Do X-linked diseases affect periodontal health?

Genetic factors play an important etiologic role in destructive periodontal diseases. There have been reports that sex chromosomes, especially disorders associated with the X chromosome, affect periodontal health. Although numerous X-linked diseases have been reported to be associated with various periodontal diseases, the association of gingivitis and/or periodontitis with these genetic syndromes should be considered tenuous and raises the question of whether the periodontal manifestation truly arises from an underlying X-linked genetic etiology. A brief overview of genetics in relation to sex chromosomes and putative X-linked genetic periodontal diseases is given.

A specific requirement for PDGF-C in palate formation and PDGFR-alpha signaling.

PDGF-C is a member of the platelet-derived growth factor (PDGF) family, which signals through PDGF receptor (PDGFR) alphaalpha and alphabeta dimers. Here we show that Pdgfc(-/-) mice die in the perinatal period owing to feeding and respiratory difficulties associated with a complete cleft of the secondary palate. This phenotype was less severe than that of Pdgfra(-/-) embryos. Pdgfc(-/-) Pdgfa(-/-) embryos developed a cleft face, subepidermal blistering, deficiency of renal cortex mesenchyme, spina bifida and skeletal and vascular defects. Complete loss of function of both ligands, therefore, phenocopied the loss of PDGFR-alpha function, suggesting that both PDGF-A and PDGF-C signal through PDGFR-alpha to regulate the development of craniofacial structures, the neural tube and mesodermal organs. Our results also show that PDGF-C signaling is a new pathway in palatogenesis, different from, and independent of, those previously implicated.

Dominant renin gene mutations associated with early-onset hyperuricemia, anemia, and chronic kidney failure.

Through linkage analysis and candidate gene sequencing, we identified three unrelated families with the autosomal-dominant inheritance of early onset anemia, hypouricosuric hyperuricemia, progressive kidney failure, and mutations resulting either in the deletion (p.Leu16del) or the amino acid exchange (p.Leu16Arg) of a single leucine residue in the signal sequence of renin. Both mutations decrease signal sequence hydrophobicity and are predicted by bioinformatic analyses to damage targeting and cotranslational translocation of preprorenin into the endoplasmic reticulum (ER). Transfection and in vitro studies confirmed that both mutations affect ER translocation and processing of nascent preprorenin, resulting either in reduced (p.Leu16del) or abolished (p.Leu16Arg) prorenin and renin biosynthesis and secretion. Expression of renin and other components of the renin-angiotensin system was decreased accordingly in kidney biopsy specimens from affected individuals. Cells stably expressing the p.Leu16del protein showed activated ER stress, unfolded protein response, and reduced growth rate. It is likely that expression of the mutant proteins has a dominant toxic effect gradually reducing the viability of renin-expressing cells. This alters the intrarenal renin-angiotensin system and the juxtaglomerular apparatus functionality and leads to nephron dropout and progressive kidney failure. Our findings provide insight into the functionality of renin-angiotensin system and stress the importance of renin analysis in families and individuals with early onset hyperuricemia, anemia, and progressive kidney failure.

Mutant DLX 3 disrupts odontoblast polarization and dentin formation.

Tricho-dento-osseous (TDO) syndrome is an autosomal dominant disorder characterized by abnormalities in the thickness and density of bones and teeth. A 4-bp deletion mutation in the Distal-Less 3 (DLX3) gene is etiologic for most cases of TDO. To investigate the in vivo role of mutant DLX3 (MT-DLX3) on dentin development, we generated transgenic (TG) mice expressing MT-DLX3 driven by a mouse 2.3 Col1A1 promoter. Dentin defects were radiographically evident in all teeth and the size of the nonmineralized pulp was enlarged in TG mice, consistent with clinical characteristics in patients with TDO. High-resolution radiography, microcomputed tomography, and SEM revealed a reduced zone of mineralized dentin with anomalies in the number and organization of dentinal tubules in MT-DLX3 TG mice. Histological and immunohistochemical studies demonstrated that the decreased dentin was accompanied by altered odontoblast cytology that included disruption of odontoblast polarization and reduced numbers of odontoblasts. TUNEL assays indicated enhanced odontoblast apoptosis. Expression levels of the apoptotic marker caspase-3 were increased in odontoblasts in TG mice as well as in odontoblastic-like MDPC-23 cells transfected with MT-DLX3 cDNA. Expression of Runx2, Wnt 10A, and TBC1D19 colocalized with DLX3 expression in odontoblasts, and MT-DLX3 significantly reduced expression of all three genes. TBC1D19 functions in cell polarity and decreased TBC1D19 expression may contribute to the observed disruption of odontoblast polarity and apoptosis. These data indicate that MT-DLX3 acts to disrupt odontoblast cytodifferentiation leading to odontoblast apoptosis, and aberrations of dentin tubule formation and dentin matrix production, resulting in decreased dentin and taurodontism. In summary, this TG model demonstrates that MT-DLX3 has differential effects on matrix production and mineralization in dentin and bone and provides a novel tool for the investigation of odontoblast biology.

Phenotype and course of Hutchinson-Gilford progeria syndrome.

BACKGROUND: Hutchinson-Gilford progeria syndrome is a rare, sporadic, autosomal dominant syndrome that involves premature aging, generally leading to death at approximately 13 years of age due to myocardial infarction or stroke. The genetic basis of most cases of this syndrome is a change from glycine GGC to glycine GGT in codon 608 of the lamin A (LMNA) gene, which activates a cryptic splice donor site to produce abnormal lamin A; this disrupts the nuclear membrane and alters transcription. METHODS: We enrolled 15 children between 1 and 17 years of age, representing nearly half of the world's known patients with Hutchinson-Gilford progeria syndrome, in a comprehensive clinical protocol between February 2005 and May 2006. RESULTS: Clinical investigations confirmed sclerotic skin, joint contractures, bone abnormalities, alopecia, and growth impairment in all 15 patients; cardiovascular and central nervous system sequelae were also documented. Previously unrecognized findings included prolonged prothrombin times, elevated platelet counts and serum phosphorus levels, measured reductions in joint range of motion, low-frequency conductive hearing loss, and functional oral deficits. Growth impairment was not related to inadequate nutrition, insulin unresponsiveness, or growth hormone deficiency. Growth hormone treatment in a few patients increased height growth by 10% and weight growth by 50%. Cardiovascular studies revealed diminishing vascular function with age, including elevated blood pressure, reduced vascular compliance, decreased ankle-brachial indexes, and adventitial thickening. CONCLUSIONS: Establishing the detailed phenotype of Hutchinson-Gilford progeria syndrome is important because advances in understanding this syndrome may offer insight into normal aging. Abnormal lamin A (progerin) appears to accumulate with aging in normal cells. (ClinicalTrials.gov number, NCT00094393.)

Emergence of corpse cremation during the Pre-Pottery Neolithic of the Southern Levant: A multidisciplinary study of a pyre-pit burial.

Renewed excavations at the Neolithic site of Beisamoun (Upper Jordan Valley, Israel) has resulted in the discovery of the earliest occurrence of an intentional cremation in the Near East directly dated to 7031-6700 cal BC (Pre-Pottery Neolithic C, also known as Final PPNB, which spans ca. 7100-6400 cal BC). The funerary treatment involved in situ cremation within a pyre-pit of a young adult individual who previously survived from a flint projectile injury. In this study we have used a multidisciplinary approach that integrates archaeothanatology, spatial analysis, bioanthropology, zooarchaeology, soil micromorphological analysis, and phytolith identification in order to reconstruct the different stages and techniques involved in this ritual: cremation pit construction, selection of fuel, possible initial position of the corpse, potential associated items and funerary containers, fire management, post-cremation gesture and structure abandonment. The origins and development of cremation practices in the region are explored as well as their significance in terms of Northern-Southern Levantine connections during the transition between the 8th and 7th millennia BC.

Exclusion of candidate genes in seven Turkish families with autosomal recessive amelogenesis imperfecta.

Amelogenesis imperfectas (AI) are a group of inherited defects of dental enamel formation that show both clinical and genetic heterogeneity. Seven Turkish families segregating autosomal recessive AI (ARAI) were evaluated for evidence of a genetic etiology of AI for the seven major candidate gene loci (AMBN, AMELX, ENAM, FAM83H, KLK4, MMP20, and TUFT1). Dental and periodontal characteristics of the affected members of these families were also described. The mean scores of DMFS and dfs indices were 9.7 and 9.6, respectively. The mean PPD was 2.2 mm and the percentage of the sites with plaque and BOP were 87.8% and 72.4%, respectively. The exons and intron/exon junctions of the candidate genes were sequenced and no gene mutations were identified in any individuals. These findings support the existence of an additional gene(s) that are etiologic for ARAI in these families.

Human and mouse enamel phenotypes resulting from mutation or altered expression of AMEL, ENAM, MMP20 and KLK4.

Amelogenesis imperfecta (AI) is caused by AMEL, ENAM, MMP20 and KLK4 gene mutations. Mice lacking expression of the AmelX, Enam and Mmp20 genes have been generated. These mouse models provide tools for understanding enamel formation and AI pathogenesis. This study describes the AI phenotypes and relates them to their mouse model counterparts. Human AI phenotypes were determined in a clinical population of AI families and published cases. Human and murine teeth were evaluated using light and electron microscopy. A total of 463 individuals from 54 families were evaluated and mutations in the AMEL, ENAM and KLK4 genes were identified. The majority of human mutations for genes coding enamel nonproteinase proteins (AMEL and ENAM) resulted in variable hypoplasia ranging from local pitting to a marked, generalized enamel thinning. Specific AMEL mutations were associated with abnormal mineralization and maturation defects. Amel and Enam null murine models displayed marked enamel hypoplasia and a complete loss of prism structure. Human mutations in genes coding for the enamel proteinases (MMP20 and KLK4) cause variable degrees of hypomineralization. The murine Mmp20 null mouse exhibits both hypoplastic and hypomineralized defects. The currently available Amel and Enam mouse models for AI exhibit enamel phenotypes (hypoplastic) that are generally similar to those seen in humans. Mmp20 null mice have a greater degree of hypoplasia than humans with MMP20 mutations. Mice lacking expression of the currently known genes associated with the human AI conditions provide useful models for understanding the pathogenesis of these conditions.

Oral rehabilitation of a patient with amelogenesis imperfecta.

Amelogenesis imperfecta is a hereditary disorder that causes defective enamel development in the primary and permanent teeth. Clinical treatment is important to address the esthetic appearance of affected teeth, reduce dentinal sensitivity, preserve tooth structure, and optimize masticatory function. The purpose of this case report was to describe the diagnosis, treatment planning, and dental rehabilitation of a patient with autosomal recessive amelogenesis imperfecta. The patient was followed for 5 years, and evaluation 3 years after restorations revealed no pathology associated with the rehabilitation. The patient's esthetic and functional expectations were satisfied.

A comprehensive analysis of normal variation and disease-causing mutations in the human DSPP gene.

Within nine dentin dysplasia (DD) (type II) and dentinogenesis imperfecta (type II and III) patient/families, seven have 1 of 4 net -1 deletions within the approximately 2-kb coding repeat domain of the DSPP gene while the remaining two patients have splice-site mutations. All frameshift mutations are predicted to change the highly soluble DSPP protein into proteins with long hydrophobic amino acid repeats that could interfere with processing of normal DSPP and/or other secreted matrix proteins. We propose that all previously reported missense, nonsense, and splice-site DSPP mutations (all associated with exons 2 and 3) result in dominant phenotypes due to disruption of signal peptide-processing and/or related biochemical events that also result in interference with protein processing. This would bring the currently known dominant forms of the human disease phenotype in agreement with the normal phenotype of the heterozygous null Dspp (-/+) mice. A study of 188 normal human chromosomes revealed a hypervariable DSPP repeat domain with extraordinary rates of change including 20 slip-replication indel events and 37 predominantly C-to-T transition SNPs. The most frequent transition in the primordial 9-basepair (bp) DNA repeat was a sense-strand CpG site while a CpNpG (CAG) transition was the second most frequent SNP. Bisulfite-sequencing of genomic DNA showed that the DSPP repeat can be methylated at both motifs. This suggests that, like plants and some animals, humans methylate some CpNpG sequences. Analysis of 37 haplotypes of the highly variable DSPP gene from geographically diverse people suggests it may be a useful autosomal marker in human migration studies.

A 4 bp deletion mutation in DLX3 enhances osteoblastic differentiation and bone formation in vitro.

A 4 base-pair deletion mutation in the Distal-less 3 (DLX3) gene is etiologic for Tricho-Dento-Osseous syndrome (TDO). A cardinal feature of TDO is an increased thickness and density of bone. We tested the effects of the DLX3 gene mutation responsible for TDO on the osteoblastic differentiation of preosteoblastic MC3T3E1 cells and multipontent mesenchymal C2C12 cells. Differential expression analysis of C2C12 cells transfected with wild type DLX3 or mutant DLX3 was performed and desmin gene expression, an early myoblastic differentiation marker in mesenchymal cells, was evaluated by RT-PCR, western blot analysis, and desmin promoter transcriptional activity. Transfection of wild type DLX3 into MC3T3E1 and C2C12 cells increased alkaline phosphatase-2 activity, mineral deposition, and promoter activities of the osteocalcin and type 1 collagen genes compared to empty vector transfected cells. Transfection of mutant DLX3 into these cells further enhanced alkaline phosphatase activity, mineral deposition, and osteocalcin promoter activities, but did not further enhance type 1 collagen promoter activity. Transfection of mutant DLX3 into C2C12 cells markedly down regulated desmin gene expression, and protein expression of desmin and MyoD, while increasing protein expression of osterix and Runx2. These results demonstrate that the DLX3 deletion mutation associated with TDO enhances mesenchymal cell differentiation to an osteoblastic lineage rather than a myoblastic lineage by changing the fate of mesenchymal cells. This DLX3 mutation also accelerates the differentiation of osteoprogenitor cells to osteoblasts at later stages of osteogenesis.

Changes in salivary proteome following allogeneic hematopoietic stem cell transplantation.

OBJECTIVE: Allogeneic hematopoietic stem cell transplantation (allo-HCT) is frequently complicated by severe infections and graft-vs-host disease (GVHD). Saliva contains many components of adaptive and innate immune response crucial for local host defenses. Changes in salivary constituents could reflect systemic processes such as immune reconstitution and development of GVHD that occur posttransplant. This study was an initial evaluation of salivary protein changes that occur after allo-HCT. PATIENTS AND METHODS: Serially collected saliva samples from 41 patients undergoing allo-HCT were evaluated. Changes in salivary proteome were initially examined by SELDI-TOF mass spectrometry. Individual protein changes were identified by 2-dimensional differential in-gel electrophoresis (2D-DIGE) with subsequent MS/MS sequencing and ELISA. RESULTS: Significant increases and decreases in multiple salivary proteins that lasted at least 2 months posttransplant were detected by SELDI-TOF mass spectrometry. Lactoferrin and secretory leukocyte protease inhibitor demonstrated elevations 1 month post-HCT that persisted at least 6 months. Secretory IgA (sIgA) levels were decreased 1 month posttransplant, with recovery at approximately 6 months. Levels of salivary beta(2)-microglobulin were elevated at 6 months and correlated with sIgA levels. CONCLUSION: Allo-HCT is associated with long-term changes in several salivary proteins important for innate immune responses. These results support further studies on the association of salivary proteins with posttransplant complications including infections and GVHD.

Muenke syndrome (FGFR3-related craniosynostosis): expansion of the phenotype and review of the literature.

Muenke syndrome is an autosomal dominant disorder characterized by coronal suture craniosynostosis, hearing loss, developmental delay, carpal and tarsal fusions, and the presence of the Pro250Arg mutation in the FGFR3 gene. Reduced penetrance and variable expressivity contribute to the wide spectrum of clinical findings in Muenke syndrome. To better define the clinical features of this syndrome, we initiated a study of the natural history of Muenke syndrome. To date, we have conducted a standardized evaluation of nine patients with a confirmed Pro250Arg mutation in FGFR3. We reviewed audiograms from an additional 13 patients with Muenke syndrome. A majority of the patients (95%) demonstrated a mild-to-moderate, low frequency sensorineural hearing loss. This pattern of hearing loss was not previously recognized as characteristic of Muenke syndrome. We also report on feeding and swallowing difficulties in children with Muenke syndrome. Combining 312 reported cases of Muenke syndrome with data from the nine NIH patients, we found that females with the Pro250Arg mutation were significantly more likely to be reported with craniosynostosis than males (P < 0.01). Based on our findings, we propose that the clinical management should include audiometric and developmental assessment in addition to standard clinical care and appropriate genetic counseling.

Disorders of human dentin.

Dentin, the most abundant tissue in teeth, is produced by odontoblasts, which differentiate from mesenchymal cells of the dental papilla. Dentinogenesis is a highly controlled process that results in the conversion of unmineralized predentin to mineralized dentin. By weight, 70% of the dentin matrix is mineralized, while the organic phase accounts for 20% and water constitutes the remaining 10%. Type I collagen is the primary component (>85%) of the organic portion of dentin. The non-collagenous part of the organic matrix is composed of various proteins, with dentin phosphoprotein predominating, accounting for about 50% of the non-collagenous part. Dentin defects are broadly classified into two major types: dentinogenesis imperfectas (DIs, types I-III) and dentin dysplasias (DDs, types I and II). To date, mutations in DSPP have been found to underlie the dentin disorders DI types II and III and DD type II. With the elucidation of the underlying genetic mechanisms has come the realization that the clinical characteristics associated with DSPP mutations appear to represent a continuum of phenotypes. Thus, these disorders should likely be called DSPP-associated dentin defects, with DD type II representing the mild end of the phenotypic spectrum and DI type III representing the severe end.

Gingival epithelial cell expression of macrophage inflammatory protein-1alpha induced by interleukin-1beta and lipopolysaccharide.

BACKGROUND: Elevated levels of the macrophage inflammatory protein-1alpha (MIP-1alpha) are reported in inflammatory bone diseases including periodontitis. We evaluated the ability of interleukin-1beta (IL-1beta) and bacterial lipopolysaccharides (LPSs) to modulate MIP-1alpha expression in epithelial cells, fibroblasts, and polymorphonuclear leukocytes (PMNs). We also evaluated the effect of MIP-1alpha as an osteoclast activating factor. METHODS: Human gingival epithelial cells and fibroblasts were obtained by primary cell culture. PMNs were isolated from healthy controls. Human MG63 osteosarcoma cells were used as osteoblastic cells. After incubation of each cell type with IL-1beta, Porphyromonas gingivalis LPS, and Actinobacillus actinomycetemcomitans LPS, MIP-1alpha mRNA and secreted protein levels were quantified by reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry. The ability of recombinant MIP-1alpha to induce osteoclast formation was determined by tartrate resistant acid phosphatase assay. RESULTS: MIP-1alpha expression in PMNs and gingival epithelial cells was induced by IL-1beta and LPS, but neither induced MIP-1alpha expression in gingival fibroblasts or osteoblastic cells. MIP-1alpha was highly expressed in the basal epithelial layer of inflamed gingiva but not in healthy gingiva. MIP-1alpha induced osteoclast formation at an optimal concentration of 0.05 to 2 ng/ml. CONCLUSIONS: MIP-1alpha expression by gingival epithelial cells may be important in initiating inflammation by facilitating accumulation and activation of leukocytes. The ability of MIP-1alpha to facilitate formation of multinuclear bone cells indicates a possible role in periodontitis-associated bone destruction. These findings indicate MIP-1alpha may play an important role in early and later stages of inflammatory-related periodontitis.

Heritability of oral microbial species in caries-active and caries-free twins.

Oral microbes that colonize in the mouths of humans contribute to disease susceptibility, but it is unclear if host genetic factors mediate colonization. We therefore tested the hypothesis that the levels at which oral microbes colonize in the mouth are heritable. Dental plaque biofilms were sampled from intact tooth surfaces of 118 caries-free twins. An additional 86 caries-active twins were sampled for plaque from carious lesions and intact tooth surfaces. Using a reverse capture checkerboard assay the relative abundance of 82 bacterial species was determined. An integrative computational predictive model determined microbial abundance patterns of microbial species in caries-free twins as compared to caries-active twins. Heritability estimates were calculated for the relative microbial abundance levels of the microbial species in both groups. The levels of 10 species were significantly different in healthy individuals than in caries-active individuals, including, A. defectiva, S. parasanguinis, S. mitis/oralis, S. sanguinis, S. cristatus, S. salivarius, Streptococcus sp. clone CH016, G. morbillorum and G. haemolysans. Moderate to high heritability estimates were found for these species (h(2) = 56%-80%, p < .0001). Similarity of the overall oral microbial flora was also evident in caries-free twins from multivariate distance matrix regression analysis. It appears that genetic and/or familial factors significantly contribute to the colonization of oral beneficial species in twins.

Using biometrics for participant identification in a research study: a case report.

This paper illustrates the use of biometrics through the application of an iris-based biometrics system for identifying twins and their parents in a longitudinal research study. It explores the use of biometrics (science of measuring physical or anatomical characteristics of individuals) as a technology for correct identification of individuals during longitudinal studies to help ensure data fidelity. Examples of these circumstances include longitudinal epidemiological and genetic studies, clinical trials, and multicenter collaborative studies where accurate identification of subjects over time can be difficult when the subject may be young or an unreliable source of identification information. The use of technology can automate the process of subject identification thereby reducing the need to depend on subject recall during repeated visits thus helping to ensure data quality. This case report provides insights that may serve as useful hints for those responsible for planning system implementation that involves participants' authentication that would require a more secure form of identification.

Genetic factors associated with gout and hyperuricemia.

Hyperuricemia and gout are common conditions that have long been known to have a heritable component. Obesity, diabetes, and chronic kidney failure are conditions with multifactorial inheritance that are associated with gout. In addition, social factors such as protein and alcohol intake affect serum uric acid levels. The current review discusses basic uric acid metabolism and the multigenetic inheritance of hyperuricemia. Several monogenic disorders affecting uric acid metabolism are reviewed. The genetics, pathophysiology, diagnosis, and treatment of familial juvenile hyperuricemic nephropathy/medullary cystic kidney disease, autosomal dominant disorders associated with hyperuricemia and progressive kidney failure, are described.

Heritability estimates for dental caries and sucrose sweetness preference.

OBJECTIVE: The aim of this study was to determine heritability estimates for dental caries traits and sucrose sweetness preference. DESIGN: Participants included 115 pairs of twins 4-7-years-old. Caries exams followed NIDCR criteria where the severity of the lesion was also determined. Twins ranked their preference for five concentrations of sucrose/grape juice solutions (0.15-1.17M) with a Face Scale. Variables submitted to analysis: (1) surface-based caries prevalence rate (SBCPR); (2) lesion severity index (LSI); (3) sucrose sweetness preference score (SSPS). Heritability analyses were performed with the SOLAR software package. RESULTS: Heritability estimates adjusted for age and gender were: SBCPR-h(2)=64.6 (p<.00001), LSI-h(2)=61.7 (p<.00001) and SSPS-h(2)=55.2 (p<.00001). Treating SPSS as a covariate in the SBCPR and LSI models did not alter heritability estimates. CONCLUSIONS: These results suggest that variation in dental caries traits and sucrose sweetness preference have a significant genetic contribution that is mediated independently.

Genetics: The Future Is Now with Interprofessional Collaboration.

With the growing complexity of health care, interprofessional communication and collaboration are essential to optimize the care of dental patients, including consideration of genetics. A dental case exemplifies the challenges and benefits of an interprofessional approach to managing pediatric patients with oligodontia and a family history of colon cancer. The interprofessional team includes dental, genetic, nutritional, and surgical experts.