Débora Pallos

A Mutation in the SOS1 Gene Causes Hereditary Gingival Fibromatosis Type 1

Hereditary gingival fibromatosis (HGF) is a rare, autosomal dominant form of gingival overgrowth. Affected individuals have a benign, slowly progressive, nonhemorrhagic, fibrous enlargement of the oral masticatory mucosa. Genetic loci for autosomal dominant forms of HGF have been localized to chromosome 2p21-p22 (HGF1) and chromosome 5q13-q22 (HGF2). To identify the gene responsible for HGF1, we extended genetic linkage studies to refine the chromosome 2p21-p22 candidate interval to approximately 2.3 Mb. Development of an integrated physical and genetic map of the interval identified 16 genes. Sequencing of these genes, in affected and unaffected HGF1 family members, identified a mutation in the Son of sevenless-1 (SOS1) gene in affected individuals. In this report, we describe the genomic structure of the SOS1 gene and present evidence that insertion of a cytosine between nucleotides 126,142 and 126,143 in codon 1083 of the SOS1 gene is responsible for HGF1. This insertion mutation, which segregates in a dominant manner over four generations, introduces a frameshift and creates a premature stop codon, abolishing four functionally important proline-rich SH3 binding domains normally present in the carboxyl-terminal region of the SOS1 protein. The resultant protein chimera contains the wild-type SOS1 protein for the N-terminal amino acids 1-1083 fused to a novel 22-amino acid carboxyl terminus. Similar SOS1 deletion constructs are functional in animal models, and a transgenic mouse construct with a comparable SOS1 chimera produces a phenotype with skin hypertrophy. Clarification of the functional role of this SOS1 mutant has implications for understanding other forms of gingival fibromatosis and corrective gingival-tissue management.

Genetic Linkage of Hereditary Gingival Fibromatosis to Chromosome 2p21

Gingival fibromatosis is characterized by a slowly progressive benign enlargement of the oral gingival tissues. The condition results in the teeth being partially or totally engulfed by keratinized gingiva, causing aesthetic and functional problems. Both genetic and pharmacologically induced forms of gingival fibromatosis are known. The most common genetic form, hereditary gingival fibromatosis (HGF), is usually transmitted as an autosomal dominant trait, although sporadic cases are common and autosomal recessive inheritance has been reported. The genetic basis of gingival fibromatosis is unknown. We identified an extended family (n=32) segregating an autosomal dominant form of isolated gingival fibromatosis. Using a genomewide search strategy, we identified genetic linkage (Zmax=5.05, straight theta=.00) for the HGF phenotype to polymorphic markers in the genetic region of chromosome 2p21 bounded by the loci D2S1788 and D2S441. This is the first report of linkage for isolated HGF, and the findings have implications for identification of the underlying genetic basis of gingival fibromatosis.

Evidence of Genetic Heterogeneity for Hereditary Gingival Fibromatosis

Hereditary Gingival Fibromatosis (HGF) is the most common genetic form of gingival fibromatosis. The condition is most frequently reported to be transmitted as an autosomal-dominant trait, but autosomal-recessive inheritance has also been reported. The clinical presentation of HGF is variable, both in the distribution (number of teeth involved) and in the degree (severity) of expression. It is unknown if the variable clinical expression of HGF in different families is due to variable expression of a common gene mutation, allelic mutations, or non-allelic mutations. The apparently different modes of Mendelian inheritance of HGF suggest genetic heterogeneity. A gene locus for HGF has been localized to a 37-cM genetic interval on chromosome 2p21-p22 (D2S1352, Zmax = 5.10, θ = 0.00) flanked by D2S1788 and D2S441. To evaluate the generality of this linkage, we tested linkage with 9 markers from this candidate region in another large family, segregating for an autosomal-dominant form of generalized HGF, and found no support for linkage with any of these markers. Furthermore, statistical tests of this apparent heterogeneity were highly significant. Analysis of these data provides direct evidence that at least two genetically distinct loci are responsible for autosomal-dominant hereditary gingival fibromatosis.

Genetic heterogeneity of gingival fibromatosis on chromosome 2p.

Gingival fibromatosis (GF) occurs in several genetic forms as a simple Mendelian trait, in malformation syndromes, and in some chromosomal disorders. Specific genes responsible for GF have not been identified. An autosomal dominant form of hereditary gingival fibromatosis (HGF, MIM 135300) was recently mapped to chromosome 2p21 in a large Brazilian family and there was an earlier report of GF in a boy with a cytogenetic duplication involving 2p13→p21. We thus hypothesised that a common gene locus may be responsible for GF in both the Brazilian family and the boy with the chromosome 2p duplication. We performed additional genetic linkage studies on the Brazilian family and molecular cytogenetic studies on the patient with the cytogenetic duplication to correlate more precisely the genetic interval of the HGF phenotype with the duplicated 2p interval. Additional linkage analysis of new family members resulted in refinement of the candidate region for HGF to an 8 Mb region. Molecular cytogenetic analysis of the 2p13→p21 duplication associated with GF showed that the duplicated region was proximal to the candidate interval for HGF. Thus, our results support the presence of two different gene loci on chromosome 2p that are involved in GF.

Germ Line Gain of Function with SOS1 Mutation in Hereditary Gingival Fibromatosis

Mutation of human SOS1 is responsible for hereditary gingival fibromatosis type 1, a benign overgrowth condition of the gingiva. Here, we investigated molecular mechanisms responsible for the increased rate of cell proliferation in gingival fibroblasts caused by mutant SOS1 in vitro. Using ectopic expression of wild-type and mutant SOS1 constructs, we found that truncated SOS1 could localize to the plasma membrane, without growth factor stimuli, leading to sustained activation of Ras/MAPK signaling. Additionally, we observed an increase in the magnitude and duration of ERK signaling in hereditary gingival fibromatosis gingival fibroblasts that was associated with phosphorylation of retinoblastoma tumor suppressor protein and the up-regulation of cell cycle regulators, including cyclins C, D, and E and the E2F/DP transcription factors. These factors promote cell cycle progression from G1 to S phase, and their up-regulation may underlie the increased gingival fibroblast proliferation observed. Selective depletion of wild-type and mutant SOS1 through small interfering RNA demonstrates the link between mutation of SOS1, ERK signaling, cell proliferation rate, and the expression levels of Egr-1 and proliferating cell nuclear antigen. These findings elucidate the mechanisms for gingival overgrowth mediated by SOS1 gene mutation in humans.

Characterization of Fibroblasts with Son of Sevenless-1 Mutation

Although non-syndromic hereditary gingival fibromatosis (HGF) is genetically heterogeneous, etiologic mutations have been identified only in the Son of Sevenless-1 gene (SOS1). To test evidence of increased cell proliferation, we studied histological, morphological, and proliferation characteristics in monolayer and three-dimensional cultures of fibroblasts with the SOS1 g.126,142–126,143insC mutation. Histological assessment of HGF gingiva indicated increased numbers of fibroblasts (30%) and increased collagen (10%). Cell proliferation studies demonstrated increased growth rates and 5-bromo-2-deoxyuridine incorporation for HGF fibroblasts. Flow cytometry showed greater proportions of HGF fibroblasts in the G2/M phase. Attachment of HGF fibroblasts to different extracellular matrix surfaces demonstrated increased formation of protrusions with lamellipodia. HGF fibroblasts in three-dimensional culture showed greater cell proliferation, higher cell density, and alteration of surrounding collagen matrix. These findings revealed that increased fibroblast numbers and collagen matrix changes are associated with mutation of the SOS1 gene in vitro and in vivo.

Evaluation of organic and inorganic compounds in the saliva of patients with chronic periodontal disease

OBJETIVO: O objetivo deste estudo foi avaliar a influencia da doenca periodontal sobre os parâmetros bioquimicos da saliva, incluindo taxa de fluxo salivar, pH, proteina total, atividade de fosfatase alcalina e a concentracao de ureia, em individuos com periodontite cronica. METODOLOGIA: Quarenta individuos foram alocados em dois grupos: vinte individuos sem doenca periodontal (grupo controle) e vinte individuos com periodontite cronica (grupo teste). Indice de placa (IP), indice gengival (IG), profundidade de sondagem (PD) e nivel de insercao clinica (CAL) foram obtidos anteriormente por um examinador treinado e calibrado clinicamente. Saliva de ambos os grupos foram coletadas para analise de seus parâmetros bioquimicos. O teste T de Student e coeficiente de correlacao (Pearson) foram utilizados em um nivel 5% de significância. RESULTADOS: Os resultados mostraram alteracoes na atividade da fosfatase alcalina, ureia e proteina total nos individuos do grupo teste em comparacao ao grupo controle (P 0,05). CONCLUSAO: Os resultados sugerem que a periodontite cronica pode afetar a composicao da saliva e que a analise dos parâmetros salivares pode ser util como um exame complementar para o diagnostico da doenca periodontal.

Salivary markers in patients with chronic renal failure

INTRODUCTION Chronic renal failure (CRF) is a progressive loss of renal function over a period of months or years. The major function of the kidneys is the removal of metabolic waste products, electrolytes and water. When this function is impaired, systemic changes, oral complications and alterations in salivary composition may occur. OBJECTIVE This study aimed to compare the levels of immunological and inflammatory components in the saliva samples from patients that undergo to hemodialysis treatment (HD), without HD and control. DESIGN This study evaluated IgA, IgG, C reactive protein (CRP) and nitric oxide (NO) in saliva samples from 119 patients, who were divided into the control group (C), chronic renal failure (CRF) patient group and CRF patients on hemodialysis treatment (HD) group. IgA and IgG levels were analyzed by ELISA. Nitric oxide levels were determined indirectly by the nitrite concentration using Griess reagent; CRP by agglutination tests; and total proteins, by Bradford assay. RESULTS The HD group showed significantly higher levels of IgG, IgA and CRP compared with the control and CRF groups. The CRF group presented the same amounts of IgG, IgA and CRP as the C group but significantly higher levels of NO similar to the HD group. CONCLUSION Renal disease, particularly hemodialysis treatment during renal disease, seems to alter salivary immunological and inflammatory components. Thus, analyzing the levels of IgA, IgG, NO and CRP in saliva may be beneficial for monitoring renal disease.

Menopausa: fator de risco para doença periodontal?

OBJETIVO: verificar se existe relacao entre os parâmetros periodontais e os niveis de estrogeno e densitometria ossea mineral (DOM). METODOS: foram avaliadas 46 mulheres na pos-menopausa entre 44 e 68 anos de idade (52,2±4,8) e 15 mulheres como grupo controle entre 35 e 54 anos de idade (44,7±7,5). Parâmetros periodontais como profundidade a sondagem (PS), perda de insercao clinica (PIC) e dentes ausentes (DA) foram comparados com os niveis de estrogeno (suficiente e deficiente) e DOM em normais, osteopenicas e osteoporoticas. Os dados foram comparados pela diferenca das medias entre os grupos e analisados pelo teste de Aspin-Welch. RESULTADOS: as medias dos parâmetros de PS, PIC e DA, quando associados ao grau da DOM em normais (2,1±0,5; 2,9±1,4 e 10,6±5,0), osteopenicas (2,3±0,7; 3,0±1,1 e 12,8±5,1) e osteoporoticas (2,4±0,6; 2,7±0,9 e 14,3±5,7), nao mostraram diferencas significativas (p>0,05). Foi encontrada diferenca significante entre o grupo controle e nas mulheres menopausadas para PIC e DA. Quando comparados com os niveis de estrogeno os resultados demonstraram igualdade para os parâmetros periodontais. CONCLUSOES: apesar de alguns estudos demonstrarem correlacao positiva da doenca periodontal com osteoporose e com os niveis de estrogenio, na populacao de mulheres menopausadas estes dados nao foram confirmados neste estudo.

Prevalence of carotid artery calcification in patients with chronic renal disease identified by panoramic radiography

OBJECTIVE This study aimed to evaluate the prevalence of carotid artery calcification (CAC) in the panoramic radiographs of patients with chronic renal disease and to ascertain the medical parameters. STUDY DESIGN A total of 100 panoramic radiographs were observed. The division of patients according to renal disease was as follows: 37 in early-stage renal disease (ESG), 32 in predialysis (PDG), and 31 in hemodialysis (HDG). RESULTS There were 21 images with opacities suggestive of CAC (6 from ESG, 7 from PDG, and 8 from HDG). The medical parameters were as follows: Triglyceride levels were significantly higher (P < .0001) in patients with CAC compared with those without CAC; potassium levels were higher in the group with CAC compared with the group without CAC (P < .0001); and the calcium levels were lower in the group with CAC compared with the group without CAC (P < .0001). CONCLUSIONS The patients with renal injury and changes in triglyceride and potassium levels had a higher prevalence of CAC on panoramic radiography.