Project description:We identified an autosomal recessive condition in 11 individuals in the Old Order Amish of northeastern Ohio. The syndrome was characterized by distinctive craniofacial dysmorphism, skeletal anomalies, and mental retardation. The typical craniofacial dysmorphism included brachycephaly, highly arched bushy eyebrows, synophrys, long eyelashes, low-set ears, microdontism of primary teeth, and generalized gingival hyperplasia, whereas Sprengel deformity of scapula, fusion of spine, rib abnormities, pectus excavatum, and pes planus represented skeletal anomalies. The genome-wide homozygosity mapping using six affected individuals localized the disease gene to a 3.3-Mb region on chromosome 1q23.3-q24.1. Candidate gene sequencing identified a homozygous frameshift mutation, c.139_140delAG, in the transmembrane and coiled-coil domains 1 (TMCO1) gene, as the pathogenic change in all affected members of the extended pedigree. This mutation is predicted to result in a severely truncated protein (p.Ser47Ter) of only one-fourth the original length. The TMCO1 gene product is a member of DUF841 superfamily of several eukaryotic proteins with unknown function. The gene has highly conserved amino acid sequence and is universally expressed in all human tissues examined. The high degree of conservation and the ubiquitous expression pattern in human adult and fetal tissues suggest a critical role for TMCO1. This report shows a TMCO1 sequence variant being associated with a genetic disorder in human. We propose "TMCO1 defect syndrome" as the name of this condition.
Project description:IntroductionDentinogenesis imperfecta type 1 (OIDI) is considered a relatively rare genetic disorder (1:5000 to 1:45,000) associated with osteogenesis imperfecta. OIDI impacts the formation of collagen fibrils in dentin, leading to morphological and structural changes that affect the strength and appearance of teeth. However, there is still a lack of understanding regarding the nanoscale characterization of the disease, in terms of collagen ultrastructure and mechanical properties. Therefore, this research presents a qualitative and quantitative report into the phenotype and characterization of OIDI in dentin, by using a combination of imaging, nanomechanical approaches.MethodsFor this study, 8 primary molars from OIDI patients and 8 primary control molars were collected, embedded in acrylic resin and cut into longitudinal sections. Sections were then demineralized in 37% phosphoric acid using a protocol developed in-house. Initial experiments demonstrated the effectiveness of the demineralization protocol, as the ATR-FTIR spectral fingerprints showed an increase in the amide bands together with a decrease in phosphate content. Structural and mechanical analyses were performed directly on both the mineralized and demineralized samples using a combination of scanning electron microscopy, atomic force microscopy, and Wallace indentation.ResultsMesoscale imaging showed alterations in dentinal tubule morphology in OIDI patients, with a reduced number of tubules and a decreased tubule diameter compared to healthy controls. Nanoscale collagen ultrastructure presented a similar D-banding periodicity between OIDI and controls. Reduced collagen fibrils diameter was also recorded for the OIDI group. The hardness of the (mineralized) control dentin was found to be significantly higher (p<0.05) than that of the OIDI (mineralized) dentine. Both the exposed peri- and intratubular dentinal collagen presented bimodal elastic behaviors (Young's moduli). The control samples presented a stiffening of the intratubular collagen when compared to the peritubular collagen. In case of the OIDI, this stiffening in the collagen between peri- and intratubular dentinal collagen was not observed and the exposed collagen presented overall a lower elasticity than the control samples.ConclusionThis study presents a systematic approach to the characterization of collagen structure and properties in OIDI as diagnosed in dentin. Structural markers for OIDI at the mesoscale and nanoscale were found and correlated with an observed lack of increased elastic moduli of the collagen fibrils in the intratubular OIDI dentin. These findings offer an explanation of how structural changes in the dentin could be responsible for the failure of some adhesive restorative materials as observed in patients affected by OIDI.
Project description:Dentin sialophosphoprotein (DSPP) is an extracellular matrix protein highly expressed by odontoblasts in teeth. DSPP mutations in humans may cause dentinogenesis imperfecta (DGI), an autosomal dominant dentin disorder. We recently generated a mouse model (named "DsppP19L/+ mice") that expressed a mutant DSPP in which the proline residue at position 19 was replaced by a leucine residue. We found that the DsppP19L/+ and DsppP19L/P19L mice at a younger age displayed a tooth phenotype resembling human DGI type III characterized by enlarged dental pulp chambers, while the teeth of older DsppP19L/+ and DsppP19L/P19L mice had smaller dental pulp chambers mimicking DGI type II. The teeth of DsppP19L/+ and DsppP19L/P19L mice had a narrower pulp chamber roof predentin layer, thinner pulp chamber roof dentin, and thicker pulp chamber floor dentin. In addition, these mice also had increased enamel attrition, accompanied by excessive deposition of peritubular dentin. Immunohistochemistry, in situ hybridization, and real-time polymerase chain reaction analyses showed that the odontoblasts in both DsppP19L/+ and DsppP19L/P19L mice had reduced DSPP expression, compared to the wild-type mice. We also observed that the levels of DSPP expression were much higher in the roof-forming odontoblasts than in the floor-forming odontoblasts in the wild-type mice and mutant mice. Moreover, immunohistochemistry showed that while the immunostaining signals of dentin sialoprotein (N-terminal fragment of DSPP) were decreased in the dentin matrix, they were remarkably increased in the odontoblasts of the DsppP19L/+ and DsppP19L/P19L mice. Consistently, our in vitro studies showed that the secretion of the mutant DSPP was impaired and accumulated within endoplasmic reticulum. These findings suggest that the dental phenotypes of the mutant mice were associated with the intracellular retention of the mutant DSPP in the odontoblasts of the DSPP-mutant mice.
Project description:Osteogenesis imperfecta (OI) is a rare heritable bone disorder characterized by low bone mineral density (BMD), recurrent bone fractures, and progressive bone deformities. P4HB encodes protein disulfide isomerase (PDI) and is identified as a novel candidate gene of OI. The purposes of the present study are to detect pathogenic mutation, to evaluate the phenotypes of a Chinese family with mild OI, and to investigate the effects of bisphosphonates on bone of the proband. We detected the pathogenic mutation by next generation sequencing and Sanger sequencing. Laboratory and radiological investigations were conducted to evaluate the phenotypes. The proband was a 12-year-old girl with low BMD, history of recurrent non-traumatic fractures, slight scoliosis, with bluish grey sclera and ligamentous laxity. Her father suffered from one fragility fracture and slight wedge changes of vertebras, with bluish grey sclera. We identified a novel heterozygous missense mutation (c.692A>C, p.His231Pro) in P4HB in the proband and her father. This mutation was predicted to affect the combination of PDI with type I procollagen and lead to the disorder of its triple helix formation. Bisphosphonates were effective in reducing bone resorption and increasing BMD of the proband with well tolerance. In conclusion, we identified a novel mutation in P4HB in a Chinese family with mild OI, which expanded the genotypic and phenotypic spectrum of OI. Bisphosphonates were effective to this extremely rare OI induced by P4HB mutation.
Project description:BackgroundSeveral studies have shown that the clinical phenotypes of dentinogenesis imperfecta type II (DGI-II) may be caused by mutations in dentin sialophosphoprotein (DSPP). However, no previous studies have documented the clinical phenotype and genetic basis of DGI-II in a Mongolian family from China.MethodsWe identified a large five-generation Mongolian family from China with DGI-II, comprising 64 living family members of whom 22 were affected. Linkage analysis of five polymorphic markers flanking DSPP gene was used to genotype the families and to construct the haplotypes of these families. All five DSPP exons including the intron-exon boundaries were PCR-amplified and sequenced in 48 members of this large family.ResultsAll affected individuals showed discoloration and severe attrition of their teeth, with obliterated pulp chambers and without progressive high frequency hearing loss or skeletal abnormalities. No recombination was found at five polymorphic markers flanking DSPP in the family. Direct DNA sequencing identified a novel A-->G transition mutation adjacent to the donor splicing site within intron 3 in all affected individuals but not in the unaffected family members and 50 unrelated Mongolian individuals.ConclusionThis study identified a novel mutation (IVS3+3A-->G) in DSPP, which caused DGI-II in a large Mongolian family. This expands the spectrum of mutations leading to DGI-II.
Project description:BackgroundOsteogenesis imperfecta (OI) is a phenotypically and genetically heterogeneous bone disease characterized by bone fragility and recurrent fractures. X-linked inherited OI with mutation in PLS3 is so rare that its genotype-phenotype characteristics are not available.MethodsWe designed a novel targeted next-generation sequencing (NGS) panel with the candidate genes of OI to detect pathogenic mutations and confirmed them by Sanger sequencing. The phenotypes of the patients were also investigated.ResultsThe proband, a 12-year-old boy from a nonconsanguineous family, experienced multiple fractures of long bones and vertebrae and had low bone mineral density (BMD Z-score of -3.2 to -2.0). His younger brother also had extremity fractures. A novel frameshift mutation (c.1106_1107insGAAA; p.Phe369Leufs*5) in exon 10 of PLS3 was identified in the two patients, which was inherited from their mother who had normal BMD. Blue sclerae were the only extraskeletal symptom in all affected individuals. Zoledronic acid was beneficial for increasing BMD and reshaping the compressed vertebral bodies of the proband.ConclusionWe first identify a novel mutation in PLS3 that led to rare X-linked OI and provide practical information for the diagnosis and treatment of this disease.
Project description:BackgroundOsteogenesis imperfecta (OI) is a clinically heterogeneous disease characterized by extreme skeletal fragility. It is caused by mutations in genes frequently affecting collagen biosynthesis. Mutations in CREB3L1 encoding the ER stress transducer OASIS are very rare and are only reported in pediatric patients. We report a large family with a novel CREB3L1 mutation, with severe adult clinical presentation.MethodsClinical examination was performed on the family members. Next generation sequencing was performed for the causative genes for OI. The mutation was confirmed in other family members with Sanger sequencing.ResultsA novel homozygous mutation in CREB3L1 was identified in the three affected patients. The parents and siblings who carry the mutation in heterozygous state were clinically unaffected. The three affected siblings, who were reported to have been born healthy, presented very severe progressive skeletal malformations and joint contractures but absence of common OI characteristics including blue sclerae, deafness, and dentinogenesis imperfecta. Resorption of a part of the humerus presumably associated with fracture nonunion and pseudarthrosis.ConclusionWe report a novel homozygous CREB3L1 mutation in a large Indonesian family; the homozygous affected members have survived to adulthood and they present a more severe phenotype than previously reported, expanding the clinical spectrum of OI for this gene.
Project description:Objectives:Osteogenesis imperfecta type III (OMIM 259420) is a severe autosomal recessive disorder. Affected individuals have multiple fractures, develop limb deformities with spinal malalignment and stunted stature. Materials and methods:The frequency of Osteogenesis imperfecta type III (OI III) is relatively high in the indigenous Black African population of South Africa. A review of the literature revealed a paucity of information regarding the craniofacial manifestations of the disorder in this ethnic group. The findings in 64 affected persons are documented. Results:These abnormalities are related to the abnormal bone matrix which results in a deformed skull and dental malocclusion. The physiological process of swallowing may be an aetiological factor in the progressive development of a flattened palate. Mild changes in the shape of the head of the mandibular condyle and a lack of cortical bone on the joint surfaces were observed on cone beam computed tomography (CBCT) images. Affected persons had marked variations in the paranasal sinuses, including sinus hypoplasia and partial opacification. Cranial base anomalies were diagnosed from cephalometric radiographs and lateral skull radiographs. Platybasia and a 'J' shaped sella turcica were observed. Conclusion:The craniofacial abnormalities emphasize the importance of a raised level of awareness in terms of dental management and the challenges.
Project description:Osteogenesis imperfecta (OI) is a heterogenous group of genetic disorders of bone fragility. OI type V is an autosomal-dominant disease characterized by calcification of the forearm interosseous membrane, radial head dislocation, a subphyseal metaphyseal radiodense line, and hyperplastic callus formation; the causative mutation involved in this disease has not been discovered yet. Using linkage analysis in a four-generation family and whole-exome sequencing, we identified a heterozygous mutation of c.-14C>T in the 5'-untranslated region of a gene encoding interferon-induced transmembrane protein 5 (IFITM5). It completely cosegregated with the disease in three families and occurred de novo in five simplex individuals. Transfection of wild-type and mutant IFITM5 constructs revealed that the mutation added five amino acids (Met-Ala-Leu-Glu-Pro) to the N terminus of IFITM5. Given that IFITM5 expression and protein localization is restricted to the skeletal tissue and IFITM5 involvement in bone formation, we conclude that this recurrent mutation would have a specific effect on IFITM5 function and thus cause OI type V.
Project description:Mutations in the DSPP gene have been identified in nonsyndromic hereditary dentin defects, but the genotype-phenotype correlations are not fully understood. Recently, it has been demonstrated that the mutations of DSPP affecting the IPV leader sequence result in mutant DSPP retention in rough endoplasmic reticulum (ER). In this study, we identified a Korean family with dentinogenesis imperfecta type III. To identify the disease causing mutation in this family, we performed mutational analysis based on candidate gene sequencing. Exons and exon-intron boundaries of DSPP gene were sequenced, and the effects of the identified mutation on the pre-mRNA splicing and protein secretion were investigated. Candidate gene sequencing revealed a mutation (c.50C > T, p.P17L) in exon 2 of the DSPP gene. The splicing assay showed that the mutation did not influence pre-mRNA splicing. However, the mutation interfered with protein secretion and resulted in the mutant protein remaining largely in the ER. These results suggest that the mutation affects ER-to-Golgi apparatus export and results in the reduction of secreted DSPP and ER overload. This may induce cell stress and damage processing and/or transport of dentin matrix proteins or other critical proteins.