Genetic analysis of hereditary gingival fibromatosis using whole exome sequencing and bioinformatics

Clinics and genetic background of hereditary gingival fibromatosis

BACKGROUND

Hereditary gingival fibromatosis (HGF) is a rare condition characterized by slowly progressive overgrowth of the gingiva. The severity of overgrowth may differ from mild causing phonetic and masticatory issues, to severe resulting in diastemas or malposition of teeth. Both, autosomal-dominant and autosomal-recessive forms of HGF are described. The aim of this review is a clinical overview, as well as a summary and discussion of the involvement of candidate chromosomal regions, pathogenic variants of genes, and candidate genes in the pathogenesis of HGF. The loci related to non-syndromic HGF have been identified on chromosome 2 (GINGF, GINGF3), chromosome 5 (GINGF2), chromosome 11 (GINGF4), and 4 (GINGF5). Of these loci, pathogenic variants of the SOS-1 and REST genes inducing HGF have been identified in the GINGF and the GINGF5, respectively. Furthermore, among the top 10 clusters of genes ranked by enrichment score, ATP binding, and fibronectin encoding genes were proposed as related to HGF.

CONCLUSION

The analysis of clinical reports as well as translational genetic studies published since the late'90s indicate the clinical and genetic heterogeneity of non-syndromic HGF and point out the importance of genetic studies and bioinformatics of more numerous unrelated families to identify novel pathogenic variants potentially inducing HGF. This strategy will help to unravel the molecular  mechanisms as well as uncover specific targets for novel and less invasive therapies of this rare, orphan condition.

Nonsyndromic hereditary gingival fibromatosis: Characterization of a family and review of genetic etiology

Our aim is to describe a family with a nonsyndromic form of hereditary gingival fibromatosis (HGF) and discuss genetic characteristics of this rare disease by reviewing reported cases. A mother and three descendants were diagnosed with HGF. There was marked variable expressivity: from severe generalized gingival overgrowth in a 16-year-old boy (the proband) to minimal manifestations in the mother. The proband was submitted to gingivectomy and gingivoplasty. In younger siblings, the disease remained stable for 5 years, suggesting that clinical surveillance is a good option. The diagnosis was supported by histopathological examination. Analysis of this family and literature-reported cases supports that HGF most frequently shows an autosomal dominant inheritance with high penetrance and variable expressivity. Neomutations and gonadal mosaicism do not seem to be a rare event. Although five loci have been mapped by linkage analysis, only two genes, SOS1 and REST, were identified in four families.

Exomic and transcriptomic alterations of hereditary gingival fibromatosis

OBJECTIVE

Hereditary gingival fibromatosis (HGF) is a rare oral disease characterized by either localized or generalized gradual, benign, non-hemorrhagic enlargement of gingivae. Although several genetic causes of HGF are known, the genetic etiology of HGF as a non-syndromic and idiopathic entity remains uncertain.

SUBJECTS AND METHODS

We performed exome and RNA-seq of idiopathic HGF patients and controls, and then devised a computational framework that specifies exomic/transcriptomic alterations interconnected by a regulatory network to unravel genetic etiology of HGF. Moreover, given the lack of animal model or large-scale cohort data of HGF, we developed a strategy to cross-check their clinical relevance through in silico gene-phenotype mapping with biomedical literature mining and semantic analysis of disease phenotype similarities.

RESULTS

Exomic variants and differentially expressed genes of HGF were connected by members of TGF-β/SMAD signaling pathway and craniofacial development processes, accounting for the molecular mechanism of fibroblast overgrowth mimicking HGF. Our cross-check supports that genes derived from the regulatory network analysis have pathogenic roles in fibromatosis-related diseases.

CONCLUSIONS

The computational approach of connecting exomic and transcriptomic alterations through regulatory networks is applicable in the clinical interpretation of genetic variants in HGF patients.

Expression of CD163 in hereditary gingival fibromatosis: A possible association with TGF-β1

BACKGROUND

Although several studies have discussed some of the molecular and cellular changes associated with hereditary gingival fibromatosis (HGF), its pathogenesis is still largely unclear. This study was directed to detect and outline the degree of relationship between the immunophenotyped macrophages (M2) expressing CD163 and TGF-β1 in patients with gingival overgrowth due to HGF.

METHODS

Biopsies from 20 patients suffering from HGF and 20 normal control subjects were harvested, histologically and immunohistochemically stained then, analyzed and statistically compared and correlated for CD163 immunoexpression and TGF-β1.

RESULTS

All HGF specimens expressed TGF-β1 by most of the connective tissue fibroblasts, with statistically high significant mean of area % (2.61 ± 0.41) compared to normal controls (0.11 ± 0.06; P = .001). All control specimens revealed negligible CD163 immunostaining of the few inflammatory cells found with a mean area of % (0.69 ± 0.12), while the specimens of HGF cases showed statistically significant higher CD163 expression (3.39 ± 0.75) at (P = .007). A statistically significant higher mean % of M2 cells expressing CD163 in relation to the total number of the inflammatory cells was revealed in HGF (34.46 ± 2.04) compared to the control group (16.36 ± 2.39; P-value ≤ .05). Moderate correlation between CD163 and TGF-β1 was detected in HGF (r = .451; P-value < .05).

CONCLUSIONS

CD163 and TGF-β1 were clearly expressed in HGF cases compared to healthy control patients, with significant correlation. In HGF, the increase in CD 163-positive cells was specific and not dependent on the chronic gingival inflammation.