A New SLC10A7 Homozygous Missense Mutation Responsible for a Milder Phenotype of Skeletal Dysplasia With Amelogenesis Imperfecta

International audienceAmelogenesis imperfecta (AI) is a heterogeneous group of rare inherited diseases presenting with enamel defects. More than 30 genes have been reported to be involved in syndromic or non-syndromic AI and new genes are continuously discovered (Smith et al., 2017). Whole-exome sequencing was performed in a consanguineous family. The affected daughter presented with intra-uterine and postnatal growth retardation, skeletal dysplasia, macrocephaly, blue sclerae, and hypoplastic AI. We identified a homozygous missense mutation in exon 11 of SLC10A7 (NM_001300842.2: c.908C>T; p.Pro303Leu) segregating with the disease phenotype. We found that Slc10a7 transcripts were expressed in the epithelium of the developing mouse tooth, bones undergoing ossification, and in vertebrae. Our results revealed that SLC10A7 is overexpressed in patient fibroblasts. Patient cells display altered intracellular calcium localization suggesting that SLC10A7 regulates calcium trafficking. Mutations in this gene were previously reported to cause a similar syndromic phenotype, but with more severe skeletal defects (Ashikov et al., 2018;Dubail et al., 2018). Therefore, phenotypes resulting from a mutation in SLC10A7 can vary in severity. However, AI is the key feature indicative of SLC10A7 mutations in patients with skeletal dysplasia. Identifying this important phenotype will improve clinical diagnosis and patient management

Evolutionary Analysis Predicts Sensitive Positions of MMP20 and Validates Newly- and Previously-Identified MMP20 Mutations Causing Amelogenesis Imperfecta

Amelogenesis imperfecta (AI) designates a group of genetic diseases characterized by a large range of enamel disorders causing important social and health problems. These defects can result from mutations in enamel matrix proteins or protease encoding genes. A range of mutations in the enamel cleavage enzyme matrix metalloproteinase-20 gene (MMP20) produce enamel defects of varying severity. To address how various alterations produce a range of AI phenotypes, we performed a targeted analysis to find MMP20 mutations in French patients diagnosed with non-syndromic AI. Genomic DNA was isolated from saliva and MMP20 exons and exon-intron boundaries sequenced. We identified several homozygous or heterozygous mutations, putatively involved in the AI phenotypes. To validate missense mutations and predict sensitive positions in the MMP20 sequence, we evolutionarily compared 75 sequences extracted from the public databases using the Datamonkey webserver. These sequences were representative of mammalian lineages, covering more than 150 million years of evolution. This analysis allowed us to find 324 sensitive positions (out of the 483 MMP20 residues), pinpoint functionally important domains, and build an evolutionary chart of important conserved MMP20 regions. This is an efficient tool to identify new- and previously-identified mutations. We thus identified six functional MMP20 mutations in unrelated families, finding two novel mutated sites. The genotypes and phenotypes of these six mutations are described and compared. To date, 13 MMP20 mutations causing AI have been reported, making these genotypes and associated hypomature enamel phenotypes the most frequent in AI

A New SLC10A7 Homozygous Missense Mutation Responsible for a Milder Phenotype of Skeletal Dysplasia With Amelogenesis Imperfecta

Amelogenesis imperfecta (AI) is a heterogeneous group of rare inherited diseases presenting with enamel defects. More than 30 genes have been reported to be involved in syndromic or non-syndromic AI and new genes are continuously discovered (Smith et al., 2017). Whole-exome sequencing was performed in a consanguineous family. The affected daughter presented with intra-uterine and postnatal growth retardation, skeletal dysplasia, macrocephaly, blue sclerae, and hypoplastic AI. We identified a homozygous missense mutation in exon 11 of SLC10A7 (NM_001300842.2: c.908C>T; p.Pro303Leu) segregating with the disease phenotype. We found that Slc10a7 transcripts were expressed in the epithelium of the developing mouse tooth, bones undergoing ossification, and in vertebrae. Our results revealed that SLC10A7 is overexpressed in patient fibroblasts. Patient cells display altered intracellular calcium localization suggesting that SLC10A7 regulates calcium trafficking. Mutations in this gene were previously reported to cause a similar syndromic phenotype, but with more severe skeletal defects (Ashikov et al., 2018;Dubail et al., 2018). Therefore, phenotypes resulting from a mutation in SLC10A7 can vary in severity. However, AI is the key feature indicative of SLC10A7 mutations in patients with skeletal dysplasia. Identifying this important phenotype will improve clinical diagnosis and patient management

Nephrocalcinosis (enamel renal syndrome) caused by autosomal recessive FAM20A mutations

Calcium homeostasis requires regulated cellular and interstitial systems interacting to modulate the activity and movement of this ion. Disruption of these systems in the kidney results in nephrocalcinosis and nephrolithiasis, important medical problems whose pathogenesis is incompletely understood

Identification of new genes involved in cranio-facial and oro-dental anomalies

Les Amélogenèses imparfaites constituent un groupe d’altération de l’émail dentaire d’origine génétique. Cette pathologie peut exister de manière isolée ou associée à d’autres symptômes dans le cadre de syndromes. Certains gènes impliqués sont déjà connus, cependant de nouvelles mutations et de nouveaux gènes restent à identifier. L’étude de familles informatives dans le cadre de ce projet de recherche sur le massif crânio-facial et bucco-dentaire, associée à des stratégies d’identification génétique telles que la sélection de gènes candidats, les zones d’homozygotie, le séquençage haut débit, ont permis d’obtenir des résultats probants. Des investigations futures passant par l’augmentation des cohortes, le développement des outils de séquençage de nouvelle génération, l’étude des modèles cellulaires et animaux permettront d'améliorer la compréhension de l’amélogenèse.Amelogenesis imperfecta (AI) represents hereditary conditions affecting the quality and quantity of enamel. This disease can exist in isolation or in association with other symptoms in the form of syndromes. Several genes involved in AI are already known, however mutations in these genes are not sufficient to explain all cases of AI. This suggests that mutations in yet unidentified genes underlie AI. The study of informative families included in this research project on cranio-facial and oro-dental anomalies, by using genetic strategies such as candidate gene mutational analysis,homozygosity mapping and next generation sequencing, allowed the discovery of novel genes and mutations in AI. Future investigations based on the recruitment of new families, the development of new next generation sequencing tools and the establishment of cellular and animal models will improve our understanding of amelogenesis

Identification de nouveaux gènes impliqués dans les anomalies crânio-faciales et bucco-dentaires

Amelogenesis imperfecta (AI) represents hereditary conditions affecting the quality and quantity of enamel. This disease can exist in isolation or in association with other symptoms in the form of syndromes. Several genes involved in AI are already known, however mutations in these genes are not sufficient to explain all cases of AI. This suggests that mutations in yet unidentified genes underlie AI. The study of informative families included in this research project on cranio-facial and oro-dental anomalies, by using genetic strategies such as candidate gene mutational analysis,homozygosity mapping and next generation sequencing, allowed the discovery of novel genes and mutations in AI. Future investigations based on the recruitment of new families, the development of new next generation sequencing tools and the establishment of cellular and animal models will improve our understanding of amelogenesis.Les Amélogenèses imparfaites constituent un groupe d’altération de l’émail dentaire d’origine génétique. Cette pathologie peut exister de manière isolée ou associée à d’autres symptômes dans le cadre de syndromes. Certains gènes impliqués sont déjà connus, cependant de nouvelles mutations et de nouveaux gènes restent à identifier. L’étude de familles informatives dans le cadre de ce projet de recherche sur le massif crânio-facial et bucco-dentaire, associée à des stratégies d’identification génétique telles que la sélection de gènes candidats, les zones d’homozygotie, le séquençage haut débit, ont permis d’obtenir des résultats probants. Des investigations futures passant par l’augmentation des cohortes, le développement des outils de séquençage de nouvelle génération, l’étude des modèles cellulaires et animaux permettront d'améliorer la compréhension de l’amélogenèse

Identification of new genes involved in cranio-facial and oro-dental anomalies

Les Amélogenèses imparfaites constituent un groupe d’altération de l’émail dentaire d’origine génétique. Cette pathologie peut exister de manière isolée ou associée à d’autres symptômes dans le cadre de syndromes. Certains gènes impliqués sont déjà connus, cependant de nouvelles mutations et de nouveaux gènes restent à identifier. L’étude de familles informatives dans le cadre de ce projet de recherche sur le massif crânio-facial et bucco-dentaire, associée à des stratégies d’identification génétique telles que la sélection de gènes candidats, les zones d’homozygotie, le séquençage haut débit, ont permis d’obtenir des résultats probants. Des investigations futures passant par l’augmentation des cohortes, le développement des outils de séquençage de nouvelle génération, l’étude des modèles cellulaires et animaux permettront d'améliorer la compréhension de l’amélogenèse.Amelogenesis imperfecta (AI) represents hereditary conditions affecting the quality and quantity of enamel. This disease can exist in isolation or in association with other symptoms in the form of syndromes. Several genes involved in AI are already known, however mutations in these genes are not sufficient to explain all cases of AI. This suggests that mutations in yet unidentified genes underlie AI. The study of informative families included in this research project on cranio-facial and oro-dental anomalies, by using genetic strategies such as candidate gene mutational analysis,homozygosity mapping and next generation sequencing, allowed the discovery of novel genes and mutations in AI. Future investigations based on the recruitment of new families, the development of new next generation sequencing tools and the establishment of cellular and animal models will improve our understanding of amelogenesis

Probiotiques et prévention de la carie dentaire

STRASBOURG-Medecine (674822101) / SudocSudocFranceF

Evolutionary Analysis Predicts Sensitive Positions of MMP20 and Validates Newly- and Previously-Identified MMP20 Mutations Causing Amelogenesis Imperfecta

International audienceAmelogenesis imperfecta (AI) designates a group of genetic diseases characterized by a large range of enamel disorders causing important social and health problems. These defects can result from mutations in enamel matrix proteins or protease encoding genes. A range of mutations in the enamel cleavage enzyme matrix metalloproteinase-20 gene (MMP20) produce enamel defects of varying severity. To address how various alterations produce a range of AI phenotypes, we performed a targeted analysis to find MMP20 mutations in French patients diagnosed with non-syndromic AI. Genomic DNA was isolated from saliva and MMP20 exons and exon-intron boundaries sequenced. We identified several homozygous or heterozygous mutations, putatively involved in the AI phenotypes. To validate missense mutations and predict sensitive positions in the MMP20 sequence, we evolutionarily compared 75 sequences extracted from the public databases using the Datamonkey webserver. These sequences were representative of mammalian lineages, covering more than 150 million years of evolution. This analysis allowed us to find 324 sensitive positions (out of the 483 MMP20 residues), pinpoint functionally important domains, and build an evolutionary chart of important conserved MMP20 regions. This is an efficient tool to identify new- and previously-identified mutations. We thus identified six functional MMP20 mutations in unrelated families, finding two novel mutated sites. The genotypes and phenotypes of these six mutations are described and compared. To date, 13 MMP20 mutations causing AI have been reported, making these genotypes and associated hypomature enamel phenotypes the most frequent in AI

Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta

Inherited dental malformations constitute a clinically and genetically heterogeneous group of disorders. Here, we report on four families, three of them consanguineous, with an identical phenotype, characterized by significant short stature with brachyolmia and hypoplastic amelogenesis imperfecta (AI) with almost absent enamel. This phenotype was first described in 1996 by Verloes et al. as an autosomal recessive form of brachyolmia associated with AI. Whole-exome sequencing resulted in the identification of recessive hypomorphic mutations including deletion, nonsense and splice mutations, in the LTBP3 gene, which is involved in the TGF-beta signaling pathway. We further investigated gene expression during mouse development and tooth formation. Differentiated ameloblasts synthesizing enamel matrix proteins and odontoblasts expressed the gene. Study of an available knockout mouse model showed that the mutant mice displayed very thin to absent enamel in both incisors and molars, hereby recapitulating the AI phenotype in the human disorder