluorescent protein (GFP) and FAM83H fusion protein analyses in vitro showed that normal cytoplasmic accumulation of the FAM83H protein was prevented by the K408X mutation in both rat dental epithelial SF2 cells and human embryonic kidney 293T cells. The mutant fusion protein localized primarily to the nucleus, in contrast to the cytoplasmic subcellular localization of the wild-type FAM83H protein. Our results provide new genetic evidence that mutations in FAM83H contribute to ADHCAI.

A novel mutation in GPR68 causes hypomaturation amelogenesis imperfecta.

OBJECTIVES: To identify the genetic cause of a Chinese family with hypomaturation amelogenesis imperfecta (AI) and to characterize the structure of GPR68 mutated enamel in order to develop a deeper understanding of the role of the GPR68 protein during the intricate process of amelogenesis. DESIGN: One Chinese family with generalized hypomaturation AI was recruited. Two of the third molars from the proband were subjected to scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Whole exome sequencing (WES) was performed, and the identified mutation was confirmed by Sanger sequencing. Bioinformatics studies were further conducted to analyze the potential deleterious effects of the mutation. RESULTS: The proband presented with a hypomaturation AI phenotype, characterized by fragile and discolored enamel surface. The AI enamel showed prismatic structure, which was sporadically obscured by areas of amorphous material and porous structure. EDX analysis showed the proband's enamel demonstrated a significant decrease in calcium and phosphorus content and a significant increase in oxygen compared with normal enamel. A novel homozygous mutation of G protein-coupled receptor 68 (GPR68) (c .149 T > A, p.Ile50Asn) was identified in the proband. Bioinformatics analysis indicated that the mutation site displayed a high level of evolutionary conservation among species, and the mutation might impact the stability and conformation of the protein. CONCLUSION: The novel homozygous GPR68 mutation resulted in hypomaturation AI. We first described the effect of GPR68 mutation on enamel structure. Our results provide new genetic evidence that mutations involved in GPR68 contribute to hypomaturation AI.