Pathogenesis of Enamel-Renal Syndrome Associated Gingival Fibromatosis: A Proteomic Approach.

The enamel renal syndrome (ERS) is a rare disorder featured by amelogenesis imperfecta, gingival fibromatosis and nephrocalcinosis. ERS is caused by bi-allelic mutations in the secretory pathway pseudokinase FAM20A. How mutations in FAM20A may modify the gingival connective tissue homeostasis and cause fibromatosis is currently unknown. We here analyzed conditioned media of gingival fibroblasts (GFs) obtained from four unrelated ERS patients carrying distinct mutations and control subjects. Secretomic analysis identified 109 dysregulated proteins whose abundance had increased (69 proteins) or decreased (40 proteins) at least 1.5-fold compared to control GFs. Proteins over-represented were mainly involved in extracellular matrix organization, collagen fibril assembly, and biomineralization whereas those under-represented were extracellular matrix-associated proteins. More specifically, transforming growth factor-beta 2, a member of the TGFß family involved in both mineralization and fibrosis was strongly increased in samples from GFs of ERS patients and so were various known targets of the TGFß signaling pathway including Collagens, Matrix metallopeptidase 2 and Fibronectin. For the over-expressed proteins quantitative RT-PCR analysis showed increased transcript levels, suggesting increased synthesis and this was further confirmed at the tissue level. Additional immunohistochemical and western blot analyses showed activation and nuclear localization of the classical TGFß effector phospho-Smad3 in both ERS gingival tissue and ERS GFs. Exposure of the mutant cells to TGFB1 further upregulated the expression of TGFß targets suggesting that this pathway could be a central player in the pathogenesis of the ERS gingival fibromatosis. In conclusion our data strongly suggest that TGFß -induced modifications of the extracellular matrix contribute to the pathogenesis of ERS. To our knowledge this is the first proteomic-based analysis of FAM20A-associated modifications.

Long-term dental intervention and laboratory examination in a patient with Vitamin D-dependent rickets type I: A case report.

RATIONALE: Vitamin D-dependent rickets type I (VDDR-I) is a rare form of rickets, which is an autosomal recessive disease caused by 1α-hydroxylase enzyme deficiency. However, long-term dental management and microscopic morphology of teeth remain largely unclear. PATIENT CONCERNS: We report the case of a 10-year-old Chinese boy complaining of yellowish-brown teeth with extensive caries. DIAGNOSES: Clinical and laboratory examinations were performed, and VDDR-I was confirmed. Scanning electron microscopy confirmed amelogenesis imperfecta. INTERVENTIONS: The patient had been taking drugs intervention for VDDR-I from the age of 3 years. The decayed teeth were treated, and metal-preformed crowns were placed to prevent further impairment. Sequence tooth extraction and remineralization therapy were also performed. OUTCOMES: After 3 years of follow-up, the patient exhibited normal tooth replacement and an acceptable oral hygiene status. However, the new erupted teeth had amelogenesis imperfecta. LESSONS: This case is the first to confirm amelogenesis imperfecta in a patient with VDDR-I that was not prevented by drug intervention. Importantly, it provides evidence that long-term dental intervention in patients with VDDR-I can result in an acceptable oral hygiene status. Therefore, early and long-term dental intervention is necessary in VDDR-I patients.

Association of molar incisor hypomineralization with premature birth or low birth weight: systematic review and meta-analysis.

Objective: Molar incisor hypomineralization (MIH) is a kind of enamel hypomineralization. MIH has a serious negative impact on patient's oral health. Whether neonates with premature birth or low birth weight are susceptible to MIH has not been rigorously evaluated. The purpose of this systematic review and meta-analysis was to determine whether premature birth and low birth weight increased the possibility of developing MIH in neonates.Method: We searched relevant studies published from 2001 to June 2018 on PubMed and Embase. The methodological quality of the studies included in the meta-analysis was assessed using the Agency for Health Care Research and Quality (AHRQ) inventory tool.Results: Premature birth promoted the prevalence of MIH (OR = 1.57, 95%CI: 1.07-2.31). Low-birth-weight neonates were approximately three times likely to suffer from MIH (OR = 3.25, 95%CI: 2.28-4.62).Conclusions: Our finding suggests that premature birth and low birth weight increase the prevalence of MIH.

Fam83h mutation inhibits the mineralization in ameloblasts by activating Wnt/ß-catenin signaling pathway.

FAM83H was identified as the major causative gene for autosomal dominant hypocalcified amelogenesis imperfect (ADHCAI). The pathogenic mechanism of FAM83H in ADHCAI remains elusive. The present study aims to investigate the effect of Fam83h mutation on the mineralization of mouse ameloblast cell line LS8 and to explore the possible pathogenesis of ADHCAI. Lentivirus package was performed for the plasmids with mouse Fam83h mutant cDNA (c.1186C > T, M3) and empty vector (Control) and transfected into LS8, which were divided into M3-FLAG and Control groups. Immunoprecipitation, western-blot and immunofluorescence were performed to detect the expression and subcellular localization of Fam83 h, CK1α and ß-catenin. ALP activity, ALP staining, expression of the mineralization factors were detected in two groups during mineralization induction. Expression of the mineralization factors was also detected in M3-FLAG and LS8 exposing to pyrvinium pamoate. Compared with the Control, the Fam83h mutation altered the expression and localization of Fam83 h, CK1α and ß-catenin in LS8, inhibited the mineralization and down-regulated the expression of mineralization factors in M3-FLAG. Pyrvinium pamoate, an inhibitor of the Wnt/ß-catenin signaling pathway, up-regulated expression of mineralization factors in LS8 and rescued the inhibited mineralization in M3-FLAG. The results indicated that the Fam83h mutation could inhibit the mineralization in ameloblasts by activating Wnt/ß-catenin signaling pathway.

MiR-153 Regulates Amelogenesis by Targeting Endocytotic and Endosomal/lysosomal Pathways-Novel Insight into the Origins of Enamel Pathologies.

Amelogenesis imperfecta (AI) is group of inherited disorders resulting in enamel pathologies. The involvement of epigenetic regulation in the pathogenesis of AI is yet to be clarified due to a lack of knowledge about amelogenesis. Our previous genome-wide microRNA and mRNA transcriptome analyses suggest a key role for miR-153 in endosome/lysosome-related pathways during amelogenesis. Here we show that miR-153 is significantly downregulated in maturation ameloblasts compared with secretory ameloblasts. Within ameloblast-like cells, upregulation of miR-153 results in the downregulation of its predicted targets including Cltc, Lamp1, Clcn4 and Slc4a4, and a number of miRNAs implicated in endocytotic pathways. Luciferase reporter assays confirmed the predicted interactions between miR-153 and the 3'-UTRs of Cltc, Lamp1 (in a prior study), Clcn4 and Slc4a4. In an enamel protein intake assay, enamel cells transfected with miR-153 show a decreased ability to endocytose enamel proteins. Finally, microinjection of miR-153 in the region of mouse first mandibular molar at postnatal day 8 (PN8) induced AI-like pathologies when the enamel development reached maturity (PN12). In conclusion, miR-153 regulates maturation-stage amelogenesis by targeting key genes involved in the endocytotic and endosomal/lysosomal pathways, and disruption of miR-153 expression is a potential candidate etiologic factor contributing to the occurrence of AI.

Novel ITGB6 mutation in autosomal recessive amelogenesis imperfecta.

OBJECTIVE: Hereditary defects in tooth enamel formation, amelogenesis imperfecta (AI), can be non-syndromic or syndromic phenotype. Integrins are signaling proteins that mediate cell-cell and cell-extracellular matrix communication, and their involvement in tooth development is well known. The purposes of this study were to identify genetic cause of an AI family and molecular pathogenesis underlying defective enamel formation. MATERIALS AND METHODS: We recruited a Turkish family with isolated AI and performed mutational analyses to clarify the underlying molecular genetic etiology. RESULTS: Autozygosity mapping and exome sequencing identified a novel homozygous ITGB6 transversion mutation in exon 4 (c.517G>C, p.Gly173Arg). The glycine at this position in the middle of the ßI-domain is conserved among a wide range of vertebrate orthologs and human paralogs. Clinically, the enamel was generally thin and pitted with pigmentation. Thicker enamel was noted at the cervical area of the molars. CONCLUSIONS: In this study, we identified a novel homozygous ITGB6 mutation causing isolated AI, and this advances the understanding of normal and pathologic enamel development.

Whole-exome sequencing, without prior linkage, identifies a mutation in LAMB3 as a cause of dominant hypoplastic amelogenesis imperfecta.

The conventional approach to identifying the defective gene in a family with an inherited disease is to find the disease locus through family studies. However, the rapid development and decreasing cost of next generation sequencing facilitates a more direct approach. Here, we report the identification of a frameshift mutation in LAMB3 as a cause of dominant hypoplastic amelogenesis imperfecta (AI). Whole-exome sequencing of three affected family members and subsequent filtering of shared variants, without prior genetic linkage, sufficed to identify the pathogenic variant. Simultaneous analysis of multiple family members confirms segregation, enhancing the power to filter the genetic variation found and leading to rapid identification of the pathogenic variant. LAMB3 encodes a subunit of Laminin-5, one of a family of basement membrane proteins with essential functions in cell growth, movement and adhesion. Homozygous LAMB3 mutations cause junctional epidermolysis bullosa (JEB) and enamel defects are seen in JEB cases. However, to our knowledge, this is the first report of dominant AI due to a LAMB3 mutation in the absence of JEB.

Phenotype-genotype correlations in mouse models of amelogenesis imperfecta caused by Amelx and Enam mutations.

Mutations in human and in mouse orthologous genes Amelx and Enam result in a diverse range of enamel defects. In this study we aimed to investigate the phenotype-genotype correlation between the mutants and the wild-type controls in mouse models of amelogenesis imperfecta using novel measurement approaches. Ten hemi-mandibles and incisors were dissected from each group of Amelx(WT), Amelx(X/Y64H), Amelx(Y/Y64H), Amelx(Y64H/Y64H), and Enam(WT), Enam(Rgsc395) heterozygous and Enam(Rgsc395) homozygous mice. Their macro-morphology, colour and micro-topography were assessed using bespoke 2D and 3D image analysis systems and customized colour and whiteness algorithms. The novel methods identified significant differences (p ≤ 0.05) between the Amelx groups for mandible and incisor size and enamel colour and between the Enam groups for incisor size and enamel colour. The Amelx(WT) mice had the largest mandibles and incisors, followed in descending order of size by the Amelx(X/Y64H), Amelx(Y/Y64H) and Amelx(Y64H/Y64H) mice. Within the Enam groups the Enam(WT) incisors were largest and the Enam(Rgsc395) heterozygous mice were smallest. The effect on tooth morphology was also reflected by the severity of the enamel defects in the colour and whiteness assessment. Amelogenin affected mandible morphology and incisor enamel formation, while enamelin only affected incisors, supporting the multifunctional role of amelogenin. The enamelin mutation was associated with earlier forming enamel defects. The study supported the critical involvement of amelogenin and enamelin in enamel mineralization.

Amelogênese imperfeita em paciente nefropata: relato de uma reabilitação oral conservadora / Amelogenesis imperfecta in a patient with kidney disease: a report of a conservative oral rehabilitation

Amelogênese imperfeita é uma doença hereditária que afeta a formação do esmalte, tanto na dentição decídua como na permanente. Ela também pode ser associada com alterações morfológicas e bioquímicas em outra parte do corpo. O diagnóstico da amelogênese imperfeita envolve a exclusão de fatores ambientais e o estabelecimento de um provável padrão de herança genética, reconhecimento do fenótipo e correlação com a formação do esmalte. Numerosas modalidades de tratamento têm sido descritas para a reabilitação de pacientes com amelogênese imperfeita. No entanto, tem-se buscado reabilitar de maneira conservadora e com um enfoque na prevenção dos efeitos dessa patologia. Este trabalho tem por objetivo relatar um caso clínico de reabilitação estética e funcional por meio do uso de resinas compostas, em um paciente com amelogênese imperfeita e que apresentava hiperplasia gengival devido ao uso de imunossupressores. Pôde-se concluir que é possível melhorar a estética e restabelecer a função destes pacientes através de procedimentos e técnicas simples e de baixo custo.

Amelogenesis imperfecta is a hereditary disease that disrupts enamel formation, affecting both the deciduous and permanent teeth. It can also be associated with morphological and biochemical changes elsewhere in the body. The diagnosis of amelogenesis imperfecta involves the exclusion of environmental factors and the establishment of a likely pattern of inheritance, recognition of the phenotype and correlation with enamel formation. Numerous treatment modalities have been described for the rehabilitation of patients with amelogenesis imperfecta. However, rehabilitation is preferably conservative, focusing on preventing the effects of this pathology. The aim of this paper is to report a case of aesthetic and functional rehabilitation of a patient with amelogenesis imperfecta and immunosuppressant-induced gingival hyperplasia using composite resins. In conclusion, it is possible to improve the aesthetics and restore the function of these patients with simple and inexpensive procedures and techniques.

Amelogenésis imperfecta: criterios de clasificación y aspectos genéticos / Amelogenesis imperfecta: classification criteria and genetic aspects

La amelogénesis imperfecta es una alteración del esmalte que se puede presentar tanto en dentición decidua como permanente con diversas consecuencias negativas para los pacientes. La presente revisión describe los criterios diagnósticos, clasificación, etiología, casos esporádicos en los que se ha relacionado con otras alteraciones clínicas o enfermedades sistémicas, y su tratamiento; enfatizando la etiología y clasificación de esta alteración puesto que son las áreas en las que se han realizado muchos avances en los últimos años, especialmente relacionado con los aspectos genéticos.

Amelogenesis imperfecta is an enamel alteration that occurs in both deciduous and permanent dentition with diverse negative consequences for the patients. The present review describes the diagnostic criteria, classification, etiology, sporadic cases in which it is related to other clinical alterations or systemic diseases, and its treatment; emphasizing in the etiology and classification of this alteration since they are the areas in which many advances have been performed in the last years, specially related to the genetic aspects.

Alterações na amelogênese e suas implicações clínicas: relatos de casos / Alterations in amelogenesis and its clinical implications: cases reports

Alterações durante a amelogênese podem acarretar distúrbios no desenvolvimento do esmalte dentário. Em consequência a estas alterações o esmalte dentário pode apresentar modificação de cor e/ou que podem ocorrer isoladamente ou de forma simultânea, envolvendo, apenas um ou mais dentes. A intensidade, a extensão e a quantidade de elementos dentários envolvidos pelas alterações no esmalte podem estar relacionadas ao estágio de desenvolvimento do órgão do esmalte dentário. As causas podem ser de origem local, sistêmica, genética ou idiopática. Após a constatação de uma alteração da amelogênese evidenciada por meio da modificação de cor e/ou estrutura do esmalte dentário pelo dentista é importante que haja um diagnóstico preciso para se proceder à terapêutica adequada, seja ela preventiva, interceptativa ou o acompanhamento clínico do caso. Os casos clínicos relatados neste estudo ilustram algumas das alterações da amelogênese no esmalte dentário humano e suas prováveis causas com base na história clínica apresentada pelo paciente e na literatura consultada.

Alterations in amelogenesis can promote disturbances on the development of dental enamel. These alterations during amelogenesis will result in different color and/or structure of dental enamel that may occur isolated or simultaneously. These alterations may involve one tooth or more, yet the causal factors may be local, systemic, genetic or idiopathic. The intensity, extension and the number of teeth presenting alterations in the dental enamel are related to the developmental stage of the enamel dental organ. After the dentist has evidenced a color and/or structural alteration due to developmental defect in amelogenesis it is very important to make a precise diagnosis so that he can proceed with an adequate therapeutic either if it is only a matter of recall appointments, preventive or interceptive approaches. The clinical cases in this study illustrates some of human dental enamel’s alterations during amelogenesis and their probable causes based on the patient’s clinical history and in the dental literature.

[Phenotype analysis and the molecular mechanism of enamel hypoplasia].

Enamel hypoplasia is a surface defect of the tooth crown caused by a disturbance of enamel matrix secretion. Enamel hypoplasia may be inherited, or result from illness, malnutrition, trauma, or high concentrations of fluorides or strontium in the drinking water or food. Different types of enamel hypoplasia have been distinguished, such as pit-type, plane-type, and linear enamel hypoplasia. Hypoplasia has been related to the intensity and duration of stress events, the number of affected ameloblasts, and their position along the forming tooth crown. Amelogenesis imperfecta (AI) is a heterogeneous group of inherited defects in dental enamel formation, most teeth are affected in both the primary and permanent dentition. The malformed enamel can be unusually thin, soft, rough and stained. The strict definition of AI includes only those cases where enamel defects occur in the absence of other symptoms. Currently, there are seven candidate genes for AI: amelogenin, enamelin, ameloblastin, tuftelin, distal-less homeobox 3, enamelysin, and kallikrein 4. Since the enamel is formed according to a strict chronological sequence, and once formed, undergoes no repair or regeneration. Then the analysis the phenotype of enamel hypoplasia can provide insights of the severity of inherited or environmental stress and the molecular mechanism during the period of enamel formation.

Amelogenesis imperfecta: revisión / Amelogenesis imperfecta: a review

Con la denominación de Amelogénesis Imperfecta(AI) se define un grupo de enfermedades hereditarias heterogéneas clínica y genéticamente que se caracterizan por alteraciones del esmalte. También pueden observarse otras alteraciones orales y extraorales. La maloclusión más frecuente en estos pacientes es la mordida abierta. Algunos casos forman parte de un síndrome. Hasta el momento se han identificado mutaciones en cinco genes, AMELX, ENAM, KLK4, MMP20 yDLX3, que participan en la formación del esmalte normal, pero quedan otros por identificar. Los autores actualizan los conocimientos sobre la etiopatogenia, clasificación, manifestaciones clínicas, diagnóstico y tratamiento interdisciplinar de la AI (AU)

Amelogenesis imperfecta (AI) is a collective designation for a clinically and genetically diverse group of disorders displaying enamel malformations. Other oral and extraoral aberrations have been reported, and open bite is the most common malocclusion. Some cases present as a part of a syndrome. Mutations in five genes involved in normal enamel formation(AMELX, ENAM, MMP20, KLK4 and DLX3) have been identified as cause of amelogenesis imperfecta, but some others remain to be identified. This paper reviews current knowledge about etiopathogenesis, classification, clinical manifestations, diagnosis and interdisciplinary treatment of AI (AU)

Alteraciones estructurales del esmalte: hipoplasias y opacidades del primer molar permanente / Enamel structural alterations: hypoplasia and hypomineralization of the first permanent molars

Las últimas décadas la odontología ha conseguido importantes avances para entender cabalmente la etiopatogenia y los mecanismos aptos para la prevención y tratamiento de una de sus enfermedades más prevalentes: la caries dental. Esto ha permitido especialmente a la odontopediatría, dirigir la atención a otras patologías que hoy se incrementan como las erosiones y las anomalías estructurales del diente. Dentro de estas últimas las hipoplasias dentales de origen genético van encontrando nuevas respuestas con el enfoque molecular merced al desarrollo de la biología molecular y la genética. El efecto nocivo que producen por vía sistémica las tetraciclinas o los fluoruros también han sido especialmente estudiados, así como el efecto deletéreo de factores locales como la infección y el trauma de las piezas primarias sobre la estructura dentaria de las piezas permanentes de reemplazo. Sin embargo la clínica muestra con una frecuencia cada vez mayor opacidades e hipoplasias de los primeros molares permanentes, con una severidad que varía desde aquellos que tienen los cuatro primeros molares afectados, donde se podría suponer que al desarrollarse simultáneamente obedecen a una causa sistémica, hasta otros que muestran una distribución azarosa afectando solo a uno, dos o tres molares. En esta materia queda aun mucho por resolver ya que plantea un esencial desconocimiento etiológico que impide el desarrollo de medidas preventivas y eficaces procedimientos terapéuticos.

Osteogénesis y dentinogénesis imperfecta / Osteogenesis and dentinogenesis imperfecta

Se trata de una afección por deficiencia de la formación de colágeno. Como consecuencia presenta fragilidad ósea y puede estar acompañada por la presencia de dentinogénesis imperfecta de la cual se dan los lineamientos básicos para su tratamiento odontológico (AU)

Hipoplasia dentaria: su etiología y tratamiento / Dental hypoplasia: its etiology and treatment

Su presentación clínica es variada, esto nos manifiesta la gran cantidad de factores etiológicos que pueden desencadenar dicha alteración. La hipoplasia dentaria es un defecto adquirido del esmalte y ocasionalmente de dentina, resultando en una de las alteraciones más frecuentes encontradas en los elementos dentarios temporarios y permanentes. La terapéutica empleada para este tipo de defecto se basa en un tratamiento conservador, que permita restaurar la estética en piezas dentarias involucradas (AU)

An atomic force microscopic study of the ultrastructure of dental enamel afflicted with amelogenesis imperfecta.

The ultrastructure of human tooth enamel from a patient diagnosed to have amelogenesis imperfecta (AI) was investigated using atomic force microscopy (AFM) and compared with normal human tooth enamel. AI is a hereditary defect of dental enamel in which the enamel is deficient in either quality or quantity. Tissue-specific proteins, especially amelogenins, have been postulated to play a central role in amelogenesis. The secondary structure of amelogenin has been assigned an important role in directing the architecture of hydroxyapatite (HA) enamel crystallites and an alteration of the secondary structure of amelogenin is expected to result in an altered architecture of the mineral phase in human enamel. Previous studies have shown that the human amelogenin gene encodes for a mutant protein in which a conserved Pro is mutated to a Thr residue (Pro-->Thr); such a mutation should be expected to cause a disoriented pattern of the mineral phase in enamel. AFM results presented for the AI tooth enamel clearly demonstrate that the apatite crystal morphology in AI tooth enamel is perturbed in the diseased state; this might result from a defective synthesis of the extracellular matrix proteins, e.g. amelogenin, by the ameloblasts.

Enamel biomineralization defects result from alterations to amelogenin self-assembly.

Enamel formation is a powerful model for the study of biomineralization. A key feature common to all biomineralizing systems is their dependency upon the biosynthesis of an extracellular organic matrix that is competent to direct the formation of the subsequent mineral phase. The major organic component of forming mouse enamel is the 180-amino-acid amelogenin protein (M180), whose ability to undergo self-assembly is believed to contribute to biomineralization of vertebrate enamel. Two recently defined domains (A and B) within amelogenin appear essential for this self-assembly. The significance of these two domains has been demonstrated previously by the yeast two-hybrid system, atomic force microscopy, and dynamic light scattering. Transgenic animals were used to test the hypothesis that the self-assembly domains identified with in vitro model systems also operate in vivo. Transgenic animals bearing either a domain-A-deleted or domain-B-deleted amelogenin transgene expressed the altered amelogenin exclusively in ameloblasts. This altered amelogenin participates in the formation an organic enamel extracellular matrix and, in turn, this matrix is defective in its ability to direct enamel mineralization. At the nanoscale level, the forming matrix adjacent to the secretory face of the ameloblast shows alteration in the size of the amelogenin nanospheres for either transgenic animal line. At the mesoscale level of enamel structural hierarchy, 6-week-old enamel exhibits defects in enamel rod organization due to perturbed organization of the precursor organic matrix. These studies reflect the critical dependency of amelogenin self-assembly in forming a competent enamel organic matrix and that alterations to the matrix are reflected as defects in the structural organization of enamel.